Mechanisms of Glycerol Dehydration

Introduction:
This text provides an in-depth analysis of the mechanisms and kinetics of sugar chemistry, specifically focusing on glycerol as a model compound due to its three adjacent hydroxyl groups. The study investigates the unimolecular decomposition of glycerol and protonated glycerol using molecular modeling and quantum mechanical CBS-qB3 computational techniques. additionally, collisional induced dissociation (CID) mass spectrometry was performed on protonated glycerol and selected isotopologues.

Key Points:

* Glycerol has three adjacent hydroxyl groups, making it a suitable model for studying sugar chemistry.
* The text focuses on the unimolecular decomposition of glycerol and protonated glycerol using molecular modeling and quantum mechanical CBS-qB3 computational techniques.
* Collisional induced dissociation (CID) mass spectrometry was performed on protonated glycerol and selected isotopologues.
* The study found that 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 interconvert 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.

Main Message:
The text emphasizes the importance of understanding the mechanisms and kinetics of sugar chemistry, particularly in the context of using sugars as a renewable source of energy, fuels, and chemicals. The study's findings contribute to a better understanding of glycerol dehydration, which can be useful in industrial processes involving triols, such as sugars. The text highlights the potential of using computational techniques and mass spectrometry to study complex chemical reactions and gain insights into their mechanisms and kinetics.

Nimlos, Mark R., Stephen J. Blanksby, Xianghong qian, Michael E. himmel, and David K. Johnson. “Mechanisms of Glycerol Dehydration.” The Journal of Physical Chemistry a 110, no. 18 (May 1, 2006): 6145–56. https://doi.org/10.1021/jp060597q.