{"id":222367,"date":"2025-05-31T09:29:54","date_gmt":"2025-05-31T09:29:54","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=222367"},"modified":"2025-05-31T09:29:56","modified_gmt":"2025-05-31T09:29:56","slug":"when-looking-at-the-ir-spectra-of-benzoin-staring-material-which-absorptions-would-you-expect-to-change-significantly-after-oxidation-via-concentrated-nitric-acid","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/31\/when-looking-at-the-ir-spectra-of-benzoin-staring-material-which-absorptions-would-you-expect-to-change-significantly-after-oxidation-via-concentrated-nitric-acid\/","title":{"rendered":"When looking at the IR spectra of benzoin staring material, which absorptions would you expect to change significantly after oxidation via concentrated nitric acid"},"content":{"rendered":"\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/05\/image-565.png\" alt=\"\" class=\"wp-image-222368\"\/><\/figure>\n\n\n\n<p>When looking at the IR spectra of benzoin staring material, which absorptions would you expect to change significantly after oxidation via concentrated nitric acid? Percent Transmission (Transmitance)<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>0.8<\/li>\n\n\n\n<li>0.6<\/li>\n\n\n\n<li>0.4<\/li>\n\n\n\n<li>0.2<\/li>\n\n\n\n<li>0.0<\/li>\n<\/ul>\n\n\n\n<p>1680 cm-1 2900 cm-1 3000-3100 cm-1 3000 3400 cm-1 BENZOIN Wavenumber (cm-1) NIST Chemistry WebBook (https:\/\/webbook.nist.gov\/chemistry) INFRARED SPECTRUM<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>2000<\/li>\n\n\n\n<li>1000<\/li>\n<\/ul>\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><strong>Correct Answer:<\/strong><\/p>\n\n\n\n<p>\u2705 <strong>1680 cm\u207b\u00b9<\/strong><br>\u2705 <strong>3400 cm\u207b\u00b9<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Explanation<\/strong><\/h3>\n\n\n\n<p>The infrared (IR) spectrum of <strong>benzoin<\/strong>, a molecule containing both a hydroxyl (-OH) group and a carbonyl (C=O) group, shows characteristic absorptions that correspond to these functional groups.<\/p>\n\n\n\n<p>In the IR spectrum:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>broad peak around 3400 cm\u207b\u00b9<\/strong> corresponds to the <strong>O\u2013H stretching vibration<\/strong> from the hydroxyl group in benzoin.<\/li>\n\n\n\n<li>The <strong>absorption around 1680 cm\u207b\u00b9<\/strong> is due to the <strong>C=O stretching vibration<\/strong> of the ketone group in benzoin.<\/li>\n<\/ul>\n\n\n\n<p>When benzoin is <strong>oxidized using concentrated nitric acid<\/strong>, it is typically converted into <strong>benzil<\/strong>, which contains <strong>two ketone (C=O) groups<\/strong> but <strong>no hydroxyl group<\/strong>.<\/p>\n\n\n\n<p>As a result, the following changes are expected in the IR spectrum:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>3400 cm\u207b\u00b9 (O\u2013H stretch)<\/strong>:\n<ul class=\"wp-block-list\">\n<li>This peak will <strong>disappear or significantly decrease<\/strong> because the hydroxyl group is oxidized to a carbonyl group.<\/li>\n\n\n\n<li>Therefore, this absorption will <strong>change significantly<\/strong> after oxidation.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>1680 cm\u207b\u00b9 (C=O stretch)<\/strong>:\n<ul class=\"wp-block-list\">\n<li>The intensity of this peak will <strong>increase<\/strong>, and the position may shift slightly depending on conjugation and environment, since there will be <strong>two C=O groups<\/strong> instead of one.<\/li>\n\n\n\n<li>This region will <strong>change significantly<\/strong> due to increased carbonyl content.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p>On the other hand:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>2900 cm\u207b\u00b9<\/strong>: This corresponds to C\u2013H stretching, which is <strong>not significantly affected<\/strong> by oxidation.<\/li>\n\n\n\n<li><strong>3000\u20133100 cm\u207b\u00b9<\/strong>: This region typically corresponds to aromatic C\u2013H stretches and may show little to <strong>no significant change<\/strong> during oxidation since the aromatic system remains intact.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Conclusion:<\/strong><\/h3>\n\n\n\n<p>The <strong>major spectral changes<\/strong> occur in the <strong>1680 cm\u207b\u00b9 and 3400 cm\u207b\u00b9<\/strong> regions due to the oxidation of the hydroxyl group to a second carbonyl. Thus, those are the correct regions to expect significant changes after oxidation.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/05\/learnexams-banner4-196.jpeg\" alt=\"\" class=\"wp-image-222369\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>When looking at the IR spectra of benzoin staring material, which absorptions would you expect to change significantly after oxidation via concentrated nitric acid? Percent Transmission (Transmitance) 1680 cm-1 2900 cm-1 3000-3100 cm-1 3000 3400 cm-1 BENZOIN Wavenumber (cm-1) NIST Chemistry WebBook (https:\/\/webbook.nist.gov\/chemistry) INFRARED SPECTRUM The Correct Answer and Explanation is: Correct Answer: \u2705 1680 [&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-222367","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/222367","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=222367"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/222367\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=222367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=222367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=222367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}