Question
Question: Which of the following group will react faster with H₂/Ni?...
Which of the following group will react faster with H₂/Ni?
A
NO₂
B
P (ketone from 471)
C
Q (alkene from 471)
D
R (alkene from 472)
Answer
R (from structure 472)
Explanation
Solution
The reactivity of functional groups towards catalytic hydrogenation with H₂/Ni generally follows the order: Alkenes > Alkynes > Aldehydes > Ketones > Nitro groups > Aromatic rings.
- In structure 471, P is a ketone and Q is a conjugated alkene.
- In structure 472, P is a nitro group, Q is a benzene ring, and R is an isolated alkene (vinyl group). Alkenes are highly reactive. Isolated alkenes, like the vinyl group R, are typically among the fastest reacting functional groups in catalytic hydrogenation. Therefore, R will react fastest.