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Two general methods for the silylation of cellulose have been developed. Silyl amides undergo silyl—proton exchange reactions with cellulose in polar solvents leading to displacement of 80–90% of the hydroxyl protons by silyl groups. The same products are obtained by reaction of the corresponding chlorosilanes with cellulose in pyridine; however, di‐ and trifunctional impurities present in commercial chlorosilanes have to be removed by scavenging with a carbohydrate in order to avoid crosslinking. Cellulose derivatives with trimethylsilyl, dimethylphenylsilyl, methyldiphenylsilyl, and γ‐cyanopropyldimethylsilyl substituents have been prepared by both methods. The properties of the new soluble polymers are largely dependent on the nature of the silyl substituents. The silyl celluloses exhibit a relatively high degree of hydrolytic stability; methyldiphenylsilyl cellulose is hydrolytically stable even under severe conditions.

Addition reactions of secondary and tertiary silylamines and of silazanes with isocyanates were studied. Spectroscopic Silylureas Reactions Isothiocyanates and silylamines Silylamine-isocyanate adducts ( 1 : 1) were obtained with secondary and tertiary silylamines. evidence favors N-silylurea structures for these thermally stable, hydrolytically sensitive adducts. containing a t least one proton on nitrogen were found to undergo a rapid silyl-proton exchange. of disilazanes with isocyanates led to disilyl-substituted ureas and biurets. formed analogous adducts which reverted to the starting materials a t elevated temperatures.

Similar trends are not observed in other petroleum families. In each case a three-ring structure is preferred, and this recalls the presence of the tetrahydroor hexahydrocarbazole nucleus in certain alkaloids (e.g., aspidospermine (33). Again it seems likely that a preference for a given structure in petroleum is rooted in a similar preference for that structure in plants.A detailed examination of the structural relationships between individual N,0 compounds and their precursors in nature will be presented elsewhere.24 (24) G. C. Speers and E. V. Whitehead, "Crude Petroleum. Organic Geochemistry: Methods and Results," Springer-Verlag, New York, N. Y., in press.

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