Infrared Absorption Frequencies Research Articles

Characteristic Infrared Absorption Frequencies of the Enol Group of 1,3-Dicarbonyl Compounds

Infrared spectra of several 1,3-dicarbonyl compounds from different organic chemical clauses have been recorded. Assignments of characteristic enol frequencies have been made, and group frequency ranges developed. In most cases, the ranges are reasonably narrow considering the great changes in overall structure of the examples studied. The enol structure affects to a significant degree the absorption frequencies of certain modes.

Thermal analysis of the interaction between stearic acid and pyrophillite or talc. IR and DTA studies

Pyrophyllite and talc sorb stearic acid on edge surfaces. The grinding of clay-stearic acid associations in the presence of alkali halides converts some of the acid into the ionic form, this occurring more readily with talc than with pyrophyllite. Heating in a closed or semi-closed system causes dissociation of stearic acid adsorbed on talc, but not on pyrophyllite. The infrared absorption frequencies of the adsorbed ionic form vary with the clay mineral and the amount of water present. The thermal stabilities of the clay-stearic acid associations depend on the rate of escape of the acid, which is determined by the strength of bonding to the clay and the nature of the system, and on the degree of dissociation of the acid on the clay surfaces.

L'oxynitrure de silicium: Si 2N 2O I. Attribution des absorptions du spectre infrarouge aux vibrations fondamentales

Infrared absorption frequencies (4000 − 200 cm −1) are assigned to stretching and bending normal vibrations of the various inter-atomic bonds in silicon oxinitride. The two kinds of atoms linked to the silicon with different force constants as well as numerous results on the Si1bO1bSi bridge in materials with quite the same symmetry make Si 2N 2O a suitable material for such an investigation. The study of silicon oxygen bonds is more particulary supported by the analysis of vibrations in a “pseudo-molecule” (N 3Si1bO1bSiN 3), with a simplified computation of valence force field, and by their correlation with normal modes in the primitive cell. The assigment is also supported by a study using internal coordinates of the reduced representation of the degrees of freedom and by the behavior of the absorption bands at low temperature.

(II) Infrared and X-ray photoelectron spectroscopy of some transition metal dithiocarbamates and xanthates

Measurements are presented for the binding energy variations of (a) (Ni, Cu) 2 p 3 2 , S 2 p and N 1 s core levels in a series of Ni and Cu disubstituted dithiocarbamates and (b) (Ni, Cu) 2 p 3 2 , and S 2 p core levels in a series of Ni xanthates. These shifts, which are observed to be negative and quite large for the S 2 p levels, are then correlated with the infrared absorption frequency variations for the associated intramolecular stretching vibrations of the same series. The results are interpreted in terms of a model based on atomic charges and their potential effects on both variations. The functional relationships between the binding energy and infrared frequency variations are shown to be in good agreement with the experimental results.

Thin-Layer Chromatographic Behavior and Separation of Thallium Valancies I and III as Their NeutralN,N-Disubstituted Dithiocarbamates

Abstract Thallium(I) and (III) species have been separated quantitatively as their neutral N,N-disubstituted dithiocarbamates on silica gel layers. The effects of solvent strength, chelate type, and adsorbent deactivation on their resolutions are discussed. The effect of charge density perturbations at the N atom of the “thioureide” bond on adsorption characteristics are discussed with infrared absorption frequencies. Slopes of Rm vs log Xs plots (Xs = fraction of more polar component in the mobile phase) showed strong adsorption of monomeric Tl(III) dithiocarbamates through three adsorption sites. However, they are found to migrate ahead of polymeric Tl(I) dithiocarbamates with mobile phases of solvent strength greater than 0.15 e ° or of solubility parameters (δ T) greater than 8.8.

Backdonation and Interrelationships between 15N, 13C Chemical Shifts and Infrared Absorption Frequencies in Heterocyclic N-Oxides

Backdonation and Interrelationships between 15N, 13C Chemical Shifts and Infrared Absorption Frequencies in Heterocyclic N-Oxides

CEPA calculations on open-shell molecules. V. The vibration frequencies of SF and SCl

Ab initio calculations for the 2Π ground states of SF and SCl have been performed on Hartree-Fock level and with inclusion of valence shell correlation effects by means of the CI and CEPA approaches. The calculated properties are: Equilibrium distances, vibration frequencies, and dipole moment curves in the vicinity of the respective equilibrium geometries. Our best estimates for the 0 → 1 infrared absorption frequencies νo for SF and SCl are 786 cm−1 and 520 cm−1, respectively, both with an uncertainty of about 10 cm−1. This confirms a recent experimental value obtained by Willner for SF (791 cm−1), but indicates that for SCl both experimental values reported previously in the literature (617 cm−1 and 574 cm−1) are wrong. The S—F and S—Cl bonds in SF and SCl are very similar to the ones in SF2 and SCl2, being essentially single p-bonds in either case. In the analogous oxygen-halogen molecules the situation is different, the O—F and O—Cl bonds in the diatomic radicals OF and OCl have partial double bond character and are much stronger than those in OF2 and OCl2 or in HOF and HOCl.

