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1.
Ying-Sing Li 《Journal of Molecular Spectroscopy》1984,104(2):302-307
The rotational spectrum of 3-methylcyclopentanone has been observed in the frequency region from 18.0 to 26.5 GHz. Both a-type and b-type transitions in the ground vibrational state and a-type transitions in five excited states have been assigned. The ground state rotational constants are determined to be A = 5423.32 ± 0.18, B = 1949.51 ± 0.01, and C = 1529.59 ± 0.01 MHz. Analysis of the measured quadratic Stark effects gives the dipole moment components ∥μa∥ = 2.97 ± 0.02, ∥μb∥ = 1.00 ± 0.03, ∥μc∥ = 0.18 ± 0.06, and the total dipole moment ∥μt∥ = 3.14 ± 0.03 D. These data are consistent with a twisted-ring conformation with a methyl group in the equatorial position. 相似文献
2.
The microwave spectra of tertiarybutylphosphine (CH3)3CPH2, (CH3)3CPHD, and (CH3)3CPD2 have been recorded in the region 26.5–40.3 GHz. Both a- and c-type transitions were observed and assigned for the “light” and “heavy” molecules and a-type transitions were observed and assigned for the d1 species. The rigid rotor rotational constants were determined to be A = 4397.63 ± 0.04, B = 2878.88 ± 0.02, and C = 2870.86 ± 0.02 MHz for (CH3)3CPH2 and A= 4261.98 ± 0.04, B = 2769.82 ± 0.02, and C = 2752.71 ± 0.02 MHz for (CH3)3CPD2 and A = 4330 ± 2, B = 2831.45 ± 0.02, and C = 2801.50 ± 0.02 MHz for (CH3)3CPHD. Dipole moment components of |μa| = 1.06 ± 0.02, |μc| = 0.49 ± 0.02 and |μt| = 1.17 ± 0.02D were determined from the Stark effect. By assuming reasonable structural parameters for the tertiarybutyl and phosphine groups, a least-squares fit of the rotational constants gave and . No splitting was observed of the first excited state of the phosphine torsional mode. 相似文献
3.
The microwave spectrum of thiane, a heterocyclic analog of cyclohexane, has been studied in the region 26.5–40 GHz. The molecule is a highly asymmetric rotor (κ = 0.050154). From the analysis of both the a-type and c-type transitions, the rotational constants determined are (in MHz): A = 3992.719, B = 3005.812, and C = 1914.683. A study of the Stark effect has yielded the dipole moment components (in Debye units) μa = 1.684 ± 0.009, μc = 0.578 ± 0.002, which give a total dipole moment of μ = 1.781 ± 0.010. Comparison of the spectral data from tetrahydropyran, thiane, and 1,4-thioxane demonstrates the similarity in structure of these three compounds. It is found that a very reasonable set of structural parameters can be found which adequately fits the spectral data of all three molecules. 相似文献
4.
JoséL. Alonso 《Journal of Molecular Spectroscopy》1980,84(2):520-530
The microwave spectrum of tetrahydropyran-4-one has been studied in the frequency region 18 to 40 GHz. The rotational constants for the ground state and nine vibrationally excited states have been derived by fitting a-type R-branch transitions. The rotational constants for the ground state are (in MHz) A = 4566.882 ± 0.033, B = 2538.316 ± 0.003, C = 1805.878 ± 0.004. From information obtained from the gas-phase far-infrared spectrum and relative intensity measurements, these excited states are estimated to be ~ 100 cm?1 above the ground state for the first excited state of the ring-bending and ~ 185 cm?1 for the first excited state of the ring-twisting mode. Stark displacement measurements were made for several transitions and the dipole moment components determined by least-squares fitting of the displacements: (in Debye) |μa| = 1.693 (0.001), |μb| = 0.0, |μc| = 0.300 (0.013) yielding a total dipole moment μtot = 1.720 (0.003). A model calculation to reproduce the rotational parameters indicates that the data are consistent with the chair conformation. 相似文献
5.
The microwave spectra of isopropylphosphine has been recorded in the region 12.4–40.0 GHz. Both a- and b-type transitions were observed and assigned. The rigid rotor rotational constants were determined to be A = 7633.34 ± 0.09, B = 4243.36 ± 0.02, and C = 3045.84 ± 0.02 MHz for (CH3)2CHPH2 and A = 7226.47 ± 0.05, B = 4041.06 ± 0.02, and C = 2946.85 ± 0.02 MHz for (CH3)2CHPD2. Dipole moment components of |μa| = 1.15 ± 0.01, |μb| = 0.43 ± 0.01, |μc| = 0.03 ± 0.02 and |μt| = 1.23 ± 0.01 were determined from the Stark effect. From the microwave spectra, the Stark effect and the experimental rotational constants, the assigned spectrum has been identified to result from the gauche form and this conformer is believed to be more stable than the other form which is present at room temperature. 相似文献
6.
