Methanol and glycolaldehyde production from formaldehyde in massive star-forming regions

Abstract

ABSTRACT Based on typical physical and chemical conditions expected in massive and dense hot cores during the protostar collapse, the formation of glycolaldehyde (CH2OHCHO) and methanol (CH3OH) was investigated from H2 and CO and formaldehyde (H2CO) as an intermediate. Thermochemical properties and rate constants were obtained for gas-phase reactions using high-level electronic structure methods and chemical kinetic calculations, and the concentrations of the molecules were evolved along time. The chemical equilibrium was reached in minutes at 1500 K, a time interval much shorter than that required time for a protostar formation process. The results indicate that the formaldehyde and methanol abundances are always larger than those for glycolaldehyde, for example, at 2000 K and [H2]0 equals to 1023 molecule cm−3, the abundances of H2CO, CH3OH, and CH2OHCHO relative to H2 are equal to 3 × 10−6, 5 × 10−6, and 1 × 10−12, while for [H2]0 equals to 1020 molecule cm−3  these abundances are 3 × 10−9, 5 × 10−12, and 2 × 10−21, respectively. Considering that our results can be applied to explain the proximity of methanol and formaldehyde maser emissions, from the whole set of results, the CH3OH abundance relative to H2CO ranges from 10−3 to 102.