Vibrational spectra of 1-chloro-2-methylpropane and 1-chloro-2,2-dimethylpropane

Infrared and Raman spectra are obtained for 1-chloro-2-methylpropane and 1-chloro-2,2-dimethylpropane. The former compound exists as a mixture of P_C and P_H' conformers in the liquid and unannealed solid states, but only the P_C conformer is present in the crystalline solid. Vibrational assignments are made for both conformers of 1-chloro-2-methylpropane and for 1-chloro-2,2-dimethylpropane with the aid of normal coordinate calculations.     

Low-resolution microwave,infrared and Raman spectra,ab initio calculations and conformational analysis of 1-bromo-2-methoxyethane

The microwave spectrum of gaseous 1-bromo-2-methoxyethane, BrCH₂CH₂OCH₃, has been recorded from 18.0 to 27.0 GHz at low resolution. The Raman spectra of the gas, liquid, and solid along with the infrared spectra of the gas and solid have been recorded from 3500 to 50 cm^–1. A comparison of the vibrational spectra obtained for the fluid phases with those obtained for the annealed solid indicates the presence of more than one conformer in the fluid phases. The presence of two asymmetric rotors allows for five possible conformations, a majority of which are present in the gaseous phase. It is concluded that the conformation present in the solid phase is that of the gauche/trans (GT) form, where the first term refers to the carbon-bromine bond and the second term to the carbon-oxygen bond (methoxy group). In the gas phase the major absorption in the microwave spectrum is a result of the trans/trans (TT) form although it is certain that other conformations are also present. From a variable temperature study of the Raman spectrum of the liquid, the enthalpy difference between the conformers of the—OCH₃ group was found to be 850 ±115 cm^–1 (2.43±0.33 kcal/mol) whereas the difference between the conformers of the—CH₂Br group as found to be 510±24cm^–1 (1.46±0.07 kcal/mol). The conformational energy differences, vibrational frequencies, and structural parameters have been obtained from ab initio calculations with the STO-3G^* basis set, and these theoretical values are compared to the experimental values. All of these results are compared to similar data for some corresponding molecules.Taken in part from the thesis of R. A. Larsen which was submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree.     

The stable form of 1, 1, 1-trifluoro-3-chloropropane molecules in the crystal II modification

The vibrational spectra of CF₃CH₂CH₂Cl in different states of aggregation is investigated and the normal coordinate analysis of trans- and gauche-conformers is carried out. The assignments in vibrational spectra for both the conformers of CF₃CH₂CH₂Cl are given. It is shown that the stable crystalline modification, crystal II, is formed by the trans-conformer of the molecule.     

Vibrational analysis of 2-fluoropropane and 2-fluorobutane

Vibrational spectra were obtained for 2-fluorobutane in the vapor, liquid, and solid states. The S_HH and Spy conformers are present in the solid, and the S_HH conformer is present in the liquid and in lower concentration in the vapor. Vibrational assignments were made with the aid of normal coordinate calculations that fit thirty-six frequencies of 2-fluoropropane and S_HH 2-fluorobutane with an average error of 3.7 cm^?1. Only a few vibrations of 2-fluorobutane seem to be dependent on conformation. The “C—F stretching” frequency cannot be used to distinguish the conformers because of extensive interaction between this coordinate and others.     

Transition metal promoted alkylations of unsaturated alcohols: the methylation and ethylation of 3-buten-1-ol using titanium tetrachloride-organoaluminum systems

The ethylation and methylation of the olefinic linkage in 3-buten 1-ol by incorporating the alkenol into a titanium-organoaluminum system was studied under a variety of conditions. Systems were derived from titanium tetrachloride and the organoaluminum compounds Al(C₂H₅)₃, Al(C₂H₅)₂Cl, Al(CH₃)₃, and Al(CH₃)₂Cl. With diethylaluminum chloride the major products obtained were 1-hexanol, 3-methyl-1-pentanol, trans-3-hexen-1-ol, and 1-butan I. Triethylaluminum gave no alkylation products. Dimethylaluminum chloride and trimethylaluminum gave product distributions similar to the analogous diethylaluminum chloride system.     

