Equilibrium constants have been measured at 25° for the formation of pseudobases from the 2-methyl-phthalazinium, 1-methylquinoxalinium, 1-methyl- 1,5-naphthyridinium, 6-methyl-1,6-naphthyridinium, 7-methyl-1,7-naphthyridinium, 1-methyl-1,8-naphthyridinium, 1-methyl-3-nitroquinolinium, and 2-methyl-4-nitroisoquinolinium cations. Ionization constants have also been obtained for ionization of some of these pseudobases to alkoxide anions. For each cation the site of hydroxide attack has been determined by comparison of the u.v. and p.m.r. spectra of the pseudobases, the corresponding methoxide adducts, and the lithium aluminum hydride reduction products. In all cases, except for the 1-methylquinoxalinium cation, only one major pseudobase species is present in solution, and ring-opening does not occur to any appreciable extent. The pseudobase of the 1-methylquinoxalinium cation exists in equilibrium with a considerable amount of its covalent hydrate from addition of water across the C3—N4 bond.

The kinetics of the formation and decomposition of the pseudobases from the 2-methyl-4-nitroisoquinolinium, 10-methylacridinium, and 10-methyl-9-phenylacridinium ions have been studied. The pH-rate profiles of these reactions indicate that for each of these ions, pseudobase formation may kinetically involve either attack of a water molecule or of hydroxide ion on the heterocyclic cation depending upon the pH of the reaction. Pseudobase decomposition to the cation may occur through either the neutral or protonated pseudobase species or their kinetic equivalents. The temperature dependences of the equilibrium and kinetics are reported for each ion, and deuterium isotope effects for the reactions of the 2-methyl-4-nitroisoquinolinium ion have been measured. Possible mechanisms for the reactions are discussed on the basis of the observed activation parameters and isotope effects and are compared with related reactions.L.es cinetiques de formation et de decomposition des pseudobases a partir des ions du methyl-2 nitro-4 isoquinolinium, methyl-10 acridinium et methyl-10 phknyl-9 acridinium ont etC Ctudiees. Les profils de vitesse en fonction du pH de ces reactions indiquent que pour chacun de ces ions, la formation de la pseudobase fait intervenir cinktiquement, soit l'attaque d'une molCcule d'eau soit un ion hydroxyde sur le cation hCtCrocyclique selon le pH de la reaction. La dCcomposition de la pseudobase en cation pourrait se produire soit par I'intermidiaire de la pseudobase sous forme neutre ou protonee ou encore leurs equivalents cinetiques. Les Cquilibres et les cinitiques en fonction de la temperature ont CtC rapportes pour chaque ion; les effets isotopiques du deuterium pour les rCactions de I'ion methyl-2 nitro-4 isoquinolinium ont ete mesurts. Les mecanismes possibles de ces reactions ont ete discutCs i partir des parametres d'activation observes et des effets isotopiques, puis compares aux reactions apparentees.[Traduit par le journal]Can. J . Chem., 51. 1965 (1973) Recently, we reported (1) the structures of the pseudobases (QOH) formed by the addition of hydroxide ion to various aromatic N-methyl heterocyclic cations (Q'), and also equilibrium constants for pseudobase formation (eq. 2; K, is the ionic product of water). We have nowcarried out a comprehensive study of the kinetics of pseudobase formation and decomposition for three such quaternary heterocyclic cations: the 10-methylacridinium2 (1; R = H), 10-methyl-9-phenylacridinium (1; R = Ph), and 2-methyl-4-nitroisoquinolinium (3) ions. The pH-rate profiles and temperature dependences 'For Part I, see ref.1. 'We previously referred to this cation as the 9-methylacridinium ion (1). In the IUPAC systematic nomenclature this is the 10-methylacridinium ion (2).of these reactions have been determined and have been used to interpret the reaction mechanisms. In addition, hydrogen isotope effects have been measured for the reactions of 3 and 4 and preliminary measurements of the catalytic effects of buffer species have been made. We have been unable, at t...

