CHEM 233 Lecture Notes - Lecture 14: Conjugate Acid, Acid Dissociation Constant, Nucleophile
Document Summary
Important principle of chemical reactivity: halogen atoms connected to sp2 carbon centers do not undergo sn2 displacement. No displacement of the br attached to the sp2 carbon. Why: the the c-lobe of the * C br orbital must be readily accessible: the c br bond must be sufficiently polarized with a + on c and a on x. Recall that the following 4 requirements must be satisfied for an sn2 reaction to occur (noted of oct 2nd): In the specific case above, one recognizes that that the lobe of the * orbital associated with the. In addition, an sp2 c is more electronegative than an sp3 c (2. 65 vs. 2. 5). Therefore, an sp2 c br (halogen) bond is less polarized than an sp3 c br (halogen) one and less capable of attracting electrons from the nucleophile: sp2-c. = 0. 70 greater polarization more + on c sp2-c. = 0. 55 less polarized less + on c.
