Vibrational frequencies,infrared absorption intensities and energy differences between rotational isomers of propyl halides

Infrared absorption intensities of fundamental bands of propyl halides n-C₃ H₇ Cl, n-C₃H₇ Br and n-C₃H₇I were measured in the pure liquid state. In order to obtain L matrix data necessary for the intensity computation, normal frequencies of the rotational isomers were calculated, and LSFF force constants were determined by the least squares method so as to attain the best fit between the observed and calculated frequencies. By applying the absolute intensity method, energy differences between the rotational isomers were evaluated, which are in quite good agreement with values obtained by the temperature variation method.     

Infrared spectra and rotational isomerization of 1-bromo-3-methyl-2-butene

Infrared spectra obtained for the title compound, (CH₃)₂CCH. CH₂Br, have revealed the co-existence of two rotational isomeric forms in the fluid phases, the geometrical structures of which cannot be ascertained by use of vibrational spectroscopy alone. The energy ditterence between the two isomers was found to be 1.1 kcal mol⁻¹ (mean value) in the liquid state. Some of the i.r. fundamental bands were assigned using the characteristic absorption frequencies of localized group.     

Vibrational analysis of trans,Trans,trans-2,3,4,5-tetrachlorohexa-1,3,5-trienes

Infrared and Raman spectra of t,T,t-2,3,4,5-tetrachlorohexa-1,3,5-triene were measured in liquid and crystalline phases. It is suggested that the non-planar structure of this compound may be due to the 1–3 effect. In the liquid state a mixture of rotational isomers, of C₂ and C_i symmetry, was confirmed by the freezing-out of some characteristic bands in the 1600 cm⁻¹ region in the IR and Raman spectra of the t,T,t-compound. Normal coordinate analysis was carried out using force constant values from the force field previously determined for chloroderivatives of buta-1,3-diene. A complete assignment of observed frequencies is proposed.     

The spectra and structure of sulphur-containing organic compounds—V. The vibrational spectra and conformations of p-RC6H4SO2CH2X sulphones

The i.r. and Raman spectra of p-RC₆H₄SO₂CH₂X (R = H, CH₃, Cl, Br; X = Cl, Br) sulphone liquid solutions and crystals have been investigated. The existence of a mixture of trans and gauche conformations in liquid and solution phases has been established. The temperature dependences of the i.r. spectra have been studied and the values of ΔH = H (gauche) - H(trans) determined. The molecular conformations in the crystal have been determined by the dichroism of polarized i.r. spectral bands. In the case of CH₃C₆H₄SO₂CH₂Br polymorphic crystal modifications, differing in molecular conformations, have been found. An interpretation of the vibrational spectra is given. See Part IV, A. B. REMizov, F. S. BILALOV and 1. S. POMINOV, Spectrochim Acta, in press.     

Magnetic circular dichroism of manganese pentacarbonyl bromide

The absorption and magnetic circular dichroism (MCD) spectra of manganese pentacarbonyl bromide Mn(CO)₅Br in a solution of 2-methyl tetrahydrofuran were measured at various temperatures over the 3500–4500 Å region. Within experimental error the MCD spectra are not temperature dependent and in addition to a negative B term exhibit a positive A term, indicative for a degenerate excited state. Following the irreducible tensor method we conclude that the transition involved will be mainly e[π, Br] → a₁[σ^*, 3d₂²] and for the excited state we calculate a magnetic moment which agrees quite closely with the experimental value.     

Activation energy of thermal decomposition of LaC2O4Br

The activation energy of the thermal decomposition of finely ground LaC₂O₄Br was determined according to the method of Ozawa asE _a=203.83 kJ mol^?1. As compared to the value for the parent oxalate La₂(C₂O₄)₃ E _a=130 kJ/mol), this value is higher by about 70 kJ/mol, which is consistent with the increased interaction between the metal and oxalate ions. The substitution of Br by Cl does not affect the decomposition kinetics profoundly.     

Hexahalogenotin(IV) complexes in aqueous mixed hydrogen halide solutions in the glassy state

The configurations of hexahalogenotin(IV) complex ions in glassy aqueous mixed hydrogen halide solutions were determined by Mössbauer and Raman spectroscopies. Trans-(SnF₄Cl₂)^2-, (SnCl₅Br)^2- and (SnCl₅Br)^2- and trans-(SnF₄Br₂)^2- ions are the main tin complex ions in the aqueous Sn(IV)-HF-HCl, Sn(IV)-HCl-HBr and Sn(IV)-HF-HBr solutions in the glassy state, respectively.     

