{"id":8776,"date":"2015-02-27T13:14:25","date_gmt":"2015-02-27T18:14:25","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=8776"},"modified":"2025-12-12T04:13:46","modified_gmt":"2025-12-12T10:13:46","slug":"making-alkyl-halides-from-alcohols","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2015\/02\/27\/making-alkyl-halides-from-alcohols\/","title":{"rendered":"Making Alkyl Halides From Alcohols"},"content":{"rendered":"<p><strong>Making Alkyl Halides From Alcohols<\/strong><\/p>\n<p>In today&#8217;s post we show that treating alcohols with HCl, HBr, or HI (which all fall under the catch-all term &#8220;HX&#8221; where X is a halide) results in the formation of alkyl halides.<\/p>\n<ul>\n<li>Primary alcohols tend to proceed through an S<sub>N<\/sub>2 mechanism<\/li>\n<li>Tertiary alcohols tend to proceed through an S<sub>N<\/sub>1 mechanism<\/li>\n<li>Watch out for rearrangements in reactions where a secondary carbocation may be formed<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-15186\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/0-summary-alcohols-converted-to-alkyl-halides-with-strong-acid-hx-conjugate-acid-of-oh-is-oh2-which-is-good-leaving-group-sn1-or-sn2-mechanism.gif\" alt=\"summary alcohols converted to alkyl halides with strong acid hx conjugate acid of oh is oh2 which is good leaving group sn1 or sn2 mechanism\" width=\"630\" height=\"271\" \/><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li><a href=\"#one\">Adding Acid To Alcohol Produces A\u00a0 Good Leaving Group (H2O)<\/a><\/li>\n<li><a href=\"#two\">Alkyl Halides From Methyl and Primary Alcohols via the SN2 Reaction<\/a><\/li>\n<li><a href=\"#three\">Alkyl Halides From Tertiary Alcohols Proceeds Through The S<sub>N<\/sub>1 Pathway<\/a><\/li>\n<li><a href=\"#four\">A Good Rule Of Thumb For Secondary Alcohols With HX: Assume S<sub>N<\/sub>1<\/a><\/li>\n<li><a href=\"#five\">Rearrangements In The Formation of\u00a0 Alkyl Halides From Alcohols<\/a><\/li>\n<li><a href=\"#six\">Rearrangement Example #1: Hydride Shift<\/a><\/li>\n<li><a href=\"#seven\">Rearrangement Example #2: Alkyl Shift<\/a><\/li>\n<li><a href=\"#eight\">Rearrangement Example #3: A Special Case of Alkyl\u00a0 Shift &#8211; Ring Expansion\u00a0 and Contraction<\/a><\/li>\n<li><a href=\"#nine\">What Doesn&#8217;t Work?<\/a><\/li>\n<li><a href=\"#ten\">Summary: Alkyl Halides From Alcohols<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quizzes\">Quiz Yourself!\u00a0<\/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. Adding Acid To Alcohol Results In A Good Leaving Group<\/h2>\n<p>We\u2019ve said many times in this series of posts that <strong>alcohols are poor substrates for\u00a0S<sub>N<\/sub>1 and S<sub>N<\/sub>2 reactions.<\/strong> \u00a0That&#8217;s because the hydroxyl ion (HO-) is a poor leaving group, and therefore not likely to either 1) depart of its own accord, leaving behind a carbocation (S<sub>N<\/sub>1 pathway) or 2) to be displaced by an incoming nucleophile (which would be an S<sub>N<\/sub>2 reaction).<\/p>\n<p>However we&#8217;ve also seen that treating an alcohol with acid leads to an interesting &#8220;personality adjustment&#8221;: the alcohol (R-OH) is converted to its conjugate acid, (R-OH<sub>2<\/sub>+) which now possesses a decent leaving group (the weak base we know as water, H<sub>2<\/sub>O). (<em>See post: <a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/10\/06\/how-to-make-alcohols-more-reactive\/\">How to Make Alcohols More Reactive<\/a><\/em>)<\/p>\n<p>We saw, in a previous post, \u00a0how this allows\u00a0for <a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/11\/14\/ether-synthesis-via-alcohols-and-acid\/\">formation of (symmetrical) ethers from alcohols<\/a>, either via S<sub>N<\/sub>2 pathway (with primary alcohols) or an S<sub>N<\/sub>1 pathway (tertiary alcohols).