Oxime formation from pyridine-2-, -3-, and -4-carboxaldehydes occurs with Tate-limiting carbinolamine dehydration under both acidic and neutral conditions. Carbinolamine dehydration of pyridine-2carboxaldehyde occurs via a transition state bearing a single positive charge, unlike the corresponding reaction for formyl-l-methylpyridinium ion and the reaction under acidic conditions for pyridine-3and -4-carboxaldehydes.Although certain equilibrium constants2-3 456and rate constants3 for addition of amines to pyridinecarboxaldehydes and to structurally related aldehydes including

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Rate and equilibrium constants for the addition of cyanide ion to a series of N-alkyl-3-carbamoylpyridinium ions are markedly increased by dilute solutions of n-alkyltrimethylammonium bromides. For example, 0.02 M hexadecyl surfactant increases the rate constant for addition of cyanide to the N-hexadecyl substrate 950-fold and increases the corresponding association constant about 25,000-fold. More concentrated solutions of these surfactants also elicit marked increases in rate and equilibrium constants for the same reactions although the increases are not quite so pronounced as with more dilute solutions. This may, in part, reflect inhibition by the surfactant counterion since it has been established that the surfactant-dependent reactions are sensitive to inhibition by anions. The effectiveness of anions as inhibitors increases in the order F-< NO3-< CI-< Br-. The extent of surfactant facilitation of the addition of cyanide ion to the pyridinium ions increases with increasing hydrophobicity in both surfactant and substrate, suggesting that hydrophobic interactions may contribute to the activation energies. The zwitterionic surfactant dodecyldimethylammoniopropane sulfonate increases the rate and equilibrium constants for addition of cyanide ion to N-dodecyl-3-carbanioylpyridinium bromide by 40-and 5000-fold, respectively. Finally, this same reaction is subject to promotion by sonicated aqueous dispersions of lecithin, lysolecithin, and sphingomyelin. series of studies in the past several years has estab-A lished that rate and equilibrium constants for a number of organic reactions are sensitive functions of the concentration of ionic s~r f a c t a n t s .~ In most such cases the observed effects are the consequence of adsorption of one or more of the reacting species onto or into micelles formed from the surfactants. Electrostatic and hydrophobic interactions between the substrates and the components of the micelle dominate both the adsorption process itself and the rate and extent of bond-changing reactions which follow.Since those factors which influence rates and equilibria of organic reactions may not only provide additional insight into the reaction mechanisms concerned but also yield data pertinent to enzyme-catalyzed reactions, it appears profitable to pursue the study of organic reactions in the presence of surfactants more fully. Moreover, recent results suggest that the presence of ionic micelles may be important in determining the course of organic reactions, as well as their rate and extent.4 In this study, the rate and equilibrium constants for the addition of cyanide ion to a series of Nsubstituted 3-carbamoylpyridinium ions have been determined in the presence of a series of n-alkyltrimethylammonium ions, one zwitterionic surfactant, and several biological lipids.

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