(a) Chair Conformations of cis<\/em>-1-bromo-4-isopropylcyclohexane<\/strong><\/h3>\n\n\n\nSince the compound is cis<\/strong>, both substituents\u2014Br at C1<\/strong> and isopropyl at C4<\/strong>\u2014must be on the same side<\/strong> of the cyclohexane ring (both axial or both equatorial, depending on the chair flip).<\/p>\n\n\n\nThere are two possible chair conformations:<\/p>\n\n\n\n
Conformation 1:<\/strong><\/h4>\n\n\n\n\n- Br at C1 axial up<\/strong><\/li>\n\n\n\n
- Isopropyl at C4 axial up<\/strong><\/li>\n<\/ul>\n\n\n\n
Conformation 2 (Ring flip):<\/strong><\/h4>\n\n\n\n\n- Br at C1 equatorial down<\/strong><\/li>\n\n\n\n
- Isopropyl at C4 equatorial down<\/strong><\/li>\n<\/ul>\n\n\n\n
So in both conformations, the groups are cis (same side), but their positions (axial or equatorial) are different due to the ring flip.<\/p>\n\n\n\n
\n\n\n\n(b) Estimate of Strain in Each Conformation<\/strong><\/h3>\n\n\n\nWe estimate strain based on 1,3-diaxial interactions<\/strong> for axial groups. The A-values<\/strong> (energy cost of having a group in axial position) are:<\/p>\n\n\n\n\n- Bromine (Br):<\/strong> ~2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n
Conformation 1 (both axial):<\/strong><\/h4>\n\n\n\n\n- Br axial \u2192 +2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl axial \u2192 +9.2 kJ\/mol
Total strain = 11.2 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\nConformation 2 (both equatorial):<\/strong><\/h4>\n\n\n\n\n- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
Total strain = 0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n(c) Energy Difference Between the Two Conformations<\/strong><\/h3>\n\n\n\nEnergy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\\text{Energy difference} = 11.2\\ \\text{kJ\/mol} – 0\\ \\text{kJ\/mol} = \\boxed{11.2\\ \\text{kJ\/mol}}Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\u200b<\/p>\n\n\n\n
\n\n\n\n(d) More Stable Conformation<\/strong><\/h3>\n\n\n\nThe more stable<\/strong> conformation is the one in which both groups are equatorial<\/strong>, due to the absence of steric strain. Therefore, Conformation 2<\/strong> (with both Br and isopropyl equatorial) is more stable<\/strong> by 11.2 kJ\/mol<\/strong>.<\/p>\n\n\n\n
\n\n\n\nTextbook-Style Explanation<\/strong><\/h3>\n\n\n\nCyclohexane adopts a chair conformation to minimize torsional and angle strain. In substituted cyclohexanes, substituents can occupy axial (parallel to the ring’s vertical axis) or equatorial (around the ring’s equator) positions. The energy of the molecule varies depending on the substituent’s size and its position.<\/p>\n\n\n\n
In cis<\/em>-1-bromo-4-isopropylcyclohexane, both substituents must be on the same side of the ring. This can be achieved in two ways: both axial or both equatorial. In the first chair conformation, if bromine is axial up at C1, then to maintain the cis relationship, the isopropyl group must also be axial up at C4. This conformation suffers from 1,3-diaxial interactions, particularly from the large isopropyl group, which has a strong steric interaction with axial hydrogens on the same side of the ring. The estimated energy penalty (A-value) is approximately 9.2 kJ\/mol for isopropyl and 2.0 kJ\/mol for bromine, totaling 11.2 kJ\/mol.<\/p>\n\n\n\nIn the second chair conformation (ring flip), bromine becomes equatorial down and the isopropyl group also becomes equatorial down. Because equatorial positions minimize steric hindrance, this conformation is much more stable. Thus, the strain is significantly lower\u2014effectively 0 kJ\/mol for both groups.<\/p>\n\n\n\n
The energy difference between the two conformations is 11.2 kJ\/mol, favoring the conformation with both substituents equatorial. Therefore, the more stable form of cis<\/em>-1-bromo-4-isopropylcyclohexane is the one where both substituents are equatorial, minimizing steric strain and resulting in greater thermodynamic stability.<\/p>\n\n\n\n![\"\"](\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/06\/learnexams-banner5-532.jpeg\")
