Ab initio structures and vibrational analysis of two planar configurations of 1,3,5-hexatriene

Theoretical analysis of spectra of short polyenes

“…Vibrational spectra were recorded by several authors112"114,122,123 and all the bands are assigned (see Table 8). Quantum chemical calcu-lations84, 89,103,116,123 and the study of deuterated and methylated derivatives support the assignments.116,124 By comparing cis-and trans-hexatriene frequencies, we notice a 100 cm'1 difference between the two C-C totally symmetric frequencies (1082 vs 1188 cm'1). Also some symmetry inversions similar to those in butadiene are noticed.…”

A reevaluation of the assignment of the vibrational fundamentals and the rotational analysis of bands in the high-resolution infrared spectra of trans- and cis-1,3,5-hexatriene

“…Initial calculations of vibration frequencies of the HTEs were done with scaling at the Hartree-Fock level by Bock et al [11] and at the semiempirical level (Parr-Pople-Pariser-CI) by Hemley et al [12]. Frequencies were also calculated ab initio by Foragasi et al [13] and Yoshida et al [14].…”

Vibrational spectra of 1,3,5-hexatriene and methylated derivatives—II. The coupling pattern for lateral methylation

“…A proper discussion of the valence force fields in Tables 7 and 8 would be quite extensive. Here, we shall only give a brief comparison of our values with the scaled ab initio values from Refs [9,20,21].…”

“…Compared to CT, we modified the in-plane force field for E-hexatriene. In our choice of starting values for the refinement we took into account the values used in two of the most recent calculations [9,20].…”