Enols

Enols

 

organic compounds with a hydroxyl group OH at a carbon-carbon double bond. The simplest enol is vinyl alcohol CH2=CHOH, which like most enols is unstable in the free state and changes into its isomer acetaldehyde:

The instability of enols is due to their being in tautomeric equilibrium with the corresponding carbonyl compounds:

Since the carbonyl form is energetically favored over the enol one by 54–71 kilojoules/mole (13–17 kcal/mole), equilibrium is usually displaced in the direction of formation of aldehydes and ketones. Thus acetone contains 2.5 x 10−4 percent enol and cyclohexanone 2.5 x 10−2 percent enol. However, in some cases the enol form is stable (for example, with β-diketones, β-ketoaldehydes, and cyclic α-diketones), because the energy difference is offset by energy gain owing to formation of a system of conjugated double bonds, as well as of a hydrogen bond owing to hydroxyl group formation. The enol content of an equilibrium mixture also depends on the solvent, temperature, and other factors.

References in periodicals archive ?
The chemicals that are produced at this point are flavor volatiles that include chemical compounds, such as alcohols, furans and enols, that contribute more and more to the overall caramel-like profile.
Sandia said the compounds, known as enols, were discovered using a new flame chemistry probe operated at the Advanced Light Source at Lawrence Berkeley National Laboratory.
Sandia noted that, the enols were discovered when the team was looking for signatures of different isomers in flames.
Enols are important reactive intermediates in organic chemistry.
Hydrogen bonding in the gaseous state of symmetrical organic acid dimers, mixed acid dimers, and enols has been investigated using molecular modeling.
Floris, The Chemistry of Enols, John Wiley and Sons, New York (1990).
The HPLC condition which was used in determination of poly phenols compounds was employed for 5 Determination of tocopherols and tocothree enols but with the different isocratic mobile phase: water, acetonitrile and methanol (47:47:4, v/v/v).
In all these cases the phosphoryl forms are at least by 10 kcal/mol more stable than the corresponding enols.
Part I The Reactions of Alcohols, Enols and Phenols: Oxidation Reduction, Substitution, Addition Elimination, and Rearrangement.
This review presents structures and describes cytotoxic activities of more than 100 acetylenic metabolites, including fatty alcohols, ketones, and acids, acetylenic cyclohexanoids, spiroketal enol ethers, and carotenoids isolated from fungi and plants.