<\/figure>\n","protected":false},"excerpt":{"rendered":"Draw two chair conformations of cis-1-bromo-4-isopropylcyclohexane. (b) Estimate the amount of strain in each conformation in kJ\/mol. (c) What is the energy difference between them in kJ\/mol? (d) Indicate which is the more stable. The Correct Answer and Explanation is: (a) Chair Conformations of cis-1-bromo-4-isopropylcyclohexane Since the compound is cis, both substituents\u2014Br at C1 and […]<\/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-234358","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358","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=234358"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
There are two possible chair conformations:<\/p>\n\n\n\n
Conformation 1:<\/strong><\/h4>\n\n\n\n\n- Br at C1 axial up<\/strong><\/li>\n\n\n\n
- Isopropyl at C4 axial up<\/strong><\/li>\n<\/ul>\n\n\n\n
Conformation 2 (Ring flip):<\/strong><\/h4>\n\n\n\n\n- Br at C1 equatorial down<\/strong><\/li>\n\n\n\n
- Isopropyl at C4 equatorial down<\/strong><\/li>\n<\/ul>\n\n\n\n
So in both conformations, the groups are cis (same side), but their positions (axial or equatorial) are different due to the ring flip.<\/p>\n\n\n\n
\n\n\n\n(b) Estimate of Strain in Each Conformation<\/strong><\/h3>\n\n\n\nWe estimate strain based on 1,3-diaxial interactions<\/strong> for axial groups. The A-values<\/strong> (energy cost of having a group in axial position) are:<\/p>\n\n\n\n\n- Bromine (Br):<\/strong> ~2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n
Conformation 1 (both axial):<\/strong><\/h4>\n\n\n\n\n- Br axial \u2192 +2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl axial \u2192 +9.2 kJ\/mol
Total strain = 11.2 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\nConformation 2 (both equatorial):<\/strong><\/h4>\n\n\n\n\n- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
Total strain = 0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n(c) Energy Difference Between the Two Conformations<\/strong><\/h3>\n\n\n\nEnergy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\\text{Energy difference} = 11.2\\ \\text{kJ\/mol} – 0\\ \\text{kJ\/mol} = \\boxed{11.2\\ \\text{kJ\/mol}}Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\u200b<\/p>\n\n\n\n
\n\n\n\n(d) More Stable Conformation<\/strong><\/h3>\n\n\n\nThe more stable<\/strong> conformation is the one in which both groups are equatorial<\/strong>, due to the absence of steric strain. Therefore, Conformation 2<\/strong> (with both Br and isopropyl equatorial) is more stable<\/strong> by 11.2 kJ\/mol<\/strong>.<\/p>\n\n\n\n
\n\n\n\nTextbook-Style Explanation<\/strong><\/h3>\n\n\n\nCyclohexane adopts a chair conformation to minimize torsional and angle strain. In substituted cyclohexanes, substituents can occupy axial (parallel to the ring’s vertical axis) or equatorial (around the ring’s equator) positions. The energy of the molecule varies depending on the substituent’s size and its position.<\/p>\n\n\n\n
In cis<\/em>-1-bromo-4-isopropylcyclohexane, both substituents must be on the same side of the ring. This can be achieved in two ways: both axial or both equatorial. In the first chair conformation, if bromine is axial up at C1, then to maintain the cis relationship, the isopropyl group must also be axial up at C4. This conformation suffers from 1,3-diaxial interactions, particularly from the large isopropyl group, which has a strong steric interaction with axial hydrogens on the same side of the ring. The estimated energy penalty (A-value) is approximately 9.2 kJ\/mol for isopropyl and 2.0 kJ\/mol for bromine, totaling 11.2 kJ\/mol.<\/p>\n\n\n\nIn the second chair conformation (ring flip), bromine becomes equatorial down and the isopropyl group also becomes equatorial down. Because equatorial positions minimize steric hindrance, this conformation is much more stable. Thus, the strain is significantly lower\u2014effectively 0 kJ\/mol for both groups.<\/p>\n\n\n\n
