Ionic spedes

Abraham, M. H., Zhao, Y. H. Determination of solvation descriptors for ionic spedes hydrogen bond addity and basicity. J. Org. Chem. 2004, 69,... 

In PhCl, reaction of [IrMe(CO)2l2]2 with CO to give [IrMe(CO)3l2] and onward reaction to give [Ir(C(0)Me)(C0)3l2] was followed by IR at temperatures up to 85 °C. The reaction is 700 times faster than the migratory carbonylation of the corresponding ionic spedes, [IrMe(CO)2l3] . A further enhancement of rate for the neutral species is observed in MeOH/PhCl. 

In fact, the values of n,m, and p will depend on the initiation pathway prevailing in the system, the values of the equilibrium constants for the relevant interactions, the aggregation state of the ionic spedes (intermediates and chain carriers), and of course... 

It is of interest to note that the systems studied till now are either-or , i.e. involving propagation exclusively dominated either by ionic species or by covalent ones. Up to now, the ionic species were found to be much more reactive than covatent ones. This can be explained on the basis of two models of 8 2 reactions involving attadc on covatent and ionic spedes, e.g. ... 

It is important to note that (i) all Arrhenius acids are Bransted adds but all Arrhenius bases are not Bransted bases, and (ii) Brans-ted-lower concept is not limited to molecules to act as acids and bases but ionic spedes may also be considered as adds or bases. 

Ed and E, may be expressed as integrals involving the molalities, activity coefficients and transport numbers of the several ionic spedes at all parts of the transition layer between the two electrode solutions. If however is made to tend to zero, the two electrode solutions approach identity and... 

This method is for generating carbocation from a dormant carbon-halogen (often chloride) bond, activated with a weak Lewis acid, such as iodine and zinc halides (Scheme 3). Suitably nucleophilic counteranions capture ionic spedes fast and effectively to convert them into the dormant counterparts. This method is suitahle for polymerization of active monomers induding VEs and p-alkoxystyrenes. 

Control of polymerization can be difficult with a nucleophilic counteranion if a strong Lewis add is used. An active catalyst would produce more free ionic spedes, some of which cause side reactions. The addition of an appropriate additive such as a Lewis base and a quaternary ammonium salt into a reaction with a strong Lewis acid shifts the equilibrium to induce living polymerization. 

The mechanism of initiation of anionic polymerization of vinyl monomers with alkyllithium compotmds and other organo-metallic compounds is complicated by association and cross-association phenomena in hydrocarbon solvents and by the presence of a variety of ionic spedes in polar media. ° The kinetics of initiation are complicated by competing propagation and the occurrence of cross-association of the alkyllithium initiator with the propagating organolithium. Thus, only the initial rates provide reliable kinetic data. 

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