title: On the formation of pyridine in the interstellar medium.
abstract: Nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) have been proposed to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block - the aromatic pyridine molecule - has remained elusive for decades. Here we reveal a potential pathway to a facile pyridine (C5H5N) synthesis via the reaction of the cyano vinyl (C2H2CN) radical with vinyl cyanide (C2H3CN) in high temperature environments simulating conditions in carbon-rich circumstellar envelopes of Asymptotic Giant Branch (AGB) stars like IRC+10216. Since this reaction is barrier-less, pyridine can also be synthesized via this bimolecular reaction in cold molecular clouds such as in TMC-1. The synchronized aromatization of precursors readily available in the interstellar medium leading to nitrogen incorporation into the aromatic rings would open up a novel route to pyridine derivatives such as vitamin B3 and pyrimidine bases as detected in carbonaceous chondrites like Murchison.
authors.affiliation: Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. ralfk@hawaii.edu.
authors.forename: Dorian S N
authors.initials: DS
authors.lastname: Parker
authors.affiliation: Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. ralfk@hawaii.edu.
authors.forename: Ralf I
authors.initials: RI
authors.lastname: Kaiser
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. mahmed@lbl.gov.
authors.forename: Oleg
authors.initials: O
authors.lastname: Kostko
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. mahmed@lbl.gov.
authors.forename: Tyler P
authors.initials: TP
authors.lastname: Troy
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. mahmed@lbl.gov.
authors.forename: Musahid
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. hhchang@mail.ndhu.edu.tw.
authors.forename: Bing-Jian
authors.initials: BJ
authors.lastname: Sun
authors.affiliation: Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. hhchang@mail.ndhu.edu.tw.
authors.forename: Shih-Hua
authors.initials: SH
authors.lastname: Chen
authors.affiliation: Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. hhchang@mail.ndhu.edu.tw.
authors.forename: A H H
authors.initials: AH
authors.lastname: Chang