Question #6902a

1 Answer
Feb 7, 2016

A and C are not tautomeric pairs.

Explanation:

Keto–enol tautomerism is a chemical equilibrium between a the carbonyl group of an aldehyde or ketone and its enol (an alcohol on a double bonded carbon).

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The equilibrium involves the movement of an alpha hydrogen to the carbonyl oxygen and the movement of electrons to form the #"C=C"# bond.

(A) 3-Methylpentan-2- one and 3-methylpentan-3-ol

(A)

These are not tautomers. The first is a ketone (which can form an enol), but the second is an alcohol.

(B) Ethenol and ethanal

(b)

These are a tautomeric pair. The second is an aldehyde, and the first is its enol.

(C) Propan-2-ol and prop-1-en-2-ol

(C)

These are not tautomers. The second is an enol, but the first is an alcohol.

(D) Pentane-2,4-dione and pent-3-en-4-ol-2-one

(D)

These are a tautomeric pair. The first is a ketone and the second is its enol.