Methylenecyclobutane: Ring-Puckering Potential Function from Mid-Infrared Combination Bands

Abstract

Articles you may be interested inFar-infrared and combination-band spectra of the ring-puckering and ring-flapping vibrations of phthalan: A failure of the one-dimensional modelThe mid-infrared spectra (4000-250 em-I) of methylenecyclobutane, methylene-d2-cyclobutane-2,2-d2, and methylene-d 2 -cyclobutane-d6 have been examined closely for the occurrence of combination bands involving the ring-puckering vibration. A progression of sum bands for methylenecydobutane and a progression of difference bands for methylene-d2-cyclobutane-2, 2-d2 have been simultaneously fit by the onedimensional potential function in the ring-puckering coordinate x: V (x) = 4.229 X 10 5 x4 -1.694 X lO'x 2 • This potential function yields a barrier of 168±10 cm-1 at the planar conformation, in good agreement with the barrier of 160±40 cm-1 determined by other workers from the vibrational dependence of the rotational constants in the microwave spectrum. The detailed shape of the function does not agree as well and particularly the failure of the infrared function to account for the observed 0-1 splitting is noted. This had been noted earlier in the case of silacyclobutane and to a lesser degree, in the case of cyclopentene.

Structure, vibrations and relative stability of 1-methylcyclobutene and methylenecyclobutane tautomers using DFT and CCSD methods

“…Experimentally, the exo-en C1-C2, C2-C3 and C3¼C5 bond lengths were reported to be 1.556, 1.527 and 1.340 # A, respectively, and the C2-C1-C4 and C2-C3-C4 bond angles were found to be 90.9 and 93.1 , respectively. 16 These results are very close with our¯ndings (Table 1). Much older results, in 1944, by Shand et al 6 using electron di®raction investigation are also comparable with our results.…”

“…Experimentally, it was found using mid-IR spectrum, microwave spectrum and Raman spectrum to be 168 AE 10, 160 AE 40 and 141 AE 5 cm À1 , respectively. 16,27,28 Another fundamental ring puckering is located at $ 658 cm À1 , which is in good agreement with the same mode found at 657.2 cm À1 using mid-IR spectrum 16 and con¯rmed by Raman spectrum. 28 The C¼C stretching theoretically located at $ 1770 cm À1 is experimentally observed at 1675 cm À1 (note that the authors did not assign which mode is which).…”

Raman Spectra of Gases. IV. Methylenecyclobutane and Trimethylene Sulfide

“…Scharpen and Laurie,7 from their microwave study, had experimentally determined a 1.12 cm-I separation for the v= 0 to v= 1 ring puckering levels .and from a proposed potential they calculated the v= 1 to 2 to have a value of 91±15 em-I. 2 (0,4) ..... (1,5) 709.0 709.7 -0.7 (0,5) ..... (1,6) 719.5 718.8 0.7 (0,6) ... .. (1, 7) 724.0 724.3 -0.3 (0,7) ..... (1,8) 728.1 729.6 -1.5 (0,8) ..... (1,9) 735.0 734.3 0.7 (0,9) ..... (1,10) 742.7 738.4 4.3 (1, 1) 658.0 (0,1) ..... (1,2) 735.0 735.7 -0.7 (0,2) ... .. (1, 3) 676.…”

Determination of the structure of methylene cyclobutane confirming a non-planar ethene and the structure of the argon–methylene cyclobutane van der Waals complex

“…The barrier to inversion of the ring was 160 ± 40 cm À1 . Malloy et al [7] measured mid-infrared combination bands with the ring-puckering vibrations of MCB and two deuterated isotopomers and derived ring-puckering potential in reduced coordinates, with a barrier of 168 ± 10 cm À1 . At this point, Pickett [8] presented an analysis of large amplitude vibration-rotation interaction Hamiltonians and used MCB as an example to favor use of a reduced axis system, RAS.…”