O-Methyl- and O-ethyl-celluloses having controlled distributions of substituents were prepared by alkylation of 6-O-triphenylmethyl ("trityl") cellulose in dimethyl sulfoxide (Me2SO) and subsequent detritylation of the alkylated products. Water-free alkylation reactions failed to give complete substitution of the hydroxyl groups at both the C-2 and C-3 positions. The addition of a small amount of water to the tritylcellulose solution in Me2SO improved the efficiency of the alkylations, yielding 2,3-di-O-substituted-6-O-tritylcelluloses which in turn gave 2,3-di-O-alkylcelluloses on detritylation with HCl gas. Repeated further alkylation of the 2,3-di-O-alkylcelluloses in Me2SO furnished products with high degrees of substitution at the C-6 position. The distribution of substituents in the alkyl cellulose ethers was determined by acid hydrolysis, reduction, and gas-chromatographic separation of the partially alkylated alditol acetates. The distribution of methyl and ethyl groups in the polymers prepared by repeated alkylation systematically changed with each alkylation step.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Organic Chemistry