Showing papers in "Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy in 1961"

Infrared and Raman spectra and normal co-ordinate analysis of dimethyl sulfoxide and dimethyl sulfoxide-d6

Abstract: The infrared spectra from 250–4000 cm−1 and the Raman spectra of dimethyl sulfoxide and dimethyl sulfoxide-d6 have been determined. From these data a complete assignment-excepting only the torsional modes-has been made and substantiated by a normal co-ordinate analysis carried out using a digital computer. Valence force constants for the C2SO skeleton were calculated and compared with those of the thionyl halides. Potential energy distributions of symmetry co-ordinates among the normal co-ordinates have also been calculated.

The vibrational spectra of benzene derivatives—I. Nitrobenzene, the benzoate ion, alkali metal benzoates and salicylates

Abstract: Infra-red and Raman spectra have been recorded for nitrobenzene and a complete vibrational assignment is given. The infra-red spectra of the alkali metal benzoates have been recorded and, together with the Raman spectra data, a substantially complete assignment is given for the benzoate ion. The infra-red spectra of the alkali metal salicylates, salicylic acid and o-nitrophenol have been measured, correlated and partial assignments made. Examination of the difference Δν between the symmetric (νs,) and antisymmetric (νas)CO2− stretching frequencies in the two series of salts shows that, whereas for the benzoates Δν increases steadily from lithium to caesium, for the salicylates, with the exception of the lithium salt, it is either constant or decreases slightly ; νas is 20–30 cm−1 higher in the salicylates than in the corresponding benzoates; νs, is lower in lithium salicylate than in lithium benzoate, but in rubidium and caesium salicylate νs is higher than in the corresponding benzoate. No simple linear relationship is found between Δν and the polarizability of the free ions or the electronegativities of the alkali metals.

Infrared studies of hydrogen bonding in alcohol-base systems

Abstract: Infrared spectroscopic studies in the 3000–4000 cm−1 region are reported for the eighteen hydrogen-bonding systems involving the proton donors methanol, ethanol and t-butanol and the proton acceptors acetone, ethyl acetate, dioxane, benzophenone, dimethylformamide and pyridine, in solution in CCl4. Equilibrium constants for the formation of 1:1 hydrogen-bonded complexes have been determined. Enthalpies of complex formation (calculated from the temperature dependence of the spectra over the range −10° to +60°C) are in the range 2.2–4.0 kcal mole . Both the frequency differences (Δν) between bands due to uncomplexed and complexed alcohol molecules and the integrated intensities (B°) of the bands due to the complexes were found to be temperature dependent, but the half-widths of the bands due to H-bonded complexes were virtually independent of temperature. Data for the fifteen O-HṫO complexes lie fairly close to the Badger-Bauer line correlating ΔH and Δν, but the results for the three pyridine complexes are in marked disagreement with this relation. Data for all eighteen systems studied, as well as other data available in the literature, show a correlation between ΔH and B°.

The vibrational spectra and assignments of nitrobenzene, phenyl isocyanate, phenyl isothiocyanate, thionylaniline and anisole

Abstract: The Raman and infrared spectra of five monosubstituted benzenes have been measured. The spectra of all five were assigned on the basis of C2v symmetry. However, the spectra indicate that thionylaniline and anisole, as was to be expected, have lower symmetry than C2v; the number of polarized Raman lines suggests that they are both Cs molecules.

The application of the Urey-Bradley force field to the in-plane vibrations of benzene

Abstract: C alifano and C rawford have recently demonstrated that a basic Urey-Bradley force field reproduces the ingold assignment of the planar B2u vibration fundamentals of benzene but does not give acceptable agreement with the M air -H ornig assignment. We have proposed a model which removes these objections to the M air -H ornig assignment, and the normal modes for this model are discussed and compared with those obtained for the I ngold assignment. This model gives a slightly better frequency fit for certain vibrational modes and, although the ingold assignment cannot be excluded, a slight preference for the M air -H ornig assignment is indicated.

The use of organic solvents in atomic absorption spectrophotometry

Abstract: The use of organic solvents in atomic absorption spectrophotometry has been investigated. It has been found that when certain organic solvents are added to aqueous solutions small increases in analytical sensitivity are obtained. With the most useful solvent of this class, a mixture containing 20 per cent acetone and 20 per cent isobutyl alchohol, the sensitivity is a little more than twice that obtained with aqueous solutions. When the element is extracted into an organic solvent immiscible with water, gains in sensitivity of up to seven times are obtained, depending on the solvent and atomizer used. It has been shown that this gain in sensitivity results, for the greater part, from an increase in the amount of solution reaching the flame.

