Hyunyong Kim

Ring Puckering in Five‐Membered Rings. III. The Microwave Spectrum, Dipole Moment, and Structure of Cyclopentanone

Microwave spectra of cyclopentanone and 2‐d‐cyclopentanone are reported. Eight vibrational satellites have been assigned for cyclopentanone, and two conformers have been observed for 2‐d‐cyclopentanone. The rotational constants of the ground states are: 6621, 3351.54, and 2410.40 MHz for the normal isotopic species of cyclopentanone; 6309, 3322.55, and 2382.82 MHz; and 6258, 3344.54, and 2361.96 MHz for the two conformers of the 2‐deutero isotopic species. It was found that the nature of the ring‐puckering potential is such that the ring is permanently twisted and undergoing bending and twisting vibration quite independently. The lower limit to the height of barrier‐hindering pseudorotation was set about 400 cm−1. The structural parameters, r;(C1–C2), r;(C2–C3), ∠(C2–C1–C5), and the twist angle τ, were calculated by the iterative procedure of the weighed least‐squares analysis. They are 1.504 ± 0.01 A, 1.557 ± 0.007 A, 110.5 ± 0.7°, and 23.6 ± 0.4°. The components of dipole moments were determined by the ...

Millimeter‐Wave Spectrum and Structure of Hypofluorous Acid: HOF and DOF

The microwave spectra of two isotopic species of hypofluorous acid, HOF and DOF, have been investigated. The values of the A0, B0, and C0 rotational constants are 590 000, 26 758.00, and 25 512.51 MHz for HOF and 316 800, 25 591.25, and 23 587.75 MHz for DOF. The structural parameters calculated with these rotational constants are: r(O–H) = 0.964 ± 0.01 A, r(O–F) = 1.442 ± 0.001 A, and > HOF = 97.2° ± 0.6° Centrifugal distortion analysis in the symmetric top approximation gave DJ and DJK values of 0.0934 and 2.417 MHz for HOF and 0.0775 and 1.745 MHz for DOF, respectively. The P6 distortion term was not significant.

Spectral Observations on Molecular XeF6: Raman Scattering and Infrared, Visible and Ultraviolet Absorption in the Vapor and in Matrix Isolation

Raman spectra and visible and ultraviolet absorption spectra of XeF6 vapor have been studied as functions of temperature. The changes that occur in the observed spectra are interpreted as due to relative population changes of the three electronic isomers postulated in the preceding paper. Evidence is presented that, even at temperatures as high as 100°C, it may take tens of minutes to reach equilibrium among the isomers. Infrared spectra of both XeF6 vapor at 25°C and of XeF6 molecules isolated in a low temperature argon matrix have been studied for a variety of previous thermal treatments of the XeF6 samples. In the spectra of the matrix, large differences in the relative intensities of absorption bands were found, depending on the thermal history of the XeF6 used in the deposition. All the spectra observed are interpreted in terms of the three electronic isomers, and the assignments appear quite plausible.

Ab Initio Calculation of the Electronic Structure of Carbon Suboxide

An ab initio LCGO MO SCF calculation with geometry search is carried out on C3O2. The structure is determined to be linear with C–C and C–O bond distances of 1.332 and 1.243 A, respectively. The electronic configuration is determined, and one‐electron properties are calculated. Potential functions are reported and discussed with particular emphasis on the low‐frequency bending mode about the central carbon atom.

Centrifugal Distortion Analysis of Hypofluorous Acid: HOF and DOF

The millimeter wave rotational spectrum of hypofluorous acid displays sizeable distortion effects. More than forty lines each for both HOF and DOF including a‐ and b‐type transitions have been measured. A semirigid rotor Hamiltonian, which includes the quartic distortion terms, was employed to fit the spectrum. The special constants (in MHz) in the notation of Watson are for HOF: A= 585 631.20, B= 26 760.31, C= 25 510.19, ΔJ= 0.09414, ΔJK= 2.4146, ΔK= 82.52, δJ= 0.00432 and δK= 1.120. For DOF: A= 316 096.02, B= 25 593.91, C= 23 585.28, ΔJ= 0.07903, ΔJK= 1.7349, ΔK= 24.82, δJ= 0.005933 and δK= 1.183. Corrections to A, B, and C given above have been applied to obtain the effective moments of inertia, and the structure is recalculated.

Gas‐Phase Infrared Spectra of HOF and DOF

The infrared spectra of HOF and DOF in the gas phase have been studied. From the analysis of rotational subbands, the fundamental frequencies are determined to be 3578.5, 1354.8, and 889.0 cm−1 for HOF; and 2643.5, 1003.9, and 891.1 for DOF. The respective values of the constants (A″ − B″) and B″ are 18.37 and 0.86 cm−1 for HOF, and 9.79 and 0.81 cm−1 for DOF.

Low‐frequency molecular vibrations in solid n ‐paraffins by neutron inelastic scattering: n ‐Pentane, n ‐hexane, n ‐heptane, and n ‐octane

The torsional and skeletal bending fundamentals in solid n ‐pentane, n ‐hexane, n ‐heptane, and n ‐octane are measured by the method of cold neutron inelastic scattering. For this series of n ‐paraffins, the maximum frequencies of the skeletal torsion and skeletal bending modes approach 190 and 500 cm−1, respectively, in agreement with previous measurements on polyethylene. The average frequency of the two end‐methyl torsions is found to be 240 cm−1. A normal coordinate analysis, performed using only intramolecular valence force fields for each molecule, is used as a guide in spectral assignments. These results are compared to theoretical dispersion curves of polyethylene, with and without intermolecular forces. Chain‐end effects appear to be of little significance for these low‐frequency modes, even in chain lengths as short as seven or eight carbons.

On Abel Inversions of Emission Data from an Inductively Coupled Plasma

In a typical inductively coupled plasma (ICP) with cylindrical symmetry, the physical system is best characterized in terms of the radial coordinate r and the height h measured from the induction coil. However, the emission (or absorption) intensity is usually measured as a function of lateral coordinate, x, and height, h, and the Abel integral equation is used to transform the lateral intensity, I(x), into the radial intensity, i(r). Therefore, an accurate Abel inversion is a prerequisite for physical characterizations of ICP at any levels of sophistication. And it follows that the error in the inverted radial intensity must be properly evaluated.

Microwave spectrum and rotational isomers of cyclopropylcarbinyl chloride and epichlorohydrin

Abstract Microwave spectra of and have been studied. is found to exist in two rotameric forms. Their rotational constants, A, B and C are 7799.5, 2858.9 and 2550.0 MHz for the cis rotamer; and 11 745.9, 2049.8 and 1892.3 MHz for the gauche rotamer. Three rotameric forms are found for and their rotational constants, A, B and C are 13 297.2, 2007.1 and 1873.1 MHz for rotamer I (gauche I); 8487.6, 2899.0 and 2531.9 MHz for rotamer II (cis); and 13 508.8, 2055.1 and 1920.4 MHz for rotamer III (gauche II).

Molecular Potential Functions Expressed in Cartesian Coordinates: Application to the Orbital Valency Force Field

Potential energy matrices are derived for molecules of the type XYn in terms of the Heath and Linnett orbital valency force field. Cartesian coordinates are used, and a simple calculation procedure is outlined that makes use of generally available computer subroutines for matrix diagonalization, etc. The method makes no use of symmetry coordinates, and is therefore particularly convenient for problems involving isotopic substitutions. Extension to larger molecules is suggested but not carried out in detail. The general method may be useful for other force field models, also.