The harmonic force field and structure of chloryl fluoride

The microwave spectra of three isotopic species of chloryl fluoride, FClO₂, previously published by Parent and Gerry (J. Mol. Spectrosc., 49, 343–364 (1974)), have been refit to rotational constants and centrifugal distortion constants using Watson's Hamiltonian in both its A and S reductions. The quartic distortion constants have been combined with the vibrational data of Smith, Begun, and Fletcher (Spectrochim. Acta, 20, 1763–1770 (1964)) to calculate a refined harmonic force field. The rotational constants and force field have been used to calculate a zero-point average structure and an approximate equilibrium structure. Both the force field and structures are in essential agreement with those published earlier.     

The microwave spectrum and structure of carbonyl fluoride

The ground state microwave rotational spectra of four isotopic species of carbonyl fluoride have been measured between 18 GHz and 77 GHz, and analyzed to obtain the quartic and some sextic centrifugal constants. The rotational constants have been used to obtain a r₀ structure and, using a harmonic force field, a r_z structure is also obtained: r_z(C---F) = 1.3166 (10) Å, r_z(C---O) = 1.1700 (26) Å.These values are considerably more precise than those of the previously estimated average structure.     

The microwave spectrum,structure, and dipole moment of propiolyl fluoride

The microwave spectrum of propiolyl fluoride has been observed in the frequency region 12.5–40 GHz. Rotational transitions have been assigned for the ground and two excited vibrational states of the normal isotopic species and for the ground vibrational state of the deuterated species. In each case, values for the rotational constants and centrifugal distortion constants have been obtained. The molecule has been shown to be planar and structural calculations suggest no anomalies in any of the internuclear parameters. Stark effect measurements have yielded a value of 2.98 ± 0.02 Debyes for the dipole moment.     

The microwave spectrum and centrifugal distortion constants of vinyl fluoride

The rotational spectrum of vinyl fluoride up to J = 40 has been assigned and measured in the frequency region 8–37 GHz. Both a- and b-type transitions were observed. These measurements have been combined with those made in other frequency regions to calculate refined rotational constants and to obtain all quartic and some sextic centrifugal distortion constants. A comparison is made between the quartic centrifugal distortion constants measured here and those calculated from vibrational data.     

The microwave spectrum and structure of fulvene

The microwave spectra of four ¹³C and two monodeutero species of fulvene have been recorded and analysed. Earlier data for the parent species has also been slightly refined. The final structure which emerges for fulvene is essentially three weakly coupled ethylenic entities with bond lengths: C₁C₂ = 1.470Å C₂C₃ = 1.355Å, C₃C₄ = 1.476Å and C₁C₆ = 1.3485Å. The CH bond distances and ring angles are close to expected values.     

The microwave spectrum and structure of chlorine isocyanate

The microwave spectra of three isotopic species of chlorine isocyanate, ClNCO, have been measured in the frequency region 8–37 GHz. Spectra have been observed for molecules in both the ground and excited vibrational states, and have yielded values for the rotational constants, inertial defects, centrifugal distortion constants, and nuclear quadrupole coupling constants for both chlorine and nitrogen. The molecule has been shown to be planar, with the following internuclear parameters: fx547-1 < (NCO) = 171° 24′ ± 1° 30′, with Cl and O trans. The principal values of the chlorine nuclear quadrupole coupling tensor were calculated, and were found to be consistent with the derived structure.     

The microwave spectrum and structure of chloromethyl cyclopropane

The microwave spectra of $\text{CH}{}_2\text{CH}{}_2\text{CH}$CH₂³⁵Cl and $\text{CH}{}_2\text{CH}{}_2\text{CH}$CH₂³⁷Cl have been observed and lines assigned to the gauche form. The rotational constants in MHz and distortion constants in KHz are: C₃H₅CH₂³⁵Cl, A = 11745.65, B = 2047.274, C = 1886.622, Δ_J = 0.85, Δ_JK = ? 0.9, Δ_K = 44., δ_J = ? 0.099, δ_K = 19.1, C₃H₅CH₂³⁷Cl, A = 11691.61B = 1997.664, C = 1842.823, Δ_J = 0.7, Δ_JK = ? 64.6, Δ_K = 2400, δ_J = 0.19, δ_K = ? 67.     