The determination of copper by atomic absorption spectrophotometry

Abstract: The investigation of various factors affecting the determination of copper by atomic absorption spectrophotometry, and the application of the method to the analysis of various agricultural materials are described. Recoveries are given for the determination of copper in plants, soils, soil extracts and fertilizers.

The assignment of infra-red absorption bands to fundamental vibrations in some metal-ethylenediamine complexes

Abstract: The infra-red spectra of ethylenediamine complexes of Pt II, Pd II, Cu II and Ni II have been compared. An assignment has been made to the fundamental vibrations of the molecules on the basis of comparison with the spectra of molecules whose assignment is established and by examining the frequency shifts produced by conversion of the NH2 groups of the ethylenediamine to ND2. The effect of hydrogen bonding with the anion on the infra-red spectra of these complexes is discussed.

Performance of a simple atomic absorption spectrophotometer

Abstract: The scope of a simple atomic absorption spectrophotometer in the determination of metal ions in solution is illustrated by the results obtained for thirty-six elements. Appropriate selection of the experimental conditions for each element has yielded lower limits of detection than those reported previously for the atomic absorption method. The use of second resonance lines permits the method to be extended to the determination of high concentrations.

The librational spectra of water and heavy water in crystalline salt hydrates

Abstract: Infrared spectra are reported of nine mono- and dihydrates of alkali halides and alkaline earth halides. These spectra in the 300–600 cm−1 region are interpreted as arising from the librational modes of the bound water molecules as shown unambiguously by the frequency changes on substitution of deuterium oxide. Potential constants for this motion are given. Samples were prepared by evaporation of salt films in situ, and the method is seen to be of value for studying the limits of phase stability of unknown hydrates and related compounds. The number of bands observed in this region indicates for all cases studied the number of water molecules with different crystalline environments.

The infrared absorption spectra of metal acetylacetonates

Abstract: Infrared absorption data in the region 5000–290 cm −1 have been obtained for twenty-four metal derivatives of acetylacetone. Shifts in the absorption maxima as the metal ion is varied are more pronounced at frequencies lower than 600 cm −1 . Among the factors which appear to influence the changes in observed spectra are: (1) crystal structure; (2) ionization potential, ionic charge, mass and radius of the metal; (3) participation of inner orbitals in the metal-ligand bonding; and (4) covalent bonding. Spectral features which are consistent with ligand field theory are discussed.

n → σ* Absorption spectra of saturated organic compounds containing bromine and iodine

Abstract: Ultra-violet absorption spectra of a total of twenty-two saturated organic iodides and bromides were extensively measured in several polar and nonpolar solvents, in order to clarify the nature of long wavelength bands characteristic of these compounds having lone pair electrons. The results show that the absorption bands appear at about 260 and 200 mμ for alkyl iodides and alkyl bromides, respectively. The oscillator strengths were calculated with LCAO MO and AO approximations for the n → σ* transitions as well as for the first Rydberg transitions of the various alkyl bromides and iodides. Comparison of the calculated and experimental results indicated that the longest wavelength absorption bands for the alkyl halides are not due to the Rydberg transition but due to the n → σ* transition, as suggested by M ulliken . The f-values calculated by the aid of AO approximation were in better agreement with the corresponding experimental values than those by the LCAO method. A sharp strong band around 1940 A was assigned to the first Rydberg transition from the comparison of experimental and calculated oscillator strengths for ethyl iodide chosen as an example. Solvent effect, as well as, alkylation effect on the ultra-violet absorption bands was investigated for the compounds. It was found that the n → σ* bands show a blue shift with the increase of solvent polarity and show a red shift in the order of the primary, secondary and tertiary alkylations of the carbon atom attached to iodine. Absorption spectra of methylene iodide and iodoform, which may be resolved to give four individual bands, were successfully interpreted in terms of the appropriate combination of upper and lower orbitals splitted by mutual interactions between the iodine atoms in these compounds.

The hydrogen bond—IV: Intramolecular hydrogen bonding in triols

Abstract: The free and intramolecularly bonded OH bands were measured in CCl4 and/or CHCl3 solution for the following compounds: catechol, pyrogallol, pyrogallol-1-methyl ether and 2-methyl ether; propane-1:3-diol; pentane-1:3:5-triol; 1:1:1-trimethylol propane; heptane-1:4:7-triol; heptane-1:4:7-triol-1-methylether and 4-methyl ether. The intensity ratio, free OH/bonded OH, is always larger for the diols than for the triols and their methyl ethers indicating that the triols exist in a conformation which allows two intramolecular hydrogen bonds. The Δν of the heptane-triol-4-methyl ether is about the same as the 1-methyl ether, indicating that an oxygen can act as a hydrogen acceptor for two OH groups and that such a hydrogen bond is as strong as the normal hydrogen bond where the oxygen accepts only one hydrogen. Evidence is presented which shows that in CCl4 the associated monohydric alcohols are cyclic, whereas in CHCl3 they are acyclic. The Δν of diols and triols is 25 per cent larger in CHCl3 than in CCl4.

