Vibrational assignments for styrene-β-D2 from the infrared and Raman spectra

The molecule styrene-β-D₂ has been prepared. The liquid-phase infrared spectrum in the region 400 to 3500 cm^?1 and the laser Raman spectrum have been recorded. Vibrational assignments for this molecule have been made largely by comparison with those of Condirston and Laposa (2) for C₆H₅CHCH₂, C₆H₅CDCD₂, C₆D₅CHCH₂, and C₆D₅CDCD₂.     

The microwave spectrum of methylene ketene

The microwave spectrum of methylene ketene has been observed from 8 to 35 GHz and assigned. Rotational constants and centrifugal distortion constants have been determined for CH₂CCO, CHDCCO, and CD₂CCO. The dipole moment was found to be μ_a = 2.14 ± 0.06 D (7.07 ± 0.2 × 10^?30 Cm). We were unable to detect propynal among the pyrolysis products of acrylic anhydride. This pyrolysis proved to be the most convenient route for generating methylene ketene for the present investigation.     

Infrared spectroscopic studies of partially deuterated ethanes and the r0, rz, and re structures

Samples of CH₃CH₂D, CH₃CHD₂, CD₃CH₂D, and CD₃CHD₂ have been prepared, and their infrared spectra recorded. Analysis of type B or type C “perpendicular” bands has enabled the rotational parameter ($\text{A}{}_0\text{-}\text{B}{}_0$) to be determined for all four species. These have been combined with existing infrared, Raman, and microwave data for CH₃CH₃, CD₃CD₃, and CH₃CD₃ species, to determine the ground state (r₀) and ground state average (r_z) structures within narrow limits. Zero point energy effects on the average structure are determined to be a CH bond shortening of 0.0015(3) Å and an HCC angle opening of 0.010(5)° on deuteration. These effects enable the equilibrium structure of ethane to be estimated. The r_z(CC) bond length is determined to be 1.5351(2) Å, which is significantly longer than previous estimates involving electron diffraction data.     

Vibrational spectra of (CD3)2Cd and (CD3)2Zn

The Raman and infrared spectra of (CH₃)₂Cd and (CH₃)₂Zn have been reexamined and are reported along with previously unreported vibrational data for (CD₃)₂Cd and (CD₃)₃Zn. The spectra have been analyzed using the double group $\text{G}{}_{36}\text{2}$, which has led to some changes in assignments made previously. Comparison is also made with a recent study of (CH₃)₂Hg and (CD₃)₂Hg. Fine structure was observed for two of the vibrations of the E_1d symmetry species, arising from internal rotation of the methyl groups. This structure has been analyzed using a recently developed theory for molecules of the freely rotating dimethylacetylene type. Problems which arise in the application of this theory have been pointed out, and it is suggested that some additional consideration of the theory may be necessary.     

Millimeter- and Submillimeter-Wave Spectra of CD2F2

The millimeter- and submillimeter-wave spectrum of ¹³CD₂F₂ present in natural abundance in methylene fluoride-d₂ (CD₂F₂) has been measured in the region 230-380 GHz. The spectrum was recorded using a frequency-modulated millimeter- and submillimeter-wave spectrometer. More than 200 rotational transitions in the ground state of ¹³CD₂F₂ with J≤45 and K_a≤8 have been assigned. A combined weighted least squares fit of the newly assigned transitions with previously reported microwave data has been carried out in the Watson's A- and S-reduced Hamiltonian. The data have been fitted with a standard deviation approaching the experimental accuracy, to provide improved values for the rotational and quartic centrifugal distortion constants, including sextic distortion constants for the ground state of ¹³CD₂F₂.     

The Coriolis interaction between the fundamentals ν2 and ν5 of CD3Br

The bands ν₂ and ν₅ of CD₃Br have been measured at a resolution of 0.010 cm^?1. They were analyzed simultaneously by taking into account the xy-Coriolis interaction. More than 1600 transitions were assigned for each isotopic species CD₃⁷⁹Br and CD₃⁸¹Br. The Coriolis coupling term proved to be ζ_2,5^y = 0.559. The band centers are (in cm^?1) ν₂: 991.401 (CD₃⁷⁹Br), 991.390 (CD₃⁸¹Br); ν₅: 1055.474 (CD₃⁷⁹Br), 1055.471 (CD₃⁸¹Br).     

