{"id":1405,"date":"2011-03-11T13:51:59","date_gmt":"2011-03-11T18:51:59","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=1405"},"modified":"2026-01-22T10:45:09","modified_gmt":"2026-01-22T16:45:09","slug":"3-factors-that-stabilize-carbocations","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2011\/03\/11\/3-factors-that-stabilize-carbocations\/","title":{"rendered":"3 Factors That Stabilize Carbocations"},"content":{"rendered":"<p><strong>Carbocations: Properties, Formation, and Stability<\/strong><\/p>\n<ul>\n<li>Carbocations are <strong>electron-deficient<\/strong> species with an empty p-orbital<\/li>\n<li>Lacking a full octet and bearing a positive charge, they tend to be fairly <strong>high-energy<\/strong> (i.e. unstable) species and are often encountered as transient <strong>intermediates<\/strong> in many chemical reactions.<\/li>\n<li>Three main factors increase the stability of carbocations:\n<ul>\n<li>Increasing the number of\u00a0<strong>adjacent<\/strong> carbon atoms: methyl (least stable carbocation) &lt; primary &lt; secondary &lt; tertiary\u00a0 (most stable carbocation)<\/li>\n<li>Adjacent <strong>pi bonds<\/strong> that allow the carbocation p-orbital to be part of a conjugated pi-system system (&#8220;delocalization through <strong>resonance<\/strong>&#8220;)<\/li>\n<li>Adjacent atoms with<strong> lone pairs<\/strong> that can provide the carbon with a full octet.<\/li>\n<\/ul>\n<\/li>\n<li>Adjacent electron withdrawing groups that are unable to donate a lone pair (e.g. CF<sub>3<\/sub>, NO<sub>2 <\/sub>) greatly <strong>decrease<\/strong> the stability of carbocations.<\/li>\n<li>Additionally, carbocations <strong>decrease<\/strong> in stability in the order alkyl (most stable) &gt; alkenyl &gt; alkynyl (least stable)<\/li>\n<li>A few additional factors that influence carbocation stability include aromaticity \/ antiaromaticity, planarity (bridgehead carbocations are unstable) and special cases involving small rings.<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-34349\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/0-summary-of-the-factors-that-affect-carbocation-stability-including-substitution-resonance-and-others.gif\" alt=\"summary of the factors that affect carbocation stability including substitution resonance and others\" width=\"640\" height=\"694\" \/><\/a><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li><a href=\"#one\">What Is A Carbocation?<\/a><\/li>\n<li><a href=\"#two\">Formation of Carbocations<\/a><\/li>\n<li><a href=\"#three\">Factors That Stabilize Carbocations &#8211; Substitution<\/a><\/li>\n<li><a href=\"#four\">Factors That Stabilize Carbocations &#8211; Resonance<\/a><\/li>\n<li><a href=\"#five\">Applying Carbocation Stability To Understand Reactions<\/a><\/li>\n<li><a href=\"#six\">Stabilization By Adjacent Lone Pairs<\/a><\/li>\n<li><a href=\"#seven\">What&#8217;s More Important &#8211; Resonance Or Substitution?<\/a><\/li>\n<li><a href=\"#eight\">Inductive Effects<\/a><\/li>\n<li><a href=\"#nine\">Some Special Cases<\/a><\/li>\n<li><a href=\"#ten\">Summary<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quiz\">Quiz Yourself!<\/a><\/li>\n<li><a href=\"#references\">(Advanced) References and Further Reading<\/a><\/li>\n<\/ol>\n<hr \/>\n<h2><a id=\"one\"><\/a>1. What is A Carbocation?<\/h2>\n<p>A positively charged carbon atom bearing three covalent bonds and an empty orbital is called a <strong>carbocation <\/strong>(<em><span style=\"color: #993366;\">or more officially, a &#8220;carbenium&#8221; ion, although for our purposes we&#8217;re going to use &#8220;carbocation&#8221;<\/span> [<\/em><a href=\"#noteone\"><span style=\"color: #ff0000;\">Note 1<\/span><\/a><em> ])<\/em><\/p>\n<p>Other than the charge of +1 on the central carbon, the structure and properties of the vast majority [<a href=\"#notetwo\"><span style=\"color: #ff0000;\">Note 2<\/span><\/a>]\u00a0 of carbocations closely resemble those of neutral <strong>boron<\/strong> compounds.<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-34309\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/1-description-of-a-carbocation-as-a-general-name-for-a-species-bearing-a-positive-charge-on-carbon.gif\" alt=\"description of a carbocation as a general name for a species bearing a positive charge on carbon\" width=\"640\" height=\"312\" \/><\/a><\/p>\n<p>Both carbocations and neutral boron compounds generally have<\/p>\n<ul>\n<li>an sp<sup>2<\/sup>-hybridized central atom<\/li>\n<li>with 6 valence electrons,<\/li>\n<li>an empty p-orbital,<\/li>\n<li><strong>trigonal planar<\/strong> geometry<\/li>\n<li>and bond angles of 120\u00b0.<\/li>\n<\/ul>\n<p>[<span style=\"color: #993366;\"><em>How do we know this? X-ray crystallography<\/em><\/span> <a href=\"#notethree\"><span style=\"color: #ff0000;\">Note 3<\/span><\/a>]<\/p>\n<p>Like boron compounds, carbocations are electron-deficient Lewis acids that will readily combine with Lewis bases, resulting in a tetrahedral, sp<sup>3<\/sup>-hybridized atom with a full octet of electrons.<\/p>\n<p>See if you can draw the curved arrow for the reaction below.<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34756\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34756\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34756\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34756\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34756\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34756 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34756\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-jrxga\" data-id=\"jrxga\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2476-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2476-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>Due to their trigonal planar geometry, carbocations can undergo attack from either face of the empty p-orbital.<\/p>\n<p>Be alert for situations where this can result in a pair of stereoisomers.