• P G Puranik

      Articles written in Proceedings – Section A

    • Raman effect in mixtures of acetone with alcohols - Hydrogen bond formation

      P G Puranik

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    • Raman effect in mixtures of benzaldehyde with alcohols and phenol - Hydrogen bond formation

      P G Puranik

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      The 1197 cm.−1 line in benzaldehyde is attributed to the C-C linkage between the aldehyde and the phenyl groups. The admixture of methyl and ethyl alcohols does not affect the C-C and C=0 frequencies in benzaldehyde. Mixtures with phenol show the formation of hydrogen bond resulting in the weakening of the C=O link and a lowering of the relative frequency. This is accompanied by an increase of the C-C frequency in the group. This phenomenon is analogous to what has been observed when hydrogen bonds are formed between acetone and alcohol molecules.

    • Assignment of the raman frequencies of methyl and ethyl benzoates and ethyl cinnamate

      P G Puranik

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      The Raman spectra of methyl and ethyl benzoates, and ethyl cinnamates have been recorded in the liquid state at 42° C. Some new lines are reported. The lines at 1181, 1280 and 1724 cm.−1 in methyl benzoate, and 1172, 1278 and 1719 cm.−1 in ethyl benzoate are assigned to the group and 1205, 1270 and 1639 cm.−1 are assigned to the group in ethyl cinnamate.

    • Raman effect in mixtures of pyridine with phenol, methanol, and water - N−H-Hydrogen bond formation

      P G Puranik A M Jaya Rao

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    • Potential constants and calculated thermodynamic properties for diiodoethylene

      P G Puranik Lalitha Ramaswamy

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      The cis andtrans diiodoethylenes have been subjected to normal coordinate analysis. The Wilson F-G Matrix method has been employed to obtain the secular equation in order to calculate the fundamental frequencies. The potential constants for the ‘bromo’ molecule were transferred to the molecule under investigation and were so adjusted as to obtain a close fit between the observed and the calculated values of the frequencies. The two low frequencies do not closely agree with the observed values.

    • The infra-red and Raman spectroscopic studies of amides

      P G Puranik K Venkata Ramiah

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      The infra-red spectra of primary and secondary amides have been recorded in solutions at various concentrations with particular reference to 3µ region. The apparent molecular extinction coefficients of various absorption bands in this region have been calculated at different concentrations and spectroscopic evidence is obtained for their dimeric manifestation in solutions. This method enabled the authors to assign the N–H asymmetric and symmetric stretching vibrations of the monomer and the associated molecules on a quantitative basis. The C=O stretch and the N–H in-plane deformation frequencies of monomer and associated molecules have also been assigned.

      The effect of donor solvents on the frequencies of the amino and carbonyl bands has been investigated. It is observed that C=O frequencies of these amides in donor solvents are either the same or slightly higher/than those of the same amides in solutions of chloroform, but the N–H stretching frequencies in the same donor solvents are less, the N–H deformation frequencies more, than the frequencies of the corresponding linkages in solutions of chloroform. These results are explained on the basis that the primary and the secondary amides dissociate in donor solvents and then the donor group of the solvents forms hydrogen bond with the amino group of the amide in the monomeric state. The C=O frequency of these amides in solutions of dioxane in the presence of phenol was studied and its diminution is accounted for as due to hydrogen bond formation. The Raman spectra of N-methyl formamide and dimethyl formamide and in various solvents have been recorded. Shifts observed in a number of Raman lines of these substances in mixtures are explained.

    • Spectroscopic studies of the associations of heterocyclic amines - 2-Amino-methyl pyridines and amino-quinolines

      P G Puranik K Venkata Ramiah

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      The infra-red spectra of 2-amino-methyl pyridines and amino-quinolines have been recorded in solutions at various concentrations. The N-H stretching frequencies have been assigned on the basis of the presence of intermolecular associations and primary amino group in these compounds. The bands in the region of 1600 cm.−1 have been studied in considerable detail and the N-H deformation frequencies of monomer and associated molecules have been assigned. In all the amines studied, an absorption band appears in solutions of chloroform in the region of 2950 cm.−1 which is not present in the spectra of pure amines or in solutions of carbon tetrachloride. The presence of this band has been explained as due to the associations between the free N-atom of the monomer amines and the H-atom of the chloroform.

