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Predictive abilities of scaled quantum-mechanical molecular force fields: application to 2-methylbuta-1,3-diene (isoprene)

“…The calculated value of 405 cm -1 of m 22 is in good agreement with the experimental wavenumber 409cm -1 [6]; the same is true for the m 31 vibration, see Table 1. The assignments of the IR bands at 991 cm -1 (m 26 ), 916 cm -1 (m 27 ), 897 cm -1 (m 28 ), 745 cm -1 (m 29 ), 655 cm -1 (m 30 ), and 550 cm -1 (m 31 ) to the ''out-of-plane'' vibrations of s-gauche-I in [9], as well as in the present work, are in accord with the fact that such bands generally display the strongest intensities in the IR spectrum for such molecules (for example, see [25]). …”

“…Interestingly, a far greater change was observed in the analogous vibration for buta-1,3-diene [25].…”

“…1 s- [9] e Gas-phase IR spectrum [4] corresponding bands with the typical C-contours. Moreover, the typical A-contours of the first overtones for these vibrations of the =CH 2 and =CD 2 moieties are characteristic [24,25]. Indeed, the IR spectrum of s-trans-I in the gas phase [10] finds the bands at 1,815 cm -1 and 1,791 cm -1 ; this corroborates the assignments of the bands at 906 cm -1 and 894 cm -1 to the out-of-plane wagging vibrations of the =C5H 2 (m 27 ) and =C1H 2 (m 28 ) moieties (Fig.…”

“…vibrations in going from s-trans-or s-gauche-buta-1,3-diene to their deuteroderivatives, viz. CD 2 (CH) 2 CD 2 and C 4 D 6 [25,27]. The assignments of the pair of wavenumbers, 412 cm -1 and 401 cm -1 , of s-trans-I requires some discussion.…”

Interplay of Thermochemistry and Structural Chemistry, the Journal (Volume 14, 2003) and the Discipline

“…Panchenko et al discusses 1,3-butadiene [66]. This species is the archetypal conjugated organic molecule.…”