9 research outputs found
Microwave spectrum, structure, barrier to internal rotation, dipole moment, and deuterium quadupole coupling constants of the ethyleneâsulfur dioxide complex
The microwave spectra of the complex between ethylene and sulfur dioxide and nine of its isotopic species have been observed in a Fourier transform microwave spectrometer. The spectra exhibit a and c dipole selection rules; transitions of the normal species and several of the isotopically substituted species occur as tunneling doublets. The complex has a stacked structure with Cs symmetry; the C2H4 and SO2 moieties both straddle the mirror plane with the C2 axis of SO2 crossed at 90â° to the carbonâcarbon bond axis (i.e., only the S atom lies in the symmetry plane). The distance between the centers of mass (Rcm) of C2H4 and SO2 is 3.504(1) Ă
and the deviation of their planes from perpendicular to Rcm is 21(2)â° and 12(2)â°, respectively. The tunneling splittings arise from a rotation of the ethylene subunit in its molecular plane. The barrier to internal rotation is 30(2) cmâ1. The dipole moment of the complex is 1.650(3)D. The deuterium nuclear quadrupole coupling constants for C2H3Dâ
SO2 are Ïaa=â0.119(1) MHz, Ïbb=0.010(1) MHz, and Ïcc=0.109(1) MHz. The binding energy is estimated to be 490 cmâ1 from the pseudoâdiatomic approximation. A distributed multipole electrostatic model is explored to rationalize the structure and binding energies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70892/2/JCPSA6-93-10-7030-1.pd
The microwave spectrum and structure of krypton--phosphorus trifluoride
The rotational spectrum of the weak complex between krypton and phosphorus trifluoride has been observed using a Fourier transform microwave spectrometer with a pulsed supersonic nozzle molecular beam source. The complex is an asymmetric top. The distance rcm between the krypton atom and the center of mass of the PF3 molecule is 4.0722 A and the angle between the rcm vector and the C3 axis of the PF3 is 68.25[deg]. Based on the centrifugal distortion constant DJ and a pseudodiatomic model, the binding energy of the complex is estimated to be 218 cm-1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27096/1/0000087.pd
The benzene-SO2 and pyridine-SO2 complexes
The benzene-SO2 and pyridine-SO2 complexes have been observed for the first time using Fourier transform microwave spectroscopy. The complexes have different geometries. In benzene-SO2, the two planar species are stacked one above the other. In pyridine-SO2, the pyridine plane rotates by 70[deg], so that it is more nearly perpendicular to the SO2 plane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27846/1/0000257.pd
Fragmentative and stereochemical isomerization probes for homolytic carbon to phosphorus bond scission catalyzed by bacterial carbon-phosphorus lyase
Three bacterial strains, Agrobacterium radiobacter, Klebsiella oxytoca, and Kluyvera ascorbata, isolated by enrichment culture for carbon to phosphorus bond cleavage ability, were analyzed for the mode of C---P bond fission. The cleavage of alkyl phosphonic acids to alkanes and inorganic phosphates proceeded both aerobically and anaerobically, and growth on trideuteromethylphosphonic acid yielded trideuteromethane as product. These data indicate that functionalization of the organic moiety does not precede carbon to phosphorus bond cleavage. As probes for radical intermediates, cyclopropylmethylphosphonic acid and cis-1,2-dideutero-1-propenylphosphonic acid were used in growth experiments and the gaseous hydrocarbon products were examined. With the cyclopropylmethylphosphonic acid probe, all three bacteria produced methylcyclopropane, but only K. oxytoca and K. ascorbata also generated the acyclic olefin 1-butene, and then only in very low quantity (0.6 and 0.3% versus methylcyclopropane, respectively). With the propenylphosphonic acid probe, cis-1,2-dideuteropropene was formed with greater than 98% retention of configuration with each bacterial strain. Only for K. oxytoca was the alternate product, in this case trans-1,2-dideuteropropene, clearly detected at 1.5%. Thus, C---P bond fission may yield radical intermediates that are trapped efficiently at the enzyme active site or, alternatively, homolysis of the C---P bond may occur as a minor reaction pathway.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26489/1/0000025.pd
The structures and dipole moments of ArâPF3 and KrâPF3
The complexes of PF3 with Ar and Kr, were studied by Fourier transform microwave spectroscopy. The force constants and amplitudes of vibration for the van der Waals modes of the complexes and the average moments of inertia and structural parameters were estimated from the centrifugal distortion constants. The distance (Rc.m. )ave between the rareâgas atom and the center of mass of PF3 is 3.959 Ă
for the Ar complex and 4.077 Ă
for Kr while the angle (Ξc.m. )ave between the Rc.m. vector and the C3 axis of the PF3 is 69.30° and 67.25°, respectively. The dipole moments of both complexes and of free PF3 were determined. The induced dipole components estimated for the rare gas using electric fields from ab initio calculations of PF3 agree with the experimental values for a conformation with the rare gas over a PF2 face. The PF2 face conformation is also consistent with the observed and ab initio estimates of the 83 Kr nuclear quadrupole coupling constant for the 83 KrâPF3 species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70747/2/JCPSA6-90-12-6949-1.pd
The Microwave Spectrum and Structure of the EthyleneâSulfur Dioxide Complex This work was supported by the National Science Foundation (Grant CHE-8614340). Dedicated to Professor Hans Bock on the occasion of his 60th birthday
No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38797/1/198813561_ftp.pd
Mikrowellenspektrum und Struktur des Ethylen-Schwefeldioxid-Komplexes Professor Hans Bock zum 60. Geburtstag gewidmet Diese Arbeit wurde von der National Science Foundation gefĂrdert (CHE-8614340).
No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38636/1/19881001024_ftp.pd
The microwave spectrum and structure of the neon-phosphorus trifluoride complex
Symmetric top spectra were observed for the 20Ne[middle dot]PF3 and 22Ne[middle dot]PF3 van der Waals dimers using a Fourier-transform microwave spectrometer. The center-of-mass distance between Ne and PF3 is 3.373(3) A. The experimental data, in conjunction with the van der Waals radii of the atoms and with ab initio calculations, are consistent with the neon atom on the symmetry axis over the F3 face of the PF3. Normal mode analysis of the van der Waals vibrations based on the centrifugal distortion constants yields force constants fR = 0.00647 mdyn A-1 and f[Theta] = 0.00464 mdyn A for the 20Ne[middle dot]PF3 isotopic species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28424/1/0000207.pd