<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34755\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34755\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34755\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34755\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34755\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34755 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34755\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-a4kjg\" data-id=\"a4kjg\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2477-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2477-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<h2><a id=\"two\"><\/a>2. Formation of Carbocations<\/h2>\n<p>Carbocations are important <strong>intermediates<\/strong> in many reactions.<span style=\"color: #993366;\"><em> (An intermediate, as opposed to a transition state, is a potentially isolable species in a reaction and occupies a potential energy minimum in a reaction coordinate diagram. Transition states have partial bonds, extremely short lifetimes and cannot be isolated).<\/em><\/span><\/p>\n<p>Lacking a full octet of electrons around carbon and bearing a positive charge, carbocations are higher in energy and more unstable than neutral carbon compounds.<\/p>\n<p>Some prominent reactions that involve carbocation intermediates are the addition of hydrogen halides (e.g. HBr, HCl, and HI) to alkenes and unimolecular substitution (S<sub>N<\/sub>1) and elimination (E1) reactions of alkyl halides.<\/p>\n<p>In the S<sub>N<\/sub>1\/E1 reactions, the first step is loss of a <strong>good leaving group<\/strong> (<em><span style=\"color: #993366;\">generally, a<\/span><\/em><span style=\"color: #993366;\"><em> very weak base &#8211; See &#8220;<span style=\"color: #993366;\"><a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2011\/04\/12\/what-makes-a-good-leaving-group\/\">What Makes A Good Leaving Group<\/a><\/span>&#8220;<\/em><\/span>) to give a carbocation. This is usually done in a highly polar solvent such as H<sub>2<\/sub>O or acetic acid which can help to stabilize the charged carbocation intermediate.<\/p>\n<p>See if you can draw the curved arrow for formation of the carbocation from this tertiary alkyl halide, along with the transition state:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34754\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34754\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34754\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34754\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34754\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34754 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34754\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-ajx2n\" data-id=\"ajx2n\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2478-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2478-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>In additions of hydrohalic acids to alkenes, the first step is attack of H+ by the pair of electrons in the C-C pi bond to give a carbocation intermediate.<\/p>\n<p>See if you can draw the curved-arrow pushing mechanism and the transition state for this reaction:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34753\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34753\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34753\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34753\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34753\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34753 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34753\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-73k9b\" data-id=\"73k9b\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2479-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2479-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>In both of these reactions, we start with a relatively low-energy starting material that passes through a high energy transition state en route to the carbocation intermediate.<\/p>\n<p>In the second step, the carbocation then reacts with a Lewis base in solution to give a product where the carbon is again tetrahedral and sp<sup>3<\/sup> hybridized.<\/p>\n<p>A sketch of the reaction coordinates for each of these two reactions would look a little like this:<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-34310\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/6-reaction-energy-coordinate-diagram-for-formation-of-a-carbocation-intermediate-leading-to-lower-activation-energy.gif\" alt=\"-reaction energy coordinate diagram for formation of a carbocation intermediate leading to lower activation energy\" width=\"640\" height=\"666\" \/><\/a><\/p>\n<p><span style=\"color: #993366;\"><em>(Note that the carbocation <strong>intermediate<\/strong> occupies a <strong>local<\/strong> <strong>minimum<\/strong> on this reaction coordinate diagram; the two transition states are local\u00a0<strong>maxima<\/strong>. )<\/em><\/span><\/p>\n<p>Why bring this up?<\/p>\n<p>Because the <strong>rate-determining step<\/strong> for each of these reactions is <strong>formation<\/strong> of the carbocation <strong>intermediate<\/strong>.<\/p>\n<p>The <strong>more stable<\/strong> the carbocation <strong>intermediate<\/strong>, the lower in energy the transition state that leads to that carbocation, which translates into a lower activation energy and a <strong>faster reaction<\/strong>.<\/p>\n<p>Therefore, if we understand the factors that govern the <strong>stability\u00a0<\/strong>of carbocations, then it will also help us understand <strong>why<\/strong> certain reactions happen quickly whereas others do not!<\/p>\n<h2><a id=\"three\"><\/a>3. Factors That Stabilize Carbocations &#8211; Substitution<\/h2>\n<p>The experimentally measured stability [<a href=\"#notefour\"><span style=\"color: #ff0000;\">Note 4<\/span><\/a>] of carbocations shows the following trend:<\/p>\n<p>Methyl (least stable) &lt; primary &lt; secondary &lt; tertiary (most stable)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34311\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/7-stability-of-carbocations-proceeds-in-the-direction-methyl-is-the-least-stable-primary-secondary-tertiary-is-the-most-stable.gif\" alt=\"stability of carbocations proceeds in the direction methyl is the least stable primary secondary tertiary is the most stable\" width=\"640\" height=\"276\" \/><\/a><\/p>\n<p>In other words, carbocation stability increases as C-H bonds are replaced with C-C bonds.<\/p>\n<p>Why?