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Determination of Relative Stability of Urea Complexes from X-Ray Powder Diffraction Data

Published online by Cambridge University Press:  06 March 2019

Jack Radell  and
J.W. Connolly
Jack Radell
Affiliation:
Wright-Patterson Air Force Base, Ohio
J.W. Connolly
Affiliation:
Wright-Patterson Air Force Base, Ohio
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Abstract

Urea complexes consist of a channel made up of hydrogen-bonded urea host molecules into which a variety of guest molecules can fit to form a crystalline complex. The urea host can accommodate, one at a time, a variety of guests having the requisite size and shape. The stability of the resulting complex is a function of the properties of the guest molecule. A procedure has been devised which produces pure complex free of any uncomplexed urea or host molecules in solution. The insoluble crystalline complexes formed from the solution of urea and guest molecule in methanol established a dynamic equilibrium. When the crystals of complex are removed from the solution, dissociation to urea and guest occurs to an extent, depending upon the dissociation constant of the complex. If the dissociation constant, KD, is very low, undetectable quantities of uncomplexed urea form along with complex. If the dlissoclation constant is high, extensive amounts of urea form in the presence of complex. Characteristic interplanar spacing s are obtained for a urea complex irrespective of the guest molecule present. The pattern obtained for the hexagonal complex is completely different from the pattern obtained for tetragonal urea. X-ray examination of a homologous series of compounds gives, for each partially dissociated complex, spacings for both urea and complex. The relative intensities of urea and complex spacings permit the estimation of the stability of such a complex compared to that of other homologues.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 4: Ninth Annual Conference on Applications of X-ray Analysis, August 10-12, 1960 , 1960 , pp. 140 - 150
Copyright
Copyright © International Centre for Diffraction Data 1960

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References

1. Smith, A. E., “The Crystal Structure of the Urea-Hydrocarbon Complexes,” Acta Cryst., Vol. 5, Part 2, March 1952, p. 224.Google Scholar
2. Simmerschled, W. J., Dinnerstsin, R. A., Weitkamp, A. W., and Marschner, R. F., “Crystalline Adducts of Urea with Linear Aliphatic Compounds,“ Ind. & Eng. Chem., Vol. 42, July 1950, p. 1304.Google Scholar
3. Krichevskiy, I. R., Efremova, G. D., and Leontyeva, G. G., “Thermal Stability of Complexes which Urea Forms with Organic Substances,” Reports of the USSR Academy of Sciences, Vol. 113, No, 4, 1957, p. 817.Google Scholar
4. Radell, J., Connolly, J. W., and Yuhas, L. D., “Urea Inclusion Compounds of Acetylene Derivatives,’ WADG Technical Report 59-672, February 1960.Google Scholar
5. Topchiev, A. V., Rozenberg, L. M., Nechitaylo, N. A., and Tereteva, E. M., “The Differential Thermal Study of the Formation of Urea Complexes with n-Paraffines.” Reports of the USSR Academy of Sciences, Vol. XCVIII. No. 2, 1954, p. 223; L. M. Rozenberg, E. M. Terenteva, H. A. Nechitaylo, and A. V. Topchley, “Thermal Stability of Complexes Formed by n-Paraffines and Urea,’ ibid., Vol. 109, No. 6, 1956. p. 1144; E, Terres and S. Nath Sur, ‘Urea Inclusion Compounds of Straight and Branched Aliphatic Compounds,” Brennstoff-Chemie, Vol. 38, No. 21/22, 1957, p. 13-16.Google Scholar
6. Radell, J. and Hunt, P. D., “Occlusion of Organosilanes by Urea,” J. Am. Chem. Soc, Vol. 80, 1958, p. 2683; J. Radell and P.D. Hunt, “Occlusion of Alkylsilanes by Urea,” WADC Techanical Report 58-14, January 1958.Google Scholar
7. Radell, J. and Connolly, J. W., “Synthesis Properties and Complex Formation of Fluorinated Compounds,” WADC Technical Report 59-118, March 1959; J. Radell and J. W. Connolly, “Urea Complexes of Partially Fluorinated Esters,” J. Org. Chem., Vol. 25. 1960.Google Scholar
8. Radell, J., Connolly, J. W., and Yuhas, L. D., “Urea Inclusion Compounds of Acetylene Derivatives,” WADC Technical Report 59-672, February 1960.Google Scholar
9. Radell, J., Connolly, J. W., and Cosgrove, W. R., “Effect of cis-trans Isomerism on the Urea Inclusion Compound Forming Ability of Molecules. A Study of the Maleate-Fumarate System,” WADC Technical Note 59-407, February 1960.Google Scholar