Rationelle stärkeacetat‐synthesen

Abstract

ZUSAMMENFASSUNG:Mit Kaliumcarbonat als Aktivator werden aus Hochamylosestarke (HAS) rnit iiberschiissigem Acetanhydrid bei Reaktionszeiten von 1-2 h in hohen Ausbeuten Produkte mit hohen Durchschnittssubstitutionsgraden (DS) erhalten.In N-Methyl-2-pyrrolidon konnen HAS mit stochiometrischen Mengen Acetanhydrid und rnit nichtfliichtigen starken organischen Basen wie 4-Dimethylaminopyridin oder 1 ,4-Diazabicyclo[2.2.2]octan als Katalysatoren in Reaktionszeiten von weniger als 1 h und in hohen Ausbeuten zu Acetaten mit DS < 2 umgesetzt werden. SUMMARY:Acetylation of high-amylose starch to products of high average degree of substitution (DS) with yield of > 90% proceeds in 1 -2 h using potassium carbonate as activating agent. Acetylstarches of DS < 2 are available by acetylation with stoichiometric amounts of acetic anhydride in N-methyl-2-pyrrolidone applying organic catalysts as 4-dimethylaminopyridine and 1,4-diazabicyclo[2.2.2]octane, respectively. Reaction times of 1 h and less are sufficient to receive the desired acetates in high yield.

Investigations on esterification reactions of starches in 1‐N‐butyl‐3‐methylimidazolium chloride and resulting substituent distribution

“…Compared with the well-known acetylation reaction, 12 not many of these esterification reactions of starch 13 are so fast or even faster like the described reaction. Most of the time, faster acetylation reactions are conducted under greater reaction temperatures.…”

“…Interactions between the IL as solvent and the polymeric hydroxyl groups may be the reason for the described substituent distribution. Therefore, the partial substitution of differently esterified starches as well as starches with different substituents were analyzed with 13 C-NMR. Also, analyses for reaction temperature and the influence of [C 4 mim] þ Cl À on polymeric degradation were made.…”

“…For esterification of starch in [C 4 mim] þ Cl À by method of Biswas and Shogren, 8 an unequal substituent distribution within the anhydro glucose unit (AGU) can be observed by liquid 13 C-NMR. Investigations for that purpose as well as influence on molecular weight average and of reaction temperature were made by synthesizing different starch esters (Fig.…”

“…The authors thank Mrs. Dr. Radosta and Mr. Dr. Ebert, Fraunhofer Institute for Applied Polymer Research, for the measurement of the GPC-MALLS and 13 C-NMR data.…”

Esterification of Polysaccharides

“…Formamide, DMF and NMP can be used as solvent in the same manner as DMSO, e.g. for the acetylation of starch [147]. DMF is used as solvent for the esterification of starch with fatty acids [148].…”