Production Of •ch2nh2 And Ch2nh In The Reactions Of Methylamine (ch3nh2) With •h Or •oh In Solid P-h2 And Its Implication In Astrochemistry

Joshi, Prasad Ramesh

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https://hdl.handle.net/2142/116611 Copy

Description

Title

Production Of •ch2nh2 And Ch2nh In The Reactions Of Methylamine (ch3nh2) With •h Or •oh In Solid P-h2 And Its Implication In Astrochemistry

Author(s)

Joshi, Prasad Ramesh

Contributor(s)

Lee, Yuan-Pern

Issue Date

2022-06-21

Keyword(s)

Radicals

Abstract

Methylamine (CH$_{3}$NH$_{2}$) is considered to be a potential precursor for the formation of interstellar glycine through the reaction between aminomethyl radical (•CH$_{2}$NH$_{2}$) and HOCO, but direct evidence of the formation and spectral identification of •CH$_{2}$NH$_{2}$ remains unreported. Taking advantage of unique properties associated with the {\it para}-hydrogen ({\it p}-H$_{2}$) matrix, we performed the reaction H + CH$_{3}$NH$_{2}$ in solid {\it p}-H$_{2}$ at 3.2 K. To generate H atoms, photolysis at 365 nm of a co-deposited mixture of CH$_{3}$NH$_{2}$/{\it p}-H$_{2}$ and Cl$_{2}$ to produce Cl atoms and subsequent IR irradiation for promoting the Cl + H$_{2}$ ($\nu$ = 1) $\rightarrow$ H + HCl reaction were carried out. IR spectra of •CH$_{2}$NH$_{2}$ and CH$_{2}$NH were observed upon UV/IR irradiation and when the matrix was maintained in darkness. The new IR spectrum of •CH$_{2}$NH$_{2}$ clearly indicates that •CH$_{2}$NH$_{2}$ can be formed from the reaction H + CH$_{3}$NH$_{2}$ in dark interstellar clouds. Experiments on CD$_{3}$NH$_{2}$ produced CHD$_{2}$NH$_{2}$, in addition to •CD$_{2}$NH$_{2}$ and CD$_{2}$NH, confirming the occurrence of H addition to •CD$_{2}$NH$_{2}$. The potential-energy scheme of H + CH$_{3}$NH$_{2}$ reactions reveals the feasibility of sequential H-abstraction and H-addition reactions for the formation of products observed in this study. The observed dual-cycle mechanism containing two consecutive H-abstraction and two H-addition steps chemically connects CH$_{3}$NH$_{2}$ and CH$_{2}$NH and might imply their quasi-equilibrium. In another experimental method, photolysis at 250 nm of a H$_{2}$O$_{2}$-doped CH$_{3}$NH$_{2}$/p-H$_{2}$ matrix was performed to generate •OH to facilitate the •OH + CH$_{3}$NH$_{2}$ reaction; further reaction of •OH + H$_{2}$ $\rightarrow$ H$_{2}$O + H might also trigger the H + CH$_{3}$NH$_{2}$ reaction. Significantly more •CH$_{2}$NH$_{2}$ was produced than in CH$_{3}$NH$_{2}$/Cl$_{2}$/{\it p}-H$_{2}$ experiments, consistent with a barrier predicted for •OH + CH$_{3}$NH$_{2}$ much smaller than that for H + CH$_{3}$NH$_{2}$. All species observed herein are plausible starting materials for interstellar glycine in molecular clouds.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116611

DOI

https://doi.org/10.15278/isms.2022.TN07

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