Carbocation

Question 1

What is carbocation?

Answer 1

It has a positive charge on sp2 hybridised carbon, triangular planar, and diamagnetic in nature.

Question 2

What are the methods of generation of a carbocation?

Answer 2

1. From pi bond shifting on alkene or alkyne. (E+ addition)
2. From Alcohols
3. From Haloalkanes
   R-X + PPS/Lewis Acid/aq. AgNO3 ‐—> R+ (more stable than 2ary)
4. From Diazotisation of Primary Amine

Question 3

What are the reactions of carbocation?

Answer 3

1. Rearrangement of Carbocation
   H->Ph->R-
   More EDG = More migratory aptitude

Ring expansion occurs due to relieve in strain.
For 6 to 7 ring expansion a driving force is needed
(Check when the positive charge is on carbon next to the ring)

2. Combination with Nucleophile
   PPS acts as nucleophile
3. Removal of Beta Proton (Elimination Reaction)

Question 4

What are the reagents used in removal of beta proton?

Answer 4

Base, alcoholic KOH, HSO4-, H2PO4-, Bulky base, nitrogenous base or PPS and heat

Question 5

Difference in combination with nucleophile and elimination.

Answer 5

We use heat with elimination.