Vibrational band intensities in substituted anilines

1957 ◽  
Vol 243 (1233) ◽  
pp. 143-153 ◽  
Keyword(s):  
Linear Relation ◽  
Vibrational Band ◽  
Vibration Band ◽  
Substituted Anilines ◽  
Absorption Bands ◽  
Bond Stretching ◽  
Infra Red ◽  
Analogous Data ◽  
Stretching Vibration ◽  
Stretching Vibrations

The infra-red absorption bands associated with the stretching vibrations of the NH 2 group in a series of meta - and para -substituted anilines have been examined. The effect of the sub­stituet groups upon the frequencies and intensities of the bands has been correlated with their Hammett σ factors. The widths of the bands have also been found to depend upon the position and nature of substituent. The linear relation between log (intensity) and σ suggested previously on the basis of other data has been found to hold in this case too. Measurements in several solvents have been compared, and surprising variations of band intensity have been found. Analogous data have been obtained for the N—H bond stretching vibration band in substituted N -methyl anilines. The effect of ortho substituents has also been examined in a few cases.

The infra-red absorption bands associated with the COOH and COOD groups in dimeric carboxylic acids. I. The region from 1500 to 500 cm -1

1953 ◽  
Vol 216 (1125) ◽  
pp. 247-266 ◽  
Keyword(s):  
Carboxylic Acids ◽  
Raman Spectra ◽  
Crystalline Solid ◽  
Cooh Group ◽  
Absorption Bands ◽  
Solid States ◽  
Infra Red ◽  
Out Of Plane ◽  
Stretching Vibrations ◽  
Skeletal Deformation

The infra-red spectra of a considerable number of carboxylic acids and their COOD derivatives have been investigated between 1500 and 500 cm -1, as dimeric units in the liquid or crystalline solid states. Under these conditions the COOH group is shown usually to give rise to strong absorption bands in the regions 1420 ±20, 1300 ± 15 and 935 ± 15 cm -1 . The first two of these are found to correspond to closely coupled OH deformation and C—O stretching vibrations occurring in the plane of the (COOH) 2 dimeric ring; the latter is caused by the out-of-plane OH deformation vibration. COOD groups have absorption bands in the ranges 1350 ±50, 1050 ± 10 and 675 ±25 cm -1 , which can be assigned respectively to the C—O stretching mode and the in-plane and out-of-plane OD deformation vibrations. Less constant absorption bands of the COOH group between 700 and 575 cm -1 are attributed to O—C = O skeletal deformation vibrations, and the corresponding bands are found at slightly lower frequencies in the spectra of the COOD derivatives. The results of the infra-red investigation are compared with the Raman spectra of such acids and with related infra-red and Raman frequencies of other molecules. Infra-red spectra of some equimolecuiar mixtures of acids with water have also been studied.

The interpretation of the infra-red and Raman spectra of the n -paraffins

1954 ◽  
Vol 247 (922) ◽  
pp. 35-58 ◽  
Keyword(s):  
Raman Spectra ◽  
Principal Series ◽  
Experimental Results ◽  
Absorption Bands ◽  
Infra Red ◽  
Complete Set ◽  
Stretching Vibrations

Infra-red spectra of a series of crystalline n -paraffins containing an odd number of carbon atoms have been obtained. The spectrum of oriented crystals of n -nonadecane has also been examined. These new experimental results have been combined with the earlier data on the crystalline n -paraffins containing an even number of carbon atoms, and many series of absorption bands have been identified in the complete set of spectra. These regularities, as well as those present in the Raman spectra, have been interpreted in terms of CH 2 , CH 3 , and C—C stretching vibrations. Very regular distributions of frequencies have been found between 720 and 1030 cm -1 and between 1200 and ca. 1370 cm -1 , which are assigned to CH 2 rocking and wagging vibrations, respectively. The majority of the absorption bands between 1150 and 880 cm -1 can be attributed to C—C stretching or CH 3 rocking modes, and assignments are suggested for the principal series observed in this region.