<\/p>\n<p>Being electron-poor, carbocations are <strong>stabilized\u00a0<\/strong>through donation of electron density from neighboring <strong>electron-rich<\/strong> atoms.<\/p>\n<p>As I&#8217;ve often told my students, &#8220;<em>when you&#8217;re poor, it helps to have rich neighbors<\/em>&#8220;.<\/p>\n<p>One way to rationalize this trend is through applying\u00a0<strong>inductive effects.\u00a0<\/strong><\/p>\n<p>Carbon is more electronegative (2.54) than hydrogen (2.20). So C-H bonds bear a small <strong>dipole <\/strong>whereby the carbon is partially negative and the hydrogen is partially positive.<\/p>\n<p>The electron density from multiple C\u2013H dipoles can add up.\u00a0 So the carbon of an alkyl group will have a small partial negative charge which can be donated to the adjacent carbocation, making it less electron-poor.<\/p>\n<p>This isn&#8217;t possible when the carbocation is directly attached to H.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34312\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/8-explanation-of-the-stability-of-carbocations-using-inductive-effects-due-to-the-c-h-bond-dipole.gif\" alt=\"explanation of the stability of carbocations using inductive effects due to the c h bond dipole\" width=\"640\" height=\"521\" \/><\/a><\/p>\n<p>A more satisfying (<span style=\"color: #993366;\"><em>to some! <\/em><\/span>) explanation comes from\u00a0<strong>hyperconjugation<\/strong>.<\/p>\n<p>Imagine lining up the two electrons in a\u00a0 C-H (or C-C) sigma bond with the empty p-orbital of the carbocation. Then imagine a form of &#8220;resonance&#8221; where those electrons are shared with the p-orbital to form a pi-bond (and H+).<\/p>\n<p>Since electron density is being donated to an empty orbital, this should be <strong>stabilizing<\/strong> for the empty p-orbital (i.e. the carbocation).<\/p>\n<p>We don&#8217;t have space in this article to go into all the implications of hyperconjugation in this article, but it does make some testable predictions that are borne out by experiment. [<em><span style=\"color: #ff0000;\"><a href=\"#notethree\">Note 3<\/a><span style=\"color: #993366;\">&#8211; the structure of the adamantyl carbocation is very instructive<\/span><\/span><\/em>]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34313\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/9-explanation-of-the-greater-stability-of-substituted-carbocations-due-to-hyperconjugation.gif\" alt=\"explanation of the greater stability of substituted carbocations due to hyperconjugation\" width=\"640\" height=\"537\" \/><\/a><\/p>\n<p>Whatever rationalization you prefer, the observed trend remains the same. The <strong>more substituted<\/strong> the <strong>carbocation<\/strong>, the <strong>greater<\/strong> its <strong>stability<\/strong>.<\/p>\n<h2><a id=\"four\"><\/a>4. Factors That Stabilize Carbocations &#8211; Resonance<\/h2>\n<p>A good working principle in organic chemistry is that <strong>concentrated charge<\/strong>\u00a0 is generally more <strong>unstable <\/strong>(higher-energy) than <strong>dilute<\/strong> <strong>charge<\/strong> (lower-energy) [<a href=\"#notefive\"><span style=\"color: #ff0000;\">Note 5<\/span><\/a>]<\/p>\n<p>One place we&#8217;ve seen this before is in the concept of <strong>polarizability<\/strong>, where a big anion like iodide I(-) is more stable than a small ion like F(-) because the negative charge is spread out over a much greater volume. [<span style=\"color: #993366;\"><em>This is the factor responsible for the greater acidity of H-I versus H-F and also the greater leaving group ability of I(-)<\/em> <\/span>]<\/p>\n<p>Another factor that results in this &#8220;spreading-out&#8221; of charges is &#8220;resonance&#8221;.<\/p>\n<p>In a carbocation such as the <em>n<\/em>-propyl cation (CH<sub>3<\/sub>CH<sub>2<\/sub>CH<sub>2<\/sub>+) , the positive charge is localized to a single carbon.<\/p>\n<p>But if a pi-bond is <strong>adjacent<\/strong> to the carbocation, we can then draw two resonance forms where the positive charge is either on C-1 or C-3.<\/p>\n<p>In the resonance hybrid, the positive charge is shared between these two carbons, which will each have a charge density of <strong>+0.5<\/strong> instead of <strong>+1<\/strong>. <em>(<span style=\"color: #993366;\">This is what is meant by &#8220;resonance delocalization&#8221; &#8211; the charge has been smeared over multiple carbons<\/span>)\u00a0<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34314\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/10-carbocations-can-be-stabilized-due-to-resonance-which-allows-for-delocalization-of-charge.gif\" alt=\"carbocations can be stabilized due to resonance which allows for delocalization of charge\" width=\"640\" height=\"575\" \/><\/a><\/p>\n<p>The greater stability of this carbocation (<span style=\"color: #993366;\"><em>known as the <strong>allyl cation<\/strong><\/em><\/span>)\u00a0relative to the parent propyl cation is borne out by numerous measurements. [<a href=\"#notefour\"><span style=\"color: #ff0000;\">Note 4<\/span><\/a>]<\/p>\n<p>A similar effect is seen when a carbocation is adjacent to an aromatic ring such as benzene. The stability of this carbocation, known as the\u00a0<strong>benzyl<\/strong> <strong>carbocation<\/strong> is considerably greater than that of a &#8220;normal&#8221; primary carbocation.\u00a0<em>(<span style=\"color: #993366;\">In fact the benzyl carbocation is roughly as stable as the t-butyl cation,<\/span> <a href=\"#notefour\"><span style=\"color: #ff0000;\">Note 4<\/span><\/a>)\u00a0<\/em><\/p>\n<p>The stability of the carbocation tends to increase as the number of potential resonance forms increases.<\/p>\n<p>For example, the &#8220;trityl&#8221; cation, Ph<sub>3<\/sub>C(+) is so stable that it forms a crystalline salt that can be put in a <a href=\"https:\/\/www.sigmaaldrich.com\/US\/en\/product\/aldrich\/164577\">bottle<\/a> and stored on a shelf indefinitely.<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34752\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34752\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34752\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34752\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34752\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34752 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34752\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-ms86v\" data-id=\"ms86v\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2480-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2480-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>A word of warning.