Thesis advisor: X. Peter Zhang / Halogenated compounds are useful synthetic organic molecules. One valuable tool for synthesizing halogen containing molecules are atom transfer radical addition (ATRA) reactions which can difunctionalize olefins with a halogen moiety. Many transition complexes can catalyze these reactions but have drawbacks such as the need for harsh conditions and additives. Herein we describe the first ATRA reaction catalyzed by cobalt metalloradical catalysis (Co-MRC) which shows a broad substrate scope, moderate temperatures and uses no additives. This reaction showed excellent regioselectivity, when applicable, and low levels of enantioselectivity (up to 33% ee). / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.