The microwave spectrum of a common decomposition product of CF2=NCl and CF2=NBr has been analyzed. The observed hyperfine structure requires the presence of 14N and the absence of Cl and Br in the molecule. The inertial defect establishes the planarity of the molecule. The observed rotational constants are A=11 464.024(4), B=11 151.892(4), and C=5643.146(4) MHz, which are very similar to those reported for CF2=O. The molecule is identified to be difluoromethanimine, CF2=NH. The dipole moment components were determined from the Stark effect to be |μa|=0.415(1), |μb|=1.330(1), and |μt|=1.393(1) D. The 14N quadrupole coupling constants are χaa=1.029(20), χbb=−2.560(17), and χcc =1.531(22) MHz. These data are compared to similar quantities for some corresponding molecules.
The microwave spectrum of N-bromocyanofluoromethanimine CF(CN)NBr in the ground vibrational state in the region from 18.0 to 38.0 GHz has been investigated. The assigned spectrum is only consistent with a planar molecule with the cyano group trans to the bromine atom. The hyperfine structure due to the nuclear quadrupole coupling of the bromine nucleus has been analyzed for the a-type R transitions of both the 81Br and 79Br isotopic species. Quadrupole splittings due to the 14N nuclei were not resolved. The rotational constants, the centrifugal distortion constant ΔJ, and the nonzero values of the diagonal and off-diagonal elements of the bromine quadrupole coupling tensor were determined by a least-squares fit for both isotopic species of bromine. The r0 structural parameters r(C–C), r(C–F), and ∢(N=C–C) were determined to have values of 1.422(9) and 1.349(15) Å, and 121.6(9)°, respectively, whereas other structural parameters were fixed at the values obtained for the corresponding parameters of similar molecules. The equilibrium geometry of the two possible isomeric forms of CF(CN)NBr were determined by an ab initio calculation which employed the various basis sets with and without electron correlations. These results are compared with the corresponding values of some similar molecules.
The microwave spectra of five isotopic species of 2-fluoropropane, (CH3)CH2DCFH, (CH3)2CFD, (CH3)CD3CFH, (CD3)2CFD, and (CH3)213CFH, have been recorded from 12.4 to 39.7 GHz. The b- and c-type R-branch transitions have been observed and assigned for the ground state. Utilizing the rotational constants for these five isotopic species along with those reported earlier for the normal species the following r0 structural parameters have been determined: r(C–C) =1.522±0.007 Å, r(C–F)=1.398±0.013 Å, CCC =113.37±0.79°, and CCF=108.19±0.41°. All of the carbon–hydrogen parameters have also been determined from the rotational constants except for the r(C–Hsec) which was obtained from its frequency in the infrared spectrum. The far infrared spectra of 2-fluoropropane-d0, -d3 and -d7 in the gas phase were recorded with a resolution of 0.10 cm−1. Both torsional fundamentals along with several hot transitions were assigned for the three isotopic species. The barrier to internal rotation of the methyl rotors has been determined with the two-coupled rotor model to be 1149±69 cm−1 (3.29±0.12 kcal/mole). Both potential coupling terms, V33 and V′33, have been determined for the -d0, -d3 and -d7 isotopic species. The complete equilibrium geometry has been determined from ab initio Hartree–Fock gradient calculations employing both the 3-21G and 6-31G* basis sets. These results are compared to the corresponding quantities for some similar molecules.
The microwave spectra of ethylphosphonothioic difluoride, CH3CH2P(S)F2, and eight isotopic species have been investigated in the region from 26.5 to 39.5 GHz. Only a-type transitions were observed and R-branch assignments have been made for all the isotopic species in the ground vibrational state for both the gauche and trans (methyl group trans to the P=S bond) conformers from which the rotational constants were determined. From these data the complete r0 structural parameters were determined for the gauche conformer with the values for the heavy atom parameters being: r(C–C)=1.532±0.006 Å, r(C–P)=1.800±0.007 Å, r(P=S)=1.880±0.003 Å, r(P–F)=1.555±0.005 Å, ∢CCP=112.6±0.3°, ∢CPS=119.4±0.4°, ∢CPF=102.0±0.2°, dih ∢FPCS=129.3±0.2°, and dih ∢CCPS=56.9±0.2°. The parameters of the trans conformer which differed significantly from the values for the corresponding ones in the gauche conformer were: r(C–P)=1.814±0.011 Å, r(P=S)=1.861±0.007 Å, and ∢CCP=114.8±0.2°. The infrared (3500 to 40 cm−1) and Raman (3500 to 20 cm−1) spectra of the gaseous and solid CH3CH2P(S)F2 and CD3CD2P(S)F2 as well as the Raman spectrum of the liquid have been recorded. Both trans and gauche conformers have been identified in the vibrational spectra of the fluid phases, but only the trans corformer remains in the solid state and a complete vibrational assignment is proposed for the trans conformer. The barrier to methyl rotation for the trans conformer was determined to be 808 cm−1 (2.31 kcal/mol). The asymmetric torsion for the trans conformer was observed as a series of closely spaced Q branches beginning at 73.25 cm−1 and falling to lower frequency and the gauche transitions begin at 70.82 cm−1. These transitions along with the dihedral angle for the gauche conformer have been used to obtain the potential
function for the asymmetric rotation which indicates that the trans conformer is more stable than the gauche conformer in the gas phase by 63±37 cm−1 (180±106 cal/mol). All of these results are compared with corresponding quantities for several similar organophosphorus compounds.
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