Local hardness: An application to electrophilic additions

Theoretical studies of reactivity and selectivity in some organic reactions

“…Hence, it becomes more reactive for a electrophilic attack, the carbon C 2 instead of C 1 , suggesting an anti-Markovnikov mechanism. However, note that the differences in the local hardness between carbon C 1 and C 2 are low [14].…”

“…This is due to the stabilization of the carbocation by the electron-donating groups, whereas the electron-withdrawing groups destabilize the formed carbocation, and prefer to form a primary carbocation in spite of being less stable. Note that the activation energies for the ethylenes with electron-donating groups are lower than the activation energy for the addition of the HCl to ethylene, whereas the activation energies of the ethylenes with electron-withdrawing groups are greater than the one for ethylene [14]. Experimental activation energies of the addition of hydrogen chloride to CH 2 CHR systems are …”

“…Note, however, that the difference between the Markovnikov-type reaction energy and the anti-Markovnikov-type reaction energy in the ethylenes with electron-donating groups are greater than in the ethylenes with electronwithdrawing groups. Again, the molecules CH 2 CHCOF and CH 2 CHNO 2 follow the anti-Markovnikov's rule [14].…”

“…In this article, it is shown that the Markovnikov's rule may be also interpreted applying the local hardness index to substituted ethylenes taking in account the electronic effects of the substituent groups [14].…”

“…In the following, the local hardness of Eq. (1) will be evaluated as an orientation index for electrophilic addition reactions [14].…”