<\/p>\n<p>We might ask: can this be extended to form other functional groups besides ethers?<\/p>\n<p>Absolutely.\u00a0 <strong>Treating alcohols with HCl, HBr, or HI<\/strong> (which all fall under the catch-all term &#8220;HX&#8221; where X is a halide) results in the formation of alkyl halides.<\/p>\n<p>This occurs in a two step process:<\/p>\n<ul>\n<li>first, the alcohol is protonated to give its conjugate acid.<\/li>\n<li>Secondly, a substitution occurs.<\/li>\n<\/ul>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15187\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-treating-alcohols-with-strong-acid-makes-great-leaving-group-if-counter-ion-is-nucleophilic-like-halide-then-substitution-reaction-can-occur.gif\" alt=\"treating alcohols with strong acid makes great leaving group if counter ion is nucleophilic like halide then substitution reaction can occur\" width=\"600\" height=\"314\" \/><\/p>\n<p>Notice how that second step (substitution) was left vague in the diagram above. \u00a0That&#8217;s because, as we&#8217;ve seen, \u00a0the type of substitution pathway depends on the substrate.<\/p>\n<h2><strong><a id=\"two\"><\/a>2. Alkyl Halides From Methyl And Primary Alcohols Via S<sub>N<\/sub>2 Reaction<\/strong><\/h2>\n<p>Knowing how sensitive the S<sub>N<\/sub>2 reaction is to steric hindrance, we should expect that for methyl alcohol and for primary alcohols, the S<sub>N<\/sub>2 pathway dominates. And it does! (<em>See post: <a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/07\/04\/the-sn2-mechanism\/\">The S<sub>N<\/sub>2 Mechanism<\/a><\/em>)<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15188\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/2-formation-of-alkyl-halides-from-alcohols-with-hb4-primary-alcohols-go-through-sn2-mechanism.gif\" alt=\"formation of alkyl halides from alcohols with hb4 primary alcohols go through sn2 mechanism\" width=\"600\" height=\"353\" \/><\/p>\n<p>Note how in each case we begin by protonating the alcohol, creating a good leaving group which is then displaced by the conjugate base of the acid. (<em>See post: <a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/04\/12\/what-makes-a-good-leaving-group\/\">What Makes a Good Leaving Group<\/a>?<\/em>)<\/p>\n<p>Alkyl chlorides, bromides, and iodides can each be made this way.<\/p>\n<h2><strong><a id=\"three\"><\/a>3. Alkyl Halides From Tertiary Alcohols Proceeds Through The S<sub>N<\/sub>1 Pathway\u00a0<\/strong><\/h2>\n<p>Likewise, understanding the trends of <a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/03\/11\/3-factors-that-stabilize-carbocations\/\">carbocation stability<\/a>, we should expect that conversion of tertiary alcohols to alkyl halides proceeds through an S<sub>N<\/sub>1 pathway. And it does. (<em>See post: <a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/07\/13\/the-sn1-mechanism\/\">The S<sub>N<\/sub>1 Mechanism<\/a><\/em>)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15189\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/3-forming-tertiary-halides-from-tertiary-alcohols-with-hx-addition-occurs-through-sn1-pathway-more-stable-carbocation.gif\" alt=\"forming tertiary halides from tertiary alcohols with hx addition occurs through sn1 pathway more stable carbocation\" width=\"630\" height=\"446\" \/><\/p>\n<p>Note in the last example that beginning with a chiral starting material will lead to a mixture of inversion and retention (often called, &#8220;<a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/05\/23\/whats-a-racemic-mixture\/\">racemization<\/a>&#8220;) because it goes through the (flat) intermediate carbocation.<\/p>\n<h2><strong><a id=\"four\"><\/a>4. A Good Rule of Thumb For Secondary Alcohols With HX: Assume S<sub>N<\/sub>1<\/strong><\/h2>\n<p>Methyl, primary, and tertiary alcohols all represent\u00a0pretty straightforward cases.