Stepwise Equilibria in Gas-Phase Reactions: The Alkylation of

In the Laboratory

Stepwise Equilibria in Gas-Phase Reactions: The Alkylation of Benzene

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E. Weltin Department of Chemistry, University of Vermont, Burlington, VT 05405

As part of a series of papers on practical calculations of equilibrium concentrations from given initial concentrations (1 ) we have extended the method for stepwise binding of ligands (2) to stepwise equilibria in gas-phase reactions. The essential modifications involve the effect of total pressure on the partial pressures and molar amounts at equilibrium. In the alkylation of benzene at elevated temperature, groups of isomers are formed (3). Alberty (4 ) has shown that such a group may be considered to be a single component in equilibrium calculations. Formally, the stepwise alkylation looks W Supplementary materials for this article are available on JCE Online at http://jchemed.chem.wisc.edu/Journal/Issues/1998/ Mar/abs370.html

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like the stepwise attachment of a ligand, (1/2) C2H4 , to a central species, C6H6 , forming complexes C7H8 to C10H14. The equations for the equilibrium composition for given initial amounts are solved for two different total pressures. A complete description is available on JCE Online at http://jchemed. chem.wisc.edu/Journal/Issues/1998/Mar/abs370.html. Literature Cited 1. Weltin, E. J. Chem. Educ. 1990, 67, 548. Weltin, E. J. Chem. Educ. 1991, 68, 486. Weltin, E. J. Chem. Educ. 1992, 69, 392. 2. Weltin, E. J. Chem. Educ. 1993, 70, 568. 3. Alberty, R. A. J. Phys. Chem. 1993, 97, 6226. 4. Alberty, R. A. J. Phys. Chem. 1985, 89, 880.

Journal of Chemical Education • Vol. 75 No. 3 March 1998 • JChemEd.chem.wisc.edu