Nitro group, determination titration

After 30mins of lively steam distillation the HCl was back-titrated with N/ 0 NaOH, Betl Berl found that the speed of decompn of nitro-compds increased with an increase in the number of nitro groups present. Mononitro derivs showed results which were too low (Ref Private communication from Dr E.Berl to Dr B-T.Fedoroff about 1943). This method can be used also when It is desired to determine the N content of nitrocompds... 

PHEMA has been effected. Reaction of p-nltro-benzenesulfonyl Isocyanate with PHEMA or copolymers containing HEMA and varying amounts of styrene followed by reduction of the nitro group with sodium dlthlonlte produced p-amlnobenzenesulfonyl carbamates of hydrogels (p-ABSC-HEMA). The precise composition of the hydrogel carbamates was determined by nonaqueous titration of the carbamate moiety with tetrabutylammonlum hydroxide In Isopropanol/dlmethylformamlde. 

Analysis of derivatives. The presence of suitable functional groups in the molecule of the derivative makes a simple analysis possible, and hence the determination of the molecular weight. It is possible, for example, to determine the presence of a carboxyl group inp-carboxyphenylhydrazones of aldehydes and ketones by alkalimetry, the substances containing nitro groups can be analyzed titanometrically, in salts the acid or the basic component can be titrated in nonaqueous media, etc. It is more convenient to analyze the substances in this way, because the analysis is more specific and usually affords more information on the composition of the preparation than, for example, elemental analysis. 

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