Vibration-rotation spectra and molecular force field of methylene fluoride and methylene fluoride-d2

Infrared spectra of CH₂F₂ and CD₂F₂ have been measured under a medium resolution. The vibration-rotation bands of CD₂F₂ fundamentals have been analyzed and the assignment for the fundamentals of CD₂F₂ is given. In addition, a number of overtone and combination bands are observed for CH₂F₂, which helps to clarify the vibrational assignment for CH₂F₂. A normal coordinate treatment has been carried out: The force constants in a modified Urey-Bradley as well as the general valence force fields have been determined, the vibrational frequencies and the centrifugal distortion constants obtained from microwave spectroscopy being used. The force constants of the methylene fluoride molecule are discussed in connection with those of the related molecules. Special features of the CH₂F₂ and CD₂F₂ spectra are also described.     

Fourier transform infrared spectrum of thioketene,CH2CS

The FTIR spectrum of the unstable species thioketene, CH₂CS, has been detected in a vapor-phase flow pyrolysis system. The region 800–3500 cm^?1 has been surveyed with a resolution of 1 cm^?1, enabling the frequencies of the six fundamentals which lie above 800 cm^?1 to be determined. Certain bands have been studied under very high resolution and the results of the analyses of the perpendicular bands ν₇ and ν₃ + ν₈, observed with a resolution of 0.01 and 0.005 cm^?1 respectively, are presented. The ground state constant, A₀, is determined as 286 453.60(58) cm^?1.     

The microwave spectrum of thioformaldehyde,CD2S,and CH2S: Average structure,dipole moments,and 33S quadrupole coupling

Microwave transitions up to J = 53 in the ground vibrational state of deuterothioformaldehyde, CD₂S, were studied between 8 and 40 GHz. A detailed centrifugal distortion analysis yields accurate constants for comparison with force field values. The isotopic species ¹³CH₂S, CH₂³⁴S, CH₂³³S, ¹³CD₂S, CD₂³⁴S, and CD₂³³S were studied in natural abundance. Accurate average zero-point structures were determined for both CD₂S and CH₂S:

$\text{CH}{}_2\text{S}\text{CS}\text{=1.6138(4)}\text{CH}\text{= 1.0962(6)}\text{A}\text{?}\text{∠}\text{HCH}\text{=116° 16(6)′,}\text{CD}{}_2\text{S}\text{CS}\text{=1.6136(4)}\text{CD}\text{= 1.0931(4)}\text{A}\text{?}\text{∠}\text{DCD}\text{=116° 25(5)′}$

Changes in the zero-point geometry for deuterium substitution were established. Quadrupole fine structure arising from the ³³S nucleus has been measured in CH₂³³S and CD₂³³S. Analysis gives the following coupling constants (for both molecules) as χ_aa = ?11.7 and χ_bb - χ_cc = 88.1 MHz. The dipole moment of CD₂S was measured to be 1.6588(8)D and an accurate comparison with CH₂S was made; the ratio of dipole moments $\text{CD}{}_2\text{S}\text{CH}{}_2\text{S}$ was found to be 1.0062(4). The spectroscopic and bonding properties of CH₂S will be compared with formaldehyde and other molecules.     

The potential function and rotation-vibration energy levels of the methyl radical CH3

The equilibrium bond length and the shape of the complete potential energy curve for the methyl radical CH₃ are determined. This is done by fitting the experimental data [mainly from C. Yamada, E. Hirota, and K. Kawaguchi, J. Chem. Phys.75, 5256–5264 (1981)] using the nonrigid invertor Hamiltonian and a model anharmonic potential function. As a result the v₂ (out-of-plane bending) dependence of the rotational constants is explained and the v₂ dependence of the spin-rotation coupling constants is modeled. In addition, some of the vibrational energies and rotational, centrifugal distortion, and spin-rotation constants are predicted for the ¹³CH₃, ¹²CD₃, and ¹²CT₃ isotopes.     

