Infrared Band Intensities Research Articles

Measurement of infrared band intensities by a digital recorder

ディジタル記録計を製作し,赤外吸収帯の絶対強度を求めるうえでのいろいろな問題点について検討した.ディジタル記録計から得られた吸光度データのせん孔紙テープを電子計算機で処理して積分強度を算出した.また,従来のアナログ記録によるチャートに対し,planimeterによる直接求積法,および切り抜き重量法を用い,ディジタル法の結果と比較した.メチレンクロライドのν8の絶対強度として2800liter・mol-1・cm-2(二硫化炭素溶液),また,塩化メチルのν6に対して,400(気相),という妥当な結果を得た.他法に比べて,精度よく迅速かつ簡単に絶対強度を求めることができた.

A correlation of infra-red band intensities with chemical reactivity

A correlation between the intensities of infra-red absorption associated with the ring stretching vibration of monosubstituted benzene compounds and the σ constants of the substituents has been explained in terms of a simple molecular orbital model. It is shown that the changes in π-electron distribution as a result of distortion of the ring due to vibration are closely parallel to those occurring during an early stage in a free-radical substitution reaction. The symmetry of the reaction coordinate is predicted.

Infra-red intensities of nitro compounds

Infra-red band intensities of vibrations corresponding to NO 2 stretching, NO 2 Symmetric bending and NC stretching in solution of nitromethane in carbon tetrachloride and carbon disulphide have been measured. The intensity of NO 2 stretching is three times that of NO 2 symmetric bending and eighteen times that of NC stretching. The normal co-ordinates and amplitudes of vibrations have been determined by W ilson's FG method. Relationships between measured intensities ( A), and dipole moments (μ) as well as derivative of dipole moment with respect to bond length (∂μ|∂ r) have been obtained. Experimental results give μ NO = 1·40D, ∂μ NC ∂ R NC = −2·49 D/Å and ∂μ NO ∂ r NO = 4·65 D/Å. These results have been discussed in terms of current theories.

Infra-red intensities in CH 2F 2, CH 2Cl 2 and CF 2Cl 2

The integrated intensities of the fundamental infra-red absorption bands of CH 2F 2, CH 2Cl 2 and CF 2Cl 2 have been measured using the pressure-broadening technique. Experimental results are interpreted in terms of displacement polar tensors, which give the change of the dipole moment of the molecule due to a set of displacements of the nuclei. The components of these polar tensors have been calculated for the nuclei of C, H, F and Cl for each of the studied molecules. The results obtained show that the bond moments hypothesis, used by most authors in the interpretation of infra-red intensities, is only a rough approximation. Thus, we have found that a bond stretching gives rise to a dipole moment change not directed along the bond but strongly deflected towards the most polarizable atom of the molecule. Similar results have been obtained for the bond bendings.

Pyrrole studies. IX. The infrared spectra of 1-substituted pyrroles

The positions and intensities of the characteristic infrared absorption bands of the pyrrole nucleus in the region 2000-600 cm-1 of 45 1-substituted pyrroles, 2,5-dimethylpyrroles, and 3,4-dimethylpyrroles are recorded and discussed.

Integrated infrared band intensity measurement of stereoregularity in polypropylene

An infrared band asymmetry method involving use of integrated infrared band intensities was devised for the measurement of stereoregularity differences in polypropylene resins. A simple digital readout apparatus was attached to a high resolution infrared spectrophotometer, and a computer program was written to calculate the integrated band intensities from the digital data. Comparison of this method with others based on crystallinity measurements of the isotactic portion and on solvent extraction techniques for measurement of the atactic portion demonstrated its sensitivity for the stereoblock portion of the polypropylene resin. A polypropylene resin which was fractioned by a temperature-controlled sequential extraction was examined by this band asymmetry method and the results reported.

On the origin of the Ham bands in the spectrum of benzene in fluid solution

The spectrum of benzene has been studied in various fluid solutions at various temperatures in the ultra-violet region and at room temperature in the infra-red, and the relations between the spectral behaviour and the intensity of the Ham bands have been examined. No positive evidence for assigning the bands to the 3 E 1 u − 1 A 1 g transition has been found, and it is believed that the bands belong to the lowest 1 B 2 u − 1 A 1 g transition. No evidence has been found that the appearance of the bands is due to chemical bond forces or charge-transfer bond forces between benzene and solvent molecules. It has been concluded that the intensity of the Ham bands has a close relation to the intensity of the anomalous infra-red bands of benzene 1177( e 2 g ) and 850( e 1 g ) cm −1 vibrations, and that the origin of the Ham bands is due to dispersion forces between benzene and solvent molecules. This conclusion is valid only if the solution is fluid.

Effect of Nonuniform Distribution of Absorbing Material on the Quantitative Measurement of Infrared Band Intensities.

Effect of Nonuniform Distribution of Absorbing Material on the Quantitative Measurement of Infrared Band Intensities.

A correlation between the configuration and infrared band intensity of the cyano group in the fused cyclohexane ring systems

A correlation between the configuration and infrared band intensity of the cyano group in the fused cyclohexane ring systems

Pyrrole Studies. I. The Infrared Spectra of 2-Monosubstituted Pyrroles

The positions and intensities of the characteristic infrared absorption bands of the nucleus are recorded and discussed for thirty-five 2-monosubstituted pyrroles.