The energy difference between the two conformations is 11.2 kJ\/mol, favoring the conformation with both substituents equatorial. Therefore, the more stable form of cis<\/em>-1-bromo-4-isopropylcyclohexane is the one where both substituents are equatorial, minimizing steric strain and resulting in greater thermodynamic stability.<\/p>\n\n\n\n<\/figure>\n","protected":false},"excerpt":{"rendered":"Draw two chair conformations of cis-1-bromo-4-isopropylcyclohexane. (b) Estimate the amount of strain in each conformation in kJ\/mol. (c) What is the energy difference between them in kJ\/mol? (d) Indicate which is the more stable. The Correct Answer and Explanation is: (a) Chair Conformations of cis-1-bromo-4-isopropylcyclohexane Since the compound is cis, both substituents\u2014Br at C1 and […]<\/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-234358","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358","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=234358"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Conformation 2 (Ring flip):<\/strong><\/h4>\n\n\n\n\n- Br at C1 equatorial down<\/strong><\/li>\n\n\n\n
- Isopropyl at C4 equatorial down<\/strong><\/li>\n<\/ul>\n\n\n\n
So in both conformations, the groups are cis (same side), but their positions (axial or equatorial) are different due to the ring flip.<\/p>\n\n\n\n
\n\n\n\n(b) Estimate of Strain in Each Conformation<\/strong><\/h3>\n\n\n\nWe estimate strain based on 1,3-diaxial interactions<\/strong> for axial groups. The A-values<\/strong> (energy cost of having a group in axial position) are:<\/p>\n\n\n\n\n- Bromine (Br):<\/strong> ~2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n
Conformation 1 (both axial):<\/strong><\/h4>\n\n\n\n\n- Br axial \u2192 +2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl axial \u2192 +9.2 kJ\/mol
Total strain = 11.2 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\nConformation 2 (both equatorial):<\/strong><\/h4>\n\n\n\n\n- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
Total strain = 0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n(c) Energy Difference Between the Two Conformations<\/strong><\/h3>\n\n\n\nEnergy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\\text{Energy difference} = 11.2\\ \\text{kJ\/mol} – 0\\ \\text{kJ\/mol} = \\boxed{11.2\\ \\text{kJ\/mol}}Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\u200b<\/p>\n\n\n\n
\n\n\n\n(d) More Stable Conformation<\/strong><\/h3>\n\n\n\nThe more stable<\/strong> conformation is the one in which both groups are equatorial<\/strong>, due to the absence of steric strain. Therefore, Conformation 2<\/strong> (with both Br and isopropyl equatorial) is more stable<\/strong> by 11.2 kJ\/mol<\/strong>.<\/p>\n\n\n\n
\n\n\n\nTextbook-Style Explanation<\/strong><\/h3>\n\n\n\nCyclohexane adopts a chair conformation to minimize torsional and angle strain. In substituted cyclohexanes, substituents can occupy axial (parallel to the ring’s vertical axis) or equatorial (around the ring’s equator) positions. The energy of the molecule varies depending on the substituent’s size and its position.<\/p>\n\n\n\n
In cis<\/em>-1-bromo-4-isopropylcyclohexane, both substituents must be on the same side of the ring. This can be achieved in two ways: both axial or both equatorial. In the first chair conformation, if bromine is axial up at C1, then to maintain the cis relationship, the isopropyl group must also be axial up at C4. This conformation suffers from 1,3-diaxial interactions, particularly from the large isopropyl group, which has a strong steric interaction with axial hydrogens on the same side of the ring. The estimated energy penalty (A-value) is approximately 9.2 kJ\/mol for isopropyl and 2.0 kJ\/mol for bromine, totaling 11.2 kJ\/mol.<\/p>\n\n\n\nIn the second chair conformation (ring flip), bromine becomes equatorial down and the isopropyl group also becomes equatorial down. Because equatorial positions minimize steric hindrance, this conformation is much more stable. Thus, the strain is significantly lower\u2014effectively 0 kJ\/mol for both groups.<\/p>\n\n\n\n