Microwave spectra of deuterated ethylenes: Dipole moment and rz structure

The pure rotational spectra of three deuterated ethylenes, CH₂CD₂, CH₂CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH₂CD₂ was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be $\text{r}{}_{\mathrm{z}}\text{(CC)}\text{= 1.3391 ± 0.0013}\text{A}\text{?}$, $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{= 1.0869 ± 0.0013}\text{A}\text{?}$, θ_z(CCH) = 121.28 ± 0.10°, and $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{- r}{}_{\mathrm{z}}\text{(CD)}\text{= 0.00137 ± 0.00037}\text{A}\text{?}$, where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θ_z(CCH) - θ_z(CCD).     

Analysis of torsional splittings in the microwave spectra of dimethylether,CH3OCH3 and its isotopes,CD3OCH3 and CD3OCD3

The multiplet splitting patterns of microwave transitions in the ground state and the first two torsional excited states of CH₃OCH₃, CD₃OCD₃, and CD₃OCH₃ were analyzed in terms of the semirigid rotor models C_2vF-C_3vT-C_3vT and $\text{C}{}_3\text{F-}\text{C}{}_{\mathrm{3v}}\text{T-}\text{C}{}_{\mathrm{3v}}\text{T}\text{?}$. The following nonzero potential coefficients were obtained for CH₃OCH₃: V₃₀ = V₀₃ = 909.05 ± 0.49 cm^?1, V′₃₃ = 5.06 ± 1.60 cm^?1; for CD₃OCH₃: V₃₀(CD₃) = 897.18 ± 2.41 cm^?1, V₀₃(CH₃) = 910.45 ± 0.33 cm^?1; for CD₃OCD₃: V₃₀ = V₀₃ = 897.00 cm^?1. These results are compared to earlier microwave studies of these molecules.     

Analysis of the ν2 + ν3 band of 12CH4 and 13CH4

The ν₂ + ν₃ bands of ¹²CH₄ and ¹³CH₄ occurring in the region 4400–4650 cm^?1 have been studied from spectra recorded with a high-resolution Fourier transform spectrometer (resolution better than 0.01 cm^?1). Champion's Hamiltonian expansion, Canad. J. Phys.55, 1802 (1977), is applied to the problem of the two interacting F₁ and F₂ vibrational sublevels of this type of a band. As the P branch of ν₂ + ν₃ is strongly overlapped by neighboring bands, a combination-difference method, adapted to tetrahedral XY₄ molecules has been developed to help assignments of lines. A fit of 700 transitions has been performed using 13 new effective constants in the case of ¹²CH₄. In the case of ¹³CH₄, 532 transitions have been fit to 18 constants. The known parameters, relative to the vibrational ground state and the ν₃ state for both methanes, and the ν₂ state for ¹²CH₄ were fixed throughout. Most of the perturbed levels, up to J′ = 12, are well reproduced and the general agreement between experimental and calculated transitions is satisfactory with standard deviations of 0.047 cm^?1 (¹²CH₄) and 0.041 cm^?1 (¹³CH₄). The results (order of magnitude of obtained (ν₂ + ν₃) parameters and comparison of observed and computed intensities) indicate that the ν₂ + ν₃ band is perturbed by many other bands.     

Far-infrared internal rotation spectrum of CH3OD and CD3OD

The far-infrared spectra of the Q branches of hindered rotation in CH₃OD and CD₃OD have been investigated in the 80- to 250-cm^?1 spectral region. The theoretical spectra are calculated using the full set of Kirtman constants and are compared with the experimental spectra of resolutions up to 0.13 cm^?1.     

