Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

270 THE DIAZO-COMPOUNDS
The great velocity of esterification of nitrous acid, exceeding that of
all other acids, is doubtless to be traced to the same cause (p. 147).
CH3.CH2—Ov
CH,.CH20H + OrN.OH > >N—OH
HO/
~ H '> CH3.CH2— 0—N=O .
Ethyl nitrite
If we apply these considerations to the behaviour of ammonia it is
clear that the acyl-product which is formed on heating must decompose
into nitrogen and water.
H3N + OrN.OH —>- | >N—OHI > N:N + 2H2O.
Fundamentally the same holds for primary aliphatic amines :
OH
H3C.NH2 + OrN.OH > [H3C.NH—N—OH] > [H3C.N:N0H]
> N=N + H3C.0H .
The second intermediate product, in brackets, is known in the
form of salts; we recognise that under the conditions of its formation
it must decompose into nitrogen and alcohol.
The simple primary amines of the aliphatic series, then, do not form
diazo-compounds because the reaction which would le%d to their formation
only occurs at a temperature at which they are destroyed. The
reactivity of the NH2-group can, however, be increased by a neighbouring
carbonyl group. Thus we come to the case of the esters of the aamino-carbozylic
acids and of the a-amino-ketones. The ethyl ester of
glycine can be diazotised even in the cold ; the diazo-compound which
does not decompose under these conditions undergoes stabilisation by
elimination of water and change into ethyl diazoacetate :
ROC.CH2.NH2 + OrN.OH |-B0.C.CH2.NH rE0.C.CH2.NH --.
I _ ' " || >N-0H
0
L 0 HO J
E0.C.CH2.N-| RO.C.CH—N
II II U^S- II \S-
0 HONJ 0 N
Ethyl diazoacetate
The unexpected feature of the reaction of the primary aromatic
amines with nitrous acid is that the diazo-compound, which is doubtless
formed at low temperatures according to the scheme so far used,
undergoes rearrangement by the acid present in the solution, and forms