Infrared absorptions characteristic of organic carbonate derivatives and related compounds

Abstract: Infrared absorption bands characteristic of carbonates , carbamates , monothiolcarbonates , chloroformates , carbamoyl chlorides , thiol carbamates , dithiol carbonates , and thiol-chloroformates have been found. The behavior of these frequencies in the various compounds can be related and explained by considering the vibrations to be roughly analogous to those of the carbonyl dihalides.

Vibrational spectrum and structure of metal cyanide complexes in the solid state—V: K2Zn(CN)4, K2Cd(CN)4 and K2Hg(CN)4

Abstract: The infrared spectra of single crystals of K2Zn(CN)4, K2Cd(CN)4 and K2Hg(CN)4 have been observed. Using Raman data of other authors along with this infrared data we have assigned all fundamental frequencies, except those of E-symmetry, for the isolated ions. Force constants were calculated using a diagonal symmetry valence force field. It is shown that in this case it is a reasonable approximation to neglect the off-diagonal symmetry valence force constants. Some details of the bonding in these complexes, as implied by the force constants, are discussed.

Infra-red absorption of heteroaromatic and benzenoid six-membered monocyclic nuclei—XI: Pyr-4-ones and pyr-4-thiones

Abstract: The infra-red spectra of six pyrones and pyrthiones in the region 2000–800 cm −1 are discussed and tentative assignments for most of the bands are suggested by analogy with other heteroaromatic compounds.

The vibrational spectra of s-triazine and s-triazine-d3

Abstract: The infrared and Raman spectra of s-triazine and s-triazine-d3 have been taken and an assignment of the fundamental vibrational modes has been made. Nearly all the remaining observed bands are accounted for as combinations or overtones. A simple valence force field normal co-ordinate analysis was made, and the values of some force constants calculated.

Infra-red spectra and molecular structure of meso and dl-2:4-dichloropentanes as model compounds of polyvinyl chloride

Abstract: The infra-red spectra of meso and dl -2:4-dichloropentanes, model compounds of polyvinyl chloride, have been measured and the rotational isomerism in these molecules is discussed in relation to the assignments of C-Cl stretching frequencies. A discussion on the configuration of polyvinyl chloride chain is also presented.

An improved structure determination for vinyl fluoride

Abstract: The previously published rotational constants of eight isotopic species of vinyl fluoride have been used to calculate an rs (substitution) structure for the molecule. The results are: r(CC) = 1.329 ± 0.006 A, r(CF) = 1.347 ± 0.009 A, ⦠ (FCC = 120.8° ± 0.3°, ∡FCH = 110° ± 1°, r(CH) = 1.082 ± 0.004 A; in the CH2 group : r(CH) = 1.077 ± 0.003 A and ∡HCC = 119.0° ± 0.3° for the CH bond trans to F; r(CH) = 1.087 ± 0.003 A and ∡HCC = 120.9° ± 0.3° for the CH bond cis to F.

Acetyl halides—I

Abstract: The infrared and Raman spectra of acetyl chloride, acetyl chloride-d3 and acetyl chloride-d1 have been studied and a vibrational assignment has been made on the basis of an approximate normal-co-ordinate calculation with a Urey-Bradley field. It is proposed that the two intense bands at 1109 and 958 cm−1 in the infrared spectrum of acetyl chloride correspond to vibrational modes which are mixtures of the C-C stretching co-ordinate and the CH3 rocking co-ordinate, and that the similar pair of intense bands in the CD3COCl spectrum arise from modes which are mixtures of CC stretching and CD3 deformation co-ordinates. Thermodynamic functions were calculated for acetyl chloride in the ideal gaseous state.

Infra-red absorption of heteroaromatic, five-membered, monocyclic nuclei—III: Isoxazoles

Abstract: The infra-red spectra of thirty-four isoxazoles are recorded and discussed, and assignments are suggested for the characteristic ring bands. Absorption due to substituents and to the ring vibrations gives information on the electronic nature of the isoxazole ring.

Spektroskopische untersuchungen an organischen ionen—III: Das infrarot-spektrum und die struktur des thiohamstoff-kations (thiouromum-ions), des s-methyIthiouromum-ions, des thioacetamid-kations und des thioacetamid-kupfer(I)chlorid-komplexes

Abstract: The cations, which are present in the salts of thiourea and thiouacetamide, respestively, with strong acids are sulphonium ions formed by addition of the proton to the sulphur atom. The normal vibrations of these ions as well as those of their free “bases” are assigned. The spectral changes on salt formation are chiefly due to changes in π-electronic structure.

