D. Van Lerberghe

High-resolution infrared spectrum and rotational constants of ethylene-H4

Abstract Four bands in the infrared spectrum of ethylene-H 4 are studied with a resolution of 0.03 – 0.04 cm −1 , the A -type ν 11 fundamental, the B -type ν 9 fundamental, and the B -type ν 5 + ν 12 and ν 6 + ν 11 combination bands. From ∼300 combination differences, the following ground-state rotational constants are determined: A 0 = 4.86596 ± 0.00018, B 0 = 1.001329 ± 0.000061, C 0 = 0.828424 ± 0.000062, D J 0 = 1.447 ± 0.070 × 10 −6 , D JK 0 = 1.468 ± 0.063 × 10 −5 , D K 0 = 9.17 ± 0.16 × 10 −5 cm −1 . Upper-state rotational constants are reported for all four bands, some Coriolis interactions are identified, and the relevant ξ constants are determined. The value of the band center of ν 5 + ν 12 leads to a suggested reassignment of Q branches in the Raman active fundamental ν 5 , and a revision of the band center to 3086 cm −1 . The new data for C 2 H 4 determined in this work are summarized in Table VII, along with all the other currently available data on the vibrational and rotational constants.

Ground state rotational constants of H2CCD2 and C2D4 and geometry of ethylene

Abstract The ν6 and ν10 B-type and the ν7 and ν8 C-type fundamentals of H2CCD2 have been studied at a resolution of ∼0.2 cm−1, and the A-type ν1 fundamental at a resolution of 0.03–0.04 cm−1. From analyses of the rotational structure in these bands, accurate values of the ground state rotational constants A0, B0, and C0 are obtained. The band centers of the very weak B-type bands are accurately located for the first time. For C2D4, values of A0, B0, and C0 are determined from the ground state combination differences obtained from the rotational Raman data of Dowling and Stoicheff and the infrared data of Allen and Plyler. For both molecules, the experimental and theoretical inertia defect values are in close agreement. The sets of ground state rotational constants for H2CCD2 and C2D4 are combined with those for C2H4 of a previous study to yield for the ground state geometry of ethylene: r CH 0 = 1.085 ± 0.002 A , r CC 0 = 1.339 ± 0.001 A , αHCH0 = 117°50′ ± 15′.

Etude par spectrométrie infrarouge de la stoechiométrie des complexes phénols-triéthylamine

Resume The complexes formed between triethylamine and phenols have been studied by infrared spectrometry in carbon tetrachloride solution at 30°C. The phenols have been chosen so that their pKα vary from 10·30 to 3·50. The apparent complexation constant, calculated on the model of a 1:1 stoichiometric complex shows a marked variation with the concentration in free proton donor. Using a method based on the variation of this “apparent constant”, the equilibrium constants of 1:1 (K1) and 2:1 (K2) stoichiometric complexes have been determined. These values are related to the sum of the Hammett σ constants (Σσ) by the following relations: log K1 = 1.73 + 1.30Σσ log K2= 1.57 + 0.05 Σσ + 0.94 (Σσ)2 Log K1 is linearly related to Δμ, the increment of dipole moment, determined by Ratajcyak and Sobczyk, in benzenic solution. On the other hand, equation (2) is compared to an expression, obtained previously in the study of the complexation of substituted phenols-substituted anilines, showing that the logarithm of the complexation constant depends on an interaction term depending on the product of the substitution constants σaσb. The formation of a complex of 2:1 stoichiometry gives a characteristic vibration band lying at some 100 cm−1 lower than the dimeric phenol; this constatation is explained in terms of the greater basicity of the oxygen atom in the 1:1 complex than in the dimeric phenol. The CH stretching vibrations of the triethylamine are disturbed in frequency and intensity by the formation of a hydrogen bond; this perturbation increases with the phenol acidity.

High resolution study of the v 7 + v 8 band of ethylene (C2H4) at 1889 cm-1

The v 7 + v 8 A-type band of C2H4 has been recorded between 1932 and 1847 cm-1 with a resolution of 0·06 cm-1. The transitions with K -1 ⩽ 8> and J ⩽ 2>5 have been assigned. Although slight Coriolis resonances perturb the band, the analysis has been made easy through the use of an elaborate set of asymmetric top computer programmes. The band centre and a set of upper state constants have been obtained. With these constants, 288 observed upper state energy levels have been fitted with a standard deviation of 0·021 cm-1. Using very simple expressions, we have predicted all the resonance effects perturbing the levels of ethylene near 2000 cm-1. This led us to the identification of the v 4 + v 8 and v 8 + v 10 combination bands in low resolution spectra.

High resolution infrared spectroscopic studies of ethylene-1,1-D2

Abstract Rotational assignments in the ν6 + ν9 type-A band and the ν9, ν6 + ν11, and ν1 + ν6 type-B bands of ethylene-1,1-D2, recorded at a resolution of ∼0.03 cm−1, enable the ground state rotational constants to be determined much more accurately than previously. A significant change in the A0 constant is noted. All upper states suffer perturbations to their rotational structures. Analyses, excluding the areas of perturbation, still enable the excited state constants to be determined with considerable precision.

High resolution infra-red study of v 12 and v 2 + v 9 absorption bands of C2H3D molecule

The fundamental v 12 and combination v 2 + v 9 infra-red absorption bands of monodeuterated ethylene C2H3D have been recorded with high resolution, respectively from 1469 to 1363 cm-1 on a ‘dual-grille’ spectrometer, and from 4826 to 4530 cm-1 on a slit spectrometer. During the analysis of these two bands, a large number of anharmonic and rotational resonances have been discovered and interpreted. From the results, the molecular ground state and appropriate excited states parameters have been refined, together with a number of Fermi and Coriolis coupling constants.

Infrared absorption bands 1-0, 2-0, 3-0, and 4-0 of the two isotopic species D/sup 79/Br and D/sup 81/Br of deuterium bromide

High resolution spectra of the 1-0, 2-0, 3-0 and 4-0 infrared absorption bands of the two isotopic species of deuterium bromide have been recorded up to very high /b J/ values. The equilibrium molecular parameters obtained in the analysis fit the 267 observed lines within their experimental uncertainties, and give precise calculated wavenumbers for some observed chemical laser lines of these molecules.