Solvent-free reactions as green chemistry procedures for the synthesis of cosmetic fatty esters

Abstract

Solid–liquid solvent-free phase transfer catalysis (PTC) and acidic catalysis in dry media were applied, as green chemistry procedures, to the synthesis under mild conditions of long chain aliphatic esters of interest in the cosmetic field. The reactions were performed under conventional heating and microwave activation, analysing the profiles of the temperature increases during the reactions and studying the yields at different reaction times. The selected esters were obtained with very good yields within short reaction times.Using Aliquat 336 as phase transfer agent, the results showed lower yields under classical heating for very short reaction times (5 min), but usually comparable to the yields obtained under microwave heating extending the reaction time up to 15 min.The simple heterogeneous mixture of reagents with catalytic amount of neat p-toluenesulfonic acid (PTSA) under classical heating leads to good results, similar to those obtained under microwave activation with regards to yields and reaction times (10 min for microwave activation/15 min for oil bath).