<\/p>\n<p>&#8220;So what about secondary alcohols?&#8221; you might ask. Ah yes. This is where things get interesting &#8211; and is, therefore, <strong>the stuff of which exam questions are made<\/strong>.<\/p>\n<p><em>In the lab<\/em>, treatment of secondary alcohols with HX leads to a mixture of products from S<sub>N<\/sub>1 and S<sub>N<\/sub>2 pathways. For practical purposes it is generally not a useful process, especially if you care about preserving stereochemistry.<\/p>\n<p>However,<strong> your introductory textbook and course notes are not &#8220;the lab&#8221;.<\/strong> The purpose of a course is to introduce you to important concepts in organic chemistry. And from an instructor&#8217;s standpoint, it so happens that the conversion of secondary alcohols to secondary alkyl halides by HX is an excellent opportunity to bring up the subject of <strong>carbocation rearrangements<\/strong>. This falls under the purview of the S<sub>N<\/sub>1 pathway.<\/p>\n<p>So a good rule of thumb is to assume &#8211; for the purposes of your course &#8211; that secondary alcohols treated with HX will proceed through an S<sub>N<\/sub>1 mechanism.<\/p>\n<h2><strong><a id=\"five\"><\/a>5. Rearrangements In The Formation Of Alkyl Halides From Alcohols<\/strong><\/h2>\n<p>We&#8217;ve covered rearrangements \u00a0(hydride and alkyl shifts) \u00a0before in the context of S<sub>N<\/sub>1 reactions. But it&#8217;s worth touching on again.<\/p>\n<p>The basic premise is this. Carbocations are unstable, electron-poor species. Their stability generally increases with the number of\u00a0attached carbons, which serve to donate electron density. Hence, the stability of carbocations increases\u00a0in the direction methyl &lt; primary &lt; secondary &lt; tertiary. \u00a0We also saw that carbocations are stabilized by resonance.<\/p>\n<p>As we saw in a <a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/08\/15\/rearrangement-reactions-1-hydride-shifts\/?_ga=1.149122099.444771887.1424714309\">previous series of posts<\/a> &#8211; consult this if you need more hand holding! &#8211; \u00a0carbocations can undergo 1,2 shifts of C-H and C-C bonds, resulting in new carbocations.<\/p>\n<p>Such rearrangements are most likely to occur if they can result in a more stable carbocation. For example, the rearrangement of a secondary to a tertiary carbocation, is a <strong>favoured<\/strong> (energetically &#8220;downhill&#8221;) process, whereas a rearrangement from a tertiary to a secondary carbocation (energetically &#8220;uphill&#8221;) is <strong>unlikely<\/strong>.<\/p>\n<p><strong>Anytime a reaction proceeds through a carbocation intermediate, we need to be on the lookout to see if it is\u00a0<span style=\"text-decoration: underline;\">adjacent<\/span> to a carbon\u00a0which can generate a more stable carbocation through a shift of a C-H or C-C bond.<\/strong><\/p>\n<p>There are three cases in particular to watch out for.<\/p>\n<h2><strong><a id=\"six\"><\/a>6. Rearrangement Example #1: A\u00a0 Hydride shift<\/strong><\/h2>\n<p>Look for a secondary alcohol adjacent to a tertiary carbon. Note this common example, where protonation leads to loss of water, followed by a hydride shift and then trapping of the carbocation by the halide ion.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15190\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/4-with-secondary-alcohols-and-srong-acid-hx-hydride-shifts-can-occur-leading-to-rearrangement-products.gif\" alt=\"with secondary alcohols and srong acid hx hydride shifts can occur leading to rearrangement products\" width=\"630\" height=\"320\" \/><\/p>\n<p>Another example of a favourable rearrangement is when a secondary carbocation is adjacent to an &#8220;allylic&#8221; or &#8220;benzylic&#8221; hydrogen. Rearrangement results in\u00a0a secondary carbon which is\u00a0stabilized by resonance.