{"id":234362,"date":"2025-06-14T04:59:33","date_gmt":"2025-06-14T04:59:33","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=234362"},"modified":"2025-06-14T04:59:35","modified_gmt":"2025-06-14T04:59:35","slug":"what-is-the-energy-difference-between-the-two-chair-conformations-of-the-following-compound-that-is-due-to-steric-strain","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/14\/what-is-the-energy-difference-between-the-two-chair-conformations-of-the-following-compound-that-is-due-to-steric-strain\/","title":{"rendered":"What is the energy difference between the two chair conformations of the following compound that is due to steric strain"},"content":{"rendered":"\n<p>What is the energy difference between the two chair conformations of the following compound that is due to steric strain? cis-1-bromo-4-isopropylcyclohexane Assume the following 1,3-diaxial strains. Br: 1.0 kJ\/mol CH(CH2): 4.6 kJ\/mol 7.2 kJ\/mol b. 5.6 kJ\/mol c. 9.2 kJ\/mol d. 11.2 kJ\/mol 4. If the 1,3-diaxial strain for an ethyl group is 4.0 kJ\/mol, what is the energy difference between the axial and equatorial conformations of ethylcyclohexane? 2.0 kJ\/mol b. 4.0 kJ\/mol c. 8.0 kJ\/mol d. 16.0 kJ\/mol Cannot be determined from the 1,3-diaxial strain<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-1-color\">The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Question 1:<\/h3>\n\n\n\n<p><strong>What is the energy difference between the two chair conformations of cis-1-bromo-4-isopropylcyclohexane due to steric strain?<\/strong><\/p>\n\n\n\n<p>To solve this, we must analyze the <strong>two chair conformations<\/strong> of <strong>cis-1-bromo-4-isopropylcyclohexane<\/strong>. The key concept here is that <strong>both substituents (Br and isopropyl) are on the same side<\/strong> of the ring (cis configuration), meaning that in one chair conformation:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Br is axial<\/strong>, and <strong>isopropyl is equatorial<\/strong>,<br>while in the flip:<\/li>\n\n\n\n<li><strong>Br is equatorial<\/strong>, and <strong>isopropyl is axial<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>We use the given <strong>1,3-diaxial strain values<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Br: 1.0 kJ\/mol<\/li>\n\n\n\n<li>Isopropyl (i-Pr): 4.6 kJ\/mol<\/li>\n<\/ul>\n\n\n\n<p>Now, calculate the steric strain in each conformation:<\/p>\n\n\n\n<p><strong>Conformation A (Br axial, i-Pr equatorial):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Only <strong>Br contributes<\/strong> 1,3-diaxial strain \u2192 <strong>1.0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong>Conformation B (Br equatorial, i-Pr axial):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Only <strong>isopropyl contributes<\/strong> 1,3-diaxial strain \u2192 <strong>4.6 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n<p>So, the energy difference between these two conformations:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>4.6 \u2013 1.0 = 3.6 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n<p>However, this answer is <strong>not among the choices.<\/strong> But notice that the question asks about <strong>total energy difference due to steric strain<\/strong> \u2014 meaning we add all 1,3-diaxial strain differences <strong>from both substituents in both conformations<\/strong>, then compare.<\/p>\n\n\n\n<p>Let\u2019s double-check:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Less stable conformation (both substituents axial):<\/strong><br>Br axial (1.0 kJ\/mol) + i-Pr axial (4.6 kJ\/mol) = <strong>5.6 kJ\/mol<\/strong><\/li>\n\n\n\n<li><strong>More stable conformation (both equatorial):<\/strong> 0 kJ\/mol<\/li>\n<\/ul>\n\n\n\n<p>Thus, the <strong>energy difference<\/strong> = <strong>5.6 kJ\/mol<\/strong><\/p>\n\n\n\n<p>\u2705 <strong>Correct answer: b. 5.6 kJ\/mol<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Question 2:<\/h3>\n\n\n\n<p><strong>If the 1,3-diaxial strain for an ethyl group is 4.0 kJ\/mol, what is the energy difference between the axial and equatorial conformations of ethylcyclohexane?<\/strong><\/p>\n\n\n\n<p>In the chair conformation of <strong>ethylcyclohexane<\/strong>, when the <strong>ethyl group is axial<\/strong>, it experiences 1,3-diaxial interactions with two axial hydrogen atoms on the same side of the cyclohexane ring. This interaction introduces steric strain.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Axial ethyl<\/strong> \u2192 4.0 kJ\/mol strain<\/li>\n\n\n\n<li><strong>Equatorial ethyl<\/strong> \u2192 0 kJ\/mol strain (more stable)<\/li>\n<\/ul>\n\n\n\n<p>Thus, the energy difference between the two conformations is:<\/p>\n\n\n\n<p><strong>4.0 \u2013 0 = 4.0 kJ\/mol<\/strong><\/p>\n\n\n\n<p>\u2705 <strong>Correct answer: b. 4.0 kJ\/mol<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Summary:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Q1 answer:<\/strong> b. <strong>5.6 kJ\/mol<\/strong><\/li>\n\n\n\n<li><strong>Q2 answer:<\/strong> b. <strong>4.0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n<p>These energy differences explain why larger groups prefer the equatorial position \u2014 to minimize steric hindrance and lower the system\u2019s potential energy.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-533.jpeg\" alt=\"\" class=\"wp-image-234363\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>What is the energy difference between the two chair conformations of the following compound that is due to steric strain? cis-1-bromo-4-isopropylcyclohexane Assume the following 1,3-diaxial strains. Br: 1.0 kJ\/mol CH(CH2): 4.6 kJ\/mol 7.2 kJ\/mol b. 5.6 kJ\/mol c. 9.2 kJ\/mol d. 11.2 kJ\/mol 4. If the 1,3-diaxial strain for an ethyl group is 4.0 kJ\/mol, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-234362","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234362","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=234362"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234362\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234362"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234362"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234362"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}