Computer simulation of liquid tetramethylurea and its aqueous solution

Abstract

Thermodynamic properties and correlation functions for the pure liquid 1,1,3,3-tetramethylurea (TMU) and its aqueous solution were obtained by Monte Carlo simulation in the isothermic and isobaric (NPT) ensemble at 25°C and 1.0 atm. An eight site potential model combining Lennard-Jones plus coulombic functions was developed to calculate intermolecular interaction between TMU molecules. In this model the methyl groups are represented by a united atom approach. The partial charges needed for Coulomb interactions and the geometry of the TMU molecule were calculated at the HF level using a 6-31g* basis set with the CHELPG formalism. The parameters needed for the Lennard-Jones potential functions were optimised to reproduce experimental values for the density and enthalpy of vaporisation of the pure liquid at 298 K and 1.0 atm. The results obtained for density, enthalpy of vaporisation and other thermodynamic properties for the pure liquid TMU are in good agreement with experimental data. Radial distribution functions (rdf) obtained for liquid TMU are broad indicating a low degree of molecular organisation. Dipole–dipole correlation shows a preference for anti-parallel molecular orientation at short distances. Therefore, the present results are consistent with experimental data indicating the formation of dimers due to dipole–dipole interaction. A further test for the potential model was also provided by studying the hydration of TMU on TIP4P water. Potential functions for water–TMU intermolecular interaction were obtained by standard combining rules. The value obtained for the free energy of hydration using statistical perturbation theory was ΔG=-16.82 kJ mol^-1, to be compared with the value ΔG=-56.48 kJ mol^-1 obtained for urea. Radial distribution functions for water–TMU interaction show features indicating hydrogen bonding between the TMU oxygen site and hydrogen of water. Compared to pure water, our results shows that the water–TMU hydrogen bonding is more stable. The results also show that in dilute TMU–water solution the influence of TMU on the energetics of water–water hydrogen bonding is negligible. Contrasting with gas phase results for the TMU–water dimer the present results do not indicate the formation of hydrogen bonding interaction with the nitrogen site of TMU in aqueous solution. This finding is in agreement with previous hydration studies of dimethylformamide and also with the hydrophobic behaviour of TMU observed in experiments. Dipole–dipole correlation results obtained for TMU and water molecules in the water–TMU solution exhibit significant differences when compared to the ones for the pure liquids.

