Nitration of starch

A fundamental difference between starch and cellulose is shown by their behaviour in the presence of nitric acid. Starch brought into contact with nitric acid of over 76% concentration swells and eventually dissolves, whereas cellulose swells only insignificantly and generally does not dissolve (as described already it can only be dissolved in nitric acid of ca. 80% HN03). 

When a nitrostarch solution in nitric acid is poured into water, sulphuric acid or phosphoric add, the nitrostarch is precipitated as an amorphous powder. 

Hackel and T. Urbanski [18] reported that a solution of starch in 10 times its weight of nitric acid (97.3% HN03) poured after 6 hr at 20°C into 20 times its weight of water yielded a nitrostarch of 11.7-11.9% N almost completely soluble in alcohol and ether-alcohol. The method has not come into practical use as the dilution of nitric acid with water is not economic. 

Nitrostarch of 12.6% N can be prepared, if starch dissolved in ten-fold quantity of nitric acid is poured into 40 times its volume of 94% sulphuric acid, at a temperature not exceeding 20°C. Such nitrostarch includes 11.4% of substance soluble in alcohol, and 95.7% of substance soluble in ether-alcohol. 

Starch exposed to the action of nitric acid for a period shorter than 6 hr is converted into nitrostarch of lower nitrogen content, e.g. 12.2% N, after 4 hr. 

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Reaction Time of Nitration of Starch as a Function of Temperature. N... 

Refs l)Beil 3, 2 2)J.Glattfeld D.Mac-millan, J ACS 56,2481 2( 1934) (Preparation of aldonic and saccharic acid amines in liquid ammonia) 3)G.V.Caesar M.Gold-frank, J ACS 68,372-5(1946)(Nitration of starches with nitrogen pentoxide in presence of sodium fluoride) 4)Karrer( 1950), 325 ... 

Nitration of amylose was carried out according to the Will Lenze method, using mixed nitric-sulfuric acid as described under nitration of starch(Ref 4). The resulting product had N=12.96%, soly in ale 20% and stability(by Abel and Bergmann-Junk tests) higher than for aminopectin nitrate(Ref 5). 

Xyloidine. Name given by Braconnot to the product obtained by him in 1833 on the nitration of starch. It was Nitrostarch with a N content below 11%. See under Nitrostarch in Vol 8, N158-L... 

Further, a noteworthy patent describing the nitration of starch in the form of flakes was obtained by Norman of the Hercules Powder Co., in 1933 [30]. 

These experiments also suggest that nitration of starch passes through the stage of hydrolysis to soluble starch before being nitrated ... 

Fig. 168. Triangular diagram of nitration of starch, according to Hackel and T. Urbanski [18] (a) in mole %, (b) in weight %.

Fig. 169. Reaction time of nitration of starch as a function of temperature, according to Kunz and T6th [46].

Recently extensive investigations on the nitration of starch, mainly by using mixed nitric and sulphuric acid have been carried out by Kunz and T6th [46]. Their object was to determine the effect of the ratio of the components in the nitrating mixture and the activity of nitric acid in the mixtures on the nitrogen content of the nitrostarch, the heat of esterification, and the relation between the nitration temperature and the viscosity of the product. Their observations concerning the time of reaction are of special interest. This varies as a linear function of the nitration temperature. In the graph (Fig. 169) the relationship is shown for two mixed acids ... 

W.R.Ashford et al, CanJRes 25B, 151- 54 (1947)(Effect of hot alkali solas on the nitrates of starch, amylose araylopectin) Ibid, 25B,... 

Nitrostarch, with various nitrogen contents (12-13.3%), is prepared by nitration of starch with nitric acid or nitrating mixtures. The resulting crude product is washed in cold water and is then dried at 35-40 °C (95-100 °F). 

Hungarian patents issued to Ipartelepek in 1938-39 covered the nitration of starch (in mixed acids containing 75-90 % of nitric acid) at temperatures below 5°C. for 30 minutes, but in two stages. Unusual stability of the products was claimed. 

During the last war, the author and his coworkers undertook a study of esterification (largely, of starches) by dinitrogen pentoxide under anhydrous conditions, with the principal objective of forming substantially undegraded esters. The literature on the pentoxide was meager, with only one reference on the nitration of starch. Chloroform is an excellent inert solvent for dinitrogen pentoxide and we decided to use it for our nitrations. We had first, however, to prepare the pentoxide in sufficient quantities our described method proved satisfactory. 

In 1950, the mechanism of the nitration of starch was studied by Israelashvili who came to the conclusion that conditions of nitration favoring the production of a high proportion of nitronium ion (NO2 ) produce... 

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