Production Of Hoch₂co, Hochcho, And Hochco In The Reaction H + Glycolaldehyde (hoch₂cho) In Solid <i>p</i>-h₂ And Its Implication In Astrochemistry

Glycolaldehyde (HOCH$_2$CHO) has been detected in the interstellar medium; it is considered to play an important role in the formation of complex organic molecules, especially higher sugars. We took the advantages of unique properties of \textit{para}-hydrogen (\textit{p}-H$_2$), which serves as a quantum-solid matrix host and a medium for efficient hydrogen-atom reaction, to investigate the reaction between HOCH$_2$CHO and H atoms. H atoms were generated on photolysis at 365 nm of a co-deposited mixture of HOCH$_2$CHO/\textit{p}-H$_2$ and Cl$_2$ and subsequent IR irradiation for promoting the Cl + H$_2$ ($\nu$ = 1) $\rightarrow$ H + HCl reaction. Based on the orientation of O-H and C=O bonds, HOCH$_2$CHO has 4 conformers; \textit{cis}-\textit{cis} conformer is found to have the least energy among all due to the intramolecular H-bonding. In the reaction H + HOCH$_2$CHO at 3.2 K, 5 lines in the first group and 6 lines in the second group are assigned to HOCH$_2$CO and HOCHCHO radicals, products of the first H-abstraction from -CHO and -CH$_2$ groups, respectively. In addition, 2 lines were assigned to HOCHCO, a product of the second H-abstraction. IR irradiation employed during H-atoms generation was also responsible for the conformational conversion of HOCH$_2$CHO, cc $\rightarrow$ \textit{tt}; which intricates the H + \textit{cc}-HOCH$_2$CHO reaction to some extent. Since photolysis at 266 nm also promotes this conversion; we photolyzed the \textit{cc}-HOCH$_2$CHO at 266 nm prior to 365 nm/IR irradiation for complete conversion to the \textit{tt}-form to facilitate the H + \textit{tt}-HOCH$_2$CHO reaction. Four lines in one group and 3 lines in the second group, those differ from their \textit{cc}-form analogs, were assigned to the \textit{tt}-HOCH$_2$CO and \textit{tt}-HOCHCHO radicals, respectively; 2 lines in the third group were assigned to HOCHCO. Besides these assignments, a line at 2079.3 \wn was tentatively assigned to the OCHCO radical, a product of the third H-abstraction. The assignments of all these products agree satisfactorily with vibrational wavenumbers predicted with the B3LYP/aug-cc-pVTZ method. The PES of H + \textit{cc}- and \textit{tt}-HOCH$_2$CHO reactions reveal the feasibility of H-abstraction processes for HOCH$_2$CO, HOCHCHO, HOCHCO, and OCHCO formations after sequential H-abstractions from the CHO, CH$_2$, CH$_2$/CHO, and OH moieties, respectively