The microwave spectrum and structure of the argon trifluoroacetonitrile complex

The rotational spectrum of argon trifluoroacetonitrile complex has been studied by pulsed-nozzle, Fourier transform microwave spectroscopy. Both a-type and b-type transitions have been observed. The rotational constants are A = 3053.0903(2) MHz, B = 1039.9570(2) MHz, and C = 895.5788(1) MHz. The ¹⁴N nuclear quadrupole hyperfine components of the rotational transitions have been resolved, the ¹⁴N nuclear quadrupole coupling constants are χ_aa = 1.746(1) MHz, and χ_bb − χ_cc = −6.426(2) MHz. The complex is T-shaped, with the argon atom located 3.73 Å from the center of mass of the trifluoroacetonitrile molecule.     

The microwave spectrum,harmonic force field,and structure of difluorodichloromethane

Very large numbers of rotational transitions have been accurately measured for ¹²CF₂³⁵Cl₂, ¹²CF₂³⁵Cl³⁷Cl, and ¹³CF₂³⁵Cl₂, and have been analyzed for rotational constants and quartic centrifugal distortion constants. The distortion constants have been combined with vibrational wavenumbers (both from the literature and from the present work), and with ab initio force constants also evaluated in the present work, to give an approximate harmonic force field. The rotational constants and force field have been used to evaluate ground state effective, substitution, and ground state average structures for the molecule.     

The microwave spectrum,structure, and dipole moment of amino acetonitrile

The microwave spectra of three isotopic species of amino acetonitrile (NH₂CH₂CN, NHDCH₂CN, and ND₂CH₂CN) have been investigated to learn something about the structure and bonding in this and similar compounds. The only rotamer observed is the form in which both NH bonds are gauche to the CN group and the structure is quite rigid. From the available data only the bond angles are well determined. The amino NCC angle is 114.5(3)°, the HCH angle is 103(2)°, the HNC angle is 109.6(4)°, and the HNH angle is 107(1)°. The dipole moment components are μ_a = 2.577(7) D and μ_b = 0.5754(10) D; these agree quite well in magnitude and direction with the sum of the acetonitrile and methyl amine dipoles. The rigidity of the molecule and its preference for the form in which the amino protons are closest to the triple bond confirms a suggestion based on earlier studies on similar molecules that there is a strong hydrogen bonding interaction between the amino group and the nitrile group, although in this molecule dipole-dipole forces also probably play a significant role in determining the structure and its rigidity.     

The microwave spectrum,structure and nuclear quadrupole coupling constants for stibabenzene

The microwave spectrum of 121-SbC₅H₅, 123-SbC₅H₅, β-dideutero 121-SbC₅H₃D₂ and 123-SbC₅H₃D₂ has been assigned in the region 26.5–40.0 GHz. The respective rotational constants and uncertainties are: A = 4512.69 ± 0.42, B = 1738.00 ± 0.01, C = 1254.51 ± 0.01; A = 4512.84 ± 0.30, B = 1729.80 ± 0.01, C = 1250.22 ± 0.01; A = 4176.18 ± 0.33, B = 1660.94 ± 0.01, C = 1188.15 ± 0.01; A = 4176.60 ± 0.61, B = 1652.94 ± 0.03, C = 1184.03 ± 0.03 (in MHz units). The structure is found to be planar, C_2v in symmetry. The $\text{d(}\text{Sb-C}\text{) = 2.050 ± 0.005}\text{A}\text{?}$ and ∠CSbC = 92.9° ± 1.0°. The nuclear quadrupole coupling constants for the 121 and 123 antimony isotopes are χ_aa = 456.4 ± 4.1 MHz, η = 0.396 ± 0.008, and χ_aa = 583.00 ± 5.3 MHz, η = 0.399 ± 0.008, respectively. Several alternate techniques using the coupling constants as data support a σ-donating property for antimony.     

