{"id":10578,"date":"2017-03-03T14:42:28","date_gmt":"2017-03-03T19:42:28","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=10578"},"modified":"2026-02-03T17:51:05","modified_gmt":"2026-02-03T23:51:05","slug":"aromatic-antiaromatic-nonaromatic-some-practice-problems","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2017\/03\/03\/aromatic-antiaromatic-nonaromatic-some-practice-problems\/","title":{"rendered":"Aromatic, Non-Aromatic, or Antiaromatic? Some Practice Problems"},"content":{"rendered":"<p><strong>Aromatic vs Antiaromatic vs Non Aromatic Practice Exercises<\/strong><\/p>\n<p>Our last post in this series on aromaticity went through <a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/02\/23\/rules-for-aromaticity\/\">the 4 conditions a molecule must fulfill in order to be aromatic<\/a>.<\/p>\n<ul>\n<li><strong>First,<\/strong> it must be cyclic<\/li>\n<li><strong>Second<\/strong>, every atom around the ring must have an available p-orbital<\/li>\n<li><strong>Third<\/strong>, the number of electrons in the pi system must be 2, 6, 10, 14, 18, or a higher number in the set that increases from 18 in increments of 4 (22, 26, 30&#8230;. etc). We usually abbreviate this as [4n+2] pi electrons.<\/li>\n<li><strong>Fourth<\/strong>, the molecule must be flat.<\/li>\n<\/ul>\n<p>In that post we tried to explain what each of those rules meant &#8211; so if any of these individual items seem unclear to you, it might be a good idea to <a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/02\/23\/rules-for-aromaticity\/\">go back to that post<\/a>.<\/p>\n<p>In this post,we&#8217;re going to apply these 4 rules with some practice examples.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-43742\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2026\/02\/0-how-to-answer-if-molecule-is-aromatic-nonaromatic-antiaromatic-practice-problems-make-a-table-system-evaluate-cyclic-conjugated-pi-electrons-huckel-number.gif\" alt=\"how to answer if molecule is aromatic nonaromatic antiaromatic practice problems make a table system evaluate cyclic conjugated pi electrons huckel number\" width=\"640\" height=\"597\" \/><\/a><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li><a href=\"#one\">A System For Determining If Molecules Are Aromatic:\u00a0 Build A Table<\/a><\/li>\n<li><a href=\"#two\">Benzene<\/a><\/li>\n<li><a href=\"#three\">The Benzene Anion<\/a><\/li>\n<li><a href=\"#four\">The Cyclopentadiene Cation<\/a><\/li>\n<li><a href=\"#five\">Pyrrole<\/a><\/li>\n<li><a href=\"#six\">Pyrrole Conjugate Acid<\/a><\/li>\n<li><a href=\"#seven\">Pyridine<\/a><\/li>\n<li><a href=\"#eight\">Thiophene<\/a><\/li>\n<li><a href=\"#nine\">Cyclobutadiene<\/a><\/li>\n<li><a href=\"#ten\">Cyclobutene Di-Anion<\/a><\/li>\n<li><a href=\"#eleven\">Naphthalene<\/a><\/li>\n<li><a href=\"#twelve\">Pyrylium Ion<\/a><\/li>\n<li><a href=\"#thirteen\">Indole<\/a><\/li>\n<li><a href=\"#fourteen\">Azulene<\/a><\/li>\n<li><a href=\"#fifteen\">Summary: Aromaticity Practice Exercises<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quizzes\">Quiz Yourself!\u00a0<\/a><\/li>\n<\/ol>\n<hr \/>\n<h2><a id=\"one\"><\/a>1. A System For Determining If Molecules Are Aromatic: Build A Table<\/h2>\n<p>Here&#8217;s my tip for those of you getting started on trying to answer the question &#8220;Is this aromatic?&#8221; .\u00a0<strong>Make a table.\u00a0<\/strong><\/p>\n<p>Tables are great for organizing information. They also serve as a built-in checklist.<\/p>\n<p>For instance, here&#8217;s\u00a0an image from a tutoring session I did with a student where we determined whether or not several molecules were aromatic:<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15771\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic.jpg\" alt=\"tutoring session with a student making a table for aromaticity cyclic conjugated pi bonds lone pairs pi electrons huckel aromatic\" width=\"630\" height=\"473\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic.jpg 1600w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-300x225.jpg 300w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-768x576.jpg 