Types of Reaction
SOS"
SCN slow
/ HCN
\ fast
CN
y
OH
- eCN
CN
Elimination reactions are, of course, essentially the reversal of
addition reactions; the mosU^ommon is the loss of atoms or groups
from adjacent carbon atoms to yield defines:
H
C— C /
\
Br
* H
OH
,-HBr
-H.O
Rearrangements may also proceed via electrophilic, nucleophilic
or radical intermediates and can involve either the mere migration of
a functional group (p. 86) as in the allylic system
\
OH
He
CH=CH, CH^CH,
+ HaO
\c
CH—CH 2.
CH—CHa—OH + H®
or the actual rearrangement of the carbon skeleton of a compound as
in the pinacol (XLII) ->pinacolone (XLI1I) change (p. 90):
Me 2 C—CMe 2
I I
OH OH
H©
Me 3 CCOMe
(XLIII)
(XLII)
the carbonyl group in simple aldehydes and ketones are usually
nucleophilic in character (p. 158). An example is the base-catalysed
formation of cyanhydrins in liquid HCN: