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Force field for planar vibrations of urea: use of CNDO/Force MO calculations

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Symmetry force field calculations have been performed for the planar vibrations of urea using CNDO/Force method. The CNDO/Force calculations predict well the signs and the magnitudes of bending and interaction force constants; the stretching force constants are found to be higher in magnitude. The bending and interaction constants obtained from these calculations and the stretching force constants obtained from the literature are considered for the initial force field. Using the observed frequencies for urea and its isotopic analogues, urea-D4, urea-15N2, urea-15N2D4 and urea-18O in the solid as well as in the solution phases, the force field is refined by carrying out iterations over the diagonal force constants. In the final stages of the refinement iterations are carried out over all the force constants keeping the signs of the interaction constants unchanged. It is found that the agreement between the calculated and the observed frequencies is excellent. The final force fields in terms of symmetry as well as redundancy free internal valence coordinates are reported. On the basis of the potential energy distribution the vibrational assignments are discussed.

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  1. Adams D M and Churchill R G 1970J. Chem. Soc. A 697

  2. Arenas J and Paralleda R 1971J. Mol. Struct. 10 253

  3. Duncan J L 1971Spectrochim. Acta A27 1197

  4. Duncan J L 1973Chem. Phys. Lett. 23 597

  5. Hadzi D, Kidric J, Khezevic Z V and Barlic B 1976Spectrochim. Acta A32 693

  6. Hirakawa A Y, Tsuboi M and Shimanouchi T 1972J. Chem. Phys. 57 1236

  7. IUPAC 1977Appl. Spectrosc. 31 569

  8. Kanakavel M Chandrasekhar J, Subramanian S and Singh S 1976Theoret. Chim. Acta 43 185

  9. Kanakavel M 1976Vibrational analysis and evaluation of force fields of polyatomic molecules, Ph.D. Thesis, Indian Institute of Techology, Madras

  10. Laulicht I, Pinchas S, Petreanu E and Samuel D 1965Spectrochim. Acta 21 1487

  11. Mallinson P D, McKean D C, Holloway J H and Oxton I A 1975Spectrochim. Acta A31 143

  12. Mills I M 1963Spectrochim. Acta 19 1585

  13. Pople J A and Beveridge D L 1970 Approximate Molecular Orbital Theory, (New York: McGraw-Hill)

  14. Pulay P and Torok F 1973Mol. Phys. 25 1153

  15. Schactschneider J H 1964 Technical Reports No. 57-65, Shell Development Co., California,

  16. Shteinberg B Ya, Mushkim Yu I and Finkelshtein A I 1972Opt. Spectrosc. 33 589

  17. Stewart J E 1957J. Chem. Phys. 26 248

  18. Usha Bai P and Venkata Ramiah K 1973Indian J. Pure. Appl. Phys. 11 171

  19. Waldron R D and Badger R M 1957J. Chem. Phys. 26 255

  20. Worsham J E, Levy H A and Peterson S W 1957Acta Crystallogr. 10 319

  21. Yamaguchi A, Miyazawa T, Shimanouchi T and Mizushima S 1957Spectrochim. Acta 10 170

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Correspondence to Surjit Singh.

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Annamalai, A., Kanakavel, M. & Singh, S. Force field for planar vibrations of urea: use of CNDO/Force MO calculations. Proc. Indian Acad. Sci., A (Chemical Sciences) 87, 337–346 (1978).

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  • CNDO/Force calculation
  • force field of urea
  • normal coordinate analysis of urea
  • optimum geometry of urea