Microwave spectrum and selenol internal rotation of 2-propaneselenol

Microwave spectra of 2-propaneselenol and its deuterated species were measured and assigned for the gauche and trans isomers. The double minimum splittings of the gauche isomers were directly observed from b-type transitions, which were assigned with the aid of a double resonance technique. Rotational constants and torsional splitting of the gauche isomer of the parent species were determined to be A = 7802.50 ± 0.75, B = 2847.68 ± 0.04, C = 2242.03 ± 0.03, ΔA = ?2.52 ± 0.74, ΔB = 0.02 ± 0.05, ΔC = ?0.34 ± 0.03, and Δν = 368.91 ± 0.94 MHz, where ΔA, and ΔB, and ΔC are the differences of the rotational constants between the (+) and (?) states. From the torsional splittings and the energy differences of the two isomers of the parent and SeD species, Fourier coefficients of the selenol internal rotation potential function were determined to be V₂ = ?88 ± 15, V₃ = 1543 ± 29 cal/mole on the assumption of V₁ = 0. Dipole moments and their components were also obtained for the two isomers.     

Internal rotation and molecular structure of ethaneselenol by microwave spectroscopy

The microwave spectra of ethaneselenol and its deuterated and ¹³C-substituted species were measured and assigned for the gauche and trans isomers. The double minimum splittings in the gauche isomers were directly observed for the species having a symmetry plane in the frame part. The rotational constants and the torsional splitting of the gauche isomer of the parent species were determined to be A = 27 148.86 ± 0.05, B = 3 623.68 ± 0.01, C = 3 399.21 ± 0.03, and Δν = 1 083.33 ± 0.04 MHz. From the torsional splittings of the parent and SeD species together with the vibrational frequencies already reported by Durig and Bucy, the Fourier coefficients of the selenol internal rotation potential function were determined to be V₁ = ?44 ± 17, V₂ = ?260 ± 3, V₃ = 1202 ± 16, and V₆ = ?43 ± 9 cal/mole. From the rotational constants obtained, the r_s structural parameters of the gauche and trans isomers were determined. The structural parameters in the skeletal part for the gauche isomer are $\text{r}\text{(CC) = 1.524}\text{A}\text{?}$, $\text{r}\text{(CSe) = 1.957}\text{A}\text{?}$, $\text{r}\text{(SeH) = 1.467}\text{A}\text{?}$, α(CCSe) = 113°31′, α(CSeH) = 93°05′, and the dihedral angle τ(CCSeH) = 61°39′. Those for the trans isomer are $\text{r}\text{(CC) = 1.525}\text{A}\text{?}$, $\text{r}\text{(CSe) = 1.962}\text{A}\text{?}$, $\text{r}\text{(SeH) = 1.440}\text{A}\text{?}$, α(CCSe) = 108°43′, and α(CSeH) = 93°30′. These parameters were compared with the corresponding ones of ethanethiol.     

Microwave spectrum and rotational isomerism of n-propyl isocyanide

The microwave spectrum of n-propyl isocyanide has revealed the existence of two rotational isomers, trans (methyl trans to the isocyanide substituent), and gauche. Plausible structures have been fitted to the data, giving the gauche dihedral angle as 119° ± 2° from the trans position. Stark effect measurements have yielded dipole moments for the two rotamers: μ_trans = 4.16 ± 0.02 D and μ_gauche = 4.10 ± 0.09 D. The rotational constants of the trans form are A = 23 700 ± 100, B = 2407.632 ± 0.020, and C = 2278.853 ± 0.030 MHz, and those of the gauche form are A = 10 208.983 ± 0.030, B = 3479.219 ± 0.015, and C = 2859.981 ± 0.015 MHz. It has been found from relative intensity measurements that the gauche ground state is slightly more stable than the trans ground state, with an energy difference of 99 ± 45 cm^?1. Several vibrationally excited states have been assigned to the torsional motion around the central carbon-carbon bond, the CNC bending motion, and the methyl internal rotation. The torsional vibration frequency is 114 ± 20 cm^?1 in the trans form and 123 ± 20 cm^?1 in the gauche form. A four-term potential function for internal rotation about the central CC bond has been determined.     

