{"id":258939,"date":"2025-07-18T15:20:16","date_gmt":"2025-07-18T15:20:16","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=258939"},"modified":"2025-07-18T15:20:18","modified_gmt":"2025-07-18T15:20:18","slug":"fully-annotate-the-ir-spectra-for-benzophenone","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/18\/fully-annotate-the-ir-spectra-for-benzophenone\/","title":{"rendered":"Fully annotate the IR spectra for benzophenone."},"content":{"rendered":"\n<p>Fully annotate the IR spectra for benzophenone. Chem 3112 Grignard IR Benzophenone $6 90 85 175.7 1075.92CT 80 1575.51cm- 75 93 1593.72cm 1447.72cm 70 764 0% 65 1321.75cm 60 1650.23cm-1 1275.19cm-1 55 50 45 7027cm 40 3500 3000 2500 cm-1 2000 1500 1000 650<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/07\/image-530.png\" alt=\"\" class=\"wp-image-258940\"\/><\/figure>\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<p>Here is the annotation of the major peaks in the IR spectrum of benzophenone:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>3055.76 cm\u207b\u00b9:<\/strong>\u00a0Aromatic C-H stretch (sp\u00b2 C-H)<\/li>\n\n\n\n<li><strong>1650.23 cm\u207b\u00b9:<\/strong>\u00a0C=O stretch (conjugated ketone)<\/li>\n\n\n\n<li><strong>1593.72 cm\u207b\u00b9, 1575.51 cm\u207b\u00b9, 1447.72 cm\u207b\u00b9:<\/strong>\u00a0Aromatic C=C ring stretching<\/li>\n\n\n\n<li><strong>1321.75 cm\u207b\u00b9, 1275.19 cm\u207b\u00b9:<\/strong>\u00a0Ph-C(O)-Ph stretch and C-H in-plane bending<\/li>\n\n\n\n<li><strong>764.49 cm\u207b\u00b9, 692.79 cm\u207b\u00b9:<\/strong>\u00a0Aromatic C-H out-of-plane (OOP) bending for monosubstituted ring<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation of the Spectrum<\/h3>\n\n\n\n<p>The provided infrared spectrum is fully consistent with the structure of benzophenone, (C\u2086H\u2085)\u2082CO. A detailed analysis of the absorption peaks confirms the presence of its key functional groups.<\/p>\n\n\n\n<p>The region above 3000 cm\u207b\u00b9 is crucial for identifying C-H bonds. The peak observed at&nbsp;<strong>3055.76 cm\u207b\u00b9<\/strong>&nbsp;is characteristic of C-H stretching vibrations where the carbon atom is sp\u00b2 hybridized. This confirms the presence of the aromatic rings in benzophenone. The absence of any significant peaks in the 2850-3000 cm\u207b\u00b9 range correctly indicates that there are no aliphatic (sp\u00b3 C-H) groups in the molecule.<\/p>\n\n\n\n<p>The most intense and diagnostically significant peak in the spectrum is the sharp absorption at&nbsp;<strong>1650.23 cm\u207b\u00b9<\/strong>. This signal is assigned to the C=O (carbonyl) stretching vibration of the ketone functional group. For a simple, non-conjugated ketone, this peak would typically appear around 1715 cm\u207b\u00b9. The lower frequency observed here is due to resonance; the carbonyl group is conjugated with both phenyl rings. This electron delocalization weakens the C=O double bond, requiring less energy to stretch, and thus lowers its absorption frequency.<\/p>\n\n\n\n<p>The series of sharp absorptions in the 1600-1450 cm\u207b\u00b9 region, specifically at&nbsp;<strong>1593.72 cm\u207b\u00b9, 1575.51 cm\u207b\u00b9, and 1447.72 cm\u207b\u00b9<\/strong>, are characteristic of C=C stretching vibrations within the aromatic rings, often referred to as ring breathing modes.<\/p>\n\n\n\n<p>Finally, the fingerprint region below 1000 cm\u207b\u00b9 provides evidence for the substitution pattern of the aromatic rings. Benzophenone contains two monosubstituted phenyl rings. The two strong peaks at&nbsp;<strong>764.49 cm\u207b\u00b9<\/strong>&nbsp;and&nbsp;<strong>692.79 cm\u207b\u00b9<\/strong>&nbsp;correspond to the C-H out-of-plane (OOP) bending vibrations that are highly characteristic of monosubstitution on a benzene ring. The absence of a broad O-H stretch (3200-3600 cm\u207b\u00b9) further confirms the identity and purity of the benzophenone product, especially in the context of a Grignard reaction where an alcohol could be a byproduct.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/07\/learnexams-banner9-272.jpeg\" alt=\"\" class=\"wp-image-258941\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Fully annotate the IR spectra for benzophenone. Chem 3112 Grignard IR Benzophenone $6 90 85 175.7 1075.92CT 80 1575.51cm- 75 93 1593.72cm 1447.72cm 70 764 0% 65 1321.75cm 60 1650.23cm-1 1275.19cm-1 55 50 45 7027cm 40 3500 3000 2500 cm-1 2000 1500 1000 650 The Correct Answer and Explanation is: Here is the annotation of [&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-258939","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/258939","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=258939"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/258939\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=258939"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=258939"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=258939"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}