Atom transfer radical polymerization (ATRP) has been a promising technique to provide polymers with well-defined composition, architecture, and functionality. In most of the ATRP processes, alkyl halides are used as an initiator. We report the synthesis of three possible potential initiators, N-phenyl(3-bromo-3-methyl)succinimide, N-phenyl(3-bromo-4-methyl)succinimide, and N-phenyl(3-bromomethyl)succinimide for ATRP of N-phenylitaconimide (PI) and methyl methacrylate (MMA). These functionalized alkyl halides, having structural similarity with PI, were characterized by FTIR, HRMS, 1H, 13C NMR spectroscopy, and elemental analysis. The equilibrium constants for the ATRP activation/deactivation process (KATRP) of these alkyl halides as well as a commercial ATRP initiator (ethyl-α-bromoisobutyrate) were determined using UV-Vis-NIR and DOSY NMR spectroscopy. Alternatively, these compounds and similar alkyl halides (R-X) were investigated using density functional theory for their possible chain initiation activity for the ATRP process. The B3LYP functional and 6-31+G(d)/LanL2DZ basis set was used for the prediction of geometries and energetics associated with the homolytic R-X bond dissociation. The relative value of KATRP and its variation with system parameters (such as substituent, temperature, and solvent) was investigated. We found a good agreement between the experimentally determined and theoretically calculated KATRP values. Our experiments show that the newly synthesized initiator N-phenyl(3-bromo-3-methyl)succinimide performs better than the commercially available initiator ethyl-α-bromoisobutyrate for the atom transfer radical copolymerization of PI and MMA. This journal is © the Partner Organisations 2014.