Infra-red spectra and the solid state. III. Potassium bifluoride

1951 ◽  
Vol 210 (1101) ◽  
pp. 206-216 ◽  
Keyword(s):  
Room Temperature ◽  
Potential Energy Function ◽  
Vibration Frequencies ◽  
Fundamental Vibration ◽  
Absorption Bands ◽  
Bending Vibrations ◽  
X Ray ◽  
Higher Power ◽  
Infra Red ◽  
Stretching Vibration

The infra-red spectrum of potassium bifluoride has been determined between 2 and 8μ at temperatures between 293 and 90° K. On passing from room temperature to that of liquid air, some of the absorption bands sharpen and split. The results have been analyzed with the object of assigning fundamental vibration frequencies to the (HF 2 ) - ion, and also of deciding whether this ion has a symmetrical or unsymmetrical structure. Values assigned to the stretching vibration frequencies are 600 and 1450 cm. -1 , and to the deformation a pair at 1225/1274 cm. -1 . The spectrum can then be satisfactorily explained in terms of the selection rules which would be expected for a symmetrical (HF 2 ) - ion lying in the particular crystal field suggested by X-ray work. Whereas the bending vibrations appear to involve little anharmonic character, there is an apparently large negative anharmonic coefficient for the overtone and combinations of the stretching vibration frequencies. This might be expected if the potential energy function for the antisymmetrical stretching vibration involved a higher power of the displacement co-ordinate than the second, and strengthens the interpretation in terms of a symmetrical ion. The molecular enviromnent of the ion in the crystal state leads to a removal of the degeneracy of the deformational vibration, the latter being found to split, although one component is not noticed in absorption when the crystal is viewed along the c -axis.

scholarly journals THE STUDY OF HYDROGEN BONDING AND RELATED PHENOMENA BY ULTRAVIOLET LIGHT ABSORPTION: PART VI. THE EFFECT OF STERIC INTERACTIONS ON THE INTRAMOLECULAR HYDROGEN BOND IN o-NITROPHENOL

1960 ◽  
Vol 38 (10) ◽  
pp. 1852-1864 ◽  
Author(s):  
J. C. Dearden ◽  
W. F. Forbes
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bond ◽  
Alkyl Substituent ◽  
Intramolecular Hydrogen Bonding ◽  
Vibration Band ◽  
Absorption Bands ◽  
Steric Interactions ◽  
Stretching Vibration ◽  
Intramolecular Hydrogen

Intramolecular hydrogen bonding occurring in o-nitrophenol is discussed with special reference to the effects of the steric interactions on the absorption bands and on the bonding. An alkyl substituent vicinal to the OH group, or a methyl group vicinal to the NO2 group appears to strengthen the intramolecular hydrogen bond in o-nitrophenol. The O—H vibrational stretching frequency in o-nitrophenol appears to be more susceptible to steric than to mesomeric interactions, and a methyl substituent vicinal to the nitro group in o-nitrophenols is found to give rise to a characteristic O—H stretching vibration band. For 6-t-butyl-2-nitrophenol, a special, "protected" hydrogen bond is postulated. In some of the o-nitrophenols, intermolecular hydrogen bonding gives rise to appreciable ultraviolet intensity decreases presumably because of increased steric interactions.

Changes in the infra-red spectra of molecules due to physical adsorption

1956 ◽  
Vol 238 (1212) ◽  
pp. 69-89 ◽  
Keyword(s):  
Absorption Band ◽  
Gas Phase ◽  
Physical Adsorption ◽  
Adsorbed Hydrogen ◽  
Vibration Band ◽  
Free Rotation ◽  
Absorption Bands ◽  
Model Free ◽  
Infra Red ◽  
Adsorbed Methane

