Spectral Study on the Alkaline Hydrolysis of Some Cyano Substituted 4-Amino-4노-Nitroazobenzene Dyes

시아노기 치환 4-아미노-4노-니트로아조벤젠계 염료의 알칼리 가수분해에 대한 분광학적 고찰

The alkaline hydrolysis behaviors of six two disperse dyes, especially for cyans substituted 4-amino-4'-nitroazobenzene dyes were studied. The dyes containing two ortho substituents in acceptor ring were very rapidly hydrolyzed by alkali and showed both large hypsochromic and hypochromic shifts. These results may be caused by the decrease of electron-withdrawing power of acceptor and steric hindrance resulted from the hydrolysis of the cyano group and certain cleavages by hydrolysis. Similarly for the dyes which have an o-cyano group in acceptor ring, hypsochromic shifts together with reductions in tinctorial strength were also observed by the alkaline hydrolysis. And only the water-insoluble products remained without hypsochromic shift during hydrolysis participated in dyeing of polyester. The dyes containing an acetoxyalkyl group in terminal amino group produced a bathochromic shift by hydrolysis of acetoxy group. In acetone/sodium hydroxide aqueous solution, the tinctorlal strengths of the dyes without o-cyano group were not reduced, but in dyeing, their dye uptakes were gradually reduced with hydrolysis time. Moreover, most of dyes showed obvious decreases of dye uptakes after washing.