Including Matrix Isolation Research Articles

Production and characterization of para-hydrogen gas for matrix isolation infrared spectroscopy

Normal hydrogen (n-H2) has 3:1 ortho/para ratio and the production of enriched para-hydrogen (p-H2) from normal hydrogen is useful for many applications including matrix isolation experiments. In this paper, we describe the design, development and fabrication of the ortho-para converter that is capable of producing enriched p-H2. The p-H2 thus produced was probed using infrared and Raman techniques. Using infrared measurement, the thickness and the purity of the p-H2 matrix were determined. The purity of p-H2 was determined to be >99%. Matrix isolation infrared spectra of trimethylphosphate (TMP) and acetylene (C2H2) were studied in p-H2 and n-H2 matrices and the results were compared with the conventional inert matrices.

Laboratory Electronic Spectra of Carbon Chains and Rings

AbstractCarriers of the diffuse interstellar bands (DIBs) cannot be definitively identified without laboratory spectra. Several techniques, including matrix isolation, cavity ringdown spectroscopy, resonance enhanced multiphoton ionization, and ion trapping, have been used to measure the electronic spectra of carbon chains and their derivatives. The gas-phase laboratory spectra could then be compared to the astronomical data of known DIBs. The choice of molecules studied in the gas phase depends on the presence of strong electronic transitions at optical wavelengths, the lifetimes of excited electronic states, and chemical feasibility in diffuse astrophysical environments. Collisional-radiative rate models have also be used in conjunction with laboratory spectra to predict absorption profiles under interstellar conditions.

The vibrational spectra including matrix isolation, conformations and ab initio calculations of 4-azidobut-1-yne

4-Azidobut-1-yne can exist in five distinct conformations denoted GG, GG′, GA, AG and AA according to the gauche and anti conformation around C–C and the C–N bonds, respectively. Fully optimised ab initio geometries for all five conformers have been calculated at the MP2(full)/TZ2P//MP2(full)/TZ2P level. The calculated conformational energies were GG (0), AG (+1.24 kJ mol −1), AA (+1.50 kJ mol −1), GG′ (+3.35 kJ mol −1) and GA (+3.75 kJ mol −1). Additional single point calculations were also performed at the MP4(DSQ)/TZ2P//MP2(full)/TZ2P level for all five conformers. IR spectra of the molecule were obtained in the vapour and liquid states at room temperature and as amorphous and crystalline solids at liquid nitrogen temperature. Additional IR spectra of argon and nitrogen matrices were recorded, applying the hot nozzle technique with temperatures between 313 and 600 K. Raman spectra of the liquid in the temperature range 232–295 K and of a crystalline solid at 148 K were also measured. A number of strong bands disappeared in the crystal phase. The same bands increased their relative intensity upon annealing of the low temperature matrices suggesting that the most stable conformer in the vapour and in the liquid is not the one present in the crystal phase. Apparently, all five conformers are present in the liquid at room temperature and in the argon matrix at 12 K, whereas only three conformers (GG, AG and AA) were observed in the nitrogen matrix. The liquid phase Raman spectra and the hot nozzle IR matrix isolation spectra showed very small temperature variations and it was not possible to estimate the energy differences between conformers. To assist in the spectral assignment, the ab initio force fields for all conformers were scaled using six scale factors. The results suggest that the conformer present in the crystal phase is AG and the most stable conformer in the liquid as well as in the low temperature matrices is GG.

The vibrational spectra, including matrix isolation, conformations and ab initio calculations of bromomethyl dimethyl chlorosilane