Pseudobase formation and methoxide ion addition have been investigated spectroscopically for some N-methylacridinium, -phenanthridinium, and -benzoquinolinium cations. Susceptibility to nucleophilic attack decreases in the order 10-methylacridinium (pKnorr = 9.86) > 5-methylphenanthridinium (pKnoa = 11.94) > 1-methyl-5,6-benzoquinolinium = 1-methyl-7,8-benzoquinolinium (~Knorr > 14). A qualitative correlation of pKnorr with loss of resonance energy upon pseudobase formation is shown to exist. For the 9,lO-dimethylacridinium cation, the C-9 pseudobase (or methoxide adduct) is the kinetically preferred product in basic solutions but this is subsequently converted to the thermodynamically more stable anhydrobase. With the corresponding 9-ethyl-and 9-benzyl-10-methylacridinium cations, the pseudobase, rather than the anhydrobase, seems to predominate at equilibrium.On a examine B l'aide de la spectroscopie la formation de pseudobases et l'addition d'ion mtthylate pour quelques cations tels N-m&thylacridinium, phtnanthridinium et benzoquinoltinium. La susceptibilitt de I'attaque nucltophile diminue dans l'ordre mtthyl-10 acridinium (pKnorr = 9.86) > methyl-5 phtnanthridinium ( p K n o~ = 11.94) > mtthyl-1 benzoquinoltinium-5,6 z mtthyl-1 benzoquinoltinium-7,8 (pKno11 > 14).On a montrt qu'une relation existe entre le p K n o~ et la perte d'tnergie de rkonnance lors de la formation de pseudobases. En solution basique, la pseudobase C-9 (ou I'addition de mtthylate sur) du cation dimtthyl-9,10 acridinium est obtenue par contrble cinttique, mais elle est transformte en anhydrobase thermodynamiquement plus stable.Parcontre la pseudobase plutbt que l'anhydrobase semble &tre majoritaire B l'equilibre pour les cations tthyl-9 et benzyl-9 mtthyl-10 acridiniums.[ Although Hantzsch and Kalb (1) first recognized the formation of the pseudobase (2; R = H) by hydroxide ion addition to the 10-methylacridinium cation (1; R = H) in 1899, it was not both this cation and the 10-methyl-9-phenylacridinium cation (1; R = C,H,).Magrath and Phillips (5) have also reported equilibrium constants for pseudobase formation from the 5-methylphenanthridinium (3; R = H; pKRoH = 10.4) and 5,6-dimethylphenanthridinium (3; R = CH,; pKRoH = 10.1) cations which suggest that the N-methylphenanthridinium cation is only slightly less susceptible t o pseudobase formation than its acridinium isomer. pendence of the equilibrium constant for pseudoWe have now extended these studies t o a series base formation upon the structure of the hetero-of 9-substituted-10-methvlacridinium cations and cyclic cation andwe later measured (4) the rates some other tricyclic caiions that are isomeric of pseudobase formation and decomposition for with 1 (R = H). Owing to thegeneral insolubility of the pseudobases in aqueous solution at p.m.r.

Contrary to previous reports, the methylation of quinazoline with methyl iodide has been shown to produce both 1-methylquinazolinium iodide and 3-methylquinazolinium iodide. These quaternary salts are formed in the ratio of 5:1 in favor of the latter isomer.

Equilibrium constants (pKRoH) have been measured for pseudobase formation from the 1-methyl-x-nitroquinolinium cations (x = 5-8), the N,N1-dimethyl-1,5-, -1,6-, a n d -2,7-naphthyridinium dications and various N-substituted quinolinium, isoquinolinium, 5-nitroisoquinolinium, and 1,8-naphthyridinium cations. The pKRoH values for N-substituted 5-nitroisoquinolinium and 1,s-naphthyridinium cations are correlated by the equations pKRoH = -3.7cr* + 11.6 and pKRoH = -4.9cr* + 12.5, respectively (cr* is Taft'ssubstituent constant for the substituent on nitrogen).Proton magnetic resonance and u.v. spectral data have been used to assign the structures of the pseudobases formed from each of the above cations. In several cases ylide formation rather than pseudobase formation has been observed. The N,N1-dimethylnaphthyridinium dications are shown to form zwitterionic alkoxide ions in strongly basic aqueous solution, rather than undergoing attack by a second hydroxide ion.Equilibration between cation and pseudobase occurs at rates near or beyond the limit of the stopped-flow technique for all the above cations, except the 2-cyanomethyl-5-nitroisoquinolinium cation. An analysis of the pH--rate profiles for reversible pseudobase formation from this latter cation is given.On a determine les constantes d'tquilibre (pKRoH) pour la formation de pseudobases a partir des cations mtthyl-1 nitro-x quinoleiniums (x = 5-8) des dications N,N'-dimethyl naphtyridiniums-1,5, -1,6, -2,7, et de divers cations N-substitutts quinoleiniums, isoquinoleiniums, nitro-5 isoquinolCiniums et naphtyridiniums-1,s. On a relit les valeurs de pKRo,, des cations N-substituts nitro-5 isoquinoltiniums et naphtyridiniums-1,s par les equations suivantes: pKROH = -3.7cr* + 11.6 et pKRoH = -4.9cr* + 12.5 (cr* est la constante de substituant de Taft pour le substituant sur l'azote).On a utilist les spectres r.m.n. et u.v. pour attribuer les structures des pseudobases obtenues de chaque cation mentionnt ci-haut. Dans plusieurs cas on a observe la formation d'ylides plutBt que de pseudo-bases. On a montre que les cations N,N1-dimethyl naphtyridiniums forment, dans des solutions fortement basiques, des alcoolates ampholytes au lieu de subir une attaque par un second ion hydroxyde.Pour tous les cations ttudits, except6 le cation cyanomtthyl-2 nitro-5 isoquinoleinium, l'equilibre se fait a une vitesse proche ou au-dela de la limite d e la technique a dtbit arr&tC. On mentionne une analyse de la courbe de p H pour la formation rdversible de pseudobase i~ partir de ce cation.[Traduit p a r le journal]Can. J. Chem., 52,962 (1974)As a further extension of our quantitative studies (1, 2) of pseudobase formation from heteroaromatic cations, we now wish to present equilibrium data for some substituent effects on pseudobase formation from substituted quinolinium, isoquinolinium, and related cations. In addition to measuring pKRoH values for each cation, in each case we have investigated the reaction by U.V. and p.m.r. spectroscopy to ensure that pseudobase formation is the pre...