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15191\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/5-favorable-hydride-shift-with-secondary-alcohol-if-hydride-shift-gives-more-stable-resonance-stabilized-benzylic-carbocation.gif\" alt=\"favorable hydride shift with secondary alcohol if hydride shift gives more stable resonance stabilized benzylic carbocation\" width=\"600\" height=\"235\" \/><\/p>\n<h2><strong><a id=\"seven\"><\/a>7. Rearrangement Example #2: Alkyl Shift<\/strong><\/h2>\n<p>Look for a secondary alcohol adjacent to a quaternary carbon (i.e. a carbon attached to 4 other carbons). Note how this is essentially the exact same process as the hydride shift above, except that CH<sub>3<\/sub> is migrating, not H.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15192\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/6-secondary-alcohols-and-hx-alkyl-shifts-mechanism-arrow-pushing-protonation-then-loss-of-leaving-group-then-alkyl-shift-then-attack-of-nucleophile.gif\" alt=\"secondary alcohols and hx alkyl shifts mechanism arrow pushing protonation then loss of leaving group then alkyl shift then attack of nucleophile\" width=\"630\" height=\"314\" \/><\/p>\n<h2><strong><a id=\"eight\"><\/a>8. Rearrangement Example #3:\u00a0 A Special Case of Alkyl Shifts &#8211; Ring Expansions And Contractions<\/strong><\/h2>\n<p>Look for a secondary alcohol that is adjacent to a strained ring (cyclobutane in the classic case). \u00a0Once the secondary carbocation is generated, a bond in the strained ring migrates, leading to expansion of the ring by one. This is particularly favourable in the case of cyclobutane to cyclopentane since cyclobutane is highly strained (about 26 kcal\/mol) whereas cyclopentane has minimal ring strain.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15193\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/7-secondary-alcohols-and-hx-ring-expansion-arrow-pushing-step-1-protonation-step-2-loss-of-h2o-step-3-alkyl-shift-step-4-attack-on-carbocation-rearrangement.gif\" alt=\"secondary alcohols and hx ring expansion arrow pushing step 1 protonation step 2 loss of h2o step 3 alkyl shift step 4 attack on carbocation rearrangement\" width=\"630\" height=\"348\" \/><\/p>\n<p>This type of alkyl shift commonly gives students a hard time, which of course makes it a favourite exam problem of instructors. Although the curved arrow drawn is no different than that for the previous two cases, I think the main difficulty is in mapping the product from the starting material. In this respect I recommend two things:<\/p>\n<ul>\n<li><strong>Number the carbons<\/strong> (not necessarily IUPAC &#8211; just number to keep track of them). For instance here the arrow in Step 3 (the alkyl shift) shows us breaking C2-C3 and forming C1-C3. Applying the rules of curved arrows implies that C1 will then be neutral and C2 will become a carbocation. That&#8217;s all that&#8217;s happening. \u00a0<strong>No other bonds are formed or broken in this step<\/strong>. It takes practice to get this right.<\/li>\n<li><strong><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/05\/31\/draw-the-ugly-version-first\/\">Draw the ugly version first<\/a>.<\/strong> THEN redraw to make it look good.<\/li>\n<\/ul>\n<p>Ring contractions are also possible, although are not as favourable as the opening of strained rings. The same principles apply.<\/p>\n<h2><strong><a id=\"nine\"><\/a>9. Alkyl Halides From Alcohols: What Doesn&#8217;t Work?\u00a0<\/strong><\/h2>\n<p>It&#8217;s always helpful to know what doesn&#8217;t work in the formation of alkyl halides from alcohols.