Charge switching

Model system Gas phase barrier height (kcal/mole) Rate of charge switching Rmd Rkr koh... 

Notice that in every example of carbocation rearrangement the migrating atom (or group) and the (+) charge switch places. 

The dynamics of this reaction is considerably more complex to simulate and to understand than that of the model Cl -I- CI2 reaction, because of the longer range Coulomb forces among solvent molecules and between solvent and solute as well as the charge switching involved in the charge transfer aspect of the reaction. In this section, we will concentrate primarily on the separate efforts of Wilson, Hynes, and co-workers > ° i° and of Warshel and co-workers o "i° used to simulate this reaction. 

The second term in Eq. [3] is a charge switching force, which results from the motion of the charge among the reactant atoms. Its inclusion is vital not only in achieving energy conservation in the trajectories, but also in interpreting the results of the dynamics. 

In the first case, charge switches from one substance to the other—as is the case in all homogeneous reactions where ions participate—but remains at the same level of potential In the second case, Ca + and migrate from the solid substance into the solution, but the charges carried along compensate for each other so that the... 

Radovic-Moreno AF, Lu TK, Puscasu VA, Yoon CJ, Danger R, Farokhzad OC. Surface charge-switching polymeric nanoparticles for bacterial cell wall-targeted dehvery of antibiotics. 2012. 

Figure 4. Current and charge switching profiles for (a,b) electrostatic and (c,d) H-bond PANI LBL films. Step duration was 5 s, limits 0.6 V and -0.2 V.

Yang, K., Dilthey, B.G. and Gross, R.W. (2013) Identification and quantitation of fatty acid double bond positional isomers A shotgun fipidomics approach using charge-switch derivatization. Anal. Chem. 85, 9742-9750. 

Hoare, T. and Pelton, R. (2008) Charge-switching, amphoteric glucose-responsive microgels with physiological sweUing activity . Biomacromolecules, 9,733-740. 

Charge switching rate r Is the standard value, r Is one half of the Case A value, r Is one eighth of the Case A value. 

Charge switching rate r Is one half that of the value for Case B, as described In Ref. 10. 

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