Apparatus for infrared measurement of sorption/desorption in strained polymeric films

AbstractA new apparatus has been developed for optical measurement of sorption/desorption in transparent polymer films at a given strain or stress. The technique utilizes a chosen infrared absorption frequency of the diffusing vapor in a spectral region where the film has negligible absorption. From the time dependence of the IR absorption at this frequency the sorption/desorption behavior of the film may be determined at any strain or stress. The simultaneous measurement of mechanical relaxation as a function of the amount of sorbed vapor is also possible. The results presented here show the applicability of the apparatus for determining the transport and mechanical properties of a low‐density polyethylene film in ethyl acetate vapor at 30°C.

Infrared spectra of 15NH3⋅H2O, 2 15NH3⋅H2O, and deuterated forms of ammonia hemihydrate at 90 °K

The infrared spectra of various deuterated samples of ammonia hemihydrate are reported with some infrared absorption frequencies of 2 15NH3⋅H2O and 15NH3⋅H2O. The spectra of the 15N-substituted samples confirm the previous general assignments, and reveal a third component of ν3(NH3) in NH3⋅H2O. The absorption by 2ND3⋅D2O, NDH2 isolated in 2NH3⋅H2O, and ND2H isolated in 2ND3⋅D2O, show, with the aid of normal coordinate calculations, that the primary splitting of the bands due to ν2 and ν3 of ammonia is multiple site splitting, due to the existence of two types of ammonia molecule in the hemihydrate. The Cs site symmetry of the ammonia molecules is revealed by the stretching vibrations of NH2D in 2NH3⋅H2O but not by the symmetric deformation vibrations of NH2D or ND2H. The stretching vibrations of NH2D in 2NH3⋅H2O at 90 °K also indicate that the type II ammonia molecules occupy both of the orientations which preserve the plane of symmetry. The uncoupled O–D stretching frequencies of HDO in 2NH3⋅H2O confirm the assignment of the two νOH(H2O) bands in the spectrum of 2NH3⋅H2O as largely due to site splitting. The low-frequency νOD(HDO) stretching band is very broad and the corresponding νOH(HDO) band is even broader, as has been seen previously for analogous bands in hexamethylenetetramine hexahydrate. Similarly, one set of isolated νND(NH2D) stretching bands is sharp while the corresponding νNH(ND2H) bands are very broad, as has also been reported previously for solid ammonia. The assignment to rotational vibrations of features below 850 cm−1 in 2NH3⋅H2O is confirmed, but no evidence indicates the degree of mixing of ammonia and water displacements in these vibrations.

ChemInform Abstract: SPECTROSCOPY OF POLYENES. 5. ABSORPTION AND EMISSION SPECTRAL PROPERTIES OF POLYENE ACIDS/ESTERS RELATED TO RETINOIC ACID/ESTER AS HOMOLOGS

A number of all-trans polyene acids and esters with chain lengths varying over a range including two longer and two shorter homologues of retinoic acid/ester have been studied for their spectral and photophysical properties. The polyene acids form intermolecularly hydrogen-bonded dimers in nonpolar solvents (3-methylpentane and carbon tetrachloride). Upon increasing the polyene chain length as well as upon dimer formation (in the cases of the polyene acids), pronounced changes occur in the absorption-emission spectral maxima, infrared absorption frequencies (carbonyl and hydroxyl stretching), and fluorescence lifetimes and quantum yields. The photophysical dynamics is discussed in terms of a fluorescing state that is primarily of /sup 1/A/sub g/*/sup -/ character (dipole forbidden) in the longer polyene systems. 29 references, 5 figures, 2 tables.

Spectroscopy of polyenes. 5. Absorption and emission spectral properties of polyene acids/esters related to retinoic acid/ester as homologs

A number of all-trans polyene acids and esters with chain lengths varying over a range including two longer and two shorter homologues of retinoic acid/ester have been studied for their spectral and photophysical properties. The polyene acids form intermolecularly hydrogen-bonded dimers in nonpolar solvents (3-methylpentane and carbon tetrachloride). Upon increasing the polyene chain length as well as upon dimer formation (in the cases of the polyene acids), pronounced changes occur in the absorption-emission spectral maxima, infrared absorption frequencies (carbonyl and hydroxyl stretching), and fluorescence lifetimes and quantum yields. The photophysical dynamics is discussed in terms of a fluorescing state that is primarily of /sup 1/A/sub g/*/sup -/ character (dipole forbidden) in the longer polyene systems. 29 references, 5 figures, 2 tables.

Heterodyne measurements of infrared absorption frequencies of D_2O

The frequencies of eight D2O infrared absorptions near 9.4 μm, which are used in optically pumped submillimeter-wave lasers, have been measured by heterodyning CO2 and tunable-diode-laser radiations.

A new approach to lattice properties of alkali halide crystals

AbstractA new form of overlap repulsion as a function of interorbital distance as suggested earlier is employed to calculate some more properties of alkali halide crystals, such as infrared absorption frequency (v0), Grüneisen (γ), and Anderson‐Grüneisen (δ) parameter. The results are compared with the observed values and those calculated by earlier workers. In general the results show a marked improvement, establishing the validity of the proposed model.