On the mechanism of the reaction of organosilicon hydrides with dichlorocarbene generated from sodium trichloroacetate

The reaction of sodium trichloroacetate with various organosilicon hydrides in 1,2-dimethoxyethane was investigated and the products, α-triorganosilyldichloromethanes, were formed in yields of 20–50%. The relative rate constants of these hydrosilanes in such insertion reactions of dichlorocarbene were determined by means of competition reactions. The relative reactivities of a series of alkyl substituted hydrosilanes correlate well with the Taft σ* constants for the substituents on silicon, with a ?* value of ?1.07, and a series of aryl substituted hydrosilanes also shows good linear correlation of the log k_rel values with Taft σ* constants, giving ?* value of ?1.18. The hydrogen isotope effect in the reaction, k_H/k_D 1.26 ± 0.02. Based on the observed results, it was concluded that the insertion of CCl₂ into the SiH bond proceeds by a three-center concerted process in which charge separation in the transition state is not large, as suggested by Seyferth for the related PhHgCCl₂Br/XC₆H₄SiMe₂H reactions.     

Synthesis of trans-Mono(silyl)palladium(II) Bromide Complexes

The stoichiometric reaction of cis-[Pd(ITMe)₂(SiR₃)₂], where (SiR₃ = SiMe₃ and SiMe₂Ph and ITMe = 1,3,4,5-tetramethylimidazol-2-ylidene) with allyl bromide affords the corresponding allylsilanes along with complexes of the type trans-[Pd(ITMe)₂(SiR₃)(Br)]. The structure of trans-[Pd(ITMe)₂(SiMe₂Ph)Br] 2b has been determined in the solid state and displays a slightly distorted square-planar geometry with the two N-heterocyclic carbene ligands in a trans-configuration.     

Structure and dynamics of room temperature ionic liquids with bromide anion: results from 81Br NMR spectroscopy

We report the results of a comprehensive ⁸¹Br NMR spectroscopic study of the structure and dynamics of two room temperature ionic liquids (RTILs), 1‐butyl‐3‐methylimidazolium bromide ([C₄mim]Br) and 1‐butyl‐2,3‐dimethylimidazolium bromide ([C₄C₁mim]Br), in both liquid and crystalline states. NMR parameters in the gas phase are also simulated for stable ion pairs using quantum chemical calculations. The combination of ⁸¹Br spin‐lattice and spin‐spin relaxation measurements in the motionally narrowed region of the stable liquid state provides information on the correlation time of the translational motion of the cation. ⁸¹Br quadrupolar coupling constants (C_Q) of the two RTILs were estimated to be 6.22 and 6.52 MHz in the crystalline state which were reduced by nearly 50% in the liquid state, although in the gas phase, the values are higher and span the range of 7–53 MHz depending on ion pair structure. The C_Q can be correlated with the distance between the cation–anion pairs in all the three states. The ⁸¹Br C_Q values of the bromide anion in the liquid state indicate the presence of some structural order in these RTILs, the degree of which decreases with increasing temperature. On the other hand, the ionicity of these RTILs is estimated from the combined knowledge of the isotropic chemical shift and the appropriate mean energy of the excited state. [C₄C₁mim]Br has higher ionicity than [C₄mim]Br in the gas phase, while the situation is reverse for the liquid and the crystalline states. Copyright © 2015 John Wiley & Sons, Ltd.     

Spectres de vibration de composés MIIMo6X14

Infrared and Raman spectra of compounds M^IIMo₆X₁₄ with M^II = Fe, Cd, Pb and X = Cl or Br were recorded in the solid state and interpreted. It was shown that if the highest infrared frequency depends only of the nature of X, the other vibrations, especially for the three lower, are complex modes, the frequencies of which vary both with the nature of X and M^II. Despite this, the Raman frequencies are unaffected by the nature of M^II and the Ag₁ mode of the MoMo vibration is situated at 104 ± 4 cm⁻¹ for all the compounds.     

Vibrational spectra and structure of cyclopropane-d1 and dicyclopropyl ketone

Infrared spectra have been obtained for cyclopropane-d₁, C₃H₅D(CP-d₁), in the vapor phase and for dicyclopropyl ketone (C₃H₅)₂ CO (DCPK) in the liquid state. Raman spectra of the latter compound in the liquid and solid phases have also been recorded. By comparing the experimental with the theoretical spectra of CP-d₁ it has been possible to assign most of the fundamental frequencies of the molecule. Additionably, empirical spectra—structure correlations from the literature for cyclopropyl derivatives containing the COX moiety (X=halogen) have been used to investigate the conformational preference of DCPK. The experimental results confirm that the molecular configuration with the carbonyl group cis to the planes of the two rings is the predominant species in the liquid state, though evidence for a second conformer, which we tentatively identify as the cis—trans conformer, is presented.     

Vibrational spectroscopic studies on some 2-substituted 1,3-dithi a-2-boracyclopentanes

Infrared and Raman spectra are reported for 2-X-1,3-dithia-2-boracyclopentanes, where X = Br, Cl, Ph or NMe₂. In all cases the vibrations of the heterocyclic ring unit can be assigned in terms of C₂ symmetry, corresponding to a “twisted-ring” conformation similar to that found for the related molecule 1,3-dithiolan-2-thione. The internal modes of the B-Ph unit are in agreement with C_2v “local” symmetry, while those for B-NMe₂ suggest a considerably lower symmetry.     

