Starch Formates: Synthesis and Modification.

Sascha Blohm,Haisong Qi,Thomas Heinze

doi:10.3390/molecules26164882

Abstract

Starch can be efficiently converted into the corresponding formates homogeneously using N-formyl imidazole obtained by the reaction of 1,1′-carbonyldiimidazole and formic acid in dimethyl sulfoxide as a solvent. Starch formates are soluble in polar aprotic solvents, not susceptible against hydrolysis, and not meltable. Thermoplastics could be generated by conversion of starch formates with long-chain fatty acids exemplified by the conversion with lauroyl chloride in N,N-dimethylacetamide, leading to mixed starch laurate formates. The mixed esters show melting temperatures mainly dependent on the amount of laurate ester moieties.

Highlights

Polysaccharide esters play an important role in various fields of application, e.g., as foils, films, filters, and thermoplastic to replace plastics based on fossil resources
The N-formyl imidazole was added to a solution of starch (1) in dimethyl sulfoxide (DMSO) at an elevated temperature (Figure 1)
An efficient process for the preparation of pure starch formates by conversion of starch with N-formyl imidazole obtained by the reaction of formic acid with 1,10 -carbonyldiimidazole was developed yielding highly substituted products with degrees of substitution (DS) of up to 2.55

Summary

Introduction

Polysaccharide esters play an important role in various fields of application, e.g., as foils, films, filters, and thermoplastic to replace plastics based on fossil resources. Thermoplastic starch may be obtained by derivatisation with long-chain fatty acids that yields a disturbance of the intra- and intermolecular hydrogen bonds of the polysaccharide [1,2,3]. Starch formate was obtained by the reaction of starch with formic acid [6,7,8,9,10,11,12,13,14,15]. The highest DS value of starch formate known was 2.14 and was reached at extended reaction time, high temperature, with extensively dried starch, and the use of a high excess of concentrated formic acid [8]. The reaction of formic acid with 1,10 -carbonyldiimidazole (CDI) has been described, resulting in N-formyl imidazole [16]. N-formyl imidazole is stable up to about 60 ◦ C and rather sensitive to hydrolysis

Methods

Results

Discussion

Conclusion