title: Pyrolysis of the Simplest Carbohydrate, Glycolaldehyde (CHO-CH2OH), and Glyoxal in a Heated Microreactor.
abstract: Both glycolaldehyde and glyoxal were pyrolyzed in a set of flash-pyrolysis microreactors. The pyrolysis products resulting from CHO-CH2OH and HCO-CHO were detected and identified by vacuum ultraviolet (VUV) photoionization mass spectrometry. Complementary product identification was provided by argon matrix infrared absorption spectroscopy. Pyrolysis pressures in the microreactor were about 100 Torr, and contact times with the microreactors were roughly 100 μs. At 1200 K, the products of glycolaldehyde pyrolysis are H atoms, CO, CH2═O, CH2═C═O, and HCO-CHO. Thermal decomposition of HCO-CHO was studied with pulsed 118.2 nm photoionization mass spectrometry and matrix infrared absorption. Under these conditions, glyoxal undergoes pyrolysis to H atoms and CO. Tunable VUV photoionization mass spectrometry provides a lower bound for the ionization energy (IE)(CHO-CH2OH) ≥ 9.95 ± 0.05 eV. The gas-phase heat of formation of glycolaldehyde was established by a sequence of calorimetric experiments. The experimental result is ΔfH298(CHO-CH2OH) = -75.8 ± 1.3 kcal mol(-1). Fully ab initio, coupled cluster calculations predict ΔfH0(CHO-CH2OH) of -73.1 ± 0.5 kcal mol(-1) and ΔfH298(CHO-CH2OH) of -76.1 ± 0.5 kcal mol(-1). The coupled-cluster singles doubles and noniterative triples correction calculations also lead to a revision of the geometry of CHO-CH2OH. We find that the O-H bond length differs substantially from earlier experimental estimates, due to unusual zero-point contributions to the moments of inertia.
authors.forename: Jessica P
authors.initials: JP
authors.lastname: Porterfield
authors.forename: Joshua H
authors.initials: JH
authors.lastname: Baraban
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratories , Berkeley, California 94720, United States.
authors.forename: Tyler P
authors.initials: TP
authors.lastname: Troy
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratories , Berkeley, California 94720, United States.
authors.forename: Musahid
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Harvard-Smithsonian Center for Astrophysics , Cambridge, Massachusetts 02138, United States.
authors.forename: Michael C
authors.initials: MC
authors.lastname: McCarthy
authors.affiliation: Department of Chemistry, Xavier University of Louisiana , New Orleans, Louisiana 70125-1098, United States.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Morgan
authors.forename: John W
authors.initials: JW
authors.lastname: Daily
authors.affiliation: Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Thanh Lam
authors.initials: TL
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: Stanton
authors.forename: G Barney
authors.initials: GB
authors.lastname: Ellison
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry; D002241:Carbohydrates / Q000737:chemistry*; D006037:Glyoxal / Q000737:chemistry*; D006358:Hot Temperature; D013058:Mass Spectrometry; D013055:Spectrophotometry, Infrared
chemical_list: D002241:Carbohydrates; D006037:Glyoxal; D000079:Acetaldehyde; C010972:glycolaldehyde