The microwave spectrum,structure, and dipole moment of cis-1,2,3-trifluorocyclopropane

The microwave spectrum of cis-1,2,3-triflurocyclopropane has been investigated in the region 8–40 GHz. A fit of the oblate symmetric top spectrum gives a rotational constant of 4064.925 ± 0.022 MHz. A molecular structure was determined using the rotational constants obtained from assignments of the monodeutero species and the carbon-13 species. The molecular parameters are $\text{r}\text{(CH) = 1.095 ± 0.002}\text{A}\text{?}$, $\text{r}\text{(CC) = 1.507 ± 0.001}\text{A}\text{?}$, $\text{r}\text{(CF) = 1.354 ± 0.001}\text{A}\text{?}$ and ∠(HCF) = 112.3 ± 0.2°. The dipole moment was determined to be 3.89 ± 0.02 D. The structural parameters are compared to other substituted cyclopropyl ring structures and to molecular orbital predictions as well as to related fluorocarbons. The molecule provides another example of the effect of fluorine substitutions on shortening adjacent bonds. It is also found that nonbonded F?F distances tend to be constant.     

The microwave spectrum and structure of the unstable molecule bromine isocyanate,BrNCO

The microwave spectra of two isotopic species of the unstable molecule bromine isocyanate, BrNCO, have been observed from the flow reaction of Br₂ vapor with silver cyanate. The spectra were observed in the frequency range 8–54 GHz. They contain strong a-type transitions, as well as b-type transitions, with the latter so weak they initially could not be assigned. The transitions show Br and N quadrupole hyperfine structure; many perturbations in the former have been found, and have been used in a novel method to evaluate accurately all the rotational constants and the Br quadrupole coupling tensor entirely from a-type R branches. This has been done using a global least-squares fitting program developed especially for the purpose. The resulting constants permitted the b-type transitions to be identified. The molecule has been shown to be planar, the BrNCO configuration has been confirmed, and a partial r₀ structure has been determined. The principal values of the Br quadrupole tensor have been evaluated and the BrN bond has been shown not to be bent.     

The microwave spectrum,harmonic force field,and structure of formyl chloride

Extensive measurements were made of the microwave spectra of nine isotopic species of formyl chloride, HCOCl. Analysis of these spectra gave accurate rotational constants, chlorine nuclear quadrupole coupling constants, and centrifugal distortion constants. The distortion constants, together with the vibrational wavenumbers, were used to evaluate a valence harmonic force field. Effective, substitution, ground-state average, and estimated equilibrium structures are presented.     

The microwave spectrum of tetrazole

Microwave spectra of tetrazole and the two singly deuterated tetrazole species have been assigned. Dipole moment measurements suggest that the tautomeric form observed in normal tetrazole and N-deuteriotetrazole is 2H-tetrazole while that observed in C-deuteriotetrazole is 1H-tetrazole. All three species are planar.     

The microwave spectrum of trioxaadamantane

The microwave spectrum of 2,8,9-trioxaadamantane has been investigated in the region from 12.4 to 26.5 GHz. The observed spectrum exhibited the expected symmetric top pattern, with the rotational constant B₀ = 1848.64 MHz. Numerous weaker lines were observed and were attributed to vibrational satellites of the main rotational transition. The transitions from J = 3 → 4 through J = 6 → 7 were studied and no centrifugal distortion effects were observed.A structure is derived that is consistent with the observed rotational constants of the normal and one isotopic species by use of the method of diagnostic-least-squares.The second order stark effect for the K = 0 state yielded a dipole moment of 3.01 ± 0.03 D.     

The microwave spectrum of HGeCl

The J = 1₀₁-0₀₀ and 2₀₂-1₀₁ transitions of nine isotopomers of chlorogermylene, H⁷⁴Ge³⁵Cl, H⁷⁴Ge³⁷Cl, H⁷²Ge³⁵Cl, H⁷²Ge³⁷Cl, H⁷⁰Ge³⁵Cl, H⁷⁰Ge³⁷Cl, H⁷⁶Ge³⁵Cl, H⁷⁶Ge³⁷Cl, and H⁷³Ge³⁵Cl are measured at 8-9 and 16-18 GHz. The effective rotational constants, the nuclear quadrupole coupling constants of ³⁵Cl, ³⁷Cl, and ⁷³Ge, and the nuclear spin-rotation coupling constants of ³⁵Cl and ³⁷Cl are determined.