Preparation of 2,2-difluoro- and 2,2,4.ALPHA.-trifluoro-steroids by the reaction of enamines with perchloryl fluoride.

The reaction of fluorinated steroidal enamines with perchloryl fluoride furnished 2, 2-difluoro-and 2, 2, 4α-trifluorinated steroids. Changes in infrared absorption frequency due to the introduction of fluorine are discussed.

Infrared spectra of matrix-isolated UO+2 and NO−2

The reactions of UO and UO2 with NO and NO2 have been studied by infrared spectroscopy using the matrix isolation technique. Codeposition of vaporized UO and UO2 with NO2 and with NO gases in an argon matrix at 14 K resulted in the production of the UO+2 molecular ion paired with either a NO−2 or NO− anion. Three different reactions have been observed to yield a UO+2 cation product: (1) UO2+NO2, (2) UO2+NO, and (3) UO+NO2. Infrared absorption frequencies in the range 1150–1190 cm−1 have been measured and interpreted as the stretching modes of bent (bond angle = 109°) N16O−2, N16O18O−, and N18O−2 ions paired with UO+2. Infrared absorption frequencies in the range 770–900 cm−1 have been measured and interpreted as the stretching modes of linear U16O+2, U16O18O+, and U18O+2 paired with either NO− or NO−2.

Infrared active modes of dielectric crystallites on a substrate

The infrared absorption frequencies of a collection of small spherical ionic crystals dispersed on a dielectric or metallic substrate are calculated. The polarization induced in the substrate, as well as the dipole-dipole interaction between the particles, are taken into account. It is found that the presence of the substrate causes the Fröhlich frequency of an isolated sphere to split into two branches and to shift to lower frequencies. The application of the theory to the case of tube shaped crystallites is presented and employed to explain results of some thermal emissivity measurements which have been performed in the past on small cubes.

Molecular Orbital Interpretation of Infrared Absorption Frequencies. II. α, β-Unsaturated Carbonyl, para-and meta-Substituted Aromatic Carbonyl Compounds, an Introduction of the Mutual Additive Substituent Parameter

The infrared frequencies of α, β-unsaturated carbonyl compounds were correlated well with their π bond orders calculated by HMO method employing hetero-atomic parameters selected in the previous paper. Carbonyl frequencies of each group of para-substituted benzaldehydes, acetophenones and methylbenzoates were also shown to be in tolerable correlation with their π bond orders, respectively. But the regression lines of these three groups of compound run parallel separately. This phenomenon was considered to show a defect of conventional method of HMO calculation of disubstituted aromatic compounds [X-C6H4-Y]. As a method of improvement of this defect a series of mutual additive substituent parameter (MASP) was introduced. The MASP of substituent [X] is added to the coulomb integral of a hetero atom of substituent [Y], and vice versa. By use of MASP to aromatic compounds, carbonyl frequencies of not only saturated, α, β-unsaturated and para-, but also meta-substituted aromatic carbonyl compounds were all found to be linearly correlated with their π bond orders.

Molecular Orbital Interpretation of Infrared Absorption Frequencies. III. Nitrobenzene Derivatives, Cyano Compounds and an Application of Mutual Additive Substituent Parameters to Benzophenone Derivatives

Molecular Orbital Interpretation of Infrared Absorption Frequencies. III. Nitrobenzene Derivatives, Cyano Compounds and an Application of Mutual Additive Substituent Parameters to Benzophenone Derivatives

Infrared absorption spectra of lithium and potassium silicate glasses at high pressure

Infrared absorption spectra of five lithium silicate and six potassium silicate glasses of varying composition (20–35 mole% Li2O and 15–40 mole% K2O, respectively) are examined in the range 1500–100 cm−1. The frequencies of the main absorption bands decrease with an increase of alkali-metal oxide (M2O) content, with the exception of the −960 cm−1 shoulder for the lithium silicate glasses. The pressure dependences to [inverted lazy s]40 kbar, of all the main infrared absorption frequencies, which are pressure sensitive, are found to be positive. The values of d νi/d P are higher for potassium silicate glasses than for sodium and lithium silicate glasses. The effects of pressure are found to be opposite to the compositional effects. The Grüneisen mode γ's, γi, evaluated from the pressure dependence of the infrared absorption frequencies, are apparently related to the polarizing power of the alkali-metal ion. The results discussed in light of previous high-pressure infrared absorption studies of fused silica and sodium silicate glasses clearly indicate that γi, γth, and γHT generally increase with M2O content in alkali silicate glasses.

Infrared absorption spectra of sodium silicate glasses at high pressures

Infrared absorption spectra of 12 sodium silicate glasses of varying composition (10 to 45 mole% Na2O) are examined at varying pressures to 58.8 kbar. The pressure dependences of all the infrared absorption frequencies studied are found to be positive. Grüneisen γ's are evaluated from the pressure dependence of the infrared vibrations and elastic parameters. The results are compared with those obtained from previous high-pressure studies of α-quartz and several other silicate glasses.