Rotamer interconversion of partially deuterated methanol species in rare gas and nitrogen matrices

Serrallach, A.; Meyer, Rolf

doi:10.1016/0022-2852(76)90130-2

Cited by 22 publications

(6 citation statements)

References 18 publications

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“…Such phenomena were observed, for instance, for some simple alcohol molecules, like methanol or ethanol, isolated in di †erent matrixes. 22,23 In all those cases where true equilibrium has been observed in low temperature matrixes, the gas-phase energy barriers are known to be relatively low (below 6 kJ mol~1) and, most times, only hydrogen atoms are involved in the movement leading to the conformational changes, i.e., no signiÐcant matrix relaxation is required during the conformational isomerization process.…”

Section: Resultsmentioning

confidence: 99%

Conformational isomerism in methyl cyanoacetate: A combined matrix-isolation infrared spectroscopy and molecular orbital study

Reva¹,

Ilieva

Fausto³

2001

Phys. Chem. Chem. Phys.

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Study of the conformational isomerism of methyl cyanoacetate MCA) aided for the Ðrst (N3CCH 2 COOCH 3 , time by matrix-isolation infrared spectroscopy is reported. The conformational isomerization processes in MCA in the temperature range from 10 to 70 K were studied in detail in argon and xenon matrixes. During annealing of the matrixes direct interconversion of the gauche into the syn conformer has been registered. A similar, but more pronounced, gauche ] syn interconversion e †ect was observed in a series of experiments in which matrixes were deposited at increased substrate temperature. The experiment is supported by theoretical predictions undertaken at di †erent levels of approximation (MP2 and DFT/B3LYP). It is shown that, for the single molecule in vacuum, the syn conformer (CÈCÈC2O dihedral angle equal to 0¡) corresponds to the conformational ground state, with the doubly degenerated by symmetry gauche conformer (CÈCÈC2O dihedral angle equal to^139.9¡) being only slightly less stable than the most stable form (MP2/6-31G** kJ mol~1). In the matrixes, the energy gap between the syn and gauche conformers *E (gauche?syn) \ 0.174 increases, with estimated to be about 1.4 kJ mol~1 in xenon. The predicted energy barriers for *E (gauche?syn) conformer interconversion were found to be signiÐcantly low : the MP2/6-31G** calculated *E (syn?gauche) energy barrier is ca. 3.65 kJ mol~1, while the calculated energy barrier separating the two symmetrically equivalent gauche conformers stays only 0.196 kJ mol~1 above the energy of these forms. In the matrixes, energy barrier increases to at least 17È18 kJ mol~1, while the energy barrier is, *E (syn?gauche) *E (gauche?gauche) with all probability, still lower than in the gaseous phase. The matrix isolation spectroscopic data indicate that interconversion between the gauche conformers occurs even in the low temperature matrixes.

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Section: Resultsmentioning

confidence: 99%

Conformational isomerism in methyl cyanoacetate: A combined matrix-isolation infrared spectroscopy and molecular orbital study

Reva¹,

Ilieva

Fausto³

2001

Phys. Chem. Chem. Phys.

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“…Hence, ( s )-CH 2 DCHSO is lower in energy than ( a )-CH 2 DCHSO, and ( a )-CHD 2 CHSO is lower in energy than ( s )-CHD 2 CHSO. This isotope effect has also been seen in deuterated isotopomers of acetaldehyde, methylamine, and methanol. , Quantitative isotopic energy differences were obtained for acetaldehyde and methylamine by using the accidental degeneracy between rotational levels of the ( s ) and ( a ) d 1 isotopomers and the resultant perturbations to obtain the overall shift of the ( s ) isotopomer levels relative to the ( a ) isotopomer levels. , The energy of the ( s )-CH 2 DCHO rotational levels must be lowered by 15.55 cm -1 relative to the ( a )-CH 2 DCHO levels to get a reasonable interaction of appropriate ( s ) and ( a ) levels. Harmonic force-field calculations confirm that ( s )-CH 2 DCHO is lower in energy than ( a )-CH 2 DCHO. , These calculations also show that the energy lowering is primarily due to a slightly larger force constant for the C−H bond in the CCO plane than for the two C−H bonds located out of the CCO plane.…”

Section: Discussionmentioning

confidence: 96%

Microwave Investigation of (Z)- and (E)-Ethanethial S-Oxide

Gillies

Grabow

et al. 1996

J. Phys. Chem.

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Pulsed-beam Fourier transform microwave spectroscopy was used to study ethanethial S-oxide, an unstable species generated in a (Z)/(E) ratio of 97/3 by pyrolysis of 2-methyl-2-propylvinyl sulfoxide at 350°C in Ar or Ne/He gas flows. Rotational transitions of the (Z) normal isotopomer exhibited A-E state splittings due to internal rotation of the methyl group. A global fit of the observed A and E state lines of the (Z) isomer to an internal rotor Hamiltonian gave rotational constants and centrifugal distortion constants of A ) 14237.0861 (5) MHz, B ) 4678.4488 (3) MHz, C ) 3594.8008 (2) MHz, ∆ JK ) -9.43 (55) kHz, ∆ J ) 3.48 (11) kHz, and δ J ) 1.11 (2) kHz and a 3-fold internal rotor barrier of 285.6 (3) cm -1 . No internal rotation splitting was observed for the (E) isomer and a pseudorigid rotor fit of the observed transitions of the normal isotopomer gave A ) 31 128 (27) MHz, B ) 3475.8521 (16) MHz, C ) 3188.4429 (23) MHz, and ∆ J ) 0.49 (12) kHz.Microwave spectra of eight (Z) isotopomers were assigned, and a partial substitution structure was derived: r(CdS) ) 1.618 (3) Å, r(SsO) ) 1.477 (4) Å, r(CsC) ) 1.493 (3) Å, θ(CSO) ) 113.9 (2)°, and θ(CCS) ) 125.4 (2)°. The electric dipole moment components of the (Z) isomer along the a and b principal axes were measured to be µ a ) 2.714 (5) D and µ b ) 1.869 (35)D, respectively.

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“…[4][5][6][7][8][9] Exhaustive vibrational studies of methanol and ethanol have revealed the presence of the monomer, dimer, and polymer species in low-temperature matrices. [10][11][12] In addition to the hydrogen bonds, conformational behavior is an important factor to characterize the physical and chemical properties of alcohols. The presence of the trans and gauche conformations about the CC-OH bond axis of ethanol has been found by microwave spectroscopic studies.…”

Section: Introductionmentioning

confidence: 99%

Conformational Study of 1-Butanol by the Combined Use of Vibrational Spectroscopy and ab Initio Molecular Orbital Calculations

Ohno¹,

Yoshida²,

Watanabe³

et al. 1994

J. Phys. Chem.

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Rotamer interconversion of partially deuterated methanol species in rare gas and nitrogen matrices

Cited by 22 publications

References 18 publications

Conformational isomerism in methyl cyanoacetate: A combined matrix-isolation infrared spectroscopy and molecular orbital study

Conformational isomerism in methyl cyanoacetate: A combined matrix-isolation infrared spectroscopy and molecular orbital study

Microwave Investigation of (Z)- and (E)-Ethanethial S-Oxide

Conformational Study of 1-Butanol by the Combined Use of Vibrational Spectroscopy and ab Initio Molecular Orbital Calculations

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