Aldehydes Ketones Question 112
Question: Which of the following has the most acidic hydrogen
[IIT-JEE (Screening) 2000]
Options:
A) 3-hexanone
B) 2, 4-hexanedione
C) 2, 5-hexanedione
D) 2, 3-hexanedione
Show Answer
Answer:
Correct Answer: B
Solution:
2, 4-hexanedione (a 1, 3-diketone) has the most acidic hydrogen. This is because the carbanion left after the removal of $ {H^{+}} $ is resonance stabilised in this case. $ \underset{2,4-Hexanedione}{\mathop{CH_3-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH_2-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH_2CH_3}}\underset{-H_2O}{\mathop{\xrightarrow{O{H^{-}}}}} $
$ CH_3-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-\overset{-}{\mathop{C}}H-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH_2CH_3 $
$ CH_3-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-\overset{-}{\mathop{C}}H-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH_2CH_3 $
$ rightarrow CH_3-\overset{{O^{-}}}{\mathop{\overset{|}{\mathop{C}}}}=CH-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH_2CH_3 $
$ rightarrow CH_3-\overset{O}{\mathop{\overset{||}{\mathop{C}}}}-CH=\overset{{O^{-}}}{\mathop{\overset{|}{\mathop{C}}}}-CH_2CH_3 $
BETA