\u00a0 \u00a0In order for a carbocation to be stabilized by resonance, the p-orbital of the carbocation <strong>must<\/strong> be able to overlap with the p-orbitals of the adjacent pi-bond. (<span style=\"color: #993366;\"><em>See article &#8211; <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2017\/01\/24\/conjugation-and-resonance\/\">Conjugation and Resonance<\/a><\/em><\/span>)<\/p>\n<p>No overlap means no delocalization, which means no added stability.<\/p>\n<p>Test your understanding of this concept by answering the quiz below.<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34751\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34751\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34751\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34751\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34751\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34751 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34751\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-68dk9\" data-id=\"68dk9\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2481-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2481-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>A common mistake is to think that carbocations directly attached to a pi-bond are resonance stabilized.<em> This is not so!<\/em> The pi-bond must be <strong>adjacent<\/strong> to the carbocation.<\/p>\n<p>Another potentially counter-intuitive situation is when a carbocation is adjacent to a C=O (or C=N) bond. One might naively think that the carbocation is stabilized by resonance.<\/p>\n<p>However, if you draw out the resonance form, you&#8217;ll find that in forming the C-C pi bond and breaking the C-O pi bond, you end up forming an electron-deficient species with only six valence electrons on oxygen. This &#8220;resonance form&#8221; is so high-energy as to make essentially no contribution to the resonance hybrid.<\/p>\n<p><span style=\"color: #993366;\"><em>(Highly electronegative atoms like O are excellent at stabilizing negative charge, but they are terrible at stabilizing empty orbitals)\u00a0<\/em><\/span><\/p>\n<h2><a id=\"five\"><\/a>5. The Importance of Carbocation Stability In Reactions<\/h2>\n<p>Let&#8217;s return to the role of carbocations as intermediates in several key organic reactions.<\/p>\n<p>The rate-determining step of the reaction below is\u00a0 <strong>protonation\u00a0<\/strong>of the pi bond with H+ to give a carbocation intermediate.<\/p>\n<p>Which of the two reactions do you think is faster?<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34750\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34750\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34750\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34750\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34750\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34750 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34750\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-0c1xk\" data-id=\"0c1xk\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2482-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2482-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>If you answered correctly, congratulations! You&#8217;ve shown you understand the reason behind Markovnikov&#8217;s rule! [<span style=\"color: #993366;\"><em>See article &#8211; <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2013\/02\/11\/markovnikovs-rule-2-why-it-works\/\">Markovnikov&#8217;s rule<\/a><\/em><\/span>]<\/p>\n<p>Let&#8217;s look at another one.<\/p>\n<p>The rate-determining step of the reaction below is loss of a leaving group to form a carbocation.<\/p>\n<p>Which of these two reactions proceeds faster?<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34749\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34749\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34749\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34749\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34749\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34749 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34749\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-6u2vw\" data-id=\"6u2vw\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2483-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2483-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<p>If you answered correctly, you&#8217;ve just shown an understanding one of the key factors that go into deciding whether a reaction will proceed via S<sub>N<\/sub>1, S<sub>N<\/sub>2, E1 or E2. (<span style=\"color: #993366;\"><em>See article: <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2012\/11\/21\/deciding-sn1sn2e1e2-1-the-substrate\/\">SN1\/SN2\/E1\/E2 &#8211; The Substrate<\/a><\/em><\/span>)<\/p>\n<h2><a id=\"six\"><\/a>6. Factors That Stabilize Carbocations &#8211; Adjacent Lone Pairs<\/h2>\n<p>There&#8217;s another factor that stabilizes carbocations that we haven&#8217;t touched on yet.<\/p>\n<p>If a carbocation is formed\u00a0<strong>adjacent\u00a0<\/strong>to an atom bearing a lone pair (i.e. a Lewis base) then that atom can donate its pair of electrons to the carbocation, forming a new pi-bond in the process.<\/p>\n<p>This is known as &#8220;pi-donation&#8221; (<span style=\"color: #993366;\"><em>See article &#8211; <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2011\/12\/15\/exploring-resonance-pi-donation\/\">Pi Donation<\/a><\/em><\/span>)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34315\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/15-stabilization-of-carbocations-due-to-donation-from-adjacent-lone-pairs.gif\" alt=\"stabilization of carbocations due to donation from adjacent lone pairs\" width=\"640\" height=\"699\" \/><\/a><\/p>\n<p>It might seem somewhat counter-intuitive that a highly electronegative atom like oxygen or nitrogen can stabilize a carbocation.