The energy difference between the two conformations is 11.2 kJ\/mol, favoring the conformation with both substituents equatorial. Therefore, the more stable form of cis<\/em>-1-bromo-4-isopropylcyclohexane is the one where both substituents are equatorial, minimizing steric strain and resulting in greater thermodynamic stability.<\/p>\n\n\n\n<\/figure>\n","protected":false},"excerpt":{"rendered":"Draw two chair conformations of cis-1-bromo-4-isopropylcyclohexane. (b) Estimate the amount of strain in each conformation in kJ\/mol. (c) What is the energy difference between them in kJ\/mol? (d) Indicate which is the more stable. The Correct Answer and Explanation is: (a) Chair Conformations of cis-1-bromo-4-isopropylcyclohexane Since the compound is cis, both substituents\u2014Br at C1 and […]<\/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-234358","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358","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=234358"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
So in both conformations, the groups are cis (same side), but their positions (axial or equatorial) are different due to the ring flip.<\/p>\n\n\n\n
\n\n\n\n
(b) Estimate of Strain in Each Conformation<\/strong><\/h3>\n\n\n\nWe estimate strain based on 1,3-diaxial interactions<\/strong> for axial groups. The A-values<\/strong> (energy cost of having a group in axial position) are:<\/p>\n\n\n\n\n- Bromine (Br):<\/strong> ~2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n
Conformation 1 (both axial):<\/strong><\/h4>\n\n\n\n\n- Br axial \u2192 +2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl axial \u2192 +9.2 kJ\/mol
Total strain = 11.2 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\nConformation 2 (both equatorial):<\/strong><\/h4>\n\n\n\n\n- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
Total strain = 0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n(c) Energy Difference Between the Two Conformations<\/strong><\/h3>\n\n\n\nEnergy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\\text{Energy difference} = 11.2\\ \\text{kJ\/mol} – 0\\ \\text{kJ\/mol} = \\boxed{11.2\\ \\text{kJ\/mol}}Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\u200b<\/p>\n\n\n\n
\n\n\n\n(d) More Stable Conformation<\/strong><\/h3>\n\n\n\nThe more stable<\/strong> conformation is the one in which both groups are equatorial<\/strong>, due to the absence of steric strain. Therefore, Conformation 2<\/strong> (with both Br and isopropyl equatorial) is more stable<\/strong> by 11.2 kJ\/mol<\/strong>.<\/p>\n\n\n\n
\n\n\n\nTextbook-Style Explanation<\/strong><\/h3>\n\n\n\nCyclohexane adopts a chair conformation to minimize torsional and angle strain. In substituted cyclohexanes, substituents can occupy axial (parallel to the ring’s vertical axis) or equatorial (around the ring’s equator) positions. The energy of the molecule varies depending on the substituent’s size and its position.<\/p>\n\n\n\n
In cis<\/em>-1-bromo-4-isopropylcyclohexane, both substituents must be on the same side of the ring. This can be achieved in two ways: both axial or both equatorial. In the first chair conformation, if bromine is axial up at C1, then to maintain the cis relationship, the isopropyl group must also be axial up at C4. This conformation suffers from 1,3-diaxial interactions, particularly from the large isopropyl group, which has a strong steric interaction with axial hydrogens on the same side of the ring. The estimated energy penalty (A-value) is approximately 9.2 kJ\/mol for isopropyl and 2.0 kJ\/mol for bromine, totaling 11.2 kJ\/mol.<\/p>\n\n\n\nIn the second chair conformation (ring flip), bromine becomes equatorial down and the isopropyl group also becomes equatorial down. Because equatorial positions minimize steric hindrance, this conformation is much more stable. Thus, the strain is significantly lower\u2014effectively 0 kJ\/mol for both groups.<\/p>\n\n\n\n
The energy difference between the two conformations is 11.2 kJ\/mol, favoring the conformation with both substituents equatorial. Therefore, the more stable form of cis<\/em>-1-bromo-4-isopropylcyclohexane is the one where both substituents are equatorial, minimizing steric strain and resulting in greater thermodynamic stability.<\/p>\n\n\n\n<\/figure>\n","protected":false},"excerpt":{"rendered":"Draw two chair conformations of cis-1-bromo-4-isopropylcyclohexane. (b) Estimate the amount of strain in each conformation in kJ\/mol. (c) What is the energy difference between them in kJ\/mol? (d) Indicate which is the more stable. The Correct Answer and Explanation is: (a) Chair Conformations of cis-1-bromo-4-isopropylcyclohexane Since the compound is cis, both substituents\u2014Br at C1 and […]<\/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-234358","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358","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=234358"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
