1.  It involves migration of a substituent to
an uncharged, electron deficient, carbon
atom called carbene
 That is a molecule containing a neutral
carbon atom with two unshared valence
electrons. The general formula is RR'C:

2.  The term "carbene" may also refers to the
compound H2C:, also called methylene
 Carbenes are classified as either singlets or triplets
depending upon their electronic structure
 Most of the carbenes are very short lived, although
persistent carbenes are known

3.  In this rearrangement α-diazoketones
lose nitrogen to form highly reactive
ketenes

4. R C CHN2
O
R
C CH N N
** +
O -N2
R R
C C C CH
**
H
O O

5.  - Synthesis of analogues of carboxylic
acids
 - Synthesis of acid amides from
carboxylic acids
 - Synthesis of esters from carboxylic
acids

6. SOCl2
R C OH R C Cl Diazomethane
O O CH2N2
R
C CH N N
** +
O -N2
R R
C C C CH
**
H
O O
CH OH
NH
H2O
3
3
O
O
O R-CH2-C-NH2
R-CH2-C-OH
R-CH2-C-O CH3