synthesis reagents and their apllication

1. DIAZOMETHANE
AS SYNTHETIC REAGENT AND IT’S APPLICATION
PRANJAL TIDKE
M.PHARM FIRST YR
PHARMACEUTICAL CHEMISTRY DEPARTMENT

2. DIAZOMETHANE
• Diazomethane is yellow, toxic and highly reactive gas which is
soluble in ether.
• It has molecular formula CH2N2
• Its boiling point is -23℃
• It is explosive but may handled safely in ethereal solution
• It is chemically very reactive and is, therefore, of great value as
synthetic reagent.
• Reactions with diazomethane carried out in ethereal solution
• Its ethereal solution stored at 0℃
Resonance structure of diazomethane

3. 1.Pechmann’s method
By this method diazomethane is prepared from methylamine by
treating it with ethyl chloroformate to form N-methyl urethane
This when treated with nitrous acid in ethereal solution yields N-methyl N-
nitrosourethane
This on warming with alcoholic potassium hydroxide decompose into
diazomethane which is collect on cool ether.
PREPARATION

4. 2. Arndt and Amende’s method
By this method, diazomethane is preparedly treating nitroso
methyl urea with very concentrated potash at 0℃ .
3. Moore and reed’s method
By this method, diazomethane is prepared by the alkaline
hydrolysis of bis-(N-methyl-nitroso) terephthalamide.

5. 4. Backer’s method
By this method, diazomethane is prepared by
distillation of N-methyl-N-nitroso-p-toluene sulphonamide with
ethanolic potassium hydroxide .

6. 5. Mckay’s method
By this method diazomethane is prepared by treating methyl amine with nitro
guanidine in the presence of potassium hydroxide the product so obtained is treated
first nitrous acid and then warmed with alkali potash .

7. 1. Methylation of acids:
this reagent is mainly used for carrying out the esterification of
carboxyl groups. This reagent is also used for the methylation of phenols and minerals
acids.
APPLICATION

8. 2. Methylation of alcohol :
Diazomethane can also methylate alcohol
in the presence of boron trifluoride ethereate or fluoroboric
acid as catalyst .

9. 3. Homologation
Diazomethane reacts with aldehyde to give methyl ketones as benzaldehyde
Converted to acetophenone, and ketones can be converted into their higher
homologues

10. 4. Ring expansion :
When certain cyclic ketones are treated with diazomethane they undergo
ring expansion forming higher ketones
5. Synthesis of heterocyclic compounds
The heterocyclic compounds such as pyrazoline and pyrazole derivatives are preapared by
condensing diazomthane with ethylenic or acetylenic compounds

11. 6. Miscellaneous
Heat or light generate carbine from diazomethane
through loss of nitrogen which can add rapidly to alkenes to give
cyclopropane derivatives.