Raman spectra of the hexachloropalladate, hexachloroplatinate and hexabromoplatinate ions in aqueous solution

Abstract: The complete Raman spectra of the ions PdCl 6 2− , PtCl 6 2− and PtBr 6 2− in aqueous solution are observed, using excitation by the helium yellow and red lines. The spectra show differences from those previously reported for species of type XY 6 in which Y is a halogen atom and X an atom of a non-transition element. In particular, for the ions PdCl 6 2− , PtCl 6 2− and PtBr 6 2− the intensity of the ν 2 line (class e g stretching) is greater than that of the ν 1 line (class a 1 g stretching), whereas for all XY 6 species previously studied the reverse is the case. It is suggested that this difference is probably connected with the presence in the transition metal complex ions of six non-bonding d -electrons in the shell which is involved in the bonding.

The vibrational spectra and structure of Si(NCO)4 and Ge(NCO)4

Abstract: Raman spectra (with polarizations) and infrared absorption from 80 to 4000 cm −1 are reported for Si(NCO) 4 and Ge(NCO) 4 . The spectra of both compounds are surprisingly simple and indicate high symmetry. For Si(NCO) 4 the data fit a tetrahedral model fairly well. An interesting consequence is that the Si-NCO group is linear, in contrast to the C-N CO group. The data for Ge(NCO) 4 would also fit a tetrahedral model except for one feature: an “extra” polarized Raman line at 670 cm −1 with an infrared counterpart. From this feature, and from other non-spectroscopic evidence, it is concluded that Ge(NCO) 4 deviates to some unknown degree from being tetrahedral. An X-ray diffraction study of Si(NCO) 4 showed that the crystal is triclinic. From the measured dimensions c = 12.865 A, d 100 = 10.65 A, d 010 = 5.94 A, γ ∗ = 86° it follows that there are four molecules per unit cell. Measurements of the C 13 NMR spectrum showed only a single broad C 13 resonance in each compound. Several attempts to prepare Sn(NCO) 4 and Ti(NCO) 4 were unsuccessful.

Vibrational spectra of benzene derivatives—II: Assignment and calculated thermodynamic functions for benzonitrile

Abstract: A complete vibrational assignment is made for benzonitrile from which the thermodynamic functions have been calculated to 1000°K.

Sign of the dipole moment derivatives in methane

Abstract: The infrared vibrational intensity of the ν 3 fundamental mode of CH 4 has been measured. Using this intensity and the intensity of the ν 4 fundamental as measured by ruf [1], we can calculate, except for the sign, the dipole moment derivatives with respect to the normal co-ordinates. The intensities of the bands of the deuterated molecules are calculated from the above-mentioned dipole derivatives in two ways, once assuming the derivatives have the same sign, and once assuming opposite signs. Only in the latter case do the observed and calculated values agree.

IR-und Raman-untersuchungen zur struktur des di-benzol-chroms, seines kations sowie verwandter verbindungen

Abstract: The infra-red spectra of Cr(C6H6)2, Cr(C6D6)2, [Cr(C6H6)2]I, Mo(C6H6)2, [Mo(C6H6)2]I, W(C6H6)2, [W(C6H6)2]I and V(C6H6)2, and the Raman spectrum of [Cr(C6H6)2]I have been measured. The assignment of vibration frequencies suggests that the symmetry of the cation of dibenzene chromium is D6h.

Metal-oxygen vibration modes in the infra-red spectra of aluminium, gallium and indium tris-acetylacetonates

Abstract: A comparison has been made of the infra-red spectrum of aluminium, gallium and indium tris-acetdelylacetonates. Metal-oxygen vibration modes have been discussed and the metal-oxygen stretching frequency has been assigned for Al-O, Ga-O and In-O bonds in these complexes.

The structure of protonated amides and ureas and their thio analogues

Abstract: The electronic absorption spectra were studied of protonated thioamides and thio-ureas, as well as the infra-red spectra of alkylated acetamide, thioacetamide, urea and thiourea and their hydrochlorides. All results consistently show that the proton is normally attached to the oxygen (or sulphur) atom. Earlier data pointing to the existence of the ammonium structure are reinterpreted. The resonance within these molecules appears to be the decisive factor in determining the site of protonation.

Frequenzen und normalkoordinaten der nicht-ebenen normal-schwingungen von symmetrischen ortho-, meta-, 1:3:5-und hexasubstituierten benzolderivaten

Abstract: Using the model described by Whiffen [1] the frequencies of the out-of-plane normal vibrations and the normal co-ordinates of symmetrically substituted benzene derivatives including the ortho-, meta- , 1:3:5- and hexa-forms have been calculated. The calculated frequencies are compared with the frequencies observed in the Raman and infra-red spectra, and an assignment is given.