{"id":11410,"date":"2018-03-05T08:00:24","date_gmt":"2018-03-05T13:00:24","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=11410"},"modified":"2025-11-20T12:37:02","modified_gmt":"2025-11-20T18:37:02","slug":"why-are-halogens-ortho-para-directors","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2018\/03\/05\/why-are-halogens-ortho-para-directors\/","title":{"rendered":"Why are halogens ortho- para- directors?"},"content":{"rendered":"<p><strong>Why are halogens\u00a0<em>ortho-, para-<\/em> directors?<\/strong><\/p>\n<ul>\n<li>All activating groups are also\u00a0<em>ortho-, para-\u00a0<\/em>directors.<\/li>\n<li>Halogens (F, Cl, Br, I) are notable in that they are\u00a0<strong>deactivating<\/strong> <em>ortho-, para-<\/em> directors. Why?<\/li>\n<li>In electrophilic aromatic substitution (EAS), addition at the\u00a0<em>ortho-<\/em> or <em>para<\/em>&#8211; position results in a carbocation intermediate with a resonance form containing a carbocation directly adjacent to the directing group.<\/li>\n<li>Halogens have a<strong> lone pair<\/strong> that can form a pi-bond with the adjacent carbocation.<\/li>\n<li>Even though halogens are <strong>deactivating<\/strong> overall, this &#8220;<strong>pi donation<\/strong>&#8221; helps to stabilize the transition state leading to\u00a0<em>ortho<\/em>&#8211; or\u00a0<em>para-<\/em> products, which is why they are\u00a0<em>ortho-, para-<\/em> directors.<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-30130\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2022\/09\/0-Halogens-ortho-para-summary.gif\" alt=\"Halogens ortho para summary\" width=\"640\" height=\"475\" \/><\/a><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li class=\"p1\"><a href=\"#one\"><span class=\"s1\">All &#8220;Activating Groups&#8221; Are <i>ortho-, para-\u00a0<\/i>Directors<\/span><\/a><\/li>\n<li class=\"p1\"><a href=\"#two\">Most &#8220;Deactivating Groups&#8221; Are <i>meta-\u00a0<\/i>Directors<\/a><\/li>\n<li class=\"p1\"><a href=\"#three\"><span class=\"s1\"><span class=\"s1\">So Why Are Halogens <i>Ortho-,\u00a0<\/i> <i>Para-<\/i> Directors?<\/span><\/span><\/a><\/li>\n<li class=\"p1\"><a href=\"#four\"><span class=\"s1\"><span class=\"s1\">The Lone Pair Of Halogens Stabilizes Adjacent Carbocations Formed In The\u00a0<i>ortho-\u00a0<\/i>And\u00a0<i>para-\u00a0<\/i>Intermediates<\/span><\/span><\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quizzes\">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. All &#8220;Activating Groups&#8221; Are <em>ortho-, para-\u00a0<\/em>Directors<\/h2>\n<p>The previous post in this series tried to show that<strong> the\u00a0key to understanding\u00a0why a substituent is an\u00a0<em>ortho-, para-\u00a0<\/em>director or\u00a0<em>meta<\/em>&#8211; director lies in understanding how it influences the stability of the <em>ortho-, para-\u00a0<\/em>and\u00a0<em>meta-\u00a0<\/em>carbocation intermediates.<\/strong><\/p>\n<p>In this post, we&#8217;ll show why halogens are\u00a0<em>ortho-, para-\u00a0<\/em>directors\u00a0<strong>even though<\/strong> they are deactivating.<\/p>\n<p>In\u00a0<em>ortho-\u00a0<\/em>and\u00a0<em>para-<\/em> addition, there&#8217;s a resonance form where the carbocation ends up directly bonded to the substituent.<\/p>\n<p>In\u00a0<em>meta<\/em>&#8211; addition, the carbocation ends up on the carbon <em>adjacent<\/em> to the carbon bonded to the substituent.<\/p>\n<p><strong>Any group that can donate electron density to a carbocation will be an ortho- , para- director.\u00a0<\/strong><\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15887\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-summary-of-ortho-para-directors-have-resonance-form-with-carbocation-adjacent-to-donor-meta-has-no-resonance-form-where-carbocation-directly-attached-to-substituent.gif\" alt=\"summary of ortho para directors - have resonance form with carbocation adjacent to donor - meta has no resonance form where carbocation directly attached to substituent\" width=\"600\" height=\"304\" \/><\/p>\n<p>We&#8217;ve seen that <strong>all activating groups\u00a0<\/strong> (such as amines, ethers, and alkyl groups) <strong>are <em>ortho-,\u00a0para<\/em>&#8211; directors.