JoséL. Alonso 《Journal of Molecular Spectroscopy》1981,87(1):110-118
The microwave spectra of 4-thiacyclohexanone in the ground state and eight vibrationally excited states have been studied in the frequency region 18.0–40.0 GHz and the corresponding rotational constants have been determined. The following values of the ground-state rotational constants (MHz) were obtained from the analysis of the a-type transitions: A = 3935.149 (0.031), B = 1829.444 (0.001), and C = 1364.609 (0.001). Analysis of the Stark effect gives for the dipole components (in Debye units) μa = 1.409 (0.002), μc = 0.391 (0.064). These data are consistent with a chair conformation for the ring. A phisically reasonable set of structural parameters which reproduce the ground-state rotational constants has been derived. A qualitative estimate of the low-frequency vibrational modes was obtained from relative-intensity measurements. The lowest vibrational frequency is believed to be a ring-bending mode and it occurs at 77 ± 22 cm?1 while the ring-twisting mode is at 204 ± 27 cm?1. 相似文献
7.
The microwave spectrum of CH3OD has been observed in the frequency region between 14 and 92 GHz. All the ground-state transitions with J ≤ 8 and J = 2 ← 1, a-type transitions in the excited torsional states (v = 1 and v = 2) have been observed. The spectrum has been analyzed and rotational constants, torsional constants, torsion-vibration-rotation interaction constants, and centrifugal distortion constants have been evaluated. The Stark effect measurements have been made and the dipole moment components have been determined as μa = 0.833 ± 0.008 D and μb = 1.488 ± 0.015 D. 相似文献
8.
The microwave spectrum of HNO has been observed and analyzed. Both a-type and b-type transitions have been measured. The rotational constants obtained are A = 553903.0 ± 2.7 MHz, B = 42308.52 ± 0.10 MHz, and C = 39169.46 ± 0.10 MHz. In the analysis of the spectrum, centrifugal distortion corrections are tentatively taken into account by using the centrifugal distortion constants determined by Dalby. The quadrupole coupling constants for nitrogen in HNO are determined to be χaa = 0.36 ± 0.56 MHz, χbb = ? 5.46 ± 0.30 MHz, and χcc = 5.10 ± 0.26 MHz. The dipole moment and its components determined from the Stark effect measurement are μtotal = 1.67 ± 0.03 D, μa = 1.03 ± 0.01 D, and μb = 1.31 ± 0.02 D. The microwave spectrum of DNO has been reanalyzed by taking into account the centrifugal distortion effect. The inertia defects for HNO and DNO have been calculated. The results are limited in precision by the lack of reliable force constants. 相似文献
9.
The microwave spectra of SiH3PD2 have been recorded in the range 26.5–40.0 GHz. Both a- and c-type transitions were observed and assigned. The rigid rotor rotational constants were determined to be A = 37589.06 ± 0.11, B = 5315.70 ± 0.02, and C = 5258.70 ± 0.02 MHz. The barrier to internal rotation has been calculated from the A-E splittings to be 1512 ± 26 cal/mole. The dipole moment components of |μa| = 0.22 ± 0.01, |μc| = 0.56 ± 0.01, and |μt| = 0.60 ± 0.01 D were determined from the Stark effect. By using previously determined microwave data for SiH3PH2, several structural parameters have been calculated and their values are compared to similar ones in other compounds. The Raman (0–2500 cm?1) spectra of gaseous, liquid, and solid SiH3PH2 and gaseous SiH3PD2 have been recorded and interpreted in detail on the basis of Cs molecular symmetry. 相似文献
10.
Ying-Sing Li 《Journal of Molecular Spectroscopy》1983,102(1):33-39
The microwave spectrum of 4-methylcyclohexanone has been observed in the frequency region from 18.0 to 26.5 GHz. Both a-type and c-type transitions in the ground state and a-type transitions in four excited states have been assigned. The ground state rotational constants are determined to be A = 4034.39 ± 0.06 MHz, B = 1455.46 ± 0.01 MHz, and C = 1174.06 ± 0.01 MHz. From these data, it is shown that the most stable conformer exists in the chair form with the methyl group in the equatorial position. 相似文献
11.
