rearrangement

1. BY
Dr. Gurumeet.C.Wadhawa
DEPARTMENT OF CHEMISTRY
K. B. P. College,Vashi,Navimumbai
Von Richter Rearrangement

2. When aromatic nitro compounds are reacted with potassium cyanide to
generate a carboxylic acid ortho to the existing nitro group is known as
Victor Von Richter reaction (in 1871).
When aromatic nitro compounds are treated with cyanide ion, the nitro
group is displaced and a carboxyl group enters with cine substitution, always
ortho to the displaced group, never meta or para. The von Richter reaction
can be inhibited in the presence of potassium ferricyanide (K3Fe(CN)6) and
sodium sulfite.

3. The rearrangement reaction of aromatic nitro-compounds with KCN
or NaCN giving carboxylation on ortho- position of the nitro groups.
The von Richter reaction, also named von Richter rearrangement, is
a name reaction in the organic chemistry. It is named after Victor von
Richter, who discovered this reaction in year 1871. It is the reaction
of aromatic nitro compounds with potassium cyanide in aqueous ethanol
to give the product of cine substitution (ring substitution resulting in the
entering group positioned adjacent to the previous location of the leaving
group) by a carboxyl group. Although it is not generally synthetically useful
due to the low chemical yield and formation of numerous side products, its
mechanism was of considerable interest, eluding chemists for almost 100
years before the currently accepted one was proposed.

4. This reaction is the example of cine aromatic nucleophilic substitution
reaction in which nitro group is replaced by carboxylic group. The
position of carboxylic group is always ortho- to the nitro group. As with
other aromatic nucleophilic substitution reaction, the reaction gives best
results when electron withdrawing group are present on ortho- or para-
position with respect to the nitro group. This reaction has limited
application in organic synthesis and yield of the reaction is very poor.
The yield is usually ranging in between 20-50%.