|MadSci Network: Chemistry|
Both, aldehydes and ketones, contain a carbonyl group ( that is carbon bonded to an oxygen with a double bond: >C=O ). The reaction with hydrogen cyanide is a typical example for addition to this group. In the course of the reaction the hydrogen cyanide adds in such a manner that the cyano group attaches to the carbon, and the hydrogen attaches to the oxygen of the carbonyl group: As you can see, in the end product the hydroxy and the cyano group are both attached to the same carbon atom. For most of the nitriles the carbon atom of the CN group is numbered as the first atom of the main chain. Therefore, the “2” refers to the number of the carbon atom to which the hydroxy group is attached. It is almost always “2”, except for some complex molecules. Here are some examples that might make the numbering clearer: (Sometmes the 2-hydroxynitriles are also called “cyanohydrines” or alpha- hydroxynitriles) A very good site to acquaint yourself with the rules for naming of the organic compounds is: http://www.sci.ouc.bc.ca/chem/nomenclature/index-2.htm From the above link you can learn how to determine which is the main carbon chain in a molecule and how to number it.
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