The Solvation of Polar Groups. I. A Study of Solvent Effects on Infrared Band Intensities

<b>The Solvation of Polar Groups. I. A Study of Solvent Effects on Infrared Band Intensities</b>

Intensities of some group characteristic infra-red bands

Molar-intensity data have been obtained, both as peak extinction coefficients and as band areas, for several infra-red bands known to be characteristic of chemical groups. In view of the fact that many compounds are insoluble in spectroscopically suitable solvents, the substances were measured as solids in potassium bromide disks. The bands considered were CN stretching band in nitriles, the CO stretching band in esters, ketones, amides, acids and salts, the NO stretching bands in nitro compounds, and the SO stretching bands in sulphones, sulphonamides and sulphonic acids. About twenty compounds were examined in each case. The usefulness of such data in analysis and structural diagnosis has been considered. It was concluded that, provided the total area under the band, rather than the peak-extinction coefficient is used as the measure of intensity, reasonably constant intensity factors could be assigned to several of the above characteristic bands. The significance of this is that rough quantitative estimates of the concentrations of certain groups in material of unknown structure can be made, and that intensity measurements may be used to supplement structural diagnosis from band frequencies.

Intensities of some group characteristic infra-red bands

Intensities of some group characteristic infra-red bands

Determination of the Dipole Moment Function from Infrared Band Intensities of Diatomic Molecules

A discussion is given of the relations which exist among vibrational matrix elements for diatomic molecules represented as Morse oscillators. This is done according to the wave function approximation of Trischka and Salwen. It is shown how the matrix element of the dipole moment Mvi′ is related to the matrix elements M0i where v′—v≤i≤v′+v with v′&amp;gt;v. This relation is examined for the case of the 1–2 band of HCl. It is also shown how the matrix element M01 for DCl can be related to the matrix elements of HCl. Finally, the influence of the vibration-rotation interaction is incorporated in the wave function approximation. In an example, it is shown that the matrix element {M0,Ji,J+1 can be expressed in terms of the set of matrix elements{M0,0i,1},i=0,1,··· .

The experimental determination of infra-red intensities. Bond polar properties in CHF3 and CHCl3

Abstract The fundamental grounds of the experimental method for measuring the intensities of infra-red absorption bands have been revised and some general conclusions about the reliability of intensity determinations in gases have been drawn. The most important sources of error in these measurements are examined. The behaviour of the apparent intensity as a function of the product pl (pressure of the gas times cell length) when pl → 0 is discussed. The intensities of the fundamental infra-red absorption bands lying above 400 cm−1 of CHF3 and CHCl3 have been measured using the pressure-broadening technique. Bond moments and their derivatives are calculated and the results are briefly discussed.

Intensities of infra-red bands - V. Bond polar properties in dimethyl acetylene

The absolute intensities of all except one of the infra-red fundamental vibration bands of dimethyl acetylene have been determined, and the results have been used to compute polar properties of the C—H and C—C bonds. It has been found that if the very probable assump­tion is made that the acetylenic carbon atoms carry a residual negative charge, the hydrogen atoms in the C—H bonds must carry a residual positive charge. The probable value of the C—H dipole is about 0-4 Debye, and that of the C—C≡ bond about 1 Debye. Comparisons have been made with the results of similar work with related molecules.

Infrared Intensities and Bond Moments in Formaldehyde

The infrared band intensities of formaldehyde have been measured in the gas phase using the pressure broadening method. From the results of the normal coordinate analysis and the experimental intensities, the bond moments and their derivatives have been calculated for the three symmetry species. The relative signs of ∂μ/∂Q5 and ∂μ/∂Q6 have been determined from the investigation of the Coriolis interaction between ν5 and ν6. The results chosen from the calculations are: μCH = 0.5D (C——H+), (∂μ/∂r)CH = 1.3×10—10 esu, μCO = 1.9D (C+—O—), (∂μ/∂r)CO = —1.9×10—10 esu. The B1 symmetry block gave an abnormally large μCH of about 1D.

The Influence of Slit-Width on the Shape and Intensity of Infra-Red Absorption Bands

Making certain assumptions as to the shape of infra-red absorption bands and the shape of the slit function of the monochromator, expressions are obtained for the dependence on spectrometer slit-width of the intensity and half-width of absorption bands. Experimental data to confirm the accuracy of these deductions are presented.

The Intensities of Several of the Infra-Red Absorption Bands of Cyanogen and Cyanogen Chloride

Measurement of the absolute intensities of several infra-red absorption bands of cyanogen and cyanogen chloride gives the following values in cycles per cm at N.T.P. CyanogenBandIntensity2150 cm−190×1010Cyanogen chlorideBandIntensity714 cm−117×10102214 cm−1220×1010 Values of the variation in bond moments with change in bond length are calculated on the basis of bond moment additivity. This leads to widely different values of this derivative for the CN bond in the two molecules. The infra-red spectrum of cyanogen chloride from 2 to 20 microns is reported.

Absolute Intensities of Characteristic Infra-Red Absorption Bands of Aliphatic Hydrocarbons

Integrated intensities of the 2900, 1460, and 1370 cm−1 infra-red absorption bands have been measured for twelve aliphatic hydrocarbons. The results are interpreted on the basis that the hydrocarbon molecule behaves like a non-interacting mixture of [Complex chemical formula] structural groups. The unit structural group intensities are 4.41×10−7, 3.81×10−7, and 1.39×10−7 cm2/(molecule second) for the CH3, CH2 and CH groups respectively in the 2900 cm−1 band; 0.544×10−7 and 0.232×10−7 for the CH3 and CH2 groups in the 1460 cm−1 band; and 0.394×10−7 for the CH3 group in the 1370 cm−1 band. Values calculated for the CH bond dipole moment divided by the equilibrium CH bond length vary from approximately 0.2×10−18 to 0.4×10−18 c.g.s. units. Values of approximately −0.75×10−10 are obtained for the change in CH bond dipole moment with change in CH bond length.