How do you draw enols?

1 Answer
anor277
May 10, 2016

By pushing electrons around (and displacing a proton).

Explanation:

As you know, the formation of enolates is the prime stratgy to make carbon-carbon bonds. Enolates are the anions of enols, which typically form from 1,3-dicarbonyls:

#RC(=O)CH_2C(=O)RrightleftharpoonsRC(=O)CH=C(-OH)R#

The neutral enol can form an unsaturated 6-membered ring stabilized by hydrogen bonding; i.e. the enolic hydrogen binds to the other carbonyl oxygen. This enolic hydrogen is potentially acidic, and can be removed by a base. Now of course, in the resultant enolate, the species could react as an #O# nucleophile (i.e. the negative charge is on the oxygen, #RC(=O)CH=C(-O^-)R#, but given the delocalization of the negative charge, it typically reacts as a carbon nucleophile, #RC(=O)C^(-)(H)C(=O)R#,

It is worthwhile reviewing your text and your lecture notes to get what is going on here completely clear.

Note that all ketones and aldehydes form enols; but given a 1,3-diketone, enol formation is facile for the reasons advanced here.

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