Titration curves of wool with 18 strong acids at 0°, 25°, or 50° C have been added to the data for 19 others presented earlier. Several have been investigated at more than one t emperature. The reversibility of the equilibria m easured has been demonstrated quantitatively. N ew anion-wool dissociation constants, based on modifications of equations previously used to calculate anion-wool affinities, are tabulated for 33 anions, and h eats of dissociation of a few anionwool complexes are also given. The previously reported t endency of affinity to rise with molecular-weight is confirmed ; fairly consist ent relationships between the affinity and the molecular weights of strong organic acids appear.
The aldehyde content of hydro cellulose may be readily estimated by titration with iodine in alkaline solution. Investigation of the rate of oxidation of hydrocellulose by iodine at 0° C and pH 10.6 showed that there is an initial rapid reaction in the first hour accompanied by a side reaction. This latter reaction continues after the rapid reaction has ceased and consumes iodine slowly at a constant rate. Purified cotton cellulose shows an initial reaction with iodine and after 1 hour exhibits a side reaction of the same rate as the hydrocellulose. By applying a correction for the amount of iodine consumed in the side reaction, it is possible to estimate the iodine utilized in the oxidation of aldehyde groups. Since iodine utilized in this way converts aldehyde to carboxyl groups, an, independent check on the value obtained with iodine is readily obtained by estimation of the carboxyl groups thus formed by titration with silver o-nitrophenolate. It is shown that the extent of hydrolytic degradation as determined by this method compared well with similar measurements by the viscosity method.
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It is the purpose of this paper to describe the behavior of sulfur in wool under conditions which are very different from those ordinarily used in studies on sulfur lability and to point out a probable mechanism by which sulfur is split from wool during alkali treatment. The data indicate tha t the primary process in the alkali cleavage of the disulfide linkage consist s in a hydrolytic rupture of the disulfide group with the formation of a sulfh ydryl compound and a sulfenic acid. The sulfenic acid is ext remely reactive a nd u nstable in alkaline solution and immediately loses hydrogen sulfide and forms a n a ld eh yde. The results of the investigation indica t e that the existence of labile sulfur in prot eins is not an indication that the bulk of the sulfur is present in more than one form.
Ketenes underwent cycloaddition reaction& with several different heterocumiilenes. Dialkylketenes and isocyanates gave malonimides, and diisocyanates gave bis(ma1onimides). Acyl isocyanates and ketenes generally underwent a 4 + 2 cycloaddition to give oxazinediones. Carbodiimides and ketenes gave azetidinones vza a 2 + 2 cycloaddition. Carbon dioxide and carbon disulfide, when catalyzed by triphenylphosphine, gave 2 + 2 + 2 cycloaddition products containing 2 equiv of dialkylketenes. A ketenimine and a dialkylketene gave as the major component a 2 + 2 + 2 cycloaddition product involving two ketenimine molecules and one dialkylketene molecule.Ketenes belong to a class of compounds known as heterocumulenes.2 The reactions of ketenes with themselves to form dimers or trimers are well documented. I n this paper we report our work on reactions of ketenes with other heterocumulenes.Isocyanates. -Staudinger reported that diphenylketene reacted with phenyl isocyanate a t 220" via a 1: 1 cycloaddition to+ give the malonimide 1 in low yield.3 Similar reactions of diphenylketene with methyl and cyclohexyl isocyanates have been r e p~r t e d .~ The adduct of pentamethyleneketene, generated in situ from the acid chloride, with phenyl isocyanate also has been reported.6The reaction of monomeric dialkylkeTenes with isocyanates to give malonimides'has not been reported. We found that, when butylethylketene was heated with phenyl isocyanate, 2-butyl-2-ethyl-N-phenylmalonimide (2b) was formed in 70% yield. Dimethylketene, in spite of its reactive nature, gave low yields of malonimides because the ketene dimerized rapidly. At 25", dimethylketene and phenyl isocyanate afforded 2,2dimethyl-N-phenylmalonimide (2a) in 10% yield; at 60°, the yield of 2a was 30%.(1) (a) Paper XI1 in this series:
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