Issue October 2002

category image Volume 20
No. 2 (p 141-310)
October 2002
ISSN 0739-1102

On the Protonation Equilibrium for the Benzimidazole Derivative Hoechst 33258: An Electronic Molecular Orbital Study (p. 301-310)

Hoechst 33258 and its deprotonated forms have been examined in the gas-phase and in solution using quantum mechanical methods. Ab initio calculations at the HF level have been used to investigate the more relevant geometrical trends of such species, while proton affinities and gas-phase basicities were derived from B3LYP and MP2 electronic energies. Solvation energies were calculated using a dielectric continuum model: MST. The ΔpKa values were estimated by combining the gas-phase basicities and the free energies of solvation. Comparison of these ΔpKa values with experimentally reported data have been used to highlight the advantages and limitations of this strategy.

Carlos Alemán1,*
Amitava Adhikary2,a
David Zanuy1,b
Jordi Casanovas3,**

1Departament
d?Enginyeria Química
E.T.S. d?Enginyers
Industrials de Barcelona
Universitat Politècnica de Catalunya
Diagonal 647
Barcelona E-08028, Spain
2Physikalisch Chemisches Institut
Im Neuenheimer Feld 253
D-69120 Heidelberg, Germany
3Departament de Química
EUP, Universitat de Lleida
C/Jaume II 69
Lleida E-25001, Spain
aOn leave from:
Department of Chemistry
Rajdhani College
University of Delhi
Raja Garden
New Delhi 110015, India
bPresent Address:
Laboratory of Experimental and Computational Biology
NCI-Frederick
Bldg 469, Rm. 151
Frederick MD, 21702, USA
*carlos.aleman@upc.es
*jcasanovas@quimica.udl.es

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