- \n
- Bromine (Br):<\/strong> ~2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n
Conformation 1 (both axial):<\/strong><\/h4>\n\n\n\n
- \n
- Br axial \u2192 +2.0 kJ\/mol<\/li>\n\n\n\n
- Isopropyl axial \u2192 +9.2 kJ\/mol
Total strain = 11.2 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\nConformation 2 (both equatorial):<\/strong><\/h4>\n\n\n\n
- \n
- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
Total strain = 0 kJ\/mol<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n(c) Energy Difference Between the Two Conformations<\/strong><\/h3>\n\n\n\n
Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\\text{Energy difference} = 11.2\\ \\text{kJ\/mol} – 0\\ \\text{kJ\/mol} = \\boxed{11.2\\ \\text{kJ\/mol}}Energy difference=11.2 kJ\/mol\u22120 kJ\/mol=11.2 kJ\/mol\u200b<\/p>\n\n\n\n
\n\n\n\n(d) More Stable Conformation<\/strong><\/h3>\n\n\n\n
The more stable<\/strong> conformation is the one in which both groups are equatorial<\/strong>, due to the absence of steric strain. Therefore, Conformation 2<\/strong> (with both Br and isopropyl equatorial) is more stable<\/strong> by 11.2 kJ\/mol<\/strong>.<\/p>\n\n\n\n
\n\n\n\nTextbook-Style Explanation<\/strong><\/h3>\n\n\n\n
Cyclohexane adopts a chair conformation to minimize torsional and angle strain. In substituted cyclohexanes, substituents can occupy axial (parallel to the ring’s vertical axis) or equatorial (around the ring’s equator) positions. The energy of the molecule varies depending on the substituent’s size and its position.<\/p>\n\n\n\n
In cis<\/em>-1-bromo-4-isopropylcyclohexane, both substituents must be on the same side of the ring. This can be achieved in two ways: both axial or both equatorial. In the first chair conformation, if bromine is axial up at C1, then to maintain the cis relationship, the isopropyl group must also be axial up at C4. This conformation suffers from 1,3-diaxial interactions, particularly from the large isopropyl group, which has a strong steric interaction with axial hydrogens on the same side of the ring. The estimated energy penalty (A-value) is approximately 9.2 kJ\/mol for isopropyl and 2.0 kJ\/mol for bromine, totaling 11.2 kJ\/mol.<\/p>\n\n\n\n
In the second chair conformation (ring flip), bromine becomes equatorial down and the isopropyl group also becomes equatorial down. Because equatorial positions minimize steric hindrance, this conformation is much more stable. Thus, the strain is significantly lower\u2014effectively 0 kJ\/mol for both groups.<\/p>\n\n\n\n
The energy difference between the two conformations is 11.2 kJ\/mol, favoring the conformation with both substituents equatorial. Therefore, the more stable form of cis<\/em>-1-bromo-4-isopropylcyclohexane is the one where both substituents are equatorial, minimizing steric strain and resulting in greater thermodynamic stability.<\/p>\n\n\n\n
<\/figure>\n","protected":false},"excerpt":{"rendered":"Draw two chair conformations of cis-1-bromo-4-isopropylcyclohexane. (b) Estimate the amount of strain in each conformation in kJ\/mol. (c) What is the energy difference between them in kJ\/mol? (d) Indicate which is the more stable. The Correct Answer and Explanation is: (a) Chair Conformations of cis-1-bromo-4-isopropylcyclohexane Since the compound is cis, both substituents\u2014Br at C1 and […]<\/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-234358","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358","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=234358"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/234358\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=234358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=234358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=234358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
- Both Br and isopropyl are equatorial \u2192 0 kJ\/mol<\/strong>
- Isopropyl (i-Pr):<\/strong> ~9.2 kJ\/mol<\/li>\n<\/ul>\n\n\n\n