Zwitterions s. Betaines

Figure 1.12 Reichardt s betaine dye in its zwitterionic ground state (a) and first excited state (b). The ground state has a larger dipole moment (15 D) than the excited state (6 D). Measurement of the energy of the transition between these two states (n - n ) is the basis for the Ej scale of solvent polarity...

The effect of a-n coupling in a series of donor/acceptor organic molecules including zwitterions and betaines has been investigated within an INDO/S sum over state approximation by Rao and Bhanuprakash.177 Yuan et al.m have investigated structural effects on ft using the CNDO/S Cl sum over states approach. 

Benzylidenehydrazinoselenazoles, by Hantzsch s synthesis, 232 table of products, 233 Betainic zwitterion, in nitrophenacvl substitution. 33... 

Proton donors may be present or formed at the beginning of copolymerization and are necessary for the formation of primary active centres. In such a case, initiation according to Fischer s mechanism 39,40 (Eq. (37)) does not take place. Although the formation of a zwitterion (betaine-like structure) supports the possibility of the generation of charge-transfer complexes between cyclic anhydrides and amines, which may yield betaine-like structures82), simple anhydrides are much weaker ti acceptors than the often employed tetrachlorophthalic anhydride. 

Snow, S.A., Fenton, W.N. and Owen, M.J. (1991) Zwitterionic organofunctional siloxanes as aqueous surfactants - synthesis and characterization of betaine functional siloxanes and their comparison to sulfobetaine functional siloxanes. Langmuir, 7(5), 868-71. 

The ideal addition polymerization is one in which there are no termination or transfer reactions, initiation (betaine formation) is instantaneous and kp lies between 102 and 104 1 moP1 s-1. Such polymerizations can be conveniently followed by adiabatic calorimetry. At very high initiator concentrations it should be possible to measure the rates of the first monomer additions and isolate zwitterion oligomers for study. Cyanoacrylate polymerizations initiated by phosphine satisfy all these conditions except the last. kp is 1051 mol-1 s-1 at —78°C. However, cyanoacrylates with more bulky alkyl substituents may have smaller kp s. It is possible that methylene malonate polymerizations may fulfil the above requirements. 

The alkylamidopropyl betaines, as a rule, are compatible with the anionic detergents over a wide range of concentration. The simpler alkyl betaines show some incompatibilities with alkyl sulfates at concentrations at which the betaine s concentration is about one half that of sodium lauryl sulfate [15-17]. The nature of these incompatibilities is largely dependent on the nature of anionic species present. The pH of the system also plays a role in compatibility. At the pHs normally encountered in shampoos, a competitive reaction occurs between the presumed zwitterionic inner salt and the complex salt formation from the interaction of the anionic detergent with the quaternary nitrogen. 

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