<\/strong><\/p>\n<p>These groups can donate electron-density to an adjacent carbocation through inductive effects (a.k.a. &#8220;sigma-donation&#8221;, as with alkyl groups) and\/or pi-donation, where donation of a lone pair from an attached oxygen or nitrogen provides\u00a0a key resonance form where all carbons have a full octet. Carbocations, being electron-poor, are stabilized by electron-rich neighbors.<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15888\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/2-activating-groups-in-eas-work-by-stabilizing-adjacent-carbocations-through-induction-and-pi-donation.gif\" alt=\"activating groups in eas work by stabilizing adjacent carbocations through induction and pi donation\" width=\"600\" height=\"458\" \/><\/p>\n<h2><a id=\"two\"><\/a>2. Most Deactivating Groups Are\u00a0<em>meta-\u00a0<\/em>Directors<\/h2>\n<p><em>Most<\/em> deactivating groups are\u00a0<em>meta-<\/em> directors.<\/p>\n<p>They withdraw electron-density through an adjacent carbocation through being &#8220;sigma-acceptors&#8221; (such as the electron-withdrawing CF<sub>3<\/sub> group, or the ammonium [\u2013NR<sub>3<\/sub><sup>+<\/sup>] group) and\/or &#8220;pi acceptors&#8221;, such as nitro, carbonyl, or sulfonyl groups.<\/p>\n<p><strong>Carbocations are destabilized by electron-poor neighbors.<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15889\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/3-deactivating-groups-destabilize-adjacent-carbocations-through-inductive-and-pi-acceptor-effects.gif\" alt=\"deactivating groups destabilize adjacent carbocations through inductive and pi acceptor effects\" width=\"630\" height=\"212\" \/><\/p>\n<p>Which brings us to the peculiar case of halogens.<\/p>\n<h2><a id=\"three\"><\/a>3. So Why Are Halogens <em>Ortho-,\u00a0<\/em> <em>Para-<\/em> Directors?<\/h2>\n<p>Halogens are\u00a0<em>deactivating<\/em> substituents, which is to say that the rate of electrophilic aromatic substitution is lowered when a halogen replaces hydrogen (H) as a substituent. <em><span style=\"color: #993366;\">[<a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2017\/09\/26\/activating-and-deactivating-groups-in-electrophilic-aromatic-substitution\/\">See this earlier post on &#8220;activating vs. deactivating substituents<\/a>&#8220;<\/span>]<\/em>\u00a0.\u00a0This reflects their high electronegativity, withdrawing electron density from the ring. [<a href=\"#noteone\">Note 1<\/a>]<\/p>\n<p>At first glance, this might seem to preclude them from being ortho-para directors.\u00a0 But lo,\u00a0 they are!<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15890\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/4-halogens-are-ortho-para-directors-example-chlorination-of-fluorobenzene.gif\" alt=\"halogens are ortho para directors example chlorination of fluorobenzene\" width=\"600\" height=\"280\" \/><\/p>\n<p>How can we rationalize this observation?<\/p>\n<p>Recall that\u00a0 &#8220;activating&#8221; vs. &#8220;deactivating&#8221; just compares how well a substituent stabilizes a carbocation <strong>relative to hydrogen<\/strong>.<\/p>\n<p>That&#8217;s not the right comparison here. Just like the <a href=\"http:\/\/jokes.cc.com\/funny-animal\/fwko9c\/bear-on-a-rampage\" target=\"_blank\" rel=\"noopener noreferrer\">old joke goes<\/a>, it&#8217;s not about outrunning the bear &#8211; <em>it&#8217;s about outrunning the other guy.\u00a0\u00a0<\/em><\/p>\n<p>The key for a substituent being an\u00a0<em>ortho-, para-\u00a0<\/em>versus\u00a0<em>meta-<\/em> director is the stability of the\u00a0<em>ortho-\u00a0<\/em>and\u00a0<em>para<\/em>&#8211; carbocation intermediates <strong>versus<\/strong> the\u00a0<em>meta-<\/em> carbocation intermediate.<\/p>\n<h2><a id=\"four\"><\/a>4. The Lone Pair Of Halogens Stabilizes Adjacent Carbocations Formed In The\u00a0<em>ortho-\u00a0<\/em>And\u00a0<em>para-\u00a0<\/em>Intermediates<\/h2>\n<p>We can rationalize the <em>ortho-<\/em>, <em>para-<\/em> directing ability of halogens by noting that these atoms have attached lone pairs, and can (albeit poorly) act as pi-donors. <strong>This results in a resonance form where carbon has a full octet.<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15891\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/5-chlorine-can-be-a-pi-donor-stabilizing-adjacent-carbocation-giving-full-octet.gif\" alt=\"chlorine can be a pi donor stabilizing adjacent carbocation giving full octet\" width=\"630\" height=\"310\" \/><\/p>\n<p>Note that I didn&#8217;t say &#8220;predict&#8221; &#8211; I said &#8220;rationalize&#8221; : &#8211; ) .