Imidazolium salt assisted hydrolysis of 1-chloro-2,2,2-trifluoroethane

The use of imidazolium-based ionic liquids as promoters was found to be highly effective for the hydrolysis reaction of CF₃CH₂Cl with aqueous potassium acetate to produce 2,2,2-trifluoroethanol (TFE). Among ionic liquids tested, 1-butyl-3-methylimidazolium chloride ([bmim]Cl) showed the highest yield of TFE, over 90%, which is almost two times higher than that obtained in the absence of an ionic liquid. The integrity of imidazolium salt was maintained during the reaction, which was confirmed from the recycling studies and ¹H NMR spectroscopy.     

Vibrational analysis of alkyl bromides: Part III. Branched-chain bromides: 1-bromo-3-methylbutane and 1-bromo-4-methylpentane

Liquid-state IR and Raman spectra and solid-state IR spectra were obtained for 1-bromo-3-methylbutane and 1-bromo-4-methylpentane. The butane exists as a mixture of P_C and P_H conformers in the liquid and amorphous solid, but only the P_H conformer is present in the crystalline solid. The pentane exists as a mixture of P_C,P_H, and P'_H conformers in the liquid and amorphous solid. The solid could not be made to crystallize. The observed bands are assigned to the appropriate conformers with the aid of normal coordinate calculations.     

Vibrational Spectra, Assignment, Conformational Stability and Ab Initio/DFT Calculations for 1-Nitropropane

The infrared spectra (4000–400 cm^{– 1}) of solid and the Raman spectra (3500–30 cm^{– 1}) of liquid and solid 1-nitropropane, CH₃CH₂CH₂NO₂, have been registered. Both the trans and gauche conformers have been identified in the fluid phase, while the trans form remains in the stable solid. Temperature dependence (190–230K) of the liquid 1-nitropropane Raman spectra has been carried out. From these data, the enthalpy difference was determined to be 870 ± 105 J-mol^–1, with the gauche conformer being the more stable rotamer. Ab initio and DFT calculations at different levels of approximation (HF, MP2, B3LYP, B3PW91) gave optimized geometries, harmonic force fields, and vibrational frequencies for the trans and gauche conformers. All the calculations (except the B3PW91/6-31G* level) predicted gauche as the low-energy conformer. Theoretical force constants are analyzed for formulating constraints in the molecular force field model of 1-nitropropane.     

Spectres de vibration et conformations du propionate et de l'isobutyrate de méthyle

Infrared and Raman spectra (3600–3620cm^?1) of methyl propionate CH₃CH₂-COOCH₃, CH₃CH₂COOCD₃ and methyl isobutyrate (CH₃)₂CHCOOCH₃, (CH₃)₂CHCOOCD₃, in liquid and crystalline states, have been recorded. Rotational isomerism, by rotation around the C-C bond α to the carbonyl group, is detected and the energy difference between the conformers is 1.1 ±0.3 kcal mol^?1 for methyl propionate and 0.5 ±0.1 kcal mol^?1 for methyl isobutyrate. Vibrational assignments in terms of group frequencies are proposed for each conformer, only the more stable being present in the crystal.     

Quantum-Chemical Study of the Electronic and Steric Structure of Vinyltetrazoles: II. 2-Vinyltetrazoles

The total Mulliken charges on the C and N atoms, populations of the S-trans-(N¹) conformers, and rotation barriers in the molecules of 2-vinyl-5-R-tetrazoles (R = H, CH₃, CH = CH₂, C₆H₅, CH₂Cl, CF₃) were calculated ab initio (HF/6-31G**, MP2/6-31G**). The results were compared with the ¹H and ¹³C NMR data for these compounds.     

