The Structure of Bases Obtained from Heterocyclic Quaternary Ammonium Salts

The Structure of Bases Obtained from Heterocyclic Quaternary Ammonium Salts 

Anionotropy and prototropy are, obviously, processes that mutually oppose each other. The more polar the C—OH bond in (5), i.e., the more the equilibrium (5) (4) will favor (4) [or in other words, the 

The polarity of the C—-OH bond, i.e., the basicity of the carbinol-amine, depends on its structure, particularly on the stability of the ring system (degree of aromatic character), and the electron affinity of the substituents on nitrogen and carbon. Of course, external factors also play an important role in the equilibrium temperature, polarity of the solvent, and presence or absence of catalysts (the solvent can also act as a catalyst). 

Combination of the hydroxyl ion with the mesomeric cation involves the removal of a double bond. For the quaternary pyridinium compounds this causes the total loss of the aromaticity. For quaternary quinolinium and isoquinolinium compounds, the aromatic character of one of the two rings is lost, and for the quaternary acridinium compounds that of one out of three. Hence., the order of stabilities of these compounds (determined by Hantzsch ) is explained. - Comparison of quaternary 3,4-dihydroisoquinolinium compounds and their isoquinolinium analogs with respect to the equilibrium (5) (4) shows that a much higher hydroxyl ion concentration is necessary for the isoquinolinium ions to form the carbinolamine. This is because the transition from the quaternary 3,4-dihydroisoquinolinium ions into the undissociated carbinolamine involves significantly smaller loss of mesomeric energy than that for the quaternary isoquinolinium hydroxides.  

The naturally occurring bases usually contain a methyl group as a substituent on nitrogen. Methyl or other electron-repelling groups on 

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