Chemistry - STRUCTURAL ISOMERISM Question with Solution | TestHub
Draw the most stable enol tautomers for each of the following compounds.
(a) 
(b) 
(c) 
(d) 
(e) 
Options:
Answer:
Solution:
(a) Propiophenone has only one enolisable alpha position (the ; the phenyl side carries no alpha hydrogen), giving 1-phenylprop-1-en-1-ol :
(b) Cyclopentanone gives cyclopent-1-en-1-ol :
(c) 1-Phenylbutan-2-one has two alpha positions; enolisation toward the benzyl side gives the most stable enol, because the is conjugated with the benzene ring :
(d) Hexane-2,4-dione enolises at the central ; the resulting enol is conjugated with the second carbonyl and locked by a strong intramolecular hydrogen bond, so it is the most stable :
(e) The spiro ketone enolises toward the spiro carbon; the resulting double bond is conjugated with the cyclopropane ring (sigma conjugation), making it the most stable enol :
