Solvent-free esterification process for the synthesis of glucose bolaform surfactants

Glucose bolaform esters or surfactants have been synthesized by esterification reaction in the absence of organic solvent using short chain acid dichlorides as linkers (spacers). The glucose was first reacted with formic acid to produce glucose formate, followed acylation with acid dichloride to produce glucose bolaform esters. No organic solvent was used in the reaction but access acid dichloride behaved like a medium for the reaction. A stream of nitrogen gas was used to eliminate the acid vapor produced during the reaction. Several structures of glucose bolaform compounds containing C3 to C9 hydrocarbon chain linkers were and characterized. The physical properties and the effects of the different spacers/linkers on surfactant properties were also evaluated. The yields of glucose bolaform esters obtained at optimum reaction condition (45oC reaction temperature, 2:1 molar ratio of glucose/ acid dichloride and 50 min. reaction time) were 71.06%, 64.39%, 57.73%, 49.60% of 1,3-propanedioatebis-glucopyranoside, 1,6-hexanedioate-bis-glucopyranoside, 1,8-octanedioate-bis-glucopyranoside, 1,9nonanedioate-bis-glucopyranoside respectively. It was noticed that short chain acid dichlorides were easier to react to form glucose bolaform esters than long chain acid dichlorides. The products obtained were lighter in colour indicating less caramelization of reactants during reaction. Surface tension and HLB values of the bolaform esters were ranged from 13 to 17, and 32.8 to 39.8 mN/m respectively. Based on the HLB values the products are potential emulsifiers for oil in water emulsion.