Complex sentence: He obtained his Ph.D. in chemistry from Northwestern University working with G. Ludwig Hofacker, did postdoctoral work in Aarhus and Munich with Jan Linderberg, and taught chemistry at New York University from 1970 until 1974.
Split into simpler sentences: He obtained his Ph.D. in chemistry from Northwestern University working with G. Ludwig Hofacker, did postdoctoral work in Aarhus and Munich with Jan Linderberg. Ratner taught chemistry at New York University from 1970 until 1974.