A vibrational spectroscopic study of bromomethyl dimethyl chlorosilane (CH 2Br(CH 3) 2SiCl) was carried out. Infrared spectra of the vapour, the amorphous and crystalline solids at liquid nitrogen temperature, and spectra of argon and nitrogen matrices (1:1000) at about 5 K were recorded. Raman spectra of the liquid were obtained at five temperatures between 295 and 190 K, and spectra of the crystalline solid were recorded. Owing to restricted rotation around the CSi bond, the compound apparently exists as anti and gauche conformers. Approximately five IR and Raman bands present in the fluid phases vanished upon crystallization. From intensity variations with temperature in the Raman spectra of the liquid, a ΔH o value of 1.0 ± 0.4 kJ mol −1 was obtained. The high energy conformer bands did not vanish in the matrix spectra after annealing to approximately 39 K in the argon matrix, suggesting a barrier higher than 10 kJ mol −1. Ab initio calculations were carried out with the gaussian 94 program using the basis sets HF/3-21G∗ and HF/6-311G∗; optimized geometries, IR and Raman intensities, and the vibrational frequencies for the anti and gauche conformers were calculated. After appropriate scaling, reasonably good agreement was obtained between the experimental and calculated wavenumbers for the anti and gauche conformers, suggesting the anti conformer to be the more stable and present in the crystal.

The vibrational spectra including matrix isolation and conformations of 1-chloro-1-fluorocyclobutane and 1-chloro-1,2,2-trifluorocyclobutane

Abstract The IR and Raman spectra of 1-chloro-1-fluorocyclobutane (CFCB) and 1-chloro-1,2,2-trifluorocyclobutane (CFCB) were recorded in various phases and at different temperatures, and included IR matrix spectra in argon and nitrogen matrices using the hot nozzle method. Both compounds have two conformers in the vapour and liquid states. CTFCB crystallized as one distinct conformer, while two conformers were present in all solid state spectra of CTFCB. The argon matrix spectrum of CFCB contained only one conformer at 13 K, suggesting a barrier lower than 5 kJ mol−1 between the conformers. In both the argon and nitrogen matrix spectra of CTFCB two conformers were observed, although the concentrations of the less stable conformer were lower than in the vapour. This suggests a partial conversion to the stable conformer during deposition and a barrier slightly higher than 6 kJ mol−1. The enthalpy difference ΔH° between the conformers was 2.2 kJ mol−1 for CFCB in the liquid and 2.7 and 2.9 kJ mol−1 in the vapour and liquid, respectively, for CTFCB. Ab initio calculations were carried out for both compounds using the 3-21G* and 6-31G* basis sets. For CFCB, both calculations gave the conformer with the fluorine atom equatorial as the more stable. For CTFCB, the smaller basis set also gave the conformer with equatorial fluorine as the more stable while the opposite was predicted with the larger basis set. Fairly complete assignments for both conformers of both compounds were made with the aid of normal coordinate calculations employing scaled ab initio force constants. Agreement was excellent between calculation and experiment for the case in which the more stable conformer was that with fluorine equatorial but impossible to achieve with fluorine axial.

Vibrational spectra including matrix isolation and conformations of 1,1,2-trichloro-2,3,3-trifluorocyclobutane

The IR and Raman spectra of 1,1,2-trichloro-2,3,3-trifluorocyclobutane have been reinvestigated, including matrix isolation IR spectroscopy in argon and nitrogen matrixes, using the hot nozzle technique. New Raman spectra of the vapour, liquid, plastic and crystalline phases were recorded, and IR high pressure spectra of the liquid and solid phases were obtained. The compound has two conformers of nearly equal stability, with an enthalpy difference (Δ H 0 ) equal to 0.0±0.9 in the vapour, 0.9±0.7 in the liquid and 0.4±0.3 kJ mol −1 in the plastic phase, while the values +0.4 (argon) and −0.2 (nitrogen) kJ mol −1 for the vapour were obtained from the unannealed matrix spectra. The argon and nitrogen matrixes favoured the more stable and the less stable conformer, respectively. A Δ H 0 value of −0.5±0.2 kJ mol −1 in the nitrogen matrix was obtained by measuring the conformational equilibrium between 30 and 33 K. The barrier to inversion was found to be about 9 kJ mol −1 in the nitrogen matrix. The Δ G 0 values for conformational change in the two matrixes were calculated from the spectra to differ by 0.8 kJ mol −1. A plastic phase containing both conformers in thermodynamic equilibrium was present between 194 and 240 K under atmospheric pressure, whereas an anisotropic phase existed below 194K. A considerable hysteresis was obtained both for the melting and phase transitions. The plastic and anisotropic crystals were also observed under pressure and studied in a polarization microscope. The more stable conformer was present both in the low temperature and in the high pressure crystals. Ab initio force constants were calculated for both conformers and an energy difference between the two of 0.79 kJ mol −1 was obtained using the 3–21 G * basis set. The scaled force constants gave wavenumbers in good agreement with the experimental values, and complete assignments of the fundamentals are presented for both conformers. From the force constant calculation it is clear that the more stable conformer is that in which the fluorine atom on the asymmetric carbon is in the equatorial position.