Infra-red spectra of the molecules methane, ethylene, acetylene and hydrogen, physically adsorbed on porous silica glass have been studied at measured surface coverages, θ . In all cases absorption bands were readily obtained for θ values considerably less than unity; for methane it was possible to obtain spectra down to θ = 0.01. Shifts occurred on adsorption for the absorption bands that were observed in the gas phase and in the adsorbed state. In several cases additional bands occurred in the spectra of the adsorbed molecules which correspond to known fundamental vibration frequencies that are forbidden in the gas phase because of molecular symmetry. Their appearance results directly from the distortion of the symmetry of the molecules by surface forces. High-resolution spectra of adsorbed methane and hydrogen obtained with a diffraction grating spectrometer enabled the shapes of the bands to be accurately determined. Although no fine-structure lines due to molecular rotation could be resolved, the overall shape of the broad and asymmetrical v 3 band of methane could be explained by using as a theoretical model free rotation of the molecule about a single axis normal to the surface. The band shape is not consistent with a three-dimensional free rotation about axes parallel as well as perpendicular to the surface. It could, however, alternatively be fitted by a Lorentz curve of half-width 28 cm -1 , corresponding to a broad vibration band without rotational contribution, plus an extra overtone absorption band near 3050 cm -1 . The shapes of the other bands of adsorbed methane and hydrogen are insensitive to the assumptions of free or highly restricted rotation on the surface. A comparison of the intensity of the absorption band due to adsorbed hydrogen with that of gaseous hydrogen in a strong electrical field (Crawford & Dagg 1953) has enabled an estimate to be made of the electrostatic field at the surface of the glass.

Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones

1983 ◽  
Vol 48 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Alexander Perjéssy ◽  
Pavol Hrnčiar ◽  
Ján Šraga
Keyword(s):  
Substituent Effects ◽  
Phenyl Group ◽  
Wave Number ◽  
Vibrational Coupling ◽  
Wave Numbers ◽  
Stretching Vibration ◽  
Stretching Vibrations ◽  
The Relationship ◽  
Derivatives Of ◽  
Effect Of Structure

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.

POSSIBILITY OF MOLECULAR-SWITCH WITH CONTROLLED HYDROGEN BOND: UTILITY OF COMBINATION OF 2,2′-BIIMIDAZOLE AND REDOX-ACTIVE LIGAND

2005 ◽  
Vol 04 (01) ◽  
pp. 333-344 ◽  
Author(s):  
HIROTOSHI MORI ◽  
EISAKU MIYOSHI
Keyword(s):  
Density Functional ◽  
Molecular Level ◽  
Molecular Switch ◽  
Vibration Band ◽  
Functional Theory ◽  
Inorganic Molecule ◽  
Redox Active Ligand ◽  
Active Ligand ◽  
Redox Active ◽  
Stretching Vibration

A new inorganic molecule [ Co(Hbim) ( C 6 H 4 O 2)( NH 3)2]2 that can be used as a new optically durable molecular switch was theoretically designed in the framework of density functional theory. Three stable minima, belonging to 1 A g , 5 A 1, and 9 A g states, were found in the complex. Theoretically predicted infrared spectra of the complexes showed that a strong peak of NH stretching vibration is observed at 2690, 2120, and 2770 cm -1 in the 1 A g , 5 A 1, and 9 A g states, respectively. The apparent red shift of the NH stretching vibration band in the 5 A 1 state make it possible to distinguish the electronic state from others (1 A g and 9 A g ). This means that the complex can be used as a molecular level switch whose memory can be stably read by IR light without any photoreaction process; namely, without memory degradation.

The infra-red spectrum and molecular configuration of sodium deoxyribonucleate

1957 ◽  
Vol 239 (1219) ◽  
pp. 446-463 ◽  
Keyword(s):  
Relative Humidity ◽  
Vapour Phase ◽  
Molecular Configuration ◽  
Absorption Bands ◽  
Oriented Films ◽  
Infra Red ◽  
Modes Of Vibration ◽  
Water Measurement ◽  
Phosphate Groups ◽  
Polarized Radiation

The infra-red spectra of oriented films of sodium deoxyribonucleate have been investigated between 700 and 4000 cm -1 using polarized radiation and under varying degrees of relative humidity. Similar spectra have been obtained when the films have been deuterated by vapour-phase exchange with heavy water. It is found that the infra-red dichroism of nearly every band increases with the relative humidity. Many of the principal absorption bands can be assigned to separable modes of vibration in the bases, the phosphate groups or the absorbed water. Measurement of the dichroic ratios of certain of these bands indicates that at high relative humidity the bases must be nearly perpendicular to the orientation direction. The configuration deduced for the phosphate groups is unlike that proposed in the Crick-Watson model, but is in essential agreement with that recently proposed by Wilkins and his co-workers. Some observations are also reported on the corresponding spectra of sodium ribonucleate. Since no dichroism was observed, no conclusions can be drawn regarding the molecular configuration of this polymer.

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