References

1. M. P. Allen and D. J. Tildesley, Computer Simulation of Liquids, Oxford University Press, Oxford, 1986.
2. D. C. Rapaport, The Art of Molecular Dynamics Simulation, Cambridge University Press, Cambridge, 1995.
3. J. Hansen and I. R. McDonald, Theory of Simple Liquids, Academic Press, London, 1986.
4. Molecular Liquids: New Perspectives in Physics and Chemistry, NATO ASI Series, ed. J. J. Teixeira-Dias, Kluwer Academic, Dordrecht, 1991.
5. Computer Simulation in Chemical Physics, ed. M. P. Allen and D. J. Tidesley, Kluwer Academic Publishers, Dordrecht, 1993.
6. N. L. Allinger, Y. H. Yuh and J. H. Lii, J. Am. Chem. Soc., 1989, 111, 8551.
7. T. A. Halgren, J. Am. Chem. Soc., 1992, 114, 7827.
8. W. L. Jorgensen, D. S. Maxwell and J. Tirado-Rieves, J. Am. Chem. Soc., 1996, 118, 11225.
9. W. D. Cornell, P. Cieplak, C. I. Bayly, I. R. Gould, K. M. Merz, Jr., D. M. Ferguson, D. C. Spellmeyer, T. Fox, J. W. Caldwell and P. A. Kollman, J. Am. Chem. Soc., 1995, 117, 5179.
10. J. C. Smith and M. Karplus, J. Am. Chem. Soc., 1992, 114, 803.
11. J. A. Riddick, W. B. Bunger and T. K. Sakano, Organic Solvents. Wiley-Interscience, New York, 1970.
12. Y. Marcus, Ion Solvation, John Wiley & Sons Limited, New York, 1985.
13. K. R. Lindorfs, S. H. Opperman, M. E. Glover and J. D. Seese, J. Chem. Phys., 1971, 75, 21.
14. L. Cser, B. Farago, T. Groszz, G. Jancsó and Yu. M. Ostanveich, physica B, 1992, 180–181, 848.
15. A. Tovchigrechko, M. Rodnikova and J. Barthel, J. Mol. Liq., 1999, 79, 187.
16. L. Cser, G. Jancsó, P. Jovari and G. Kali, J. Phys. Chem. B, 1998, 102(13), 2313.
17. I. A. Chaban, M. N. Rodnikova, J. Barthel, L. L. Chaikov, S. V. Krivokhiza and V. V. Zhackova, J. Mol. Liq., 1999, 80(1), 27.
18. V. Castelletto, E. P. G. Arêas, J. A. G. Arêas and A. F. Craievich, J. Chem. Phys., 1998, 109(14), 6133.
19. K. Tóth, P. Bopp and G. Jancsó, THEOCHEM, 1996, 381, 181.
20. M. Mantle and S. D. Husar, Infect. Immun., 1993, 61(6), 2340.
21. N. Devaraj, M. Sheykhnazari, W. S. Warren and V. P. Bhavanandan, Glycobiology, 1994, 4(3), 307.
22. E. P. G. Arêas, H. H. A. Menezes, P. S. Santos and J. A. G. Arêas, J. Mol. Liq., 1999, 79(1), 45.
23. L. C. G. Freitas, THEOCHEM, 1993, 282, 151.
24. L. C. G. Freitas and J. M. M. Cordeiro, THEOCHEM, 1995, 333, 189.
25. A. L. L. Sinoti, J. R. Politi and L. C. G. Freitas, J. Braz. Chem. Soc., 1996, 7(2), 133.
26. A. L. L. Sinoti, J. R. Politi and L. C. G. Freitas, THEOCHEM, 1996, 366, 249.
27. L. C. G. Freitas, J. M. M. Cordeiro and F. L. L. Garbujo, J. Mol. Liq., 1999, 79, 1.
28. J. M. M. Cordeiro and L. C. G. Freitas, Z. Naturforsch., A., 1999, 54(2), 110.
29. A. K. Rappé and C. J. Casewit, Molecular Mechanics across Chemistry, University Science Books, Suasalito, 1997.
30. GAUSSIAN 94, revision E.2, M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheese-man, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghava-chari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 1995.
31. C. S. Frampton and K. E. B. Parkes, Acta Crystallogr. Sect. C, 1996, 52, 3246.
32. C. E. Dykstra, Chem. Rev., 1993, 93(7), 2339.
33. W. L. Jorgensen and J. Tirado-Rieves, J. Am. Chem. soc., 1988, 110, 1657.
34. W. L. Jorgensen and D. L. Severance, J. Am. Chem. Soc., 1990, 112, 4768.
35. W. L. Jorgensen, J. Chem. Phys., 1986, 90, 1276.
36. W. L. Jorgensen, J. A. Briggs and M. L. Contreras, J. Phys. Chem., 1990, 94, 1683.
37. W. L. Jorgensen, Chemtracts: Org. Chem., 1991, 4, 91.
38. M. Breneman and K. B. J. Wiberg, J. Comput. Chem., 1990, 11, 361.
39. E. M. Duffy, D. L. Severance and W. L. Jorgensen, Isr. J. Chem., 1993, 33, 323.
40. L. C. G. Freitas, DIADORIM program, version 3.0, Departamento de Química, UFSCar, São Carlos, 1999.
41. W. L. Jorgensen, J. Chem. Phys., 1983, 86(26), 5304.
42. SPARTAN 5.0, 1995, Wavefunction Inc., 18401 Van Karman Ave., Ste 370, Irvine, CA 92612.
43. M. Newmann, J. Chem. Phys., 1985, 82, 5663.
44. H. E. Alper and R. M. Levy, J. Chem. Phys., 1989, 91, 1242.
45. R. W. Zwanzig, J. Chem. Phys., 1954, 22, 1420.
46. D. L. Beveridge and F. M. DiCapua, Annu. Rev. Biophys. Biol., 1989, 18, 431.
47. J. C. Owick and H. A. Scheraga, Chem. Phys. Lett., 1977, 47, 600.
48. A. A. Kozyro, A. P. Simirskii and V. S. Markovinik, Russ. J. Phys. Chem. (Transl. of Zh. Fiz. Khim.), 1988, 62, 895–897.
49. W. L. Jorgensen, J. Chandrasekhar, J. D. Madura, R. W. Impey and M. L. Klein, J. Chem. Phys., 1983, 79, 926.
50. J. F. Coetzee and C. D. RitchieSolute–solvent interactions, Marcel Dekker, New York, 1969.
51. C. J. Cramer and D. G. Truhlar, J. Comput. Aided Mol. Des., 1992, 6(6), 629.
52. V. Yu. Bezzabotnov, L. Cser, T. Grósz, G. Jancsó and Yu. M. Ostanevich, J. Phys. Chem., 1992, 96, 976.
53. G. Barone, G. Castronuovo, C. D. Volpe and V. Elia, J. Solution Chem., 1971, 6, 117.
54. R. Sayle, RASMOL Program, v. 5, Biomolecular Structure Group, Glaxo Research & Development, Stevenage, UK, 1994.
55. R. C. Rizzo and W. L. Jorgensen, J. Am. Chem. Soc., 1999, 121, 4827.
56. M. Neumann, Mol. Phys., 1983, 50, 841.