Electrophilic agents Elimination, rate

Steric effects on the rates of quaternization of quinoline are magnified as the size of the alkylating agent is increased in the series methyl, ethyl, and isopropyl iodide. In order to reveal the changing steric effect, it is first necessary to eliminate the reduction in rate that naturally occurs as the electrophilic carbon atom of the alkylating agent undergoes sub-... 

About (i) and (2) there can be no dispute, but (3) must be rejected. The implication that the nitronium ion, effectively freed from a close association with another entity, is not the nitrating agent in those reactions of benzene and its homologues, under conditions in which substantial intermolecular selectivity is observed, conflicts with previous evidence ( 3.2). Thus, in nitration in organic solvents and in aqueous nitric acids, the observation of kinetically zeroth-order nitration, and the effect of added nitrate on this rate, is compelling evidence for the operation of the nitronium ion. The nitric acidium ion is not the electrophile under these conditions, and it is difficult to envisage how a species in which the water is loosened but not yet completely eliminated could be formed in a slow step independent of the aromatic and be capable of a separate existence. It is implicit that this species should be appreciably different from the nitronium ion in its electrophilic properties. There is no support to be found for the participation of the aromatic in the formation of the electrophile. 

The rates of addition of nucleophiles to carbonyl groups and the rates of elimination from the tetrahedral intermediates constitute another class, probably similar to the activated aromatic nucleophilic substitution. The carbonyl group is an electrophile, and no obvious source of any barrier exists, outside of desolvation. Therefore, a resemblance to Ritchies systems is found. No obvious relation between our kinetic nucleophilic characters (Nx) and the additions occurs, but a possible parallel to the equilibrium methylating powers, KYX (in Tables I and II), of the conjugate methylating agent of the... 

Thus, three types of reactions were divided into reactions of nucleophilic and electrophilic substitution, addition, and elimination. The kinetic study showed that some reactions involving two reactants occur as bimolecular reactions, whereas others occur as monomolecular reactions with the rate proportional to the substrate concentration and independent of the agent concentration. Thus, all variety of heterolytic reactions involving two reactants is divided into the following 10 groups ... 

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