TY - JOUR

T1 - Neighborhood matters

T2 - Steric effects on methyl internal rotation and chlorine nuclear quadrupole coupling in 2-fluoro-4-chlorotoluene

AU - Nair, K. P.Rajappan

AU - Herbers, Sven

AU - Grabow, Jens Uwe

AU - Nguyen, Ha Vinh Lam

N1 - Funding Information: The authors thank the Land Niedersachsen and the Deutsche Forschungsgemeinschaft (DFG) for funding. This work was supported by the Agence Nationale de la Recherche ANR (project ID ANR-18-CE29–0011). We greatly acknowledge Dr. V. Ilyushin for his help in performing the RAM36hf fits and for making his code available to the spectroscopic community. We also thank Dr. W.C. Bailey for checking our NQCC calculations.

PY - 2021/12/15

Y1 - 2021/12/15

N2 - The rotational spectrum of 2-fluoro-4-chlorotoluene was studied in the frequency range 4 to 24 GHz by Fourier transform microwave spectroscopy. Fine torsional splittings into doublets were found for all rotational transitions due to methyl internal rotation hindered with a barrier of about 230 cm−1. In combination with the quadrupole coupling hyperfine splittings on the same order of magnitude originating from the chlorine nucleus, rich spectral features were observed. Rotational and quadrupole coupling constants for the 35Cl and 37Cl isotopologues studied in natural abundance were precisely determined. Results from the experiment were supported by quantum chemical calculations at several levels of theory for the rotational constants and by Bailey's semi-experimental method for the quadrupole coupling constants. The χcc quadrupole coupling tensor element and the barrier to methyl internal rotation were compared with those of other halogen-substituted toluene derivatives.

AB - The rotational spectrum of 2-fluoro-4-chlorotoluene was studied in the frequency range 4 to 24 GHz by Fourier transform microwave spectroscopy. Fine torsional splittings into doublets were found for all rotational transitions due to methyl internal rotation hindered with a barrier of about 230 cm−1. In combination with the quadrupole coupling hyperfine splittings on the same order of magnitude originating from the chlorine nucleus, rich spectral features were observed. Rotational and quadrupole coupling constants for the 35Cl and 37Cl isotopologues studied in natural abundance were precisely determined. Results from the experiment were supported by quantum chemical calculations at several levels of theory for the rotational constants and by Bailey's semi-experimental method for the quadrupole coupling constants. The χcc quadrupole coupling tensor element and the barrier to methyl internal rotation were compared with those of other halogen-substituted toluene derivatives.

KW - Chlorine nuclear quadrupole coupling

KW - Internal rotation

KW - Large amplitude motion

KW - Microwave spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85111534623&partnerID=8YFLogxK

U2 - 10.1016/j.molstruc.2021.131096

DO - 10.1016/j.molstruc.2021.131096

M3 - Article

AN - SCOPUS:85111534623

VL - 1246

JO - Journal of molecular structure

JF - Journal of molecular structure

SN - 0022-2860

M1 - 131096

ER -