<\/p>\n<p>But the net result of pi-donation is that all atoms have a full octet, which is highly <strong>stabilizing<\/strong>. (<span style=\"color: #993366;\"><em>Note that even though oxygen and nitrogen will bear a <strong>formal<\/strong> charge of +1, they still have a full octet of electrons! See article &#8211;<a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/09\/24\/how-to-calculate-formal-charge\/\"> How To Calculate Formal Charge<\/a><\/em><\/span>)<\/p>\n<p>The extent to which an atom&#8217;s lone pair can stabilize an adjacent carbocation is proportional to its basicity. The more basic the atom, the better the pi-donor.<\/p>\n<p>Across a row of the periodic table, the ability to donate a pair of electrons is inversely proportional to electronegativity. So, all other factors being equal, a lone pair from nitrogen will be more stabilizing than a lone pair from oxygen, which is more stabilizing than a lone pair from fluorine.<\/p>\n<p>Going <strong>down<\/strong> the periodic table, the ability of an atom to donate a pair of electrons is related to the ability of the atom&#8217;s valence orbital to overlap with the empty carbon 2p orbital.<\/p>\n<p>Generally, as the orbital increases in size, orbital overlap (and pi-donation ability) will <strong>decrease<\/strong>.<\/p>\n<p>Thus fluorine is a better pi-donor to carbon than chlorine, which is a better pi-donor than bromine, which is better than iodine <em>(<span style=\"color: #993366;\">in iodine the valence orbitals are the 5p and 5s orbitals, which do not match up well with the smaller 2p orbital of carbon<\/span>).\u00a0<\/em><\/p>\n<p>This is an article about carbocation stability and I want to keep it focused, but the contents of this particular section are extraordinarily important, and will come up again and again throughout organic chemistry. <span style=\"color: #993366;\"><em>One application you&#8217;ll see later &#8211; <a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/11\/09\/electrophilic-aromatic-substitution-the-mechanism\/\">Electrophilic Aromatic Substitution<\/a>.\u00a0<\/em><\/span><\/p>\n<h2><a id=\"seven\"><\/a>7. Which Factor is More Important &#8211; Substitution or Resonance?<\/h2>\n<p>So we have two factors that influence carbocation stability: substitution (primary, secondary, tertiary) and resonance.<\/p>\n<p>So which is more important?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34316\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/16-what-is-more-stable-benzylic-carbocation-or-tert-butyl-carbocation-they-are-of-relatively-equal-stability.gif\" alt=\"what is more stable benzylic carbocation or tert butyl carbocation - they are of relatively equal stability\" width=\"640\" height=\"586\" \/><\/a><\/p>\n<p>&#8220;they&#8217;re <em>both<\/em> important&#8221; is my non-answer to this question.<\/p>\n<p>The actual way to answer this question is to look at experimental results.<\/p>\n<p>One way to measure carbocation stability is to take a related series of alkyl halides and measure the <strong>rate<\/strong> of their hydrolysis in a polar protic solvent under conditions where SN1 would be likely.<\/p>\n<p><span style=\"color: #993366;\"><em>(The advantage of this method is that it more closely approximates actual reaction conditions. One disadvantage is that it is really only applicable to carbocations that can form under S<sub>N<\/sub>1 conditions. )<\/em><\/span><\/p>\n<p>Another method is to measure what is called <strong>hydride affinity <\/strong>&#8211; the energy released by the reaction of the carbocation with one equivalent of hydride ion (H<sup>&#8211;<\/sup>). <span style=\"color: #993366;\"><em>(Although this can be applied to a greater range of carbocations, it is really only applicable in the gas phase).\u00a0<\/em><\/span><\/p>\n<p>The hydride affinity of a primary benzylic carbocation is about 239 kcal\/mol versus 231 kcal\/mol for a\u00a0<em>t<\/em>-butyl carbocation, so these are quite comparable in energy.<\/p>\n<p>A table with some values is below. See <a href=\"#notefour\"><span style=\"color: #ff0000;\">Note 4<\/span>.<\/a><\/p>\n<h2><a id=\"eight\"><\/a>8. Some Factors That Destabilize Carbocations<\/h2>\n<p>Since electron-donating groups help to stabilize carbocations, it would make sense to expect that electron-withdrawing groups will destabilize carbocations.<\/p>\n<p>As we touched on above, electronegative atoms with lone pairs like O, N, and F that are <strong>directly<\/strong> attached to a carbocation will actually help to <strong>stabilize<\/strong> carbocations through pi-donation.<\/p>\n<p>I would not consider those &#8220;electron-withdrawing groups&#8221; for these purposes.<\/p>\n<p>By &#8220;electron-withdrawing groups&#8221; I would include<\/p>\n<ul>\n<li>Carbon atoms attached to electron-withdrawing groups (e.g. CF<sub>3<\/sub>, CCl<sub>3<\/sub>)<\/li>\n<li>Electronegative atoms without lone pairs (e.g. NR<sub>3<\/sub>(+) )<\/li>\n<li>Atoms containing a pi-bond to a <strong>more electronegative<\/strong> atom (e.g. C=O, CN, NO<sub>2<\/sub>, SO<sub>2<\/sub>R, etc.)<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34317\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/17-carbocations-are-greatly-destabilized-by-adjacent-electron-withdrawing-groups-such-as-nitro-cyano-carbonyl-sulfonyl-and-trifluoroalkyl.gif\" alt=\"carbocations are greatly destabilized by adjacent electron withdrawing groups such as nitro cyano carbonyl sulfonyl and trifluoroalkyl\" width=\"640\" height=\"536\" \/><\/a><\/p>\n<p>Another factor that destabilizes carbocations is the amount of s-character in the carbon atom.<\/p>\n<p>You may recall that alkyne C-H bonds are particularly\u00a0<strong>acidic<\/strong> because their sp-orbitals have 50% s-character, and since the s-orbital is closer to the positively charged nucleus, this helps to stabilize the negative charge of the conjugate base (a carb<strong>anion<\/strong>).<\/p>\n<p>Well, when it comes to the stabilization of carbo<strong>cations<\/strong>, this all gets thrown into <em>reverse<\/em>.<\/p>\n<p>The more s-character the carbocation has, the closer that empty orbital is held to the positively charged nucleus. This has the effect of making the carbon nucleus have a greater effective electronegativity.