Aminolysis of P-trichloro-N-dichlorophosphorylmonophosphazene and the crystal structure of 1-(dichlorophosphinyl)-2-chloro-2,2-bis(diisopropylamino)phosphazene

The reactions of Cl₃PN P(O)Cl₂ ( 1 ) with primary and secondary amines have been studied. The following monophosphazenes, (RRN)₃PN P(O)(NRR)₂, and bis(phosphinoyl)amines, [(RRN)₂P(O)]₂NH were isolated: NRR = NHCH₂Ph, Net₂, NH(CH₂)₂CH₃ groups for monophosphazenes, and Net₂, NH(CH₂)₂CH₃ for phosphinoyl amines. The unexpected geminal phosphazene, Cl(RRN)₂PN P(O)Cl₂, {RRN = N[CH(CH₃)₂]₂}, was also obtained in moderate yield. The spectral data (IR, ¹H, ¹³C, and ³¹P NMR, and MS) are presented. The structure of 1-(dichlorophosphinyl)-2-chloro-2,2-bis(diisopropylamino)phosphazene ( 5 ) was determined by X-ray crystallography. The basicities of these and related compounds in nonaqueous nitrobenzene solution were obtained by potentiometric titration.     

35Cl NQR Spectra and ab initio Calculations of gem-Substituted 1-Chlorocyclohexane Derivatives

The ³⁵Cl NQR spectra of gem-substiutted 1-chlorocyclohexane derivatives C₆H₁₀XCl (X = H, CH₃, CH₃O, Cl) at 77 K were measured. Ab initio RHF/6-31G(d) calculations of their conformers, and also of conformers of monosubstituted cyclohexanes were performed. Based on the calculation results, the NQR lines were assigned and the conformational energies of the substituents were evaluated. The relative conformational energies of the Cl atom and CH₃O group disagree with previous data.     

Spectra and Structure of Silicon-Containing Compounds. XXV. Raman and Infrared Spectra,r 0 Structural Parameters,Vibrational Assignment,and Ab Initio Calculations of Ethyl Chlorosilane-Si-d2

The infrared (3200 to 400 cm^–1) spectra of gaseous and solid and Raman (3200 to 20 cm^–1) spectra of liquid and solid ethyl chlorosilane-Si-d₂, CH₃CH₂SiD₂Cl, have been recorded. Both the gauche and trans conformers have been identified in the fluid phases, but only the gauche conformer remains in the solid phase. Variable temperature (–105 to –150°C) studies of the infrared spectra of CH₃CH₂SiH₂Cl dissolved in liquid krypton have been carried out. From these data, the enthalpy difference has been determined to be 78±11 cm^–1 (0.93±0.13 kJ/mol), with the gauche conformer the more stable form. Utilizing the frequencies of the silicon-hydrogen stretches, from the chlorosilane-Si-d isotopomer, Si—H bond distances of 1.481 and 1.480 Å have been obtained for the gauche conformer and 1.481 Å for the trans conformer. Complete vibrational assignments are proposed for both isotopomers which are consistent with the predicted frequencies utilizing the force constants from ab initio MP2/6-31G(d) calculations. Both the infrared intensities and the Raman activities and depolarization values have been obtained from the ab initio calculations. Complete equilibrium geometries have been determined by ab initio calculations employing the 6-31(d), 6-311++G(d,p), and 6-311+G(2d,2p) basis sets with full electron correlation by the Moller–Plesset (MP) perturbation method to second order. Continuing the previously reported rotational constants from five different isotopomers and the ab initio predicted structural parameters, adjusted r ₀ parameters have been calculated, which are compared to the corresponding r _s parameters. The results are discussed and the theoretical values are compared to the experimental values when appropriate.Taken in part from the dissertation of Y. E. Nashed, which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree     

Chemie polyfunktioneller liganden: LXXIII. Synthese,struktur und reaktionsverhalten von cryptanden (bzw. spheranden) mit den heteroelementen arsen,sauerstoff, schwefel und stickstoff

