Advices For Studying Organic Chemistry

6.12 CARBOCATIONS

1. In 1962, George A. Olah (Nobel Laureate in chemistry in 1994; now at the
   University of Southern California) and co-workers published the first of a series
   of papers describing experiments in which alkyl cations were prepared in an
   environment in which they were reasonably stable and in which they could be
   observed by a number of spectroscopic techniques.

6.12A THE STRUCTURE OF CARBOCATIONS

1. The structure of carbocations is trigonal planar.

Figure 6.8 (a) A stylized orbital structure of the methyl cation. The bonds are
sigma (σ) bonds formed by overlap of the carbon atom’s three sp^2
orbitals with 1s orbitals of the hydrogen atoms. The p orbital is
vacant. (b) A dashed line-wedge representation of the tert-butyl
cation. The bonds between carbon atoms are formed by overlap of sp^3
orbitals of the methyl group with sp^2 orbitals of the central carbon
atom.

6.12B THE RELATIVE STABILITIES OF CARBOCATIONS

1. The order of stabilities of carbocations:

R C

R

R

+ R C

R

H

R C

H

H

H C

H

H

>> >

3 o 2 o 1 o Methyl

++

>> >

(most stable) (least stable)

+