ChemInform Abstract: The Conformations and Vibrational Spectra Including Matrix Isolation of 1,3‐Dibromo‐2,2‐dimethylpropane.

ChemInformVolume 20, Issue 6 Physical Organic Chemistry ChemInform Abstract: The Conformations and Vibrational Spectra Including Matrix Isolation of 1,3-Dibromo-2,2-dimethylpropane. A. GATIAL, A. GATIAL Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorP. KLAEBOE, P. KLAEBOE Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorC. J. NIELSEN, C. J. NIELSEN Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorD. L. POWELL, D. L. POWELL Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this author A. GATIAL, A. GATIAL Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorP. KLAEBOE, P. KLAEBOE Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorC. J. NIELSEN, C. J. NIELSEN Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this authorD. L. POWELL, D. L. POWELL Dep. Chem., Univ. Oslo, 0315 Oslo 3, NorwaySearch for more papers by this author First published: February 7, 1989 https://doi.org/10.1002/chin.198906045AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue6February 7, 1989 RelatedInformation

ChemInform Abstract: Aluminum Dichloride and Dibromide. Preparation, Spectroscopic (Including Matrix Isolation) Study, Reactions, and Role (Together with Alkyl(aryl)aluminum Monohalides) in the Preparation of Organoaluminum Compounds.

AbstractThe paramagnetic aluminum dichloride and dibromide associated in the condensed state are prepared and isolated for the first time by the reaction of Al metal with AlCl3 or AlBr3, Al2(iBu)4 with HCl, and Al atoms with Cl2 using matrix isolation techniques.

Aluminum dichloride and dibromide. Preparation, spectroscopic (including matrix isolation) study, reactions, and role (together with alkyl(aryl)aluminum monohalides) in the preparation of organoaluminum compounds

Preparation de dichlorure ou dibromure d'Al et de Al 2 (i-Bu) 4−x Cl x . Etude des reactions de (AlCl 2 ) 2 avec les olefines. Le traitement par les ultrasons active ces reactions

The conformation and vibrational spectra including matrix isolation of 1,1,2-trichlorotrifluoroethane

The IR spectra of 1,1,2-trichlorotrifluoroethane (FREON 113) have been observed in the vapour phase, in the liquid, in solution, at low temperatures and at high pressures between 4000 and 50 cm −1. Additional IR spectra of the compound isolated in argon and nitrogen matrices at ca. 12 K have been recorded in the 1300–200 cm −1 range. Raman spectra of the vapour, neat liquid and solid at various temperatures have been obtained. When compressed in a diamond anvil cell at ambient temperature, the compound forms a plastic phase at ca. 15 kbar, containing the same two conformers, C 1 and C s, as in the vapour and the liquid. At a pressure exceeding 125 kbar an anisotropic crystal is formed containing the C 1 conformer. All the low temperature solid phases studied, appear to be plastic, and both conformers are present. No crystal containing one conformer has ever been achieved at low temperature, in spite of numerous attempts with different cooling techniques down to 15 K. Variation of the nozzle temperature of the matrix isolation unit between ambient temperature and 900 K gives rise to different conformer ratios in the matrices. By comparing band intensities at the various nozzle temperatures, the enthalpy difference of the two conformers is estimated to be 1.06 ± 0.11 kJ mol −1 with C 1 as the more stable. A tentative assignment of IR and Raman bands to the C 1 and C s fundamentals is carried out, supported by a normal coordinate calculation involving related molecules.