Electronic effects in organic reaction

Beyond simply classifying reagents, organic chemistry also needs a way to explain WHY particular parts of a substrate molecule end up being electron-rich or electron-deficient in the first place, since that is exactly what lets a nucleophile or an electrophile find something to attack. The general name for this is an ELECTRONIC EFFECT: the displacement of an organic molecule's own valence electrons, in a way that leaves the molecule POLARISED (carrying regions of relatively greater or lesser electron density). Electronic effects fall into two genuinely distinct categories, based on WHEN they operate. A PERMANENT electronic effect is one that is already present in the molecule's ordinary GROUND state -- that is, it exists all the time, regardless of whether any reagent happens to be nearby -- and it arises because of some specific atom, substituent, or structural feature that is simply built into the molecule itself. This chapter develops two distinct examples of a permanent electronic effect in the sections immediately following: the INDUCTIVE effect (section 14.6.4) and the RESONANCE effect (sections 14.6.5-14.6.6). A TEMPORARY electronic effect, by direct contrast, only arises in the first place because a reagent happens to be APPROACHING or actively attacking the substrate at that moment -- this is called the ELECTROMERIC effect (or polarisability effect), developed later in section 14.6.7. Together, this permanent-versus-temporary framework -- inductive …