\u00a0 Removing a pair of electrons to form a carbocation becomes increasingly difficult as the s-character increases. (<span style=\"color: #993366;\"><em>This can be quantified by measuring hydride affinity or electron affinity<\/em><\/span>)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34318\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/18-carbocation-stability-is-affected-by-the-amount-of-s-character-the-greater-the-s-character-the-more-unstable-the-carbocation.gif\" alt=\"-carbocation stability is affected by the amount of s character - the greater the s character the more unstable the carbocation\" width=\"640\" height=\"732\" \/><\/a><\/p>\n<p>Bridgehead carbocations are also particularly unstable due to the fact that they cannot attain the ideal trigonal planar geometry, [<a href=\"#notesix\"><span style=\"color: #ff0000;\">Note 6<\/span><\/a>] as are carbocations on small rings (such as the cyclopropyl cation and cyclobutyl cation). [<a href=\"#noteseven\"><span style=\"color: #ff0000;\">Note 7<\/span><\/a>]<\/p>\n<h2><a id=\"nine\"><\/a>9. Some Special Cases<\/h2>\n<p>For the sake of completeness we should probably mention one last factor that is more of a second-semester topic but has a very large impact on the stability of certain carbocations.<\/p>\n<p>Some molecules have a particularly <strong>stable<\/strong> property known as\u00a0<strong>aromaticity<\/strong>. (<em>See article &#8211;<span style=\"color: #800080;\"> <a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2017\/02\/23\/rules-for-aromaticity\/\">Rules For Aromaticity<\/a><\/span><\/em>)<\/p>\n<p>A related phenomenon called\u00a0<strong>antiaromaticity<\/strong> is responsible for the unusual <strong>instability<\/strong> of certain compounds. (<span style=\"color: #800080;\"><em>See article &#8211; <a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2017\/03\/27\/antiaromaticity\/\">Antiaromatic Compounds and Antiaromaticity<\/a><\/em><\/span>)<\/p>\n<p>The heptatrienyl (&#8220;tropylium&#8221;) cation, C<sub>7<\/sub>H<sub>7<\/sub>+\u00a0 is <strong>aromatic<\/strong> and due to its unusual stability, forms a stable salt that can be put in a bottle and sold <a href=\"https:\/\/www.sigmaaldrich.com\/US\/en\/product\/aldrich\/164623\">commercially<\/a>. The cyclopropenium ion C<sub>3<\/sub>H<sub>3<\/sub>+ is also aromatic and unusually stable.<\/p>\n<p>On the other hand, the cyclopentadienyl cation, which by all appearances should be resonance-stabilized, is actually <strong>anti-aromatic<\/strong> and has only a fleeting existence under carefully controlled conditions at very low temperatures.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34319\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/03\/19-aromatic-carbocations-are-more-stable-whereas-antiaromatic-carbocations-are-less-stable.gif\" alt=\"aromatic carbocations are more stable whereas antiaromatic carbocations are less stable\" width=\"640\" height=\"243\" \/><\/a><\/p>\n<h2><strong><a id=\"ten\"><\/a>10. Summary<\/strong><\/h2>\n<p>Carbocations are positively charged, six-electron carbon atoms with an empty p-orbital. They are important intermediates in many reactions and are highly reactive towards Lewis bases.<\/p>\n<p>Three key factors stabilize carbocations:<\/p>\n<ul>\n<li>First, they are stabilized by adjacent alkyl groups, which can donate electron density to the electron-deficient carbon atom.<\/li>\n<li>Secondly, they can be stabilized through conjugation with pi bonds, which allows the positive charge to be delocalized through resonance.<\/li>\n<li>Third, carbocations are stabilized by atoms with a lone pair capable of forming a pi bond.<\/li>\n<\/ul>\n<p>Being electron-deficient, carbocations are destabilized by strongly electron-withdrawing substituents incapable of donating electron pairs (e.g. CF<sub>3<\/sub>, C=O). They are also destabilized if they are unable to attain the ideal trigonal planar geometry, which can happen in bridgehead carbocations. For similar reasons, carbocations that are part of highly strained rings such as cyclopropanes and cyclobutanes tend to be quite unstable.<\/p>\n<hr \/>\n<h2><strong><a id=\"notes\"><\/a>Notes<\/strong><\/h2>\n<p><strong><a id=\"noteone\"><\/a>Note 1<\/strong>. For most purposes, &#8220;carbocation&#8221; refers to a carbon with three bonds and an empty orbital, and in the vast majority of cases, this is the terminology that is used. There is a lot of inconsistency in the older literature as to whether these are &#8220;carbonium&#8221; or &#8220;carbenium&#8221; ions. The isolation of the CH<sub>5<\/sub>(+) species in extremely strong acid solution by the research group of George Olah at USC led IUPAC to define the term &#8220;carbenium ion&#8221; as a trivalent carbon and &#8220;carbonium ion&#8221; as a five-coordinate carbon. [<a href=\"http:\/\/refone\">Ref<\/a>].<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34941\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F1-iupac-definition-of-carbonium-and-carbenium-ions-according-to-which-is-trivalent-and-which-pentavalent.gif\" alt=\"iupac definition of carbonium and carbenium ions according to which is trivalent and which pentavalent\" width=\"640\" height=\"287\" \/><\/a><\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2. <\/strong>Two prominent exceptions to this are the vinyl carbocation and the acylium ion.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34942\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F2-examples-of-carbocations-that-are-not-trigonal-planar-include-vinyl-carbocation-and-acylium-ion.gif\" alt=\"examples of carbocations that are not trigonal planar include vinyl carbocation and acylium ion\" width=\"640\" height=\"335\" \/><\/a><\/p>\n<p>Note that the vinyl carbocation has a linear geometry and the central carbon is sp-hybridized.<\/p>\n<p>The acylium ion is an excellent example of a carbocation that is stabilized through donation of an adjacent lone pair. (For examples of the acylium ion, see <span style=\"color: #993366;\"><em>&#8211; <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2018\/05\/17\/friedel-crafts-alkylation-acylation\/\">The Friedel Crafts Alkylation and Acylation<\/a><\/em><\/span>).<\/p>\n<p><strong><a id=\"notethree\"><\/a>Note 3. <\/strong>The structures of several carbocations have been determined through X-ray crystallography.