Microwave spectrum,conformation, and quadrupole coupling constants of 1-iodopropane

The molecular rotational spectrum of 1-iodopropane (n-propyl iodide) has been investigated in the frequency region 9–33 GHz. The 1-iodopropane molecule has been confirmed to exist in two rotational isomers, trans and gauche. The rotational constants of the ground state were determined to be A = 10 595.450(60) MHz, B = 1781.669(8) MHz, and C = 1614.200(7) MHz for gauche, and B = 1305.247(8) MHz and C = 1269.365(7) MHz for trans. The nuclear quadrupole coupling constants were determined to be χ_aa = −1020(3) MHz, χ_bb = 193(2) MHz, χ_cc = 827(4) MHz, χ_ab = 1173(2) MHz, χ_ac = −369(7) MHz, and χ_bc = 230(5) MHz for gauche, and χ_aa = −1509(8) MHz, χ_bb = 610(9) MHz, χ_cc = 899(12) MHz, and χ_ab = −789(9) MHz for trans. The centrifugal distortion constants were also determined using all of the assigned transitions. From the relative intensity measurements the skeletal torsional frequencies for the gauche and trans forms were estimated to be 117 and 108 cm⁻¹, respectively.     

Infrared,Raman, and microwave spectra of ethaneselenol and the determination of the barriers to internal rotation

The infrared, Raman, and microwave spectra of gaseous ethaneselenol have been investigated. The rotational constants for both the more stable gauche and for the trans conformers are reported for the Et⁷⁸SeH, Et⁷⁸SeD, Et⁸⁰SeH, and Et⁸⁰SeD isotopic species. A proposed structure has been derived from a least-squares analysis of the moments of inertia. Dipole moment components have been obtained from each conformer using second-order Stark effects. For the gauche conformer, they are μ_a = 1.42 ± 0.01, μ_c = 0.37 ± 0.03, and μ_total = 1.47 ± 0.01 D. For the trans isomer they are μ_a = 1.217 ± 0.002, μ_b = 0.850 ± 0.001, and μ_total = 1.485 ± 0.002 D. The methyl barrier to internal rotation was calculated using observed frequencies obtained from the infrared and Raman spectra; a value of 3.59 ± 0.01 kcal/mole was obtained. Asymmetric potential functions have been calculated for both the EtSeH and EtSeD isotopic species. For the light species the potential constants for internal rotation around the CSe bond are V₂ = ?96.4 ± 1, V₃ = 432 ± 4, and V₆ = ?20 ± 2 cm^?1. The difference between ground-state energy levels of the two conformers was found to be 66 cm^?1. A vibrational assignment based on infrared and Raman spectra of the gaseous phase is presented.     

Microwave spectrum and rotational isomerism in isopropyl mercaptan

A microwave investigation of isopropyl mercaptan has established the existence of both trans and gauche conformers, the trans being more stable by 57 cal mole^?1. Stark effect measurements give the dipole moments as 1.61 ± 0.2 D for the trans and 1.53 ± 0.2 D for the gauche species. The spectra of the isotopic species (CH₃)₂CH³²SD, (CH₃)₂CH³⁴SH, and (CH₃)₂CH³⁴SD of the trans form have also been analyzed, providing a limited amount of structural data.The rotational spectrum of the gauche isomer is noticeably influenced by inversion. Interactions between energy levels in the two lowest inversion states have been satisfactorily accounted for in terms of rotational constants, coupling parameters (G_a and G_c), and ΔE₀, the inversion level splitting. ΔE₀ is found to be 562.4 MHz for the ground state of (CH₃)₂CHSH and 10.0 MHz for (CH₃)₂CHSD. A value of 1.98 kcal mole^?1 has been calculated for the barrier to internal rotation of the -SH group in terms of a V₃ potential.     

