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

• Published in: Green chemistry letters and reviews Vol. 17; no. 1
• Main Authors: Faustino dos Santos, Priscila, da Silva, Fernanda Priscila Nascimento Rodrigues, da Silva, Sara Raposo Benfica, Pereira, Vera Lúcia Patrocinio
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 31.12.2024; Taylor & Francis Group
• Subjects: A26; Amberlyst; AmberlystTM A26 −OH form; Glycerol; heterogeneous medium; KOH/Al; KOH/Al2O3; OH form; Williamson ether synthesis
• ISSN: 1751-8253; 1751-7192
• DOI: 10.1080/17518253.2024.2360477

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 A26 TM − OH form and KOH supported on alumina (KOH/Al 2 O 3 ) 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 A26 TM − OH form or KOH/Al 2 O 3 . When Amberlyst A26 TM − 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/Al 2 O 3 , 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 A26 TM − OH could be regenerated and reused in the process.