Obtaining glycerol alkyl ethers via Williamson synthesis in heterogeneous media using amberlyst-A26TM −OH form and KOH/Al2O3 as basic solid reagents

Abstract

Two innovative and efficient routes were developed to produce glycerol-alkyl ethers employing Williamson reaction conditions in a heterogeneous medium. Thus, the ion exchange resin Amberlyst A26TM −OH form and KOH supported on alumina (KOH/Al2O3) were used as basic solid reagents for alkoxide ion formation. First, glycerol-1,3-iodohydrin and glycerol-1,3-bromohydrin were converted into 1,3-methyl- and 1,3-ethyl glycerol ethers (98–100%) when reacted with MeOH and EtOH, both as solvent and reagent. A second route employed glycerol as an alkoxide ion source and different organic halides such as electrophiles (ethyl iodide, ethyl bromide, allyl bromide, and benzyl bromide) in the presence of Amberlyst A26TM −OH form or KOH/Al2O3. When Amberlyst A26TM −OH resin was used glycerol was converted (100%) to glycerol-1-monoether (73%), -1,3-diether (21%), and -triether (6%) by treating with ethyl bromide or ethyl iodide at 60°C in 1,4-dioxane for 24 h. The use of more reactive halides produced a complex mixture of products. Additionally, the use of ethyl bromide in the presence of KOH/Al2O3, under reflux in 1,4-dioxane for 24 h, led to the consumption of 90% of glycerol with the formation of glycerol-1-ethyl ether (98%) and glycerol-1,3-ethyl ether (2%). The ion exchange resin Amberlyst A26TM −OH could be regenerated and reused in the process.

Keywords

• Glycerol
• Williamson ether synthesis
• heterogeneous medium
• AmberlystTM A26 −OH form
• KOH/Al2O3