The microwave spectrum of gauche-ethylamine

The microwave spectrum of the ground state of the normal species of gauche-ethylamine CH₃CH₂NH₂ and that of -NHD, -NDH, as well as -ND₂ isotopic species were measured and assigned. The ground state splits into four substates due to two internal large amplitude motions: inversion (s and a) and internal rotation (o and e) about the CN axis. Intersystem transitions due to tunneling as well as vibrational-rotational perturbations affect not only the absorption frequencies but also the Stark effect and NQHFS. The rotational constants for the two symmetrical inversion states (s) were fitted for the normal species as (all values in MHz) A^se = 32 423.470 ± 0.184, B^se = 8 942.086 ± 0.039, and C^se = 7 825.520 ± 0.048, and A^so = 32 378.733 ± 0.182, B^so = 8 940.906 ± 0.052, and C^so = 7 825.551 ± 0.042 with the interaction constants Q_a^s = 151.12 ± 0.52 and Q_b^s = 44.4 ± 7.0. The antisymmetrical inversion states (a) were fitted as A^ae = 32 423.347 ± 0.142, B^ae = 8 942.027 ± 0.029, and C^ae = 7 825.525 ± 0.031, and A^ao = 32 378.720 ± 0.142, B^ao = 8 940.984 ± 0.029, and C^ao = 7 825.573 ± 0.031 with the interaction constants Q_a^a = 167.10 ± 0.31, Q_b^a = 48.1 ± 5.4. The energy splitting due to intersion was determined (in MHz) as Δν_inv = 1 391.39 ± 0.19 and that due to internal rotation as Δν_tors = 1 170.58 ± 0.18. The cis barrier separating the two equivalent torsional states was calculated as 690 cm^?1, and the inversion barrier between the inversion states was calculated as 1400 cm^?1, both using the Dennison-Uhlenbeck model. A simple model explaining the inversion splittings of the monodeuterated species is proposed. Comparing the relative intensities for several temperatures the gauche form was observed to be energetically higher than the trans form by 110 ± 50 cm^?1. The dipole moment could only be fitted by taking into account the internal motions yielding (in Debye) μ_a^eff = 0.11 ± 0.01, μ_b^eff = 0.65 ± 0.01, and μ_c^eff = 1.014 ± 0.015. The quadrupole coupling constants (in MHz) were found as χ_aa = ?χ⁺ = 2.268 ± 0.043 and χ_bb ? χ_cc = χ^? = 3.120 ± 0.035.     

Microwave spectrum,centrifugal distortion constants,and quadrupole coupling constants of 3-chloropyridine

The microwave spectrum of 3-chloropyridine has been measured in the frequency region of 8.2 to 18 GHz. The rotational constants, centrifugal distortion constants, and the quadrupole coupling constants for the ³⁵Cl species are A = 5839.448 ± 0.027 MHz, B = 1604.152 ± 0.005 MHz, C = 1258.327 ± 0.004 MHz, Δ_J = 0.10 ± 0.01 KHz, Δ_JK = 0.36 ± 0.09 KHz, Δ_K = 1.18 ± 0.07 KHz, δ_J = ?0.008 ± 0.005 KHz, δ_K = 0.88 ± 0.20 KHz, χ_aa = ?70.04 ± 0.38 MHz, χ_bb = 36.68 ± 0.19 MHz. The values of rotational constants and quadrupole coupling constants for the ³⁷Cl species are A = 5840.052 ± 0.034 MHz, B = 1559.354 ± 0.01 MHz, C = 1230.739 ± 0.016 MHz, χ_aa = ?54.20 ± 1.26 MHz, χ_bb = 29.49 ± 0.48 MHz. The double bond character in the CCl bond is found to be 2%. The smaller than expected value of rotational constant A points to a “fattening” of the pyridine ring about the a-axis in contrast to 2-chloropyridine, where no such substitution effect was observed.     

Microwave spectrum,conformation, quadrupole coupling constants,and barrier to internal rotation of methoxyamine

The microwave spectra of three isotopic species of methoxyamine (CH₃ONH₂) have been studied. For the normal species the ground-state rotational constants are A = 42488 ± 150 MHz, B = 10049.59 ± 0.03 MHz, and C = 8962.85 ± 0.03 MHz. From these data and those from the -NHD and -ND₂ species, the amino protons have been shown to occupy a symmetrical trans position relative to the methyl group. The barrier to internal rotation of the methyl group has been found to be 873 ± 15 cm^?1 by analysis of ground-state splittings. Analysis of hyperfine splittings has yielded the ¹⁴N quadrupole coupling constants, which have the following values for the normal isotopic species: χ_aa = 3.63 ± 0.03 MHz, χ_bb = ?3.69 ± 0.07 MHz, and χ_cc = 0.06 ± 0.07 MHz.     

