Conformational isomers oftrans-urocanic acid observed by rotational spectroscopy

Abstract

Rotational spectra have been measured and assigned for four conformers of trans-urocanic acid.

Microwave Spectrum of Two‐Top Molecule: 2‐Acetyl‐3‐Methylthiophene

“…Each vibrational level is three-fold degenerated, and therefore, no torsional splitting is observed in the spectrum. [4] The molecule can be considered as a rigid rotor, with thousands of examples previously studied using high resolution rotational spectroscopy, stretching several important subjects from fundamental interest, [5][6][7] structure determination, [8][9][10] astrophysics, [11][12][13] biomolecules, [14][15][16] chirality [17][18][19] to microsolvation [20][21][22] and complexes. [23,24] A barrier of zero, on the other hand, describes a free internal rotor where all energy levels except the first one are two-fold degenerated, as shown, e. g., for the methyl group in CH 3 À C�CÀ CF 3 .…”

Methyl Internal Rotation in Fruit Esters: Chain-Length Effect Observed in the Microwave Spectrum of Methyl Hexanoate

“…The B3LYP method is also extended with the Coulomb-attenuating method (CAM) [34]. Such method/basis set combinations have been used popularly and yielded good results to various types of molecules [35][36][37][38]. Results from this basis set variation, mainly including the rotational constants and their differences to the experimental values, are summarized in Table S3.…”