94 Synthetic Routes to Nitrate Esters
N 2 O 5 , CCl 4 , 0 °C98–100 %HOOHOHOHOHOH(^1314)
O 2 NO
ONO 2
ONO 2
ONO 2
ONO 2
ONO 2
Figure 3.11
Passing a mixed stream of ozone and dinitrogen tetroxide through a solution of the alcohol or
suspension of the polyol in methylene chloride or chloroform usually gives the nitrate ester in
excellent yield.^26 The substrate may only show sparing solubility in the chlorinated solvent but
reactions are still fast and efficient. This is the case with mannitol (13), which can be suspended
in carbon tetrachloride and nitrated to mannitol hexanitrate (14) in near quantitative yield.^33
The nitration of carbohydrates with dinitrogen pentoxide is usually conducted between 10
and 15◦C and sometimes with added sodium fluoride, an acid-binding agent.^32 Acid removal is
not usually a problem with most substrates, but can be a big problem with higher carbohydrates
such as cellulose and starch which stubbornly retain occluded acid. The use of sodium fluoride
circumvents such problems. The effectiveness of dinitrogen pentoxide as a nitrating agent
is illustrated by the facile conversion of cellulose to nitrocellulose of 13.9–14.0 % nitrogen
content.^34
O
OH
O
ONO 2
1 eq N 2 O 5 , CH 2 Cl 2
- 25 °C, 10 mins, 85 %
18 19
Figure 3.12O-Nitration with dinitrogen pentoxide is exceptionally fast, a point illustrated during the
synthesis of glycidyl nitrate (19) from glycidol (18); although nitric acid is formed during
the reaction, initialO-nitration is much faster than the acid-catalyzed epoxide ring opening.^35
This method can be used for the industrial synthesis of glycidyl nitrate,^36 which is used as a
precursor to energetic polymers/binders^36 ,^37 (Section 3.10).
Dinitrogen pentoxide has been used for the synthesis of other energetic nitrate esters.
Lustig and co-workers^38 synthesizedgem-dinitrates by treating acetaldehyde and trifluoroac-
etaldehyde with dinitrogen pentoxide under super-cooled conditions. Peroxynitrates^39 and
peroxyacid nitrates^40 have also been prepared by treating the corresponding hydroperoxides
and peroxyacids with dinitrogen pentoxide at subambient temperatures. The poor stability of
these products prevents their use as practical energetic materials.
3.2.4O-Nitration with nitronium salts
ROH + NO 2 BF 4 RONO 2 + HBF 4 (Eq. 3.7)Figure 3.13Nitronium tetrafluoroborate is a very efficient reagent for theO-nitration of alcohols and glycols
containing both primary and secondary hydroxy functionality (Equation 3.7).^41 −^43 Yields of
nitrate ester are high and frequently quantitative.O-Nitration with nitronium salts produces a
strong acid and so an acid-binding agent should be present for acid sensitive substrates.