Structures and spectra of the isomers HNCO,HOCN, HONC,and HCNO from ab initio quantum mechanical calculations

Ab initio calculations are reported on the equilibrium geometries, dipole moments, rotational constants, and force constants of the isomers HOCN, HNCO, HCNO, and HONC. The most accurate calculations on the unknown isomer HOCN lead to a predicted geometry of $\text{R}{}_{\mathrm{<mtext>OH</mtext>}}\text{= 0.96 ± 0.005}\text{A}\text{?}$,$\text{R}{}_{\mathrm{<mtext>OC</mtext>}}\text{= 1.302 ± 0.007}\text{A}\text{?}$, $\text{R}{}_{\mathrm{<mtext>CN</mtext>}}\text{= 1.153 ± 0.007}\text{A}\text{?}$, 〈HOC = 109 ± 1°, 〈OCN = 177 ± 1° in a planar trans conformation. This structure has rotational constants B = 10.64 ± 0.12 GHz and C = 10.47 ± 0.12 GHz, accurate enough to encourage a radio search for this species in dense interstellar clouds as well as experiments designed for terrestrial identification. In much less accurate calculations, not extensive enough to provide error bars, an approximate structure for the other unknown isomer, HONC, is $\text{R}{}_{\mathrm{<mtext>HO</mtext>}}\text{= 1.05}\text{A}\text{?}$, $\text{R}{}_{\mathrm{<mtext>ON</mtext>}}\text{= 1.14}\text{A}\text{?}$, $\text{R}{}_{\mathrm{<mtext>NC</mtext>}}\text{= 1.26}\text{A}\text{?}$, 〈HON = 109°, 〈ONC = 172.5°, in a planar trans conformation. The calculated structures of HNCO and HCNO are in good agreement with experiment. The nonlinearity of the heavy-atom axis is firmly established for HOCN, HNCO, and HONC. In all of the molecules the angle of the hydrogen-bending motion is strongly coupled to the angle formed by the heavy atoms. These hydrogen-bending motions are discussed in detail, especially the potential for inversion in HNCO and the quasi-linear potential in HCNO.     

The microwave spectrum,conformation, and vibration-rotation interaction of N-cyanopyrrolidine

The microwave spectrum of N-cyanopyrrolidine was observed and assigned in the ground and nine excited states. In the lowest two states, split 3.9 cm^?1 by a ring-puckering, nitrogen-inversion motion, the rotational constants are (for v = 0) A = 6585.05 ± 3.83, B = 1919.54 ± 0.05, C = 1583.84 ± 0.05, and (for v = 1) A = 6575.31 ± 6.01, B = 1922.37 ± 0.08, C = 1586.44 ± 0.08 MHz. Deviations from rigid rotor behavior in the lowest two states were described and analyzed by inclusion of a Hamiltonian term coupling the states via the internal vibrational angular momentum. The observed conformation of the five-membered ring system was found to be the envelope equatorial form. The tunneling motion which interconverts equivalent conformers has been discussed, and the qualitative nature of the potential energy surface has been described and compared to the parent unsubstituted molecule.     

Microwave spectral studies of rotational isomerism in substituted ethanethiols: 2-Aminoethanethiol and 2-chloroethanethiol

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 μ_a = 2.68 D, μ_b = 0.88 D, and μ_c = 0.37 D, while for the non-H-bond form the values are μ_a = 1.51 D, μ_b = 0.0 D, and μ_c = 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.     

Microwave spectrum and rotational isomerism of 3,3-difluoropropene CHF2CHCH2

The analysis of the microwave spectrum of 3,3-difluoropropene has confirmed the existence of two rotational isomers, cis and gauche. The rotational constants in the ground vibrational state are A = 9126.08 MHz, B = 3722.120 MHz, and C = 2946.598 MHz for the cis form and A = 8901.64 MHz, B = 4192.759 MHz, and C = 3107.718 MHz for the gauche form. The dipole moment and its components along the principal axes of intertia are μ_a = 2.369 ± 0.015 D, μ_c = 0.70 ± 0.03 D, and μ_t = 2.47 ± 0.03 D for the cis form and μ_a = 1.535 ± 0.015 D, μ_b = 0.53 ± 0.04 D, μ_c = 1.36 ± 0.03 D, and μ_t = 2.12 ± 0.05 D for the gauche form. The relative intensity measurement indicates that the cis form is more stable than the gauche form by 260 ± 80 cm^?1. The energy of the first excited state with respect to the ground state was found to be 63 ± 8 cm^?1 for the cis form and 85 ± 10 cm^?1 for the gauche form. Two Fourier coefficients of the potential function restricting the torsion around the CC bond were determined to be V₁ = 266 ± 40 cm^?1 and V₃ = 508 ± 200 cm^?1, using the available data. The potential function thus obtained is compared to a prediction model which is derived assuming additivity of the potential as a function of substitution.     

