title: Mechanisms of glycerol dehydration.
abstract: Dehydration of neutral and protonated glycerol was investigated using quantum mechanical calculations (CBS-QB3). Calculations on neutral glycerol show that there is a high barrier for simple 1,2-dehydration, E(a)=70.9 kcal mol(-1), which is lowered to 65.2 kcal mol(-1) for pericyclic 1,3-dehydration. In contrast, the barriers for dehydration of protonated glycerol are much lower. Dehydration mechanisms involving hydride transfer, pinacol rearrangement, or substitution reactions have barriers between 20 and 25 kcal mol(-1). Loss of water from glycerol via substitution results in either oxirane or oxetane intermediates, which can inter-convert over a low barrier. Subsequent decomposition of these intermediates proceeds via either a second dehydration step or loss of formaldehyde. The computed mechanisms for decomposition of protonated glycerol are supported by the gas-phase fragmentation of protonated glycerol observed using a triple--quadrupole mass spectrometer.
authors: National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA. mark_nimlos@nrel.gov
authors: Mark R
authors: MR
authors: Nimlos
authors: Stephen J
authors: SJ
authors: Blanksby
authors: Xianghong
authors: X
authors: Qian
authors: Michael E
authors: ME
authors: Himmel
authors: David K
authors: DK
authors: Johnson