{"id":6170,"date":"2014-06-17T12:05:37","date_gmt":"2014-06-17T19:05:37","guid":{"rendered":"http:\/\/blogs.reed.edu\/chemistry201-202-test\/?page_id=6170"},"modified":"2023-06-05T13:48:17","modified_gmt":"2023-06-05T20:48:17","slug":"ir-characteristic-vibration-frequencies","status":"publish","type":"page","link":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/appendices\/nmr-ir-tables\/ir-characteristic-vibration-frequencies\/","title":{"rendered":"IR Characteristic Vibration Frequencies"},"content":{"rendered":"<p>Complex molecules produce a rich assortment of IR bands, but only a few of these can be assigned with confidence. The easiest bands to assign are the ones that appear between 1500-4000 cm<sup>-1<\/sup>. These bands are usually due to one of three kinds of groups: XH, double bonded XY, and triple bonded XY. Characteristic frequencies (in cm<sup>-1<\/sup>)   for the most important categories are listed below.<\/p>\n<ul>\n<li><strong>OH (alcohol)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3650-3580 (&#8220;free&#8221;; often sharp)<\/li>\n<li>3550-3200 (hydrogen-bonded; often &#8220;U&#8221; shaped)<\/li>\n<\/ul>\n<li><strong>OH (carboxylic acid)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3300-2500 (very broad, strong, and c entered near 3000)<\/li>\n<\/ul>\n<li><strong>NH<\/strong> and <strong>NH<sub>2<\/sub> (amine)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3500 + 3400 (&#8220;free&#8221; NH<sub>2<\/sub>; often &#8220;V&#8221; shaped)<\/li>\n<li>3400-3330 + 3330-3250 (hydrogen-bonded NH<sub>2<\/sub>)<\/li>\n<li>3350-3310 (NH; weak, often &#8220;V&#8221; shaped)<\/li>\n<\/ul>\n<li><strong>CH (alkyne)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3330-3260 (strong, sharp)<\/li>\n<\/ul>\n<li><strong>CH (benzene)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3100-3000 (weak)<\/li>\n<\/ul>\n<li><strong>CH<sub>n<\/sub> (alkane)<\/strong><\/li>\n<ul type=\"circle\">\n<li>3000-2840 (weak, but they add up)<\/li>\n<\/ul>\n<li><strong>CN <i>triple<\/i><\/strong><strong> bond<\/strong><\/li>\n<ul type=\"circle\">\n<li>2300-2100 (medium, sharp)<\/li>\n<\/ul>\n<li><strong>CC <i>triple<\/i><\/strong><strong> bond<\/strong><\/li>\n<ul type=\"circle\">\n<li>2260-2100 (terminal, weak; internal, very weak)<\/li>\n<\/ul>\n<li><strong>C=O (aldehyde, ketone)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1740-1720 (1690-1670 if conjugated)<\/li>\n<\/ul>\n<li><strong>C=O (carboxylic acid)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1720-1700 (1710-1680 if conjugated)<\/li>\n<\/ul>\n<li><strong>C=O (ester, lactone)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1750-1735 (1730-1715 formate esters)<\/li>\n<\/ul>\n<li><strong>C=O (amide)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1700-1650<\/li>\n<\/ul>\n<li><strong>C=O (acid chloride)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1815-1770<\/li>\n<\/ul>\n<li><strong>C=O (anhydride)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1818 + 1750 (1775 + 1720 if conjugated)<\/li>\n<\/ul>\n<li><strong>C=C (alkene)<\/strong><\/li>\n<ul type=\"circle\">\n<li>1670-1640 (terminal, medium; internal, weak)<\/li>\n<\/ul>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Complex molecules produce a rich assortment of IR bands, but only a few of these can be assigned with confidence. The easiest bands to assign are the ones that appear between 1500-4000 cm-1. These bands are usually due to one of three kinds of groups: XH, double bonded XY, and triple bonded XY. Characteristic frequencies &hellip; <a href=\"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/appendices\/nmr-ir-tables\/ir-characteristic-vibration-frequencies\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;IR Characteristic Vibration Frequencies&#8221;<\/span><\/a><\/p>\n","protected":false},"author":316,"featured_media":0,"parent":6164,"menu_order":3,"comment_status":"closed","ping_status":"closed","template":"page-child.php","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-6170","page","type-page","status-publish","hentry"],"acf":[],"featured_image_src":null,"_links":{"self":[{"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/pages\/6170","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/users\/316"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/comments?post=6170"}],"version-history":[{"count":5,"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/pages\/6170\/revisions"}],"predecessor-version":[{"id":6787,"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/pages\/6170\/revisions\/6787"}],"up":[{"embeddable":true,"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/pages\/6164"}],"wp:attachment":[{"href":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/wp-json\/wp\/v2\/media?parent=6170"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}