The reaction between wool and phenyl isocyanate.

During some studies on the reactivity of the cystine linkages in wool, it was necessary to find methods for blocking the various polar side chains with minimum degradation of the fibre as a whole, and without introducing any coloration due to the reagent used. Various workers have found that the amino groups of proteins react readily with i8ocyanates in aqueous solution at pH 8 and 00 (Hopkins & Wormall, 1933, 1934a, b; Miller & Stanley, 1941). There have also been claims that i2ocyanates react with thiol and tyrosine hydroxyl groups (Fraenkel-Conrat, 1944; Miller & Stanley, 1941). This appeared to be an excellent method for the required purpose, although it was realized that reaction with wool would be more difficult than with the soluble proteins as penetration of the insoluble fibrous protein by the reagent would have to be accomplished. Fraenkel-Conrat, Cooper & Olcott (1945) found that iwocyanates reacted with proteins under anhydrous conditions at elevated temperatures. Besides reaction with the amino, thiol and phenolic groups, reaction with carboxylic, amide, guanidino and glyoxaline groups occurred. The changes produced by reaction in aqueous media and under anhydrous conditions were of interest for the particular studies involved, so attempts were made to bring about reaction ofwool withphenyli8ocyanate underboth sets ofconditions. Very little success was achieved when using aqueous media, but by varying the conditions used by Fraenkel-Conrat et al. (1945), it has been found possible to obtain maximum reaction with wool, up to 44% of its weight of phenyl isocyanate being combined. The reaction has also been carried out on wools modified in various ways.