Synthesis and substituent distribution of Na‐cellulose sulphates via O‐trimethylsilyl cellulose as intermediate

Abstract

Abstract Sulphation of cellulose was performed in an homogeneous aprotic system with SO 3 or CISO 3 H, resp., via O‐trimethylsilyl celluloses as reactive intermediates. Na‐cellulose sulphates completely soluble in water and showing small chain degradation could be obtained at DS s ≥ 0.25. The DS s in the range between 0.2 and 2.5 as well as the distribution of the sulphate half‐ester groups within the AGU were regulated via the DS si at one hand, the type and amount of sulphating agent at the other. Sulphation was performed either with the isolated and redissolved trimethylsilyl cellulose in N,N‐dimethylformamide or tetrahydrofurane, or starting with an activated cellulose suspension, by achieving silylation and subsequent sulphation in one system of reaction. Obviously, the silyl group acts as a reactive group in subsequent sulphation, and the sites previously silylated are preferentially sulphated in the subsequent step of reaction, and the DS s is limited by the degree of silylation (DS si ) previously obtained. The homogeneous sulphation of trimethysilyl cellulose indicates a reactivity of silyl ether groups in the order of C‐6 > C‐2 ≫ C‐3.