Nitrogen Quadrupole Coupling Constants of Nitrobenzene and o‐Nitrophenol

Abstract

The microwave spectra of nitrobenzene, C6H5NO2, and o‐nitrophenol, C6H4 (OH)NO2, have been observed with high resolution using a waveguide microwave Fourier transform spectrometer. Nuclear quadrupole hyperfine structures have been resolved and analysed to obtain the following nitrogen quadrupole coupling constants: χaa = ‐1.1589 (24) MHz, χbb = 0.3195 (36) MHz, χcc = 0.8394 (36) MHz for nitrobenzene; χaa = ‐1.234 (4) MHz, χbb = 0.348 (3) MHz, χcc = 0.886 (3) MHz for o‐nitrophenol. For nitrobenzene, the variation of the coupling constants with torsional state has also been studied.

Electron-withdrawing effects on the molecular structure of 2- and 3-nitrobenzonitrile revealed by broadband rotational spectroscopy and their comparison with 4-nitrobenzonitrile

“…The experimentally determined quadrupole coupling constants for 4-nitroanisole are very similar to those determined for the ground state of nitrobenzene, where χ aa = −1.1589 (24) MHz and χ bb−cc = −0.5199(68) MHz 35 . Nuclear quadrupole coupling constants are sensitive to the local electronic environment, as well as the orientation of the principal axis system for the molecule.…”

Theoretical Studies of the Solvent Effect on the Conformation of the HO–C–C–X (X = F, NH2, NO2) Moiety with Competing Intra- and Intermolecular Hydrogen Bonds

“…However, from studies of the microwave spectrum, the molecule is planar. 28,29 Taking the lower limit from ref 27, the predicted structure is also close to planar. In good accord, all but the MP2/6-311+ +G** geometry optimization (not shown) found a planar heavy atom skeleton.…”

“…On the basis of an electron diffraction investigation, the experimental torsion angle is 7.3 ± 5.7° (at 1 SD, 67% probability). However, from studies of the microwave spectrum, the molecule is planar. , Taking the lower limit from ref , the predicted structure is also close to planar. In good accord, all but the MP2/6-311++G** geometry optimization (not shown) found a planar heavy atom skeleton.…”

“…In order to find a relevant method for geometry optimization, geometries of 2F-ethanol, 2NH 2 -ethanol, and 2NO 2 -phenol have been optimized at different theoretical levels in the gas-phase, and the obtained structural parameters were compared with available experimental data. − The optimized geometry does depend both on the considered theoretical level and the applied basis set. For the test calculations, the DFT B3LYP, , B97D, M062X, and ab initio MP2 methods were considered by applying the 6-311++G**, aug-cc-pvdz, and aug-cc-pvtz basis sets − in different combinations.…”

Structural determination and population transfer of 4-nitroanisole by broadband microwave spectroscopy and tailored microwave pulses

“…The experimentally determined quadrupole coupling constants for 4-nitroanisole are very similar to those determined for the ground state of nitrobenzene, where χ aa = 1.1589 (24) MHz and χ bb-cc = 0.5199(68) MHz. 35 Nuclear quadrupole coupling constants are sensitive to the local electronic environment as well as the orientation of the principal axis system of the molecule. A difference in the nuclear quadrupole coupling constants of only 5 and 49 kHz for χ aa and χ bb-cc , respectively, would suggest that the addition of a paramethoxy group to nitrobenzene has only a small effect on the local electronic environments of the respective nitrogen atoms or the orientation of the principal axis system.…”