\u00a0 Rationalization involves looking backward from a result and trying to understand why something might have happened.\u00a0 There are several variables at work here that tug in opposite directions, and predicting the magnitude of these individual effects in the absence of a strong computational model is a fool&#8217;s errand. <strong>That&#8217;s why we run experiments!<\/strong><\/p>\n<p>From these experiments, it\u00a0<em>seems<\/em> that a carbocation intermediate which has a pi-donor is more important toward determining whether it is an\u00a0<em>ortho-, para-\u00a0<\/em>director than whether it is a strong electron withdrawing group.<\/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\/2017\/07\/11\/electrophilic-aromatic-substitution-introduction\/\" class=\"\"><span>Electrophilic Aromatic Substitution: Introduction<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/11\/09\/electrophilic-aromatic-substitution-the-mechanism\/\" class=\"\"><span>Electrophilic Aromatic Substitution \u2013 The Mechanism<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2018\/04\/18\/electrophilic-aromatic-substitutions-1-halogenation\/\" class=\"\"><span>Electrophilic Aromatic Substitutions (1) \u2013 Halogenation of Benzene<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/12\/15\/exploring-resonance-pi-donation\/\" class=\"\"><span>Exploring Resonance:  Pi-Donation<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/09\/26\/activating-and-deactivating-groups-in-electrophilic-aromatic-substitution\/\" class=\"\"><span>Activating and Deactivating Groups In Electrophilic Aromatic Substitution<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2018\/03\/19\/eas-disubstituted-benzenes\/\" class=\"\"><span>Disubstituted Benzenes: The Strongest Electron-Donor \u201cWins\u201d<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/organic-chemistry-practice-problems\/electrophilic-aromatic-substitution-practice-problems\/\" class=\"\"><span>Electrophilic Aromatic Substitution Practice Problems (MOC Membership)<\/span><\/a><\/li><\/ul><\/div>\n<p><a id=\"noteone\"><\/a><strong>Note 1.\u00a0<\/strong> It is interesting to note, however, that despite having the highest electronegativity, fluorine is actually the\u00a0<em>most<\/em> activating of the halogens (the other halogens are relatively similar in their deactivating powers). This can be attributed to the better orbital overlap of the fluorine sp<sup>3<\/sup> orbitals with the 2p orbitals of the pi system. [For similar reasons, BF<sub>3<\/sub> is a worse Lewis acid than BCl<sub>3 <\/sub>and BBr<sub>3<\/sub> ,\u00a0\u00a0since the fluorine orbitals overlap much better with the empty boron 2p orbital].<\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2.\u00a0<\/strong><\/p>\n<p>Are there any other deactivating\u00a0<em>ortho-, para-<\/em> directors?<\/p>\n<p>Yes. <strong>NO<\/strong>.<\/p>\n<p><strong>NO<\/strong>?<\/p>\n<p>Yes, <strong>NO<\/strong>. <strong>Nitroso<\/strong>.<\/p>\n<p>Knowing what we now know about halogens, what predictions would you make for the nitroso group, a group that is somewhat electron withdrawing, but also bears a lone pair on the nitrogen.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15892\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/F1-nitroso-is-another-example-of-deactivating-ortho-para-director.gif\" alt=\"nitroso is another example of deactivating ortho para director\" width=\"600\" height=\"487\" \/><\/p>\n<p>The yields aren&#8217;t great, but there you go.<\/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\/3562-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\/3563-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\/3564-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\/3565-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\/3566-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\/3567-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\/3568-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<ol>\n<li><strong> A. F. Holleman, Die direkte Einf\u00fchrung von Substituenten in den Benzolkern<br \/>\n<\/strong><em>Rec. Trav. Chim. Pays-Bas<\/em> <strong>1910<\/strong>, <em>12<\/em>, 455-456<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/recl.19100291205\">10.1002\/recl.19100291205<\/a><br \/>\nA.F Holleman from 1910 said that <em>ortho<\/em>&#8211;<em>para<\/em> orientation is associated with activation and meta orientation with deactivation.