<\/p>\n<p>For example, the structure of the <em>t<\/em>-butyl cation shows a trigonal planar structure (bond angles 120\u00b0) with C-C bond length of 1.44 Angstroms\u00a0 [<a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja00069a023\">Ref<\/a>] which is about halfway between a typical C-C single bond (1.50 \u00c5) and a C-C double bond (1.40 \u00c5)<\/p>\n<p>The structure of the adamantyl cation is particularly interesting. In adamantane, all C-C bonds are approximately the same length (1.53 \u00c5). However, in the adamantyl <strong>carbocation<\/strong>, the carbon directly bonded to the carbocation becomes noticably shorter (1.43 \u00c5) while the C-C bond that is able to overlap with the p-orbital of the carbocation is noticeably longer (1.608 \u00c5).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34946\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/F3-comparison-of-bond-lengths-in-adamantane-and-adamantyl-carbocation.gif\" alt=\"comparison of bond lengths in adamantane and adamantyl carbocation\" width=\"640\" height=\"397\" \/><\/a><\/p>\n<p>This is exactly what we would have predicted from using the hyperconjugation model for carbocation stabilization, where one C-C bond gains partial double bond character and another bond is weakened.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34947\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/F4-hyperconjugation-explanation-for-C-C-pi-bond-and-C-C-single-bond-lengthening.gif\" alt=\"comparison of bond lengths in adamantane and adamantyl carbocation\" width=\"640\" height=\"260\" \/><\/a><\/p>\n<p>For a lot more detail on this,\u00a0 I highly recommend lecture 30 from Prof. David Evans&#8217; Advanced Organic Chemistry 206 at Harvard, <a href=\"https:\/\/archive.org\/details\/evans-d.-a.-myers-a.-g.-advanced-organic-chemistry-lecture-notes-problem-sets-an\/page\/n121\/mode\/2up\">link here<\/a>.<\/p>\n<p><strong><a id=\"notefour\"><\/a>Note 4.\u00a0<\/strong>One way to quantify the stability of carbocations is through measuring their hydride affinities, that is, the energy released upon reaction of the carbocation with a hydride ion. The hydride affinities of a large number of carbocations have been measured in the\u00a0<strong>gas phase\u00a0<\/strong>(where they have longer lifetimes).<\/p>\n<p>A selection is provided below:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34948\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/F5-table-of-carbocation-stability-based-on-hydride-ion-affinity.gif\" alt=\"comparison of bond lengths in adamantane and adamantyl carbocation\" width=\"640\" height=\"1044\" \/><\/a><\/p>\n<p>Solution-phase hydride affinities have also been measured for some of the more stable carbocations (gas phase hydride affinities in parentheses)<\/p>\n<ul>\n<li>Ph<sub>3<\/sub>C(+) : 96 kcal\/mol<\/li>\n<li>Ph<sub>2<\/sub>CH(+): 105 kcal\/mol<\/li>\n<li>PhCH<sub>2<\/sub>(+): 118 kcal\/mol (238 kcal\/mol)<\/li>\n<li>Tropylium ion:\u00a0 83 kcal\/mol (200 kcal\/mol)<\/li>\n<\/ul>\n<p><strong><a id=\"notefive\"><\/a>Note 5.\u00a0<\/strong>Carbocation formation is easier in solvents with a high dielectric constant such as water or carboxylic acids (e.g. acetic acid, formic acid).<\/p>\n<p><strong><a id=\"notesix\"><\/a>Note 6<\/strong> One class of tertiary carbocations that are particularly unstable are carbocations that are constrained in a bridgehead. Ring strain prevents these carbocations from adopting a trigonal planar geometry.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34631\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F7-bridgehead-carbocations-are-less-stable.gif\" alt=\"bridgehead carbocations are less stable\" width=\"640\" height=\"416\" \/><\/a><\/p>\n<p><strong><a id=\"noteseven\"><\/a>Note 7<\/strong>. Carbocations that are part of small rings such as cyclopropyl and cyclobutyl carbocations are also unusually unstable.<\/p>\n<p><strong><a id=\"notenine\"><\/a>Note 8.\u00a0<\/strong>An alternative method of measuring carbocation stability is through measuring rates of hydrolysis in a nucleophilic solvent. However, as this graphic from <a href=\"https:\/\/archive.org\/details\/evans-d.-a.-myers-a.-g.-advanced-organic-chemistry-lecture-notes-problem-sets-an\/page\/n121\/mode\/2up\">Evans<\/a> shows, these two measures do not always correlate well&#8230;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34952\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F9-rates-of-hydrolysis-versus-hydride-affinity-1.png\" alt=\"rates of hydrolysis versus hydride affinity (1)\" width=\"640\" height=\"436\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F9-rates-of-hydrolysis-versus-hydride-affinity-1.png 908w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F9-rates-of-hydrolysis-versus-hydride-affinity-1-300x204.png 300w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F9-rates-of-hydrolysis-versus-hydride-affinity-1-768x523.png 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/03\/F9-rates-of-hydrolysis-versus-hydride-affinity-1-760x517.png 760w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/a><\/p>\n<hr \/>\n<h2><strong><a id=\"quiz\"><\/a>Quiz Yourself!<\/strong><\/h2>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3680-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3646-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2503-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <br \/>\n<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2504-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <br \/>\n<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2505-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <br \/>\n<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2506-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <br \/>\n<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2514-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <\/p>\n<hr \/>\n<h2><strong><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/strong><\/h2>\n<p>References<\/p>\n<ol>\n<li><strong><a id=\"refone\"><\/a>100 Years of Carbocations and Their Significance in Chemistry<sup>1<\/sup><\/strong>\n<div>George A. Olah<\/div>\n<div><cite>The Journal of Organic Chemistry<\/cite>\u00a0<strong>2001<\/strong>\u00a0<em>66<\/em>\u00a0(18), 5943-5957<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo010438x\">10.1021\/jo010438x<\/a><br \/>\nA historical perspective from Prof. George Olah, who won the Nobel Prize in Chemistry in 1994 for &#8220;contributions to carbocation chemistry&#8221;.