<\/p>\n<p>First of all, since we&#8217;re dealing with substitution\u00a0reactions here, some familiar rules apply. \u00a0<strong>Only alkyl alcohols (alcohols on sp<sup>3<\/sup> hybridized carbons) will undergo\u00a0S<sub>N<\/sub>1 and SN2 reactions. <\/strong>Both the S<sub>N<\/sub>1 and S<sub>N<\/sub>2 pathways involve buildup of positive charge on carbon, and sp<sup>2<\/sup> and sp hybridized carbocations are extremely unstable. This attempted S<sub>N<\/sub>1 of phenol, for example, will fail miserably:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15194\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/8-replacement-of-phenol-oh-with-br-or-cl-does-not-work-because-phenyl-carbocation-is-very-unstable.gif\" alt=\"replacement of phenol oh with br or cl does not work because phenyl carbocation is very unstable\" width=\"600\" height=\"243\" \/><\/p>\n<p>You might also wonder if we can use reagents like HCN, HOAc, or HN<sub>3<\/sub> to convert alcohols to nitriles, esters, and azides respectively. Generally, no. The problem is that <strong>each of these are fairly weak acids (pK<sub>a<\/sub> 4 and above)\u00a0<\/strong>\u00a0so these will only give a low concentration of the protonated alcohol. Since the reaction rate is proportional to concentration, formation of these products will be slow. [<span style=\"color: #993366;\"><em>With azides, there are also potential complications with a different type of rearrangement, but as a\u00a0<span style=\"text-decoration: underline;\">curtiusy<\/span>\u00a0we&#8217;re not going to deal with that <a style=\"color: #993366;\" href=\"https:\/\/en.wikipedia.org\/wiki\/Schmidt_reaction\">schmidt<\/a>\u00a0right now : &#8211; )<\/em> <\/span>]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15195\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/9-good-rule-of-thumb-for-replacement-of-alcohols-with-hx-is-it-works-best-when-acid-has-pka-lower-than-zero-does-not-work-for-hcn-hoac-hn3.gif\" alt=\"good rule of thumb for replacement of alcohols with hx is it works best when acid has pka lower than zero does not work for hcn hoac hn3\" width=\"600\" height=\"352\" \/><\/p>\n<p>For our purposes, conversion of alcohols to other substitution products\u00a0using strong acid is limited to HCl, HBr, HI, and the special case of H+\/ROH which gives symmetrical ethers.\u00a0A good rule of thumb is that the conjugate acid of the nucleophile should have a pK<sub>a<\/sub> of 0 or less in order for the reaction to occur.<\/p>\n<h2><a id=\"ten\"><\/a>10. Summary: Making Alkyl Halides From Alcohols<\/h2>\n<p>So alcohols can be converted to alkyl halides. You might ask, &#8220;why should we care?&#8221;. The answer is that, as we said, converting an alcohol (which has a poor leaving group) into an alkyl halide (which has a great leaving group) now allows us to do all kinds of functional group interconversions that were not previously possible. The <a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/07\/11\/why-the-sn2-reaction-is-powerful\/\">S<sub>N<\/sub>2 is a very useful and powerful reaction, for example<\/a>. Once a primary alcohol has been converted to a primary alkyl halide, we can then treat it with all varieties of nucleophiles to make a multitude of functional groups.<\/p>\n<p>However nice it is to be able to do this, though, \u00a0it&#8217;s far from ideal. \u00a0We have to use strong acid, which can often cause complications if we have acid-sensitive functional groups on our molecule. Furthermore, all those pesky rearrangements on secondary carbons are a hassle. They can screw with our stereochemistry and lead to undesired products. \u00a0You might ask, &#8220;isn&#8217;t there some way to get around that?&#8221;.<\/p>\n<p>Yes! We\u2019ll talk about a very nice way around this dilemma in the next post!