Abstract. The mechanism of cross-linking of cellulose by glyoxal has been investigated using various alcohols as models for cellulose. Competitive hemiacetalizations of glyoxal show that vicinal diols are much more reactive than isolated alcohols. With a catalyst, both kinds of alcohols react with the hemiacetals, but the isolated alcohols are the most reactive. The main products of acetalization are mixed dioxane bisacetals. Methyl 4-O-methyl-~-glucoside, considered as a monomeric unit of cellulose, reacts in the same way. The cross-linking of cellulose by glyoxal is thought to proceed according to the same pattern. The pathways of cross-linking in the presence of ethylene glycol and diethylene glycol, currently used as co-reactants of glyoxal, are discussed.
The structure and stereochemistry of products obtained when vicinal diols are allowed to react with glyoxal were established with the aid of "C N M R structure relationships. Hemiacetalization yields 1,4-dioxane-2,3-diols regardless of the diol reacted. The course of acetalization depends on the structure of the diol: trans-l,2-cyclohexanediol and analogs yield only 1,4,5,8-tetraoxadecalins as acetals, whereas cis-1,2-cyclohexanediol and 1,2-ethanediol yield mixturqs containing mostly 2,2'-bi-1,3-dioxolanes. The isomeric distribution of products depends on the reaction conditions.
206 ChemInform Abstract The structure and stereochemistry of products obtained from hemiacetalization and acetalization of glyoxal (I) with various diols are established by 13C NMR. Hemiacetalization of (I) with 1,2-ethanediol, cis-1,2-cyclohexanediol or trans-1,2-cyclohexanediol yields the dioxanediols (II)-(IV) regardless of the diol reacted. The course of acetalization depends on the structure of the diol: 1,2-ethanediol or cis-1,2-cyclohexanediol yield mixtures containing mostly the dioxolanes (V) or (VI), while trans-1,2-cyclohexanediol affords only the tetraoxadecalins (VII) and (VIII). The isomer ratios of the products depend on the reaction conditions.
When glyoxal (I) is treated with a seven‐ to tenfold excess of the alcohols (II) in the presence of zirconium disulfate, the monoacetals (III) are predominantly formed, together with only minor amounts of the diacetals (IV).
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