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-1024x768.jpg 1024w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-320x240.jpg 320w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-640x480.jpg 640w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-360x270.jpg 360w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-720x540.jpg 720w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-1080x810.jpg 1080w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-800x600.jpg 800w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-1280x960.jpg 1280w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-tutoring-session-with-a-student-making-a-table-for-aromaticity-cyclic-conjugated-pi-bonds-lone-pairs-pi-electrons-huckel-aromatic-760x570.jpg 760w\" sizes=\"(max-width: 630px) 100vw, 630px\" \/><\/p>\n<p>You&#8217;ll notice that my checklist doesn&#8217;t usually bother having a column for &#8220;flatness&#8221; because it&#8217;s generally assumed. (You need to know the few exceptions that come up &#8211; we covered that last time).<\/p>\n<p>Today, we&#8217;re\u00a0going to look at the following 13 molecules and try to determine if they are aromatic or not:<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15772\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/2-list-of-molecules-are-these-molecules-aromatic-practice.gif\" alt=\"list of molecules are these molecules aromatic practice\" width=\"630\" height=\"273\" \/><\/p>\n<p>Let&#8217;s get started!<\/p>\n<h2><strong><a id=\"two\"><\/a>2. Benzene<\/strong><\/h2>\n<p>The easiest example to start with is benzene, and it demonstrates how to use the table. \u00a0It&#8217;s cyclic, conjugated, has 3 pi bonds and those pi bonds are all in the pi system. It has zero lone pairs that contribute to aromaticity. Therefore it has (3 \u00d7\u00a02) + 0 = 6 pi electrons. We&#8217;re assuming it&#8217;s flat (it is). Checking off all the boxes, we can say that it&#8217;s aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15773\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/3-is-benzene-aromatic-how-to-find-out-it-is-cyclic-conjugated-3-i-bonds-6-pi-electrons-4n2-aromatic.gif\" alt=\"is benzene aromatic how to find out it is cyclic conjugated 3 i bonds 6 pi electrons 4n+2 aromatic\" width=\"630\" height=\"142\" \/><\/p>\n<h2><strong><a id=\"three\"><\/a>3. The Benzene Anion<\/strong><\/h2>\n<p>If you remove a proton from benzene, you get the\u00a0<strong>benzene anion.\u00a0<\/strong>Like benzene, it&#8217;s cyclic, conjugated, had 3 pi bonds and those pi bonds are all in the pi system. It&#8217;s tempting to look at that lone pair and to think that it might contribute to the pi system as well, giving 8 pi electrons total. However, that lone pair is in the\u00a0<em>plane<\/em> of the molecule (along with the other C-H bonds) and thus can&#8217;t overlap with the p-orbitals. Therefore, for the purposes of determining aromaticity, we can ignore the lone pair.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15774\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/4-is-the-benzene-anion-aromatic-practice-worked-example.gif\" alt=\"is the benzene anion aromatic practice worked example\" width=\"630\" height=\"145\" \/><\/p>\n<h2><strong><a id=\"four\"><\/a>4. The Cyclopentadiene Cation<\/strong><\/h2>\n<p>The cyclopentadiene cation below is cyclic and conjugated (that positive charge represents a carbocation with an empty p-orbital). There are two pi bonds and zero lone pairs to contribute to the pi system. This gives us 4 total pi electrons, which is <strong>not<\/strong> a H\u00fcckel number.\u00a0\u00a0Therefore it isn&#8217;t aromatic.