N-Nitration of amides and related compounds 209of 70 % PETN and 30 %N, N′-dinitro-N, N′-dimethyloxamide melts at 100◦C and has a VOD
∼8500 m/s. Replacing 10 % of the PETN with dimethyl oxalate lowers the melting point to
82 ◦C but the VOD drops to 7900 m/s.
55
56NHCO 2 EtNHCO 2 EtNCO 2 EtNCO 2 EtNO 2NO 2SOONHCH 3NHCH 3SOONCH 3NCH 3NO 2(^54) NO 2
10
Figure 5.31
A solution of fuming or absolute nitric acid in acetic anhydride is another commonly used
reagent for theN-nitration ofN-alkylamides. Curry and Mason^71 used this reagent to syn-
thesize a series of aliphatic and alicyclicN-nitro-N-alkylcarbamates from the corresponding
N-alkylcarbamates. Aromatic ring nitration is observed if aryl groups are present in the car-
bamate substrate.
HNO 3 , Ac 2 O
NCOCH 3
NCOCH 3
NO 2
NO 2
NHCOCH 3
NHCOCH 3
57
58
83 %
Figure 5.32
Nitric acid–acetic anhydride reagent has been used to synthesizeN, N′-dinitro-N, N′-
ethylenebisacetamide (58) fromN, N′-ethylenebisacetamide (57); the former is a secondary
high explosive and a precursor to the powerful explosive ethylenedinitramine (Section 5.10).^70
It is interesting to note that (58) is not formed when (57) is treated with nitric acid alone or
with strong mixed acid.
NHAc
NHAcAcHN
N(NO 2 )Ac
2 )N N(NO 2 )AcAc(NO
59 60
Ac 2 O, HNO 3
or
TFAA, HNO 3
Figure 5.33
The energetic nitramide (60) has been prepared from the nitration of the tris-acetamide (59)
with nitric acid and acetic anhydride or trifluoroacetic anhydride.^72 Nitric acid–trifluoroacetic
anhydride mixtures are powerful nitrating agents and well suited for amide and urea
N-nitration.
Nitric acid–acetic anhydride mixtures give poor yields for the nitration of amides with groups
that hinder the amide nitrogen against electrophilic attack. The use of higher temperatures in
these reactions leads to variable amounts of theN-nitroso compound as a by-product.^71