The reaction of N(CH₂CH₂Cl)₃ (I) with KAs(C₆H₅)₂·dioxane ($\text{1}\text{2}$) in THF yields, as Sacconi et al. reported earlier, 80% of N[CH₂CH₂As(C₆H₅)₂]₃ (II). II is now obtained in a still higher quantity from the reaction of [HN(CH₂CH₂Cl)₃]Cl (III) with NaAs(C₆H₅)₂ in liquid ammonia. Treatment of II with gaseous HI in dry CH₂Cl₂ results in the formation of [HN(CH₂CH₂AsI₂)₃]I (IV), which is isolated by recrystallisation from THF as [HN(CH₂CH₂AsI₂)₃]I · THF ($\text{1}\text{1}$) (IVa). IVa reacts with H₂O/NH₃ or H₂S/N(C₂H₅)₃ to give the novel cryptands [N(CH₂CH₂)₃]₈-(As₄O₄)₆ (V) or [N(CH₂CH₂)₃]₈(As₄S₄)₆ (VI), which also can be denoted as spherands. The reaction of V with dry gaseous HCl in benzene leads to [HN(CH₂-CH₂AsCl₂)₃]Cl (VII). All the new compounds are characterized, as far as possible, by their IR, FIR, Raman, ¹H NMR and mass spectra. To determine the structure of V a single X-ray crystal study was carried out. Moreover II, which is already well-known but not completely characterized, is included in this discussion only for spectroscopic comparison.     

Far-IR spectrum,conformation stability,barriers to internal rotation,vibrational assignment,and ab initio calculations of 3-chloro-2-methylpropene

The far-IR spectrum from 375 to 30 cm⁻¹ of gaseous 3-chloro-2-methylpropene, CH₂=C(CH₃)CH₂Cl, has been recorded at a resolution of 0.10 cm⁻¹. The fundamental asymmetric torsional mode for the gauche conformer is observed at 84.3 cm⁻¹ with three excited states falling to lower frequency. For the higher energy s-cis conformer, where the chlorine atom eclipses the double bond, the asymmetric torsion is observed at 81.3 cm⁻¹ with two excited states falling to lower frequency. Utilizing the s-cis and gauche torsional frequencies, the gauche dihedral angle and the enthalpy difference between conformers, the potential function governing the interconversion of the rotamers has been calculated. The determined potential function coefficients are (in reciprocal centimeters): V₁=189±12, V₂=−358±11, V₃=886±2 and V₄=−12±2 with an enthalpy difference between the more stable gauche and s-cis conformers of 150 ±25 cm⁻¹ (430 ± 71 cal mol⁻¹). This function gives values of 661 cm⁻¹ (1.89 kcal mol⁻¹), 1226 cm⁻¹ (3.51 kcal mol⁻¹) and 812 cm⁻¹ (2.32 kcal mol⁻¹), for the s-cis to gauche, gauche to gauche, and gauche to s-cis barriers, respectively. From the methyl torsional frequency of 170 cm⁻¹ for the gauche conformer, the threefold barrier of 678 cm⁻¹ (1.94 kcal mol⁻¹) has been calculated. The asymmetric potential function, conformational energy difference and optimized geometries of both conformers have also been obtained from ab initio calculations with both the 3–21G^* and 6–31G^* basis sets. A normal-coordinate analysis has also been performed with a force field determined from the 3–21G^* basis set. These data are compared with the corresponding data for some similar molecules.     