The microwave spectrum of 3,6-dioxabicyclo[3.1.0.]hexane has been obtained. The rotational lines of one ring conformation only have been observed and assigned. Ground state rotational constants are A0 = 6287.302 ± 0.011 MHa, B0 = 4683.546 ± 0.008 MHz, and C0 = 3358.517 ± 0.089 MHz. The diploe moment components obtained from Stark effect measurements are μa = 0.276 ± 0.010 D and μc = 2.47 ± 0.04 giving μ = 2.485 ±0.040 for the dipole moment of the molecule. The rotational constants and dipole moment components obtained experimentally can be satisfactorily explained only if the boat form is the most stable ring conformation. 相似文献
12.
The microwave spectra of the ground state and three excited states of the most abundant species of phenyl isocyanate have been recorded between 8 and 40 GHz. From aR-type transitions the ground-state rotational constants were calculated. The A value showed clearly a tilt of the NCO group from the C2v axis. They yielded the r0-type parameters. A centrifugal distortion treatment confirmed the validity of the rigid rotor approximation. The dipole moment components μa and μb were derived from the field strength dependence of six Stark lobes of five transitions. The values found were μa = (2.50 ± 0.02) D, μb < 0.2 D. From relative intensity measurements, the lowest vibrational excitation energies were determined. We assigned the lowest one to the NCO group torsion. All aR-type transitions of excited states were found unsplit by the internal rotation of the NCO group. The weakness of the μb dipole moment component and of the overall spectrum intensity did not allow us to find μb-type transitions and so, no splitting was observed on the ground-state spectrum. An evaluation of the V2 high barrier is given. 相似文献
13.
Microwave spectra have been observed and assigned for the axial and equatorial conformations of 4-cyanocyclopentene. For the axial species the rotational constants in megahertz are A = 5095.77, B = 2185.81, and C = 1936.50; for the equatorial species the values are A = 6762.66, B = 1916.72, and C = 1590.60. Dipole moment measurements yielded |μa| = 3.48 D and |μc| = 2.51 D for the axial form and |μa| = 3.85 D and |μc| = 1.10 D for the equatorial form. Relative intensity measurements showed the equatorial conformer to be 400 ± 60 cal mole?1 lower in energy. Several sets of vibrational satellites were observed and natural abundance C13 spectra were obtained for the equatorial conformer. 相似文献
14.
Thomas B. Malloy 《Journal of Molecular Spectroscopy》1974,49(3):432-438
The microwave spectrum of 3-oxabicyclo(3.1.0.)hexane has been studied in the range 26.5–40 GHz (R-band) with a Hewlett Packard Model 8400 spectrometer. Both a and c-type R-branch transitions were used to derive the rotational constants for the ground state and first two excited states of the ring-puckering mode. The data are consistent with a single stable conformation, in agreement with a previous far-infrared study (1) and this is shown to be the boat conformation, as was the case with the similar molecules cyclopentene oxide (2, 3) (6-oxabicyclo(3.1.0.)hexane) and 3,6-dioxabicyclo(3.1.0.)hexane (1, 4). The rotational constants for the ground state are (in MHz) A = 6038.06; B = 4432.47; C = 3303.43 yielding κ = ? 0.174268. The electric dipole moment components of the ground state (in Debye units) are |μa| = 1.36 ± 0.02; |μc| = 1.03 ± 0.02 yielding a total dipole moment μ = 1.71 ± 0.03. 相似文献
15.
R.N. Nandi Michael F. Boland Marlin D. Harmony 《Journal of Molecular Spectroscopy》1982,92(2):419-430
Microwave spectra were observed and analyzed for 2-aminoethanethiol and 2-chloroethanethiol. The amino compound exists in two gauche rotameric conformations, one exhibiting an intramolecular SH?N hydrogen bond. The hydrogen-bonded conformer lies higher in energy by 274 ± 90 cal mole?1 and has the following rotational constants (in MHz): A = 12 040.1 ± 11.3, B = 3352.24 ± 0.03, and C = 2881.99 ± 0.03. For the non-hydrogen-bonded conformer the rotational constants (in MHz) are A = 11 929.9 ± 10.2, B = 3395.01 ± 0.03, and C = 2877.82 ± 0.03. Dipole moment measurements for the H-bond conformer led to μa = 2.68 D, μb = 0.88 D, and μc = 0.37 D, while for the non-H-bond form the values are μa = 1.51 D, μb = 0.0 D, and μc = 0.62 D. In the case of chloroethanethiol, the only assigned spectral lines were the unresolved J → J + 1 a-type bands of a trans conformation. For this molecule the combination rotational constant B + C has the value 2955.17 ± 0.02 MHz for the 35Cl species and 2879.73 ± 0.02 MHz for the 37Cl species. 相似文献
16.