Vibrational spectroscopic studies on 1,3-dithiacyclohexane and some 2-substituted 1,3-dithia-2-boracyclobexanes

Infrared and Raman spectra are reported for 1,3-dithiacyclohexane and 2-X-1,3-dithia-2-boracyclohexanes, where X = Cl, Br or Ph. Assignments are made in each case assuming a molecular symmetry of C_s. The assignments of ring modes for the dithiaboracyclohexanes are almost all very close to those for the corresponding dithiaboracyclopentanes.     

Molecular motions of SF6 dissolved in cryogenic liquids

Infrared and Raman spectra of SF₆ dissolved in liquid oxygen and krypton were recorded. Angular momentum correlation times have been determined with the help of the extended J-diffusion model and used to obtain an estimate of the vibrational dephasing time in the ν₃ mode. Raman profiles are interpreted in terms of the rough hard sphere model.     

Carbene complexes : IV. Far infrared and 31P NMR spectra of palladium and platinum carbene complexes

Infrared bands mainly associated with v(M—X₂) stretching modes (M = Pd or Pt, and X = Cl, Br, or P) have been identified in the spectra of 35 carbene complexes. Based on these results and on |¹J| (³¹ P—¹⁹⁵ Pt) the trans-influence of the carbene ligands is assessed.     

1-Hexadecyl-3-methylimidazolium Ionic Liquid as a New Cationic Surfactant for Separation of Phenolic Compounds by MEKC

The ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C₁₆MIm]Br) has been used as a novel cationic surfactant for separation of phenolic compounds, including quinol, phloroglucinol, resorcinol, phenol, p-cresol, and m-nitrophenol, by micellar electrokinetic capillary chromatography (MEKC). The effects of buffer concentration and pH, concentration of [C₁₆MIm]Br, and applied potential were studied. Use of the optimized buffer (25 mmol L^?1 NaH₂PO₄), 10 mmol L^?1 [C₁₆MIm]Br, and an applied potential of ?15 kV enables optimum separation with regard to resolution and migration time. The phenolic compounds were detected at 214 nm. The micelle of this long-alkyl-chain imidazolium ionic liquid acts as a pseudo-stationary phase in this MEKC separation.     

Spectroscopic studies of 1,4-dibromobutyne-2

Infrared spectra of 1,4-dibromobutyne-2 have been recorded over the 4000-200 cm^?1 region in the vapour, liquid, amorphous and crystalline states Raman spectra were extended to ca. 20 cm^?1 in the same states of aggregation, except for the non-recorded vapour phase spectrum. The temperature was varied between ?190 and 160 °C, and the pressure up to 10 kbar.A high proportion of the molecules exhibited free, internal rotation in the vapour and liquid phases, but to a smaller extent in the amorphous state at ?190 °C. For those molecules not being excited beyond the potential barrier, an unsymmetric conformation was preferred, whereas in the crystalline state the molecules possessed the anti conformation (C_2h) both at low temperature and at high pressure at ambient temperature.A vibrational analysis based upon force field calculations was carried out and the mean amplitudes of vibration computed. The data have been related to preliminary results from dipole moment and electron diffraction investigations.     

Preparation and properties of chlorocarbonylsulphenyl bromide,ClC(O)SBr

Chlorocarbonylsulphenyl bromide, ClC(O)SBr, was prepared from fluorocarbonyl sulphenyl bromide and BCl₃. Infrared data of the vapour, liquid and matrix-isolated ClC(O)SBr in Ne, Ar and N₂ at low temperature, together with the Raman spectrum of the liquid, suggest the existence at room temperature of only one conformer in both the vapour and liquid phases with symmetry Cs (trans with respect to the halogens). Band positions are reported for all but the out-of-plane and torsional fundamental modes. Valence force constants were calculated for the A′ species and the result is compared with the corresponding constants of related molecules. The study was completed with the characterization of the compound by mass, ultraviolet and ¹³C NMR spectra.     

Calorimetric investigations of the MBr−NdBr3 melts (M=Li,Na, K,Cs)

Present work is a part of thermodynamic research program on the MX?LnX₃ system (M=alkali metal,X=Cl, Br andLn=lanthanide). Molar enthalpies of mixing in the LiBr?NdBr₃, NaBr?NdBr₃ and KBr?NdBr₃ liquid binary systems have been determined at temperature 1063 K by direct calorimetry in the whole range of composition. Investigated systems are generally characterized by negative enthalpies of mixing with minimum atX _NdBr3≈0.3–0.4. These enthalpies decrease with decrease of ionic radii of alkali metals. Molar enthalpies of solid-solid and solid-liquid phase transitions of K₃NdBr₆ and Cs₃NdBr₆ have been also determined by differential scanning calorimetry (DSC). K₃NdBr₆ is formed at 689 K from KBr and K₂NdBr₅ with enthalpy of 44.0 kJ·mol^?1 whereas Cs₃NdBr₆ is stable at ambient temperature and undergoes phase transition in the solid state at 731 K with enthalpy of 8.8 kJ·mol^?1. Enthalpies of melting have been also determined.