* [<a href=\"#noteone\">Note 1<\/a>]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15775\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/5-is-the-cyclopentadienyl-cation-aromatic-practice-problem-worked-example.gif\" alt=\"is the cyclopentadienyl cation aromatic practice problem worked example\" width=\"630\" height=\"156\" \/><\/p>\n<h2><strong><a id=\"five\"><\/a>5. Pyrrole<\/strong><\/h2>\n<p>Pyrrole is cyclic and conjugated (that lone pair on nitrogen can contribute to the pi-system). There are two pi bonds and one lone pair of electrons that contribute to the pi system. This gives us 6 total pi electrons, which is a Huckel number (i.e. satisfies 4n+2). Therefore it&#8217;s aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15776\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/6-is-pyrrole-aromatic-worked-example-practice-problem.gif\" alt=\"is pyrrole aromatic worked example practice problem\" width=\"630\" height=\"153\" \/><\/p>\n<h2><strong><a id=\"six\"><\/a>6. Pyrrole Conjugate Acid<\/strong><\/h2>\n<p>If pyrrole is protonated on the nitrogen, the lone pair can no longer participate in the pi-system. Therefore the molecule drawn below is not aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15777\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/7-is-the-conjugate-acid-of-pyrrole-aromatic-worked-example-not-conjugated.gif\" alt=\"is the conjugate acid of pyrrole aromatic worked example - not conjugated\" width=\"630\" height=\"149\" \/><\/p>\n<h2><strong><a id=\"seven\"><\/a>7. Pyridine<\/strong><\/h2>\n<p>Pyridine is cyclic, conjugated, and has three pi bonds. It&#8217;s a lot like the benzene anion in that the lone pair\u00a0<em>looks<\/em> like it might contribute to the pi system, but in fact is in the plane of the ring (along with the C-H bonds) and thus cannot contribute (the nitrogen is already contributing a p-orbital towards the pi-system &#8211; note that it&#8217;s drawn as participating in a double bond with an adjacent carbon). \u00a0Therefore we can ignore the lone pair for the purposes of aromaticity and there is a total of six pi electrons, which is a Huckel number and the molecule is aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15778\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/8-is-pyridine-aromatic-worked-example-cyclic-and-conjugated.gif\" alt=\"is pyridine aromatic worked example cyclic and conjugated\" width=\"630\" height=\"151\" \/><\/p>\n<h2><strong><a id=\"eight\"><\/a>8. Thiophene<\/strong><\/h2>\n<p>Thiophene, the sulfur analog of <a href=\"https:\/\/en.wikipedia.org\/wiki\/Furan\">furan<\/a>, is cyclic and conjugated all the way around the ring. It has two pi bonds. What&#8217;s interesting about thiophene (and furan) is that although there is an atom bearing two lone pairs in the ring, we can<strong> only count one of those lone pairs toward the pi-system.<\/strong> [Each atom can contribute a maximum of one orbital and two electrons towards aromaticity]. The other lone pair is in the plane of the ring, much like the lone pair on the nitrogen of pyridine, above. Therefore thiophene has six pi electrons total, which is a Huckel number, and thiophene is aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15779\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/9-is-thiophene-aromatic-practice-problem-worked-example.gif\" alt=\"is thiophene aromatic practice problem worked example\" width=\"630\" height=\"148\" \/><\/p>\n<h2><strong><a id=\"nine\"><\/a>9. Cyclobutadiene<\/strong><\/h2>\n<p>Cyclobutadiene is cyclic and conjugated. There are two pi bonds and zero contributing lone pairs. Two pi bonds gives us a total of 4 pi electrons, which is\u00a0<em>not<\/em> a Huckel number. Therefore it is not aromatic, just like the cyclopentadienyl cation, above. [<a href=\"#noteone\">Note 1<\/a>]<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15780\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/10-is-cyclobutadiene-aromatic-practice-problem-worked-example.gif\" alt=\"is cyclobutadiene aromatic practice problem worked example\" width=\"630\" height=\"156\" \/><\/p>\n<h2><strong><a id=\"ten\"><\/a>10. Cyclobutene Di-Anion<\/strong><\/h2>\n<p>Cyclobutadiene is not aromatic. If we somehow pump two electrons into cyclobutadiene, however, then the situation changes considerably. The cyclobutadiene dianion is cyclic and conjugated. It has a single pi bond, and now two carbons bearing lone pairs which can contribute to the pi system, giving us a total of six pi electrons. This\u00a0<em>is<\/em> a Huckel number and thus the cyclobutadiene di-anion is aromatic!