<\/p>\n<p><strong>Next Post &#8211; <a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/03\/10\/tosylates-and-mesylates\/\">Tosylates And Mesylates<\/a><\/strong><\/p>\n<hr \/>\n<h2><a id=\"notes\"><\/a>Notes<\/h2>\n<div class=\"related-articles\"><p><strong>Related Articles<\/strong><\/p><ul><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/03\/10\/tosylates-and-mesylates\/\" class=\"\"><span>Tosylates And Mesylates<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/07\/13\/the-sn1-mechanism\/\" class=\"\"><span>The SN1 Mechanism<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/07\/04\/the-sn2-mechanism\/\" class=\"\"><span>The SN2 Mechanism<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/08\/15\/rearrangement-reactions-1-hydride-shifts\/\" class=\"\"><span>Rearrangement Reactions (1) \u2013 Hydride Shifts<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/11\/14\/ether-synthesis-via-alcohols-and-acid\/\" class=\"\"><span>Alcohols To Ethers via Acid Catalysis<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/04\/12\/what-makes-a-good-leaving-group\/\" class=\"\"><span>What makes a good leaving group?<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/03\/11\/3-factors-that-stabilize-carbocations\/\" class=\"\"><span>3 Factors That Stabilize Carbocations<\/span><\/a><\/li><\/ul><\/div>\n<hr \/>\n<h2><a id=\"quizzes\"><\/a>Quiz Yourself!<\/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\/1337-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\/1338-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\/3609-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\/3323-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\/3324-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\/1362-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\/2425-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><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/h2>\n<p>Alkyl chlorides from alcohols:<\/p>\n<ol>\n<li><strong>-BUTYL CHLORIDE<br \/>\n<\/strong>James F. Norris and Alanson W. Olmsted<strong><br \/>\n<\/strong><em>Organic<\/em> <em>Syntheses<\/em>, Coll. Vol. 1, p.144 (1941); Vol. 8, p.50 (1928). <strong><br \/>\nDOI: <\/strong><a href=\"http:\/\/www.orgsyn.org\/demo.aspx?prep=CV1P0144\">10.15227\/orgsyn.008.0050<\/a><br \/>\nAn example of an S<sub>N<\/sub>1 conversion of tert-butanol to t-butyl chloride with HCl. This is from <em>Organic Syntheses<\/em>, a source of reliable and independently tested organic chemistry experimental procedures.Alkyl iodides from alcohols:<\/li>\n<li><strong>Reaction between unsaturated alcohols and potassium iodide in the presence of polyphosphoric acid<br \/>\n<\/strong>Richard Jones and J. B. Pattison<br \/>\n<em>J. Chem. Soc. <\/em><strong>1969, <\/strong>1046<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/1969\/j3\/j39690001046\/unauth#!divAbstract\">10.1039\/J39690001046<\/a><br \/>\nThis paper uses KI + phosphoric acid to generate HI <em>in situ<\/em>, which converts alcohols to iodides.<\/li>\n<li><strong>1,6-DIIODOHEXANE<br \/>\n<\/strong>Herman Stone and Harold Shechter<strong><br \/>\n<\/strong><em> Synth. <\/em><strong>1951<\/strong>, <em>31<\/em>, 31<br \/>\n<strong>DOI: <\/strong><a href=\"http:\/\/www.orgsyn.org\/demo.aspx?prep=CV4P0323\">10.15227\/orgsyn.031.0031<\/a><br \/>\nA procedure from <em>Organic <\/em>Syntheses, a source of reliable and independently tested synthetic organic experimental procedures, for converting alcohols to iodides with KI + PPA (polyphosphoric acid).<\/li>\n<li><strong>Synthetic methods and reactions. 63. Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride): a convenient reagent for organic fluorination reactions<br \/>\n<\/strong>George A. Olah, John T. Welch, Yashwant D. Vankar, Mosatomo Nojima, Istvan Kerekes, and Judith A. Olah<br \/>\n<em>The Journal of Organic Chemistry<\/em><strong> 1979, <\/strong><em>44<\/em> (22), 3872-3881<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01336a027\">1021\/jo01336a027<\/a><br \/>\nPyridinium poly(hydrogen fluoride), also known as PPHF or \u201cOlah\u2019s reagent\u201d can be used as a Bronsted acid for converting alcohols to iodides, along with KI or NaI.<\/li>\n<li><strong>A Simple, Efficient, and General Method for the Conversion of Alcohols into Alkyl Iodides by a CeCl<sub>3<\/sub>7H<sub>2<\/sub>O\/NaI System in Acetonitrile<\/strong><br \/>\nMilena Di Deo, Enrico Marcantoni, Elisabetta Torregiani, Giuseppe Bartoli, Maria Cristina Bellucci, Marcella Bosco, and Letizia Sambri<br \/>\n<em>The Journal of Organic Chemistry<\/em><strong> 2000, <\/strong><em>65<\/em> (9), 2830-2833<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo991894c\">10.1021\/jo991894c<\/a><br \/>\nLewis acids can be used for this reaction instead of a Bronsted acid, allowing for milder reaction conditions.<\/li>\n<li><strong>Direct conversion of alcohols into the corresponding iodides<br \/>\n<\/strong>Reni Joseph, Pradeep S. Pallan, A. Sudalai, T. Ravindranathan<br \/>\n<em>Tetrahedron Lett. <\/em><strong>1995<\/strong> <em>36<\/em> (4), 609-612<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/0040403994023153\">10.1016\/0040-4039(94)02315-3<\/a><br \/>\nElemental iodine (I<sub>2<\/sub>) can also be used for directly converting alcohols to iodides.Alcohols can be converted to alkyl bromides with PBr<sub>3<\/sub>:<\/li>\n<li><strong>Convenient synthesis of labile optically active secondary alkyl bromides from chiral alcohols<br \/>\n<\/strong>Robert O. Hutchins, Divakar. Masilamani, and Cynthia A. Maryanoff<br \/>\n<em>The Journal of Organic Chemistry<\/em><strong> 1976, <\/strong><em>41<\/em> (6), 1071-1073<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/jo00868a034\">1021\/jo00868a034<\/a><\/li>\n<li><strong>Synthesis of Optically Active Alkyl Halides<\/strong><br \/>\nHarry R. Hudson<br \/>\n<em>Synthesis<\/em> <strong>1969<\/strong>, 112-119<br \/>\n<strong>DOI:<\/strong> <a href=\"https:\/\/www.thieme-connect.com\/products\/ejournals\/abstract\/10.1055\/s-1969-34195\">1055\/s-1969-34195<\/a><br \/>\nThe main utility of PBr<sub>3<\/sub> is that it allows the conversion of chiral alcohols to bromides with <em>inversion of configuration without rearrangement<\/em>, as the above two papers demonstrate. They also illustrate the mechanism of the reaction, going through the intermediate alkyl phosphites.<\/li>\n<li><strong>TETRAHYDROFURFURYL BROMIDE<br \/>\n<\/strong>L. H. Smith<br \/>\n<em>Org. Synth.<\/em><strong> 1943, <\/strong><em>23<\/em>, 88<br \/>\n<strong>DOI<\/strong>: <a href=\"http:\/\/www.orgsyn.org\/demo.aspx?prep=CV3P0793\">10.15227\/orgsyn.023.0088<\/a><br \/>\nThis procedure from <em>Organic Synthesis<\/em>, a source of reliable and independently tested experimental organic chemistry procedures, shows how PBr<sub>3<\/sub> is compatible with ethers.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Making Alkyl Halides From Alcohols In today&#8217;s post we show that treating alcohols with HCl, HBr, or HI (which all fall under the catch-all term <\/p>\n","protected":false},"author":1,"featured_media":15186,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1420],"tags":[167,299,864,397,891,861,293,865,502,271],"post_folder":[],"class_list":["post-8776","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-alcohols-epoxides-ethers","tag-alcohols","tag-alkyl-halides","tag-alkyl-shift","tag-carbocations","tag-hcl","tag-hydride-shift","tag-rearrangements","tag-ring-expansion","tag-sn1","tag-sn2"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Making Alkyl Halides From Alcohols &#8211; 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