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Year 2007, Month 12 (Section Full Articles, Page 2376)

Solvent effect on the equilibrium constant of the chain reversible reaction of N,N´-diphenyl-1,4-benzoquinonediimine with 2,5-dichlorohydroquinone

S. Ya. Gadomsky and V. T. Varlamov

The temperature dependences of the equilibrium constant K of the reversible chain reaction of N,N´-diphenyl-1,4-benzoquinonediimine with 2,5-dichlorohydroquinone in benzene, chlorobenzene, anisole, benzonitrile, and CCl₄ were studied. The enthalpies and entropies of the reaction in these solvents were determined, and a linear dependence between them in aromatic solvents was found. The equilibrium constant depends on the solvent nature: the replacement of CCl₄ by benzene at Т = 298 K increases K from 13.6 to 140. The solvation effects are caused by several types of intermolecular interactions of participants of equilibrium with the medium. The decrease in K in the benzene—anisole—benzonitrile series is related, to a great extent, to complex formation with hydrogen bonding between 2,5-dichlorohydroquinone and the solvents. In anisole a charge-transfer complex is formed between the solvent and reaction product (2,5-dichloroquinone). The constant and enthalpy of the complexation were estimated.

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