Microwave spectrum of methylene fluoride-d2, CD2F2 in the excited vibrational states

The rotational spectra of ¹²CD₂F₂ in the ν₂, ν₃, ν₄, 2ν₄, ν₅, ν₇, ν₈, and ν₉ states were observed and assigned. Weak Coriolis interactions between ν₃ and ν₇, ν₃ and ν₉, and ν₅ and ν₇ were analyzed using approximate expressions for the rotational energy levels. The resonance between the ν₂ and the ν₈ state was found much stronger, and an effective two-dimensional Hamiltonian with the Coriolis term in the off-diagonal block was set up to analyze the spectra. The effect of the Fermi resonance between ν₃ and 2ν₄ was found to be very small.The ground-state spectrum of ¹³CD₂F₂ was observed and the rotational constants and the centrifugal distortion constants were determined. The data on ¹²CD₂F₂ and ¹²CDHF₂ were also improved very much in accuracy.The Coriolis coupling constants and the differences between two vibrational levels in resonance, which were determined by the analysis of the satellite spectra, are in good agreement with those obtained from vibrational spectra, except for the ν₂ band center, which is revised to 1170.3 cm^?1. The force constants were also checked using the centrifugal distortion constants of ¹²CD₂F₂, ¹³CD₂F₂, and ¹²CHDF₂.     

Diode laser spectroscopy of the ν6 band of 13CH3l and the ν″6 band of 12CH2Dl

The ν₆ band of ¹³CH₃I and the ν″₆ band of ¹²CH₂DI have been recorded under Doppler-limited resolution in the region 820–866 cm^?1 using a tunable diode laser spectrometer. For ¹³CH₃I the constants for the ν₆ band were determined by simultaneous analysis of seven ^pQ(J,K) branches and several ^pP(J,K) and ^pR(J,K) transitions. For ¹²CH₂DI, the slight asymmetry introduced by the single D atom gives rise to noticeable asymmetry effects in the spectra of some of the ^pQ(J,K) subbands. From the analysis of six such subbands, the molecular constants for the ν″₆ level were determined.     

Microwave spectrum,structure, and nuclear quadrupole coupling of cis-1-chlorobutadiene-1,3

The microwave spectra of the two natural isotopic species of cis-1-chlorobutadiene-1,3, CH³⁵ClCHCHCH₂ and CH³⁷ClCHCHCH₂, together with all monosubstituted species with deuterium or ¹³C isotopes have been measured and assigned and the complete substitution structure has been determined. The spectral region investigated was between 18 and 40 GHz. The molecule was found to be planar and the following values were found for the principal parameters: r(CC)_chlorovinyl = 1.327(6), $\text{r(}\text{CC}\text{)}{}_{\mathrm{<mtext>vinyl</mtext>}}\text{= 1.343(2)}\text{A}\text{?}$, <(CCC)_chlorovinyl = 126.5(3)° and <(CCC)_vinyl = 123.0(7)°. The nuclear quadrupole coupling constants, χ_aa and χ_bb, for the parent molecule were calculated and further used to estimate the symmetry of the field gradient around the CCl bond. Force-field calculations were used to predict the centrifugal distortion constants and inertial defect of some isotopic species. Thermodynamic functions were calculated for cis- and trans-1-chlorobutadiene-1,3 and used to estimate the energy difference between them.     

Laser Stark spectroscopy of the coriolis coupled ν2 and ν5 bands of CD3Cl

About 940 Stark resonances for CD₃³⁵Cl and 610 resonances for CD₃³⁷Cl have been measured by using a CO₂ laser with the 9- and 10-μm regions. They were assigned to 59 rovibrational transitions of ν₂ (J′ ≤ 37, K ≤ 14) and 200 of ν₅ (J′ ≤ 47, ?14 ≤ k′l′ ≤ +10) for ³⁵Cl, and 31 of ν₂ (J′ ≤ 12, K ≤ 10) and 175 of ν₅ (J′ ≤ 46, ?14 ≤ k′l′ ≤ +9) for ³⁷Cl. These data, combined with the microwave and FIR data in the ν₂ and ν₅ states, were analyzed by taking account of the Coriolis interaction between ν₂ and ν₅, and the (2, 2) and (2, ?1) interactions in ν₅. Several ΔK = +2 transitions of the ν₅ band were observed in the Stark spectra, and the ground state constants, A₀ and D_K0, were determined precisely for both ³⁵Cl and ³⁷Cl species. Also, the vibrationally induced dipole moments were obtained. The molecular constants and the zero-field transition frequencies of the ν₂ and ν₅ bands were determined.     

