A Guidebook to Mechanism in Organic Chemistry

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: