{"id":532,"date":"2010-06-18T21:53:41","date_gmt":"2010-06-18T19:53:41","guid":{"rendered":"http:\/\/masterorganicchemistry.wordpress.com\/?p=532"},"modified":"2026-05-03T07:38:56","modified_gmt":"2026-05-03T12:38:56","slug":"know-your-pkas","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2010\/06\/18\/know-your-pkas\/","title":{"rendered":"The pKa Table Is Your Friend"},"content":{"rendered":"<p>The importance of pK<sub>a<\/sub> values in organic chemistry can&#8217;t be overestimated, in my opinion.\u00a0 <strong>Not knowing pK<sub>a<\/sub>\u00a0 values in organic chemistry is like not knowing the value of the hands in poker. <\/strong>In this scheme, alkyl anions are the equivalent of the royal flush &#8211; they win the proton from everything underneath them in the table.<\/p>\n<p>Why is pK<sub>a<\/sub> so important? Because every <strong>nucleophile<\/strong> is potentially a <strong>base<\/strong>, and vice versa. If you have a reaction where it looks like you might get S<sub>N<\/sub>2 or E2, look closely first &#8211; is there any chance of a simple acid-base reaction? For instance, take NaOH plus an alkyl thiol, R\u2013SH. Is it an S<sub>N<\/sub>2? Or possibly an E2? Both are incorrect. The reaction that happens is the simplest one &#8211; deprotonation of SH, to provide water and the deprotonated thiol.<\/p>\n<p>Also, the pK<sub>a<\/sub>table tells you about leaving group ability. <a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/04\/12\/what-makes-a-good-leaving-group\/\" target=\"_blank\" rel=\"noopener noreferrer\">Good leaving groups are weak bases<\/a>!<\/p>\n<p>If you don&#8217;t know the relative values of the pK<sub>a<\/sub>&#8216;s of the major functional groups, you&#8217;ll be flying blind in the course. Expect to hit a tree.<\/p>\n<p><strong><a href=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2010\/06\/PKAs.pdf\" rel=\"\">PDF VERSION NOW AVAILABLE (click here)<\/a><\/strong><\/p>\n<p>For more complete lists, be sure to check out <a href=\"https:\/\/organicchemistrydata.org\/hansreich\/resources\/pka\/pka_data\/evans_pKa_table.pdf\">Evans<\/a> and <a href=\"https:\/\/organicchemistrydata.org\/hansreich\/resources\/pka\/\">Reich<\/a>. (check out the resources on Reich&#8217;s page by the way \u2013 fantastic!) Blessed are the OCD, for they produce the most beautiful and complete web resources.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"aligncenter wp-image-14154\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/11\/1-pka-table-long-going-from-strongest-to-weakest-acid-introductory-organic-chemistry-showing-conjugate-bases.gif\" alt=\"pka-table-long-going-from-strongest-to-weakest-acid-introductory-organic-chemistry-showing-conjugate-bases\" width=\"495\" height=\"1324\" \/><\/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\/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\/2012\/05\/09\/acid-base-reactions-ka-and-pka\/\" class=\"\"><span>Acid-Base Reactions: Introducing Ka and pKa<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/09\/29\/how-to-use-a-pka-table\/\" class=\"\"><span>How to Use a pKa Table<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/04\/25\/walkthrough-of-acid-base-reactions-3-acidity-trends\/\" class=\"\"><span>Walkthrough of Acid-Base Reactions (3) \u2013 Acidity Trends<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/09\/22\/five-key-factors-that-influence-acidity\/\" class=\"\"><span>Five Key Factors That Influence Acidity<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/organic-chemistry-practice-problems\/acid-base-practice-problems\/\" class=\"\"><span>Acid Base Practice Problems (MOC Membership)<\/span><\/a><\/li><\/ul><\/div>\n<hr \/>\n<h2><a id=\"quizyourself\"><\/a>Quiz Yourself!<\/h2>\n<p>&nbsp;<\/p>\n\n<p class=\"p1\"><img decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/0307-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 decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/0298-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\/3650-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\/0273-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\/0272-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\/2366-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\/2367-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\/2371-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=\"appendix\"><\/a>Appendix: Tables of pKa Values By Functional Group<\/h2>\n<p>Some pK<sub>a<\/sub> tables broken down by functional group (Source: ACS Division of Organic Chemistry and references within)<\/p>\n<p>Rather than memorize these values, just try to spot the key trends:<\/p>\n<ul>\n<li>What is the effect of additional electron-withdrawing groups?<\/li>\n<li>How does addition of different halogen atoms compare?<\/li>\n<li>What is the effect of being able to delocalize the conjugate base through resonance<\/li>\n<li>What is the effect of moving electron-withdrawing groups further away?<\/li>\n<\/ul>\n<p><strong>Alcohols<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-45805\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2026\/05\/T7-Summary-pka-values-of-alcohols-and-thiols-primary-secondary-tertiary-alcohol-pka-substituted-phenol-pka.gif\" alt=\"Summary-pka values of alcohols and thiols primary secondary tertiary alcohol pka substituted phenol pka\" width=\"640\" height=\"708\" \/><\/a><\/p>\n<p><strong>Carboxylic Acids<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-45803\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2026\/05\/T5-Summary-pka-values-of-some-carboxylic-acids-determined-in-h2o.gif\" alt=\"Summary-pka values of some carboxylic acids determined in h2o\" width=\"640\" height=\"826\" \/><\/a><\/p>\n<p><strong>Protonated Nitrogen<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-45804\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2026\/05\/T6-Summary-Some-pka-values-of-protonated-amines-pkaH-primary-secondary-tertiary-amines-heterocycles-hydrazoic-acid-and-more.gif\" alt=\"Summary-Some pka values of protonated amines - pkaH - primary secondary tertiary amines heterocycles hydrazoic acid and more\" width=\"640\" height=\"857\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The importance of pKa values in organic chemistry can&#8217;t be overestimated, in my opinion.\u00a0 Not knowing pKa\u00a0 values in organic chemistry is like not knowing <\/p>\n","protected":false},"author":1,"featured_media":14154,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1407],"tags":[163,177,688,586,256,514,763,764,282],"post_folder":[],"class_list":["post-532","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-acid-base-reactions","tag-acidity","tag-basicity","tag-conjugate-acid","tag-conjugate-base","tag-pkas","tag-stability","tag-strong-acids","tag-strong-bases","tag-tables"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>The pKa Table Is Your Friend<\/title>\n<meta name=\"description\" content=\"Why are pKas so important? Because every nucleophile is potentially a base, and vice versa. If you have a reaction where it looks like you might get SN2 or E2, look closely first - is there any chance of a simple acid-base reaction? For instance, take NaOH plus an alkyl thiol, R\u2013SH. Is it an SN2? Or possibly an E2? Both are incorrect. The reaction that happens is the simplest one - deprotonation of SH, to provide water and the deprotonated thiol. Also, the pKa table tells you about leaving group ability. Good leaving groups are weak bases!\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.masterorganicchemistry.com\/2010\/06\/18\/know-your-pkas\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The pKa Table Is Your Friend\" \/>\n<meta property=\"og:description\" content=\"Why are pKas so important? Because every nucleophile is potentially a base, and vice versa. If you have a reaction where it looks like you might get SN2 or E2, look closely first - is there any chance of a simple acid-base reaction? For instance, take NaOH plus an alkyl thiol, R\u2013SH. Is it an SN2? Or possibly an E2? Both are incorrect. The reaction that happens is the simplest one - deprotonation of SH, to provide water and the deprotonated thiol. Also, the pKa table tells you about leaving group ability. Good leaving groups are weak bases!\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.masterorganicchemistry.com\/2010\/06\/18\/know-your-pkas\/\" \/>\n<meta property=\"og:site_name\" content=\"Master Organic Chemistry\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/Master-Organic-Chemistry-242610599108055\/\" \/>\n<meta property=\"article:published_time\" content=\"2010-06-18T19:53:41+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-05-03T12:38:56+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/11\/1-pka-table-long-going-from-strongest-to-weakest-acid-introductory-organic-chemistry-showing-conjugate-bases.gif\" \/>\n\t<meta property=\"og:image:width\" content=\"740\" \/>\n\t<meta property=\"og:image:height\" content=\"1980\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/gif\" \/>\n<meta name=\"author\" content=\"James Ashenhurst\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"James Ashenhurst\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"5 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/\"},\"author\":{\"name\":\"James Ashenhurst\",\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/#\\\/schema\\\/person\\\/78d83ec7d02b4b7365bade2cedaef80c\"},\"headline\":\"The pKa Table Is Your Friend\",\"datePublished\":\"2010-06-18T19:53:41+00:00\",\"dateModified\":\"2026-05-03T12:38:56+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/\"},\"wordCount\":531,\"commentCount\":27,\"publisher\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/wp-content\\\/uploads\\\/2019\\\/11\\\/1-pka-table-long-going-from-strongest-to-weakest-acid-introductory-organic-chemistry-showing-conjugate-bases.gif\",\"keywords\":[\"acidity\",\"basicity\",\"conjugate acid\",\"conjugate base\",\"pKas\",\"stability\",\"strong acids\",\"strong bases\",\"tables\"],\"articleSection\":[\"Acid Base Reactions\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/\",\"url\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/\",\"name\":\"The pKa Table Is Your Friend\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/2010\\\/06\\\/18\\\/know-your-pkas\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.masterorganicchemistry.com\\\/wp-content\\\/uploads\\\/2019\\\/11\\\/1-pka-table-long-going-from-strongest-to-weakest-acid-introductory-organic-chemistry-showing-conjugate-bases.gif\",\"datePublished\":\"2010-06-18T19:53:41+00:00\",\"dateModified\":\"2026-05-03T12:38:56+00:00\",\"description\":\"Why are pKas so important? Because every nucleophile is potentially a base, and vice versa. If you have a reaction where it looks like you might get SN2 or E2, look closely first - is there any chance of a simple acid-base reaction? For instance, take NaOH plus an alkyl thiol, R\u2013SH. Is it an SN2? Or possibly an E2? Both are incorrect. The reaction that happens is the simplest one - deprotonation of SH, to provide water and the deprotonated thiol. Also, the pKa table tells you about leaving group ability. 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Good leaving groups are weak bases!","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.masterorganicchemistry.com\/2010\/06\/18\/know-your-pkas\/","og_locale":"en_US","og_type":"article","og_title":"The pKa Table Is Your Friend","og_description":"Why are pKas so important? Because every nucleophile is potentially a base, and vice versa. If you have a reaction where it looks like you might get SN2 or E2, look closely first - is there any chance of a simple acid-base reaction? For instance, take NaOH plus an alkyl thiol, R\u2013SH. Is it an SN2? Or possibly an E2? Both are incorrect. The reaction that happens is the simplest one - deprotonation of SH, to provide water and the deprotonated thiol. Also, the pKa table tells you about leaving group ability. 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