{"id":232324,"date":"2025-06-11T23:01:22","date_gmt":"2025-06-11T23:01:22","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=232324"},"modified":"2025-06-11T23:01:25","modified_gmt":"2025-06-11T23:01:25","slug":"choose-the-correct-compound-for-the-given-ir-spectrum-2","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/06\/11\/choose-the-correct-compound-for-the-given-ir-spectrum-2\/","title":{"rendered":"Choose the correct compound for the given IR spectrum."},"content":{"rendered":"\n<p>Choose the correct compound for the given IR spectrum. % Transmittance 100 80 60 40 20 0 4000 3500 3000 2500 2000 The correct compound is HO OH OH 1500 1000 Wavenumber (cm<br>) SUPP -\/1<\/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\/image-386.png\" alt=\"\" class=\"wp-image-232325\"\/><\/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><strong>Analysis of the IR Spectrum:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Broad O-H Stretch (Carboxylic Acid):<\/strong>\u00a0The most prominent feature is the extremely broad and strong absorption that spans from approximately 3300 cm\u207b\u00b9 down to 2500 cm\u207b\u00b9. This characteristic &#8220;hairy beard&#8221; shape, which overlaps with the C-H stretching region, is the definitive signature of the O-H stretching vibration in a hydrogen-bonded carboxylic acid. The extensive hydrogen bonding in carboxylic acid dimers causes this significant peak broadening.<\/li>\n\n\n\n<li><strong>C(sp\u00b3)-H Stretch:<\/strong>\u00a0There are sharp peaks just below 3000 cm\u207b\u00b9 (around 2950-2850 cm\u207b\u00b9). These absorptions are due to the stretching vibrations of C-H bonds where the carbon atom is sp\u00b3-hybridized (i.e., saturated carbons).<\/li>\n\n\n\n<li><strong>C=O (Carbonyl) Stretch:<\/strong>\u00a0A very strong and sharp absorption peak is observed at approximately 1710 cm\u207b\u00b9. This is characteristic of a C=O carbonyl stretch. Its position is consistent with that of a saturated carboxylic acid, which typically absorbs in the 1700-1725 cm\u207b\u00b9 range.<\/li>\n\n\n\n<li><strong>Fingerprint Region:<\/strong>\u00a0There are additional peaks below 1500 cm\u207b\u00b9, including a C-O stretch (around 1300-1200 cm\u207b\u00b9) and a broad O-H bend (around 920 cm\u207b\u00b9), which further support the presence of a carboxylic acid.<\/li>\n<\/ol>\n\n\n\n<p><strong>Evaluation of the Options:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>First compound (A dicarboxylic acid, likely malonic or succinic acid):<\/strong>\u00a0This molecule contains two carboxylic acid (-COOH) functional groups and saturated C(sp\u00b3)-H bonds. This structure is perfectly consistent with all the major peaks identified in the spectrum: the very broad O-H stretch, the strong C=O stretch at ~1710 cm\u207b\u00b9, and the C(sp\u00b3)-H stretches.<\/li>\n\n\n\n<li><strong>Second compound (An alkene):<\/strong>\u00a0This molecule contains C=C double bonds and C-H bonds (both sp\u00b2 and sp\u00b3). It lacks both the O-H and C=O functional groups. Its spectrum would show C(sp\u00b2)-H stretches above 3000 cm\u207b\u00b9 and a C=C stretch around 1650 cm\u207b\u00b9, but none of the key features observed.<\/li>\n\n\n\n<li><strong>Third compound (An ester):<\/strong>\u00a0This molecule has a C=O group and C(sp\u00b3)-H bonds. While it would show a strong C=O peak (typically higher, around 1735-1750 cm\u207b\u00b9) and C-H stretches, it completely lacks an O-H group and therefore would not have the very broad absorption from 3300-2500 cm\u207b\u00b9.<\/li>\n\n\n\n<li><strong>Fourth compound (An alcohol):<\/strong>\u00a0This molecule has an O-H group and C(sp\u00b3)-H bonds. It would show a broad O-H stretch (typically centered around 3300 cm\u207b\u00b9) and C-H stretches. However, it lacks a C=O group, so the strong peak at 1710 cm\u207b\u00b9 would be absent.<\/li>\n<\/ul>\n\n\n\n<p><strong>Conclusion:<\/strong><\/p>\n\n\n\n<p>The simultaneous presence of a very broad O-H stretch (3300-2500 cm\u207b\u00b9) and a strong C=O stretch (~1710 cm\u207b\u00b9) is conclusive evidence for a carboxylic acid functional group. Among the given choices, only the first compound is a carboxylic acid.<\/p>\n\n\n\n<p>The correct compound is:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>O        O\n      \/\/       \/\/\nHO - C - CH\u2082 - C - OH<\/code><\/pre>\n\n\n\n<p>content_copydownloadUse code\u00a0<\/p>\n\n\n\n<p>(This specific structure is malonic acid, a dicarboxylic acid, which fits the spectral data.)<\/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-banner9-258.jpeg\" alt=\"\" class=\"wp-image-232326\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Choose the correct compound for the given IR spectrum. % Transmittance 100 80 60 40 20 0 4000 3500 3000 2500 2000 The correct compound is HO OH OH 1500 1000 Wavenumber (cm) SUPP -\/1 The Correct Answer and Explanation is: Analysis of the IR Spectrum: Evaluation of the Options: Conclusion: The simultaneous presence 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 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