Conformations of conjugated hydrocarbons. Part 1. A spectroscopic and thermodynamic study of buta-1,3-diene and 2-methylbuta-1,3-diene (isoprene)

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

“…3, however, band contours can be of great utility in assigning modes and are particularly useful in this instance. In agreement with Compton et al (1976), the band at 2956 cm −1 is clearly a fundamental as it is the strongest C-H band in the spectrum. Moreover, its C-type profile uniquely indicates that it is an A mode, namely the highest-frequency A mode, ν 23 , and it is assigned as such.…”

“…Nonetheless, there is an abundance of studies on the vibrational spectra of isoprene, but most have focused on elucidating the structure and identifying its conformational equilibria (Compton et al, 1976;Traetteberg et al, 1984;Bock et al, 1987;Bock and Panchenko, 1989;; fundamental modes typically were assigned during the structural analyses. Based on these previous vibrational assignment studies and structural determinations, and the need for quantitative absorption cross-section data, this paper makes the first comprehensive report of the infrared band strengths of isoprene.…”

“…Frequencies and vibrational assignments are listed in Table 4. Vibrational assignments follow primarily from and Compton et al (1976), and ab initio frequencies from also are listed for reference. Although the two sources generally agree with respect to the fundamental modes of the s-trans conformer, there are minor differences in a few of the assignments and mode descriptions.…”

“…Although the two sources generally agree with respect to the fundamental modes of the s-trans conformer, there are minor differences in a few of the assignments and mode descriptions. For example, Compton et al (1976) originally assigned the peak found at 2956 cm −1 , shown in Fig. 3, to an out-of-plane asymmetric CH 3 stretch, ν 23 , and the peak at 2985 cm −1 to ν 4 , a symmetric CH 2 stretch.…”

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

“…As seon from Table 7, we refined some of the isoprene force constants, using the VFF programs and experimental frequencies cited in CT (mostly from Ref. [42]). …”