Microwave spectrum,structure, quadrupole coupling constants,dipole moment,and barrier to internal rotation of N-methylhydroxylamine

The microwave spectrum has been observed and analyzed for five isotopic species of N-methylhydroxylamine. For the normal species the rotational constants (in Megahertz) are A = 38 930.771 ± 0.005, B = 3939.607 ± 0.002, and C = 8690.716 ± 0.001. These data show that the molecule exists in the trans conformation, with structural parameters that include the following: CN = 1.460, NO = 1.461, NH = 1.007, and OH = 0.962. Hyperfine structure analyses have yielded the complete inertial axis ¹⁴N quadrupole coupling constant tensor, and thus the tensor values in the electric field-gradient principal axis system as follows: χ_xx = 4.41 ± 0.30, χ_yy = 1.93 ± 0.45, and χ_zz = ?6.34 ± 0.30 MHz. The total electric dipole moment has been found to have the value μ_T = 0.71 D, and the barrier to internal rotation of the methyl group is 3.55 kcal/mole.     

The microwave spectrum,structure, and quadrupole coupling constants of boron chloride difluoride,BCIF2

The microwave spectrum of boron chloride difluoride, BClF₂, has been investigated in the region 26.5–40.0 GHz. R-branch transitions belonging to the isotopic species ¹¹B³⁵Cl¹⁹F₂, ¹¹B³⁷Cl¹⁹F₂, and ¹⁰B³⁵Cl¹⁹F₂ have been observed and the derived rotational constants yield the following ground-state structural parameters: $\text{r}{}^0\text{(BF) = 1.315 ± 0.006}\text{A}\text{?}$, $\text{r}{}^{\mathrm{s}}\text{(BCl) = 1.728 ± 0.009}\text{A}\text{?}$, < FBF = 118.1 ± 0.5°. The ground-state rotational constants of the most abundant species ¹¹B³⁵Cl¹⁹F₂ are: A₀ = 10 449.32 ± 0.13, B₀ = 4705.811 ± 0.020, C₀ = 3239.702 ± 0.026 MHz, Δ_JK = 8.9 ± 1.7, and Δ_J = 1.86 ± 0.48 KHz. The asymmetry parameter κ = ?0.593291 and the inertial defect δ⁰ = 0.2361 amu Ų which is consistent with that expected for this type of molecule if planar. The ³⁵Cl quadrupole coupling constants for ¹¹B³⁵Cl¹⁹F₂ are χ_aa = ?42.8 ± 1.0, χ_bb = 30.2 ± 1.5, χ_cc = 12.6 ± 1.5 MHz with the asymmetry parameter η = 0.41.     

The microwave spectrum,substitution structure,internal rotation barrier,and dipole moment of thioacetaldehyde,CH3CHS

The microwave rotational spectrum of the unstable species thioacetaldehyde, CH₃CHS, has been studied in a flow pyrolysis system. Eight isotopic variants have been studied allowing an accurate substitution structure to be derived. Most of the spectral lines show splittings due to internal rotation, analysis of which has allowed a barrier study to be made. For the torsional ground state of the most abundant species, V₃ = 1572 ± 30 cal/mole or 375.7 ± 7 J/mole. The dipole moment is μ = 2.33 ± 0.02 D with components μ_A = 2.26 ± 0.02 and μ_B = 0.56 ± 0.01 D.     

The microwave spectrum and conformations of halomethyl oxiranes: Bromomethyl oxirane

The microwave spectrum of bromomethyl oxirane

has been recorded in the range 12.5–18 and 26.5–40 GHz. Lines of the two bromine isotopic species of three rotamers, gauche-1 (Br near the O atom), gauche-2 (Br near the CH₂ of the ring) and cis have been identified. The gauche-1 lines are strongest, and the cis lines the weakest. The rotational constants (in MHz) are: gauche-1 (⁷⁹Br) A = 12 296.050, B = 1 391.677, C = 1 317.360, (⁸¹Br) A = 12 199.162, B = 1 378.321, C = 1 309.142; gauche-2 (⁷⁹Br) A = 12 278.436, B = 1 378.830, C = 1 304.852, (⁸¹Br) A = 12 189.869, B = 1 369.696, C = 1 301.584; cis (⁷⁹Br) A = 7 733.314, B = 1 808.087, C = 1 737.340, (⁸¹Br) A = 7 726.16, B = 1 801.159, C = 1 730.125.     

