Syntheses of potential initiators N-(O-(1-phenylethyl)oxy)phthalimide, N-(O-(1-phenylmethyl)oxy)phthalimide (POP), cyclohexanone-O-(1-phenylethyl)oxime, and cyclohexanone-O-(1-phenylmethyl)oxime (CHPO) are described. Bulk polymerization of styrene in the presence of POP or CHPO and molecular weight measurement by GPC indicate that the polymerization is not a living process. Ab initio calculations show that the C-O or O-N bond cleavage energies of POP and CHPO are close to each other (3: C-O: 46.4, O-N: 47.3 kcal/mol; 1: C-O: 46.9, O-N: 63.0 kcal/mol) and much higher than the similar analogs of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) (C-O: 20.9, O-N: 34.4 kcal/mol). The similar CO and O-N bond cleavage energies of the synthesized initiators (POP/CHPO) indicate two possible cleavage pathways and may explain the non-living nature of the polymerization. These results may be helpful in finding future reversible terminator compounds for living polymerization.