The microwave spectrum of 3,4-epoxy-1-butene has been studied in the region 26.5–40 GHz. For the ground-state molecule, 170 lines have been assigned up to J = 34. From these the rotational constants and the centrifugal distortion constants were determined by least-squares fitting. The rotational constants are (in MHz): A = 17367.284 ± 0.011, B = 3138.186 ± 0.004, C = 3043.697 ± 0.004. The dipole moment has been determined from the Stark effect as (in Debye): μa = 0.72 ± 0.01, μb = 1.688 ± 0.003, μc = 0.39 ± 0.02, μ = 1.875 ± 0.005. The rotational constants and dipole moment components indicate that the assigned conformer is the s-trans form. A rotational assignment has also been made for the first excited state of the torsional mode. The fundamental frequency of the torsional mode has been estimated as 142 ± 20 cm?1 from relative intensity measurement. 相似文献
17.
Observation of the direct l-type resonance transitions in the microwave spectrum of the v4 = 1 state of PF3 has been extended to J = 36. The w-type interaction, (Δl = 0, ΔK = 6), has been found from measurements on the “forbidden” Stark trasitions in the series. Also in this series a close accidental degeneracy was found between J = 30, and 0, leading to new zero-field “forbidden” transitions through the r-type interaction (Δl = 2, ΔK = ?1) and to the determination of the C rotational constant. Nine spectroscopic parameters were determined using 140 observed frequencies including two “forbidden” trasitions. After suitable correction the B and C constants were used to determine the r0, rz, and re structures for PF3. The equilibrium structure is estimated to be P-F = 1.561 ± 0.001 Å and ∠FPF = 97.7 ± 0.2°. 相似文献
18.
The microwave spectrum of heptafulvene (C8H8) has been investigated in the frequency range from 26 to 40 GHz. The following rotational constants have been obtained from a least-squares fit of the measured transition frequencies: A = 3665.972(66)MHz, B = 2004.3165(59)MHz, and C = 1297.5029(90)MHz. From the corresponding moments of inertia it was concluded that heptafulvene has a planar equilibrium structure. The quantitative measurement of the Stark splittings of three transitions have yielded a dipole moment of 0.477(5) D along the a principal axis. A series of satellite transitions accompanied each rotational transition. The satellites have been assigned to the lowest out-of-plane vibration ν42 (B2) for which a frequency of 70(11) cm?1 has been determined from relative intensity measurements. 相似文献
19.
P.D. Mallinson 《Journal of Molecular Spectroscopy》1977,68(1):68-76
The ground vibrational state microwave spectrum of CHD2Cl has been studied in the region 26.5–40.0 GHz. From the observation of weak c-type transitions the A0 rotational constants of CHD235Cl and CHD237Cl have been determined to be 95 426.08 ± 0.06 and 95 425.23 ± 0.11 MHz, respectively. The observed a-type and c-type transitions have been used to obtain A, B, C, all five quartic and one sextic distortion constants present in the reduced Hamiltonian of Watson for the 35Cl and 37Cl isotopic modifications of CHD2Cl. 相似文献
20.
Richard D. Suenram Nancy S. True Robert K. Bohn 《Journal of Molecular Spectroscopy》1978,69(3):435-444
The microwave spectrum of ethyl cyanoformate displays a-type band spectra from three nearly prolate conformers. High-resolution spectra of the two more stable species have been assigned. One form, designated extended, has rotational constants A″ = 6453.3(4) MHz, B″ = 1500.47(6) MHz, C″ = 1236.36(6) MHz, which are consistent with a syn-anti [τ1 (OCOC) = 0°, τ2 (COCC) = 180°] structure. The second form, labeled compact, has rotational constants A″ = 6787.8(7) MHz, B″ = 1549.38(8) MHz, C″ = 1406.80(8) MHz, which are consistent with a syn-gauche [τ1 (OCOC) = 0°, τ2 (COCC) ~ 90°] structure. The extended form is marginally more stable, ΔE = 55 ± 27 cm?1. The extended conformer has dipole moment components μa = 4.44(7), μb ~ 0 D and the compact conformer has dipole moment components μa = 4.25(7), μb = 0, μc = 1.08(23) D. The third conformer (relative energy 600 ± 140 cm?1) has the most intense band series even at ?63°C. the bands of this conformer are unresolvable into individual rotational transitions. 相似文献