New analysis of the Coriolis-interacting v2 and v5 bands of CH3Br and CH3Br

The and fundamental bands of CH₃⁷⁹Br and CH₃⁸¹Br have been studied by Fourier transform infrared spectroscopy with an unapodized resolution of 0.004 cm⁻¹, corresponding to an improvement of one order of magnitude compared to previous studies. For both isotopomers, some 2427 (2239) lines were newly assigned for the parallel and the perpendicular bands and, in addition, 80 perturbation-allowed transitions were also added. The ground-state axial rotational constants A₀ were redetermined from allowed and perturbation-allowed infrared transitions observed in the v₂ and v₅ bands around the local crossing. The A₀ values obtained for both isotopomers are more accurate but fully compatible with those obtained previously. Using those results, and the variation of the rotational constants with vibration, new accurate equilibrium constants A_e and B_e have been also determined for CH₃⁷⁹Br and CH₃⁸¹Br. The excited states v₂=1 and v₅=1 are coupled by Coriolis-type interactions (Δl=±1,ΔK=±1) and (Δl=?1,ΔK=±2), while the l₅=±1 levels of v₅ interact also through “l(2,2)”-type interaction (Δl=±2,ΔK=±2). The Coriolis coupling term was determined to be for CH₃⁷⁹Br and for CH₃⁸¹Br. All interaction parameters have been determined with higher accuracy, compared to previous studies. A total of 4213 (3704) line positions with J?68(64) and K?16(11) including all available data was fitted using 20 (18) parameters with a root-mean-square deviation of 0.0007 (0.0006) cm⁻¹ for CH₃⁷⁹Br and CH₃⁸¹Br, respectively. Two different but equivalent forms of reduced Hamiltonians with two different sets of constrained constants were successfully applied according to Lobodenko's reduction [J. Mol. Spectrosc. 126 (1987) 159]. The ratio of the transition moments, |d₂/d₅|=1.65, and a positive sign of the Coriolis intensity perturbation d₂×ζ₂₅×d₅ were determined. Therefore, it has been possible to generate an accurate prediction of the whole spectrum between 1200 and 1650 cm⁻¹, including Q branches.     

Electron paramagnetic resonance of gamma irradiated [(CH3)4N]InCl4 and [(CH3)4N]2CdCl4 single crystals

Gamma irradiated [(CH₃)₄N]InCl₄ and [(CH₃)₄N]₂CdCl₄ single crystals were investigated by electron paramagnetic resonance at ambient temperature, and it has been found that both compounds indicate the existence of (CH₃)₃N⁺ radicals. The g factors were found to be isotropic, and the hyperfine constant for H atoms was measured as 2.86 mT and is isotropic for this radical in these substances. The hyperfine coupling constant of the N nucleus with the hole in (CH₃)₃N⁺ in [(CH₃)₄N]InCl₄ was found to be anisotropic with the A_zz=2.92, A_yy=1.62 and A_xx=1.40 mT. From these, it has been revealed that the C_3v-axis of (CH₃)₃N⁺ radical performs rotational or jumping reorientational motions around a fixed axis, in addition to the rotations of protons in CH₃ groups and the rotational motions of CH₃ groups around the C_3v-axis of the radical. The g, and the hyperfine coupling factors of the N nucleus were isotropic in (CH₃)₃N⁺ in [(CH₃)₄N]₂CdCl₄. This indicates the motional behaviour of the radical in this compound is as in a liquid. This isotropic behaviour of the hyperfine coupling constants was found to be same until the attainable lowest temperature of 113 K in our laboratory.