The Preparation of Sucrose Monoesters

Abstract

The Snell procedure for the preparation of sucrose monoesters of the higher saturated fattp acids by transesterilication of sucrose and rnethyl esters in N,N-dirnethylfor~~ia~~iide was found to yield variable results due to the use of solid potassium carbonate as catalyst and to inlpurities in the solvent. A kinetic study of the reaction revealed that yields of sucrose ester and rates of reaction were reproducible when conditions for homogeneous catalysis were established. The reaction followecl first-ordcr kinetics in methyl ester and s~~c r a t e ion and the rate of reaction was essentially independent of the sucrose concentration, the molecular weight of the fattp acid, and the nature of the metal sucrate used to catalyze the reaction. The activation energy for the reaction \x7as 0.0 Ixal n~ole-I. Eq~~ilibrium constants for the principal reactions were determined, and it was established that only the thermodynamic product prevailed a t any t i~n e thro~~gllout the transesterilication reaction. A preparative method for the synthesis of sucrose monoesters was developed that gave yields of sucrose ester, based on the amount of methyl estcr which had reacted, which were essentially quantitative. The product contained a l~o u t 20'7; of di-and 80% of mono-ester.In 1'354 Snell and co-workers developecl a process for the preparation of fatty acid esters of sucrose ( I ) using the transesterificatioi~ reaction, which was subsequently published in 195G (2). The procedure was based on the reaction of sucrose with the methyl ester of a fatty acid, in N,N-dimethylfoi-~namide ( D M F ) solution, using solid potassium carbonate as a catalyst. The methanol formed in the reaction was removed i 7 z vaclro uitder co~lditions for fractioilal distillation. This process attracted considerable interest from industry as a means for the preparation of sucrose monoesters of the higher fatty acids for use as low-cost, 11011-ionic cletergents (3, 4).The elucidation of the structures of the sucrose monoesters formed and the determ i~l a t i o i~ of their relative amounts in the products obtained first attracted our attention to this process. I-Iowever, when an attempt was made to prepare samples of sucrose mo~loester, by the original Snell proceclure (2), for structural analysis, it soon became apparent that the product clid riot warrant such an investigation since it coulcl not be prepared uncler fully controlled ancl reproducible conditions. For un1;nown reasons, l~i g l~l y variable yields mere obtained and the products differed considerably in the degree of substitution, solubility, and color even when the reaction was performecl under apparently iclentical experimental conclitions ( 5 ) . Although other workers have claimed more success in this respect a critical assessment of their results clearly inclicates that they have been equally unsuccessful i l l preparing reproducibly a product in high yield (2, 6-8). Furthermore, the concl~~sions which the various workers have drawn (2, 6-11) from their experimental results are o...

The Composition of the Sucrose Monomyristate Prepared by Transesterification

“…Methyl a-D-glucopyranoside tetramesylate underwent quantitative replacement of the 6-mesyloxy group (15). T h e relative amounts of the two isorneric mono-0-myristoyl sucroses together with the evidence (6) t h a t they were formed as an equilibrium mixture requires the equilibrium constant, I<,, for the reaction 6-myristoyl sucrose Ft, 6'-myristoyl sucrose This corresponds to a difference in standard free energy of approxinlately 0.6 lccal mole-1 a t 80°, which likely arises mainly from the difference in the non-bonded interactions about the ester groupings. T h e pyranose ring of the glucose moiety of sucrose exists in the chair form wherein the a t o m on neighboring carbons in the ring are in the staggered FIG.…”

One‐Stage Synthesis of Raffinose Fatty Acid Polyesters

“…The reaction apparatus of Lemieux and McInnes (1962) was modified to substitute (1) liquid nitrogen (-196°C) in the cold trap for carbon dioxide-acetone ( -79°C); (2) a magnetic stirring bar instead of a stirring motor in the three-necked round bottom flask; (3) an additional Friedrichs condenser (in series) leading to the vacuum takeoff line instead of only one Liebig condenser leading to the vacuum take-off line; and (4) a dewatering CaS04 trap to assure a dry nitrogen atmosphere. Heat was supplied by an external, electrically heated and thermostatically controlled hot oil bath to maintain a constant temperature.…”

Influence of solvent on degree of acylation in the formation of sucrose esters

“…Previous work (4,8) indicated such reaction times to be sufficient at the catalyst level used. Previous work (4,8) indicated such reaction times to be sufficient at the catalyst level used.…”