Answer:
Explanation:
Structure of the 2,2,4,4-tetramethyl-3-pentanone is give in the attachment
In 2,2,4,4-tetramethyl-3-pentanone, no alpha hydrogen is present, therefore, enol form is not possible and hence, exist only in keto form.
Explanation for existence of cyclohexa-2,4-diene-1-one only in enol form:
keto form of cyclohexa-2,4-diene-1-one not aromatic and hence less stable.
Whereas enol form it is aromatic which makes it highly stable. that's why cyclohexa-2,4-diene-1-one exists only in enol form.
