TY - JOUR

T1 - Rotational Spectroscopy of the Lowest Energy Conformer of 2-Cyanobutane

AU - Müller, Holger S.P.

AU - Zingsheim, Oliver

AU - Wehres, Nadine

AU - Grabow, Jens Uwe

AU - Lewen, Frank

AU - Schlemmer, Stephan

N1 - Funding Information: We thank Marius Hermanns and Dennis Wachsmuth for help during the FTMW measurements in Hannover. We are grateful to Arnaud Belloche for communicating the results of a search for 2-cyano-anti-butane in the EMoCA survey. We thank the reviewers for helpful suggestions and questions. This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) through the collaborative research grant SFB 956 “Conditions and Impact of Star Formation”, project area B3. O.Z. is grateful for a stipend from the Bonn-Cologne Graduate School of Physics and Astronomy (BCGS). Publisher Copyright: © 2017 American Chemical Society. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.

PY - 2017/9/28

Y1 - 2017/9/28

N2 - Isopropyl cyanide was recently detected in space as the first branched alkyl compound. Its abundance with respect to n-propyl cyanide in the Galactic center source Sagittarius B2(N2) is about 0.4. Astrochemical model calculations suggest that for the heavier homologue butyl cyanide the branched isomers dominate over the unbranched n-butyl cyanide and that 2-cyanobutane is the most abundant isomer. We have studied the rotational spectrum of 2-cyanobutane between 2 and 24 GHz using Fourier transform microwave spectroscopy and between 36 and 402 GHz employing (sub)millimeter absorption spectroscopy. Transitions of the lowest energy conformer were identified easily. Its rotational spectrum is very rich, and the quantum numbers J and Ka reach values of 111 and 73, respectively. This wealth of data yielded rotational and centrifugal distortion parameters up to tenth order, diagonal and one off-diagonal 14N nuclear quadrupole coupling parameters, and one nuclear spin-rotation coupling parameter. We have also carried out quantum chemical calculations in part to facilitate the assignments. The molecule 2-cyanobutane was not found in the present ALMA data of Sagittarius B2(N2), but it may be found in the more sensitive data that have been completed very recently in the ALMA Cycle 4. (Graph Presented).

AB - Isopropyl cyanide was recently detected in space as the first branched alkyl compound. Its abundance with respect to n-propyl cyanide in the Galactic center source Sagittarius B2(N2) is about 0.4. Astrochemical model calculations suggest that for the heavier homologue butyl cyanide the branched isomers dominate over the unbranched n-butyl cyanide and that 2-cyanobutane is the most abundant isomer. We have studied the rotational spectrum of 2-cyanobutane between 2 and 24 GHz using Fourier transform microwave spectroscopy and between 36 and 402 GHz employing (sub)millimeter absorption spectroscopy. Transitions of the lowest energy conformer were identified easily. Its rotational spectrum is very rich, and the quantum numbers J and Ka reach values of 111 and 73, respectively. This wealth of data yielded rotational and centrifugal distortion parameters up to tenth order, diagonal and one off-diagonal 14N nuclear quadrupole coupling parameters, and one nuclear spin-rotation coupling parameter. We have also carried out quantum chemical calculations in part to facilitate the assignments. The molecule 2-cyanobutane was not found in the present ALMA data of Sagittarius B2(N2), but it may be found in the more sensitive data that have been completed very recently in the ALMA Cycle 4. (Graph Presented).

UR - http://www.scopus.com/inward/record.url?scp=85030527031&partnerID=8YFLogxK

U2 - 10.1021/acs.jpca.7b06072

DO - 10.1021/acs.jpca.7b06072

M3 - Article

C2 - 28862854

AN - SCOPUS:85030527031

VL - 121

SP - 7121

EP - 7129

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 38

ER -