    • Raman and infra-red spectra of amines - Toluidines andpara-amino-acetophenone

      P G Puranik K Venkata Ramiah

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      The Raman and infra-red spectra of toluidines andpara-amino-acetophenone have been recorded and the N-H stretching and bending frequencies of these amines have been assigned. The effect of solvent on the N-H stretching and deformation frequencies of the amines is investigated and their variation in solutions of pyridine is accounted for as due to the N-H ... N bonding. The empirical formula proposed by Bellamy for the N-H stretching frequencies of amines has been used for the amines under investigation. The formula is obeyed for the N-H stretching frequencies of amines and in solutions of carbon tetrachloride, chloroform or dioxane, but it breaks down for the same frequencies in pyridine. These results are explained.

    • Hydrogen bonding in amides - Electrostatic interaction and resonance

      K Venkata Ramiah P G Puranik

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      The shift in the N-H stretching frequency in the infra-red spectra of amides, due to intermolecular associations, calculated on the basis that the hydrogen bonding is essentially an electrostatic interaction and that the ionic character of the bond diminishes on hydrogen bonding. The calculated and the observed values of the frequencies agree only when the two possible resonance structures in amides are taken into consideration for calculations.

    • Structure of formamide and its force constants

      P G Puranik Lalitha Sirdeshmukh

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      A new procedure has been adopted in subjecting formamide—a molecule which has no symmetry—to normal co-ordinate treatment by the Wilson’s F-G matrix method. The molecule is split into two parts for the purposes of calculation. One part is and the other is where R is the CHO group. Both the parts have C-N bond in common. Assuming the part one to be planar and the part two to be pryamidal as suggested by Costain and Dowling, the normal co-ordinate treatment of both the parts has been carried out and the fundamental frequencies calculated. The close agreement between the observed and the calculated values confirms the non-planar structure of formamide. Among all the fundamental frequencies, the frequency due to C-N stretch alone appears to be mass sensitive. On the basis of all these considerations some of the frequencies have been assigned to the wagging and twisting modes, which are different from those that are assigned by Evans.

    • Hydrogen bonding in alcohols, acids and secondary amides - Electrostatic interaction and resonance

      K Venkata Ramiah P G Puranik

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      The free OH and NH stretching frequencies of methanol, ethanol, formic and acetic acids and of N-methyl acetamide are used to calculate the shift in their frequencies due to hydrogen bonding. These calculations are based on the fact that the hydrogen bonding is an electrostatic interaction and that the ionic character of the bond diminishes on hydrogen bonding. The observed and the calculated bonded stretching frequencies agree fairly in methanol and ethanol, but in formic and acetic acids and N-methyl acetamide, the agreement between the corresponding observed and calculated frequencies is obtained only when the two possible resonance structures in these molecules are taken into consideration for calculations.

    • Vibrational spectra, potential constants and thermodynamic properties of diphenyl methane

      P G Puranik E V Rao

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      Diphenyl methane has been subjected to normal co-ordinate treatment assuming the phenyl groups to be point masses. The Wilson F-G matrix method has been employed to obtain the secular equation in order to calculate the fundamental frequencies. In calculating the thermodynamic properties, contributions from the ring frequencies are also included.

    • The charge transfer theory of the hydrogen bond - I. Theoretical

      P G Puranik Vijay Kumar

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      A charge transfer theory of the hydrogen bond has been developed by using a combination of the Second Order Perturbation and Molecular Orbital Theories. Expressions have been derived for both frequency shifts in the X-H stretching frequency and the changes in the infra-red integrated intensity. A relation between the frequency shifts and the changes in the intensity has also been worked out.

    • The charge transfer theory of the hydrogen bond - II. Experimental. SH band in thiophenol (Integrated infra-red absorption intensities)

      P G Puranik Vijay Kumar

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      The infra-red-integrated intensity of the SH band in thiophenol and in its complexes with a number of electron donors was measured. The increase in the value of∂μ/∂r on H-bond formation is determined and compared with the value evaluated on the basis of Charge Transfer Theory. Dependence of both the frequency shifts and the intensity changes on the ionisation potential of the electron donor, as predicted by the Theory, is given.

    • Mean amplitudes of vibrations of C=O and C−CPh stretching modes in benzophenone

      P G Puranik E V Rao

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      The mean amplitudes of the vibrations of C = O and C − CPh stretching modes of benzophenone have been evaluated with the help of L matrices and the percentage contribution of different normal modes to the C=O and C−CPh stretching modes are given.

    • Vibrational spectra, force constants and mean amplitudes of vibrations of urea and deuterated urea

      P G Puranik Lalitha Sirdeshmukh

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      The vibrational spectra of urea and deuterated urea have been recorded. Using a most general potential function, the force constants and the mean amplitudes of vibration have been calculated.

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