D. Damiani

Direct l doublet transitions for the 0110 state of cyanogen iodide

Abstract Direct l doublet transitions for the 01 1 0 state of 127 I 12 C 14 N and 127 I 13 C 14 N were observed between 4 and 25 GHz using a computer-controlled Stark modulation spectrometer. Values of the l doubling constants and the asymmetry parameters of the 127 I nuclear quadrupole coupling tensors were derived. Some details of the construction of the spectrometer are also given.

Structure of cyclopentadiene from microwave spectra of several deuterated species

Abstract The microwave rotational spectra of hexadeuterated, pentadeuterated and of three different monodeuterated species of cyclopentadiene have been measured. Structural parameters for hydrogen atoms have been deduced from rotational constants of these species. From these structural data for the hydrogens and from those relative to the ring determined by Scharpen and Laurie the r s and r o structures have been obtained.

Direct l-doublet transitions in the 0110 state of cyanogen chloride and cyanogen bromide

Abstract Direct l doublet transitions have been observed for the 01 1 0 state of the 35 Cl 12 C 14 N and 37 Cl 12 C 14 N isotopic species of cyanogen chloride and the 79 Br 12 C 14 N and 81 Br 12 C 14 N isotopic species of cyanogen bromide in the frequency range 4–22 GHz. The l -doubling constants ( q 0 , q 1 , q 2 ) and the asymmetry parameters ( ηeQq z ) of the halogen nuclear quadrupole coupling tensors have been derived. The constants q 1 have been calculated form the vibrational force fields of Whiffen for the four cyanogen halides using the formulation of Watson. Agreement with the observed values is found to be 10% or better and for cyanogen fluoride and cyanogen chloride the isotopic shifts in q 1 are also well predicted.

Microwave spectrum and structure of equatorial chlorocyclohexane

Abstract The microwave rotational spectra of C6H1135Cl and C6H1137Cl have been measured. The rotational constants A, B and C and quadrupole coupling constants were determined. Some structural information was obtained.

Microwave spectrum of axial cyclohexyl chloride and conformational equilibrium in cyclohexyl chloride

Abstract The high-resolution microwave spectrum of the axial conformer of cyclohexyl chloride has been assigned for both the Cl(35) and Cl(37) isotopic species, in natural abundance. Moreover, the high-resolution microwave spectrum of the equatorial conformer, previously assigned in the ground state [ Chem. Phys. Lett. 21 , 592–594 (1973)], has been further investigated. Several low-energy vibrational satellites have been studied for the Cl(35) isotopic species of both the axial and the equatorial isomers. The ground state centrifugal distortion constants for both the isotopic species of the two rotamers, and the quadrupole coupling constants of Cl(35) and Cl(37) axial isomer and of Cl(37) equatorial isomer (not reported previously) have been determined. From line relative intensity measurements the energy difference between the two conformers has been calculated to be 0.51 ± 0.15 kcal/mol, the equatorial isomer being more stable. In the same way, the vibrational energies of the investigated vibrational satellites have been computed. A structural model for axial cyclohexyl chloride is proposed on the basis of the available experimental data.

Higher-order centrifugal distortion effects in ONCl

Abstract One hundred and nine new rotational transitions of ONCl in the ground vibrational state have been measured. A centrifugal distortion analysis of these transitions yields the values of six sextic and one octic centrifugal distortion constants. A comparison between experimental and calculated sextic distortion constants is reported.

Microwave spectrum, dipole moment and structure of 1,1-difluorocyclohexane

Abstract From the analysis of the microwave rotational spectrum of 1,1-difluorocyclohexane in the frequency region 8–40 GHz the rotational constants (A = 3191.781, B = 1759.768, C = 1512.293 MHz), the centrifugal distortion coefficients (DJ = 124 × 10−4, DJK = 2.92 × 10−4, DK = -8.20 × 10−3) and the dipole moment and its components (μ = 2.556, μa = 2.415, μb = 0, μc = 0.837 debye) have been derived. Assuming that the CC and CH distances are the same as those of propane and that the ring structure in the chair form is symmetrical, the following structural parameters are obtained: ∠CCC = 111.95°, ∠FCF = 108.68°, C–F = 1.356 A.

Microwave spectra of cyclohexyl bromide and cyclohexyl iodide

Abstract The microwave spectra of cyclohexyl bromide and cyclohexyl iodide have been investigated in the gas phase between 8 and 40 GHz. While for cyclohexyl bromide only low resolution spectra have been recorded, for cyclohexyl iodide high resolution spectra of both the equatorial and the axial isomer have been analyzed. The energy difference between the axial and the equatorial form is Δ G ° = 0.8 ± 0.4 kcal/mole and Δ E 0,0 = 0.54 ± 0.15 kcal/mole in C 6 H 11 Br and C 6 H 11 I, respectively, the equatorial forms being more stable. Iodine nuclear quadrupole coupling constants for equatorial and axial C 6 H 11 I have been obtained. The present analysis contributes to the microwave investigation of the cyclohexyl halides.

High-resolution microwave spectrum of cyclohexyl bromide

Abstract The high-resolution microwave spectra of the79Br and81Br isotopic species of cyclohexyl bromide, C6H11Br, have been assigned for the equatorial and axial isomers, respectively. The ground-state energy of the axial isomer is 0.72 ± 0.30 kcal/mole higher than that of the equatorial one. The quadrupole coupling constants have been obtained for the equatorial and axial ground states of both the isotopes. Several vibrational excited states of the equatorial and axial conformers (79Br) have also been analyzed.

Structure of the amine group in m-fluoroaniline by microwave spectroscopy

Microwave spectra of the normal and amine deuterated isotopic species of m-fluoroaniline have been observed. The structure of the amine group determined using the normal isotopic species as the parent molecule is rN–H= 1.00 A(assumed), ∠ HNH = 115.0°, ϕ= 36.2°(ϕ is the angle between the bisector of the HNH angle and the extension of the CN bond) and is similar to that in aniline. The structure of the amine group determined using m-fluoroaniline-ND2 as the parent molecule is rN–H= 1.00 A(assumed), ∠ HNH = 117.5°, ϕ= 42.0°.