Most organic compounds are transparent to the relatively high-energy radiation that\u00a0constitutes\u00a0the ultraviolet (200\u2013400 nm) and visible (400\u2013700 nm) portion of the electromagnetic spectrum, and consequently they appear colourless in solution. This is because the electrons in the \u03c3 bonds of organic molecules require wavelengths of even higher energy (such as those of X-rays) to excite them to the next higher accessible energy level. Electrons in \u03c0 bonds, however, can be promoted to higher energy levels by ultraviolet and visible light, and UV-visible spectroscopy consequently provides useful structural information for molecules that contain \u03c0 bonds. When multiple \u03c0 bonds are separated from each other by intervening single bonds, they are said to be\u00a0conjugated.<\/p>\n\n\n\n
The UV-visible spectrum of a molecule is dramatically affected by the presence of conjugation. As the number of conjugated \u03c0 bonds increases, the UV-visible spectrum shows light absorption at a greater number of different wavelengths (i.e., the spectrum contains more absorption peaks), and light of longer wavelengths (and lower energy) is absorbed. The many individual peaks of UV-visible spectra normally coalesce to produce a continuous absorption spectrum, with some of the strongest individual absorption peaks appearing as sharp spikes. For example, the UV-visible spectrum of azulene, a molecule that contains five conjugated \u03c0 bonds, shows a strong absorbance in the visible region of the electromagnetic spectrum, which\u00a0correlates\u00a0with its intense blue colour.<\/p>\n\n\n\n
Naturally occurring organic compounds that are highly coloured contain an extensive system of conjugated \u03c0 bonds. The compound largely responsible for the bright orange colour of carrots, \u03b2-carotene, contains 11 conjugated \u03c0 bonds. UV-visible spectroscopy is especially informative for molecules that contain conjugated \u03c0 bonds.<\/p>\n","protected":false},"excerpt":{"rendered":"
Most organic compounds are transparent to the relatively high-energy radiation that\u00a0constitutes\u00a0the ultraviolet (200\u2013400 nm) and visible (400\u2013700 nm) portion of the electromagnetic spectrum, and consequently they appear colourless in solution. This is because the electrons in the \u03c3 bonds of organic molecules require wavelengths of even higher energy (such as those of X-rays) to excite […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[],"class_list":["post-2161","post","type-post","status-publish","format-standard","hentry","category-organic-compounds"],"Cooking_time":"","jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/2161","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=2161"}],"version-history":[{"count":1,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/2161\/revisions"}],"predecessor-version":[{"id":2162,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/2161\/revisions\/2162"}],"wp:attachment":[{"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=2161"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=2161"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cake.appscodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=2161"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}