Studies on the Synthesis of 2,3‐ O ‐Hydroxyalkyl Ethers of Cellulose

Summary: Novel 2,3‐ O ‐hydroxyethyl‐ and 2,3‐ O ‐hydroxypropyl cellulose products were synthesized by heterogeneous etherification of 6‐ O ‐(4‐monomethoxytrityl) cellulose (MMTC). Due to the very hydrophobic character of MMTC, the reaction was successful in the presence of anionic and non‐ionic detergent in the reaction mixture yielding the 2,3‐ O ‐cellulose ethers with a molar degree of substitution (MS) varying between 0.25 and 2.00 after detritylation. The products were characterized by means of 1 H and 13 C NMR spectroscopy including two‐dimensional methods. The 2,3‐ O ‐hydroxypropyl cellulose samples are soluble in water at a MS as low as 0.8. The spectroscopic studies showed that the unusual solubility results from a preferred substitution of hydroxy groups of the anhydroglucose unit while the newly formed hydroxy moieties are included in the reaction to a minor extent only. In contrast, conventionally synthesized hydroxypropyl cellulose is soluble in water starting at a MS of about 4.0 because of the formation of oxyethylene side chains.13 C DEPT 135 NMR spectrum of 2,3‐ O ‐hydroxypropyl cellulose.