Infrared and Raman spectra, conformational stability, ab initio calculations and vibrational assignment for 1,2-pentadiene (ethyl allene)

The infrared (3500-50 cm⁻¹) and Raman (3500-20 cm⁻¹) spectra of 1,2-pentadiene, H₂C=C=C(H)CH₂CH₃ (ethyl allene), have been recorded for both the gaseous and solid states. Additionally, the Raman spectrum of the liquid has been obtained with qualitative depolarization values. In the fluid phases both the cis and gauche conformers have been identified, with the gauche rotamer being the predominant form although it may not be the conformer of lowest energy. In the solid state only the cis conformer remains after repeated annealing of the crystal. The asymmetric torsion of the cis conformer is observed as a series of Q-branch transitions beginning at 103.4 cm⁻¹ and falling to lower frequency. An estimate of the potential function governing conformer interconversion is provided. A complete assignment of the normal modes for the cis conformer is given and several of the fundamentals are assigned for the gauche rotamer. Ab initio electronic structure calculations of energies, conformational geometries, vibrational frequencies, and potential energy functions have been made to complement and assist the interpretation of the infrared and Raman spectra. In particular, the transitions among torsional energy levels for both the symmetric (methyl) and asymmetric (ethyl) motions have been calculated. The results are compared to the corresponding quantities for some similar molecules.     

Vibrational and conformational analysis of chloromethylacetate and some deuterated derivatives

The i.r. spectra of gaseous, amorphous and crystalline solid and the Raman spectra of liquid and amorphous solid chloromethylacetate, CH₃COOCH₂Cl, and three deuterated derivatives, CH₃COOCD₂Cl, CD₃COOCH₂Cl and CD₃COOCD₂Cl, were obtained and an assignment proposed. Only one conformer of CMA was found to be present in all phases. Band contour simulation of the i.r. vapour phase bands showed this to be the s-cis gauche conformer. This was confirmed by a study of the partially deuterated compound CD₃COOCDHCl, of which the separate transitions originating from the antiperiplanar and synclinal isolated CH stretches were observed in the i.r. spectra of the vapour and crystalline solid and in the Raman spectrum of the vapour.     

Formation of Methane versus Benzene in the Reactions of (C5Me5)2Th(CH3)2 with [CH3PPh3]X (X=Cl,Br, I) Yielding Thorium‐Carbene or Thorium‐Ylide Complexes

The reaction of (C₅Me₅)₂Th(CH₃)₂ with the phosphonium salts [CH₃PPh₃]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C₅Me₅)₂Th[CHPPh₃]X, rare terminal phosphorano‐stabilized carbenes with thorium. These complexes feature the shortest thorium–carbon bonds (≈2.30 Å) reported to date, and electronic structure calculations show some degree of multiple bonding. However, when X=Cl, only one equivalent of methane is lost with concomitant formation of benzene from an unstable phosphorus(V) intermediate, yielding (C₅Me₅)₂Th[κ²‐(C,C′)‐(CH₂)(CH₂)PPh₂]Cl. Density functional theory (DFT) investigations of the reaction energy profiles for [CH₃PPh₃]X, X=Cl and I showed that in the case of iodide, thermodynamics prevents the production of benzene and favors formation of the carbene.     

Formation of Methane versus Benzene in the Reactions of (C5Me5)2Th(CH3)2 with [CH3PPh3]X (X=Cl,Br, I) Yielding Thorium‐Carbene or Thorium‐Ylide Complexes

The reaction of (C₅Me₅)₂Th(CH₃)₂ with the phosphonium salts [CH₃PPh₃]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C₅Me₅)₂Th[CHPPh₃]X, rare terminal phosphorano‐stabilized carbenes with thorium. These complexes feature the shortest thorium–carbon bonds (≈2.30 Å) reported to date, and electronic structure calculations show some degree of multiple bonding. However, when X=Cl, only one equivalent of methane is lost with concomitant formation of benzene from an unstable phosphorus(V) intermediate, yielding (C₅Me₅)₂Th[κ²‐(C,C′)‐(CH₂)(CH₂)PPh₂]Cl. Density functional theory (DFT) investigations of the reaction energy profiles for [CH₃PPh₃]X, X=Cl and I showed that in the case of iodide, thermodynamics prevents the production of benzene and favors formation of the carbene.