203for data sets 5-8. For butanol, the value for A. was taken from Marcus (1977) and a good overall fit was obtained.The established additivity of Ff and Fb calculated from appropriate data is an indication, though not proof, of the validity of the proposed model.A few additional conclusions concerning the dissociation of the different acids in the alcohol can also be drawn from the model: HC1 is fully dissociated to ions. H,S04 is dissociated to H+ and HSO,, and also possibly slightly to SO:-. However, dissociation to SO4* cannot be significant, in view of the accuracy of the correlation that did not take this effect into consideration. HN03 appears to partly dissociate reversibly to N2OP This dissociation is a function of the amounts of total acids present.is not significantly dissociated to ions below concentrations of about 1 g-mol/kg of alcohol. AcknowledgmentWe are indebted to IMI Institute for Research and Development for permission to use ita proprietary data in this study. Nomenclature a = activity A , B = van Laar coefficients Ai, Bi = coefficients A. = concentration of water in alcohol phase in equilibrium with pure water E = percent error in correlation fc, f ' , . , f", = unit correction factors Fb = bound water concentration Ff = free water concentration H = linear coefficient K = distribution coefficient, chemical equilibrium coefficient N = number of experimental points X = mole fraction or molality in aqueous phase Y = mole fraction or molality in alcohol phase Greek Letters y = activity coefficient u = standard deviation Subscripts aq = aqueous 1 = species NH = unreacted HNO, S = solvent W = water Literature Cited Bromley, L. A. AIChEThe influence of water on guaiacol pyrolysis was examlned through a series of pyrolyses spanning reduced water densities from 0.00 to 1.6 at 383 'C. Neat guaiacol pyrolysis yielded catechol and char as major products and minor products including phenol and o-cresol; methanol was not observed. Water provided a parallel reaction pathway that was formally equivalent to guaiacol hydrolysis to catechol and methand. The overall reaction selectivity to hydrolysis was a continuous function of water density at the condiiins examined. The observed product spectra and qualitative kinetics were summarized in terms of free-radical steps for neat pyrolysis, to which guaiacol soivatlon and hydrolysis steps were added to account for the influence of water.

The importance of fit in the recognition reaction and the subsequent hydrolysis can be demonstrated by variation of the "receptor" of the barbituric acid (by methylation of the pyrimidine nitrogen atoms; lipid 2). At pH 3, TAP is inserted into the monolayer of lipid 2 significantly more slowly than into that of lipid 1 (slow disappearance of the aggregation band) due to steric hindrance caused by the space-demanding methyl groups. The rate of the hydrolysis of lipid 2 on a TAP-containing subphase at pH 6.5 is linked to the rate of the insertion (Fig. 6). The aggregation band is observed until the hydrolysis is complete. 0.61 250 300 350 400 450 500 550 600 A [nm) -Fig. 6. UVjVIS reflection spectra of lipid 2 on a 1 0 -4~ TAP subphase at pH 6.5. Slow insertion (slow disappearance of the aggregation hand) followed by hydrolytic cleavage of the C=C bond (see Fig. 2b).This experiment particularly emphasizes the importance of the organization of lipids at the gas-water interface. AIthough lipid 2 does not associate with TAP in CDCI, according to 'H NMR spectra, ['] it does at the gas-water interface even though the solvent is changed from an aprotic to a protic one. The preorientation of the recognition structure by the lipid monolayer ensures that the complex, otherwise weak in solution, is stabilized by this arrangement. In this system the formation of the complex is the rate-determining step.The importance of molecular recognition is underlined by the investigation of the interaction of the pyrazolidine-3,sdione lipid 3 with TAP at the gas-water interface. In this case the aggregation band of the chromophore is not interrupted by TAP, because the five-and six-membered ring structures of lipid 3 and TAP do not fit together well enough. The monolayer of lipid 3 is stable on a TAP-containing subphase at pH 3 and pH 6.5 (no changes at all in the UV/VIS reflection spectra).Preliminary experiments with subphases containing nucleobases indicate a defined interaction, for example, between cytosine and lipid 1, which is only possible via the enol form of the base. In addition, the reverse systems-water-soluble barbituric acid derivatives and monolayers of amphiphilic triaminopyrimidine and melamine derivatives-are currently under investigation.

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