<\/div>\n<\/li>\n<li><strong>Stabilities of carbocations in solution. 14. An extended thermochemical scale of carbocation stabilities in a common superacid<\/strong><br \/>\nEdward M. Arnett and Thomas C. Hofelich<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1983,<\/strong> <em>105<\/em> (9), 2889-2895<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/ja00347a060\">10.1021\/ja00347a060<\/a><br \/>\nThis paper provides a table of the stability of 39 carbocations, measured calorimetrically by heat of formation (ionization in superacid from the corresponding carbinol).<\/li>\n<li><strong>X-ray Crystal Structures of Carbocations Stabilized by Bridging or Hyperconjugation<\/strong><br \/>\nThomas Laube<br \/>\n<cite>Accounts of Chemical Research<\/cite>\u00a0<strong>1995<\/strong>\u00a0<em>28<\/em>\u00a0(10), 399-405<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ar00058a001\">10.1021\/ar00058a001<\/a><br \/>\nVery interesting review from Prof. Laube comparing and contrasting the structures of various carbocations, including very clear evidence for hyperconjugation in the\u00a0 adamantyl carbocation. C-C bond shortened to 1.431 from 1.528 . C-C lengthenend to 1.608 from 1.530. 100 deg angle vs 110 deg angle<\/li>\n<li><strong>Carbonium Ions. I. An Acidity Function (C0) Derived from Arylcarbonium Ion Equilibria<br \/>\n<\/strong> C. Deno, J. J. Jaruzelski, and Alan Schriesheim<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1955,<\/strong> <em>77<\/em> (11), 3044-3051<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja01616a036\">10.1021\/ja01616a036<\/a><br \/>\nCarbocation stability can also be expressed in p<em>K<\/em><sub>R+<\/sub>, which is defined in the paper. The carbocations studied in this paper are all relatively stable arylcarbonium ions.<\/li>\n<li><strong>Hydride affinities of carbenium ions in acetonitrile and dimethyl sulfoxide solution<br \/>\n<\/strong>Jinpei Cheng, Kishan L. Handoo, and Vernon D. Parker<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1993,<\/strong> <em>115<\/em> (7), 2655-2660<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja00060a014\">10.1021\/ja00060a014<\/a><br \/>\nCarbocation stabilities can also be expressed in terms of hydride affinity (R<sup>+<\/sup> + H<sup>&#8211;<\/sup> -&gt; RH). The carbocations studied in this paper are also fairly stable arylcarbonium ions, as these are measured electrochemically in either DMSO or acetonitrile.<\/li>\n<li><strong>Photoelectron spectroscopy of methyl, ethyl, isopropyl, and tert-butyl radicals. Implications for the thermochemistry and structures of the radicals and their corresponding carbonium ions<br \/>\n<\/strong> A. Houle and J. L. Beauchamp<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1979,<\/strong> <em>101<\/em> (15), 4067-4074<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja00509a010\">10.1021\/ja00509a010<\/a><br \/>\nTable III in this paper has heats of formation for the basic alkyl cations (methyl, ethyl, isopropyl, and t-butyl), but in the gas phase. The numbers agree with intuition from solution-phase experiments; stability increases from methyl -&gt; ethyl -&gt; isopropyl -&gt; t-butyl.<\/li>\n<li><strong>Quantitative preparation and enthalpy of rearrangement of the sec-butyl cation<br \/>\n<\/strong> W. Bittner, E. M. Arnett, and M. Saunders<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1976,<\/strong> <em>98<\/em> (12), 3734-3735<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja00428a072\">10.1021\/ja00428a072<\/a><br \/>\nThis paper describes a novel calorimetric method for measuring the heat of isomerization of the <em>sec<\/em>-butyl cation to the <em>tert<\/em>-butyl cation in superacid solution. Using this, the value obtained is 14.5 \u00b1 0.5 kcal\/mol.<\/li>\n<li><strong>Stability of Alkyl Carbocations<br \/>\n<\/strong>Thomas Hansen, Pascal Vermeeren, F. Matthias Bickelhaupt, and Trevor A. Hamlin<br \/>\n<em>Chem. Commun.\u00a0<\/em><strong>2022<\/strong>,\u00a0<em>58<\/em>, 12050-12053<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/2022\/cc\/d2cc04034d\">10.1039\/D2CC04034D<\/a><br \/>\nA theoretical study on carbocation stability trends. From the paper: &#8220;<em>we quantitatively established a generally overlooked driving force behind the stability of carbocations, namely, that the parent substrates are substantially destabilized by the introduction of substituents, often playing a dominant role in solution. This stems from the repulsion between the substituents and the C\u2013X bond.<\/em>&#8220;<\/li>\n<li><strong>The Story of the Wagner-Meerwein Rearrangement<\/strong>\n<div>Ludmila Birladeanu<\/div>\n<div><cite>Journal of Chemical Education<\/cite>\u00a0<strong>2000<\/strong>\u00a0<em>77<\/em>\u00a0(7), 858<\/div>\n<p><strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/ed077p858\">10.1021\/ed077p858<\/a><br \/>\nAn article of historical interest on the development of understanding of the Wagner-Meerwein rearrangement of carbocations.<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Carbocations: Properties, Formation, and Stability Carbocations are electron-deficient species with an empty p-orbital Lacking a full octet and bearing a positive charge, they tend to <\/p>\n","protected":false},"author":1,"featured_media":34349,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1410],"tags":[333,397,605,537,609,379,608,607,514,606],"post_folder":[],"class_list":["post-1405","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-organic-reaction-primer","tag-carbanions","tag-carbocations","tag-electron-donation","tag-hyperconjugation","tag-intermediates","tag-opposite-charges-attract","tag-primary","tag-secondary","tag-stability","tag-tertiary"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>3 Factors That Stabilize Carbocations<\/title>\n<meta name=\"description\" content=\"Three main factors increase the stability of carbocations: Increasing the number of\u00a0adjacent carbon atoms (methyl &lt; primary &lt; 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