<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15781\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/11-is-cyclobutadiene-di-anion-aromatic-practice-problem-worked-example.gif\" alt=\"is cyclobutadiene di-anion aromatic practice problem worked example\" width=\"630\" height=\"156\" \/><\/p>\n<h2><strong><a id=\"eleven\"><\/a>11. Naphthalene<\/strong><\/h2>\n<p>Naphthalene has two rings and is thus a bicyclic compound. It is conjugated around the perimeter of the rings and there are a total of 5 pi bonds and zero lone pairs, giving us 10 pi electrons total. 10 is a Huckel number (satisfying 4n+2 for n=2) and naphthalene is an aromatic molecule.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15782\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/12-is-naphthalene-aromatic-practice-problem-worked-example.gif\" alt=\"is naphthalene aromatic practice problem worked example\" width=\"630\" height=\"151\" \/><\/p>\n<h2><strong><a id=\"twelve\"><\/a>12. Pyrylium Ion<\/strong><\/h2>\n<p>The pyrylium ion is a six-membered ring that, like benzene, has three pi bonds. It also bears a lone pair on the oxygen. Like pyridine and the benzene anion, this lone pair is actually in an orbital at right angles to the pi system so it does not in fact count towards aromaticity. Therefore the molecule has only 6 electrons in the pi system and is in fact aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15783\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/13-is-pyrilium-ion-aromatic-practice-problem-worked-example.gif\" alt=\"is pyrilium ion aromatic practice problem worked example\" width=\"630\" height=\"151\" \/><\/p>\n<h2><strong><a id=\"thirteen\"><\/a>13. Indole<\/strong><\/h2>\n<p>Indole is a bicylic molecule that looks like a molecule of benzene fused to a molecule of pyrrole. \u00a0It is conjugated; every atom around the perimeter of the two rings participates in the pi system. It has 4 pi bonds and a single pair of electrons on the nitrogen that participates in the pi system, giving 10 pi electrons in total. This is a Huckel number and indole is in fact aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15784\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/14-is-indole-aromatic-practice-problem-worked-example.gif\" alt=\"is indole aromatic practice problem worked example\" width=\"630\" height=\"151\" \/><\/p>\n<h2><strong><a id=\"fourteen\"><\/a>14. Azulene<\/strong><\/h2>\n<p>Azulene is another example of a bicyclic molecule, like\u00a0naphthalene and indole, above. It&#8217;s conjugated all around the perimeter of the pi system. There are five total pi bonds and zero lone pair electrons, giving a total of 10 pi electrons, which is a Huckel number. And azulene is, in fact, aromatic.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15785\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/15-is-azulene-aromatic-practice-problem-worked-example.gif\" alt=\"is azulene aromatic practice problem worked example\" width=\"630\" height=\"154\" \/><\/p>\n<p>If it&#8217;s hard to visualize azulene as aromatic, it might be helpful to draw a resonance form where both rings look like they have aromatic components. For example, in the resonance form below, you can think of azulene as being composed of the cycloheptatriene cation (aromatic) fused to the cyclopentadiene anion (also aromatic).<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15786\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/16-important-resonance-form-of-azulene-has-dipole-moment.gif\" alt=\"important resonance form of azulene has dipole moment\" width=\"600\" height=\"256\" \/><\/p>\n<p>Note that one ring bears a negative charge and the other one bears a positive charge. It turns out that this resonance form has a significant contribution to the hybrid, since azulene itself has a substantial dipole moment (1.08 D). Naphthalene, in contrast, completely lacks a dipole moment.<\/p>\n<h2><strong><a id=\"fifteen\"><\/a>15. Summary: Aromaticity Practice Exercises<\/strong><\/h2>\n<p>The whole point of using a table like the one above is to organize your thoughts. Like a set of training wheels, if you do problems like this often enough, you&#8217;ll start to find that you don&#8217;t need it.