<\/li>\n<li><strong>\u2014The nature of the alternating effect in carbon chains. Part XXII. An attempt further to define the probable mechanism of orientation in aromatic substitution<br \/>\n<\/strong>Christopher Kelk Ingold and Florence Ruth Shaw<strong><br \/>\n<\/strong><em>J. Chem. Soc.<\/em><strong> 1927, <\/strong>2918-2926<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/1927\/JR\/JR9270002918#!divAbstract\">10.1039\/JR9270002918<\/a><br \/>\nAn early paper by the influential Physical Organic Chemist, Prof. C. K. Ingold, stating that halogenobenzenes are inductively electron-withdrawing but simultaneously resonance-stabilizing.<\/li>\n<li><strong> Influence of directing groups on nuclear reactivity in oriented aromatic substitutions. Part IV. Nitration of the halogenobenzenes<br \/>\n<\/strong>Marjorie L. Bird and Christopher K. Ingold<strong><br \/>\n<\/strong><em>J. Chem. Soc.<\/em><strong> 1938, <\/strong>918-929<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/Content\/ArticleLanding\/JR\/1938\/JR9380000918#!divAbstract\">10.1039\/JR9380000918<\/a><strong><br \/>\n<\/strong>The relative rates of nitration for the halobenzenes are determined here, and it is seen that the order of reactivity is PhF&gt;PhI&gt;PhCl, PhBr<\/li>\n<li><strong>The Anomalous Reactivity of Fluorobenzene in Electrophilic Aromatic Substitution and Related Phenomena<br \/>\n<\/strong>Joel Rosenthal and David I. Schuster<strong><br \/>\n<\/strong><em>Journal of Chemical Education<\/em><strong> 2003, <\/strong><em>80<\/em> (6), 679<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ed080p679\">1021\/ed080p679<\/a><br \/>\nA very interesting paper, suitable for curious undergrads, and discusses something that most practicing organic chemists will know empirically \u2013 fluorobenzene is almost as reactive as benzene in EAS or Friedel-Crafts reactions, which is counterintuitive when one considers electronic effects.<\/li>\n<li><strong>\u2014A new orientation rule and the anomaly of the nitroso-group<br \/>\n<\/strong>Dalziel Llewellyn Hammick and Walter S. Illingworth<strong><br \/>\n<\/strong><em>J. Chem. Soc.<\/em><strong> 1930<\/strong>, 2358-2364<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/1930\/JR\/jr9300002358#!divAbstract\">10.1039\/JR9300002358<\/a><\/li>\n<li><strong>93. The orienting power of the nitroso-group<br \/>\n<\/strong>Dalziel Ll. Hammick, Randal G. A. New, and Leslie E. Sutton<br \/>\n<em>J. Chem. Soc.<\/em> <strong>1932<\/strong>, 742-748<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.rsc.org\/en\/Content\/ArticleLanding\/JR\/1932\/JR9320000742#!divAbstract\">10.1039\/JR9320000742<\/a><br \/>\nThese two papers discuss the electronics of the nitroso substituent. Both papers refer to C. K. Ingold\u2019s experiment where he observed <em>p-<\/em>substitution of nitrosobenzene from bromination in CS<sub>2<\/sub>. The authors attempt to explain this by suggesting that in certain solvents nitrosobenzene dimerizes, and the dimer prefers <em>o,p<\/em>-substitution. This is worth reevaluating with modern methods (hint, hint)!<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Why are halogens\u00a0ortho-, para- directors? All activating groups are also\u00a0ortho-, para-\u00a0directors. Halogens (F, Cl, Br, I) are notable in that they are\u00a0deactivating ortho-, para- directors. <\/p>\n","protected":false},"author":1,"featured_media":30130,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1297],"tags":[1298,1303,319,571],"post_folder":[],"class_list":["post-11410","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aromatic-reactions","tag-activating","tag-deactivating","tag-electrophilic-aromatic-substitution","tag-halogens"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Why are halogens ortho- para- directors? &#8211; Master Organic Chemistry<\/title>\n<meta name=\"description\" content=\"Why are halogens ortho para directors? Well, they have attached lone pairs, and can (poorly) act as pi-donors. 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