Microwave and photoelectron study of cis- and trans-isocyanato ethene,CH2CHNCO (vynyl isocyanate)

The microwave and photoelectron spectra of isocyanato ethene CH₂CHNCO have been studied. The microwave results indicate that the species is planar and possesses both a cis and a trans form. The appearance of dense and complicated vibrational satellite lines indicates that the molecule is quite flexible, a general property of molecules containing the isocyanate group. The rotational constants are:

$\text{cis: A}{}_0\text{= 20 146.8, B}{}_0\text{= 3107.267, C}{}_0\text{= 2689.513}\text{MHz}\text{; trans: A}{}_0\text{= 62 584.051, B}{}_0\text{= 2437.730, C}{}_0\text{= 2346.507}\text{MHz}$

These constants are shown to be consistent with structures in which $\text{r(}\text{CN}\text{) = 1.382 ± 0.005}\text{A}\text{?}$, ∠(CCN) = 122 ± 1° (for both conformers), and ∠(CNC) = 142.4 ± 0.5° (cis) and 138.4 ± 1.5° (trans). The dipole moments are μ(cis) = 2.120 ± 0.015 and μ(trans) = 2.207 ± 0.007 D. Several distinct peaks are observed in the photoelectron spectrum; however, the structure is not resolved into features belonging to the different isomers. The first ionization potential lies at 9.80 ± 0.1 eV. The spectrum has been assigned with the aid of theoretical calculations.     

Microwave spectrum and quadrupole coupling constant tensor of chloroiodomethane

The microwave spectrum of ³⁵Cl and ³⁷Cl species of chloroiodomethane was investigated in the frequency region of 9–35 GHz. The b-type R-branch and Q-branch transitions were assigned. The rotational constants of the ground state were determined to be A = 27 418.81 ± 0.10, B = 1621.879 ± 0.024, and C = 1545.730 ± 0.044 MHz for the ³⁵Cl species; and A = 27 261.46 ± 0.16, B = 1562.240 ± 0.047, and C = 1491.008 ± 0.092 MHz for the ³⁷Cl species. From the hyperfine splitting of the I, ³⁵Cl, and ³⁷Cl nuclei, the nuclear quadrupole coupling constants were determined to be χ_aa = −1404.5 ± 3.8, χ_bb = 383.4 ± 2.1, χ_cc = 1021.1 ± 4.3, and ∥χ_ab∥ = 1176.5 ± 3.6 MHz of iodine; χ_aa = −26.8 ± 2.3, χ_bb = −11.0 ± 1.2, and χ_cc = 37.8 ± 2.6 MHz of ³⁵Cl for the ³⁵Cl species; χ_aa = −1423.2 ± 5.5, χ_bb = 389.1 ± 2.9, χ_cc = 1034.1 ± 6.2, and ∥χ_ab∥ = 1170.2 ± 6.9 MHz of iodine; and χ_aa = −20.4 ± 3.3, χ_bb = −9.1 ± 1.8, and χ_cc = 29.5 ± 3.7 MHz of ³⁷Cl for the ³⁷Cl species, respectively. The centrifugal distortion constants were also determined using all of the assigned transitions. A brief discussion of the procedure for analyzing the quadrupole hyperfine structures of a molecule containing two quadrupolar nuclei is also provided.     

The microwave spectra and conformations of chloromethyl oxirane: cis and gauche-2 forms

The microwave spectra of two conformations of chloromethyl oxirane ($\text{CH}{}_2\text{OC}$HCH₂³⁵Cl, epichlorohydrin) is reported. In the gauche-2 form the chlorine is situated trans to the oxygen, in the cis form the chlorine is cis to the ring. The rotational constants in megahertz are gauche-2; A = 12 739.35, B = 2066.83, C = 1881.49, and cis; A = 8378.66, B = 2840.67, C = 2510.55.