<\/p>\n<p>The most common part where students get tripped up is in counting the number of pi electrons. Just remember that each atom can at most contribute one p-orbital towards the pi system, and that the p-orbital can have (at most) two pi electrons.<\/p>\n<p>Are there any other examples you&#8217;re not sure about that we should apply this system towards? Leave a comment!<\/p>\n<hr \/>\n<h2><strong><a id=\"notes\"><\/a>Notes<\/strong><\/h2>\n<div class=\"related-articles\"><p><strong>Related Articles<\/strong><\/p><ul><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/05\/05\/the-pi-molecular-orbitals-of-benzene\/\" class=\"\"><span>The Pi Molecular Orbitals of Benzene<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/05\/10\/the-pi-molecular-orbitals-of-cyclobutadiene\/\" class=\"\"><span>The Pi Molecular Orbitals of Cyclobutadiene<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/01\/24\/conjugation-and-resonance\/\" class=\"\"><span>Conjugation And Resonance In Organic Chemistry<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/02\/16\/molecular-orbitals-of-the-allyl-cation-allyl-radical-and-allyl-anion\/\" class=\"\"><span>Molecular Orbitals of The Allyl Cation, Allyl Radical, and Allyl Anion<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/03\/03\/is-this-molecule-aromatic-some-practice-problems\/\" class=\"\"><span>\u201cIs This Molecule Aromatic?\u201d Some Practice Problems<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/organic-chemistry-practice-problems\/aromaticity-practice-quizzes\/\" class=\"\"><span>Aromaticity Practice Quizzes (MOC Membership)<\/span><\/a><\/li><\/ul><\/div>\n<p><strong><a id=\"noteone\"><\/a>Note 1. <\/strong>\u00a0there are two molecules in particular in the list above which will deserve\u00a0further discussion. The cyclopentadiene cation and cyclobutadiene were each described, above, as &#8220;not aromatic&#8221;, which is technically true.<\/p>\n<p>Just as we saw that benzene is\u00a0unusually stable compared to the theoretical &#8220;cyclohexatriene&#8221; , cyclobutadiene and the cyclopentadiene cation are interesting in that they are\u00a0<strong>unusually unstable.\u00a0<\/strong>This is a property called &#8220;<strong>antiaromaticity&#8221;<\/strong>, which we will describe in some detail in the next post.<\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/03\/27\/antiaromaticity\/\"><strong>Antiaromaticity and Antiaromatic Compounds<\/strong><\/a><\/p>\n<p>Thanks to Matt Struble for assistance with this post.<\/p>\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\/1034-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\/1026-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\/1003-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\/1004-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\/1006-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a 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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\/3622-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","protected":false},"excerpt":{"rendered":"<p>Aromatic vs Antiaromatic vs Non Aromatic Practice Exercises Our last post in this series on aromaticity went through the 4 conditions a molecule must fulfill <\/p>\n","protected":false},"author":1,"featured_media":43742,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[844],"tags":[846,929,320,1191,1190,845,1189,1180,847],"post_folder":[],"class_list":["post-10578","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aromaticity-2","tag-4n2","tag-antiaromatic","tag-aromaticity","tag-azulene","tag-furan","tag-huckels-rule","tag-is-this-aromatic","tag-pi-electrons","tag-pyridine"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Aromatic, Antiaromatic, or Non-Aromatic? 13 Worked Examples<\/title>\n<meta name=\"description\" content=\"In this post we present an easy-to-use system for solving &quot;aromatic vs antiaromatic vs non-aromatic&quot; problems, with 13 worked examples.\" \/>\n<meta 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