Nitrile-forming eliminations from $(E)-2,4,6-(NO_2)_3C_6H_2CH=NOC_6H_4-2-X-4-NO_2$ (1) promoted by $R_3NH/R_3NH^+$ in 70 mol % MeCN(aq) have been studied kinetically. When X = $NO_2$, the reactions exhibited second-order kinetics as well as Br$"{o}$nsted ${eta}$ = 0.63 and ${mid}{eta}_{lg}{mid}$ = 0.34-0.46, and an E2 mechanism is evident. As the leaving group was made poorer (X = H, Cl, and $CF_3$), Br$"{o}$nsted ${eta}$ value increased from 0.63 to 0.85-0.89 without much change in the ${mid}{eta}_{lg}{mid}$ value E2, indicating that structure of the transition state changed to an E1cb-like with extensive $C_{eta}-H$ bond cleavage, significant negative charge development at the ${eta}$-carbon, and limited $C_{alpha}$-OAr bond cleavage.