Electron-withdrawing groups ranking

For reaction (a) to proceed, the Y group must form a stable Li salt. The reactivity of a carbon-element bond in Eq. (a) may be estimated by the acidity of the add, HY. Therefore, the ease of cleaving representative substrates by Li rank RCl > RSCgH > ROCgHj > RP(CgH5)2. However, even C—C bonds can be cleaved by Li when both carbon atoms contain electron-withdrawing groups. 

A Free-Wilson analysis by Borea of in vivo data of 55 benzodiazepines led to the following rank orders of contributions to activity of substituents at position 7 and 2 (as depicted in Fig. 5.9), thus showing the importance of electron withdrawing groups at these positions (111) ... 

CARBON ACIDS AND RANKING OF ELECTRON-WITHDRAWING GROUPS... 

Section 3.5 Carbon Acids Ranking of Electron-Withdrawing Groups... 

Haskins [6] also compared the empirical ranking of explosive behavior proposed by Bates and Jenkins [4] with one devised according to the total charge in the substituent group. Extended Hiickel molecular orbital (EHMO) calculations provided a quantitative measure of electron-withdrawing power of the substituents in the following order ... 

---