Kharasch brought free radicals, previously considered esoteric species, into the mainstream of organic chemistry. His experiments on the addition of hydrogen bromide to the carbon-carbon double bond of allyl bromide showed that anti-Markownikoff addition (to give 1,3-dibromopropane) was a free radical chain process initiated by peroxides present in old samples of the allyl bromide, whereas in the absence of peroxides addition occurred by the usual ionic mechanism in the Markownikoff sense (to give 1,2-dibromopropane). Elaboration of this chemistry lead to the invention of numerous synthetically useful free radical chain reactions (examples include alkane chlorination with sulfuryl chloride, alkane carboxylation with oxalyl chloride, additions to alkenes of carbon tetrachloride, bromotrichloromethane, bromo esters, and many others). In other researches, Kharasch made pioneering studies on organomercurials important in agriculture (as seed disinfectants) and medicine (the antiseptic merthiolate), in polymer chemistry and on reactions of Grignard reagents (with O. Reinmuth he co-authored a 1267-page book on this subject).
Kharasch came to Chicago from the Ukraine at the age of 13, and spent most of his professional career at the University of Chicago. He was an excellent teacher, and many of his students went on to impressive careers of their own (three are represented in this portrait collection, H. C. Brown, C. Walling and F. H. Westheimer). Kharasch was a founder of the Journal of Organic Chemistry, a member of the National Academy of Sciences and received awards such as the Scott Award of the Franklin Institute (1949) and the Richards Medal of the ACS (1952).