(S)-(+)-Ibuprofen, alpha-methyl-4-(2-methylpropyl)-benzeneacetic acid,
crystallizes with two molecules in the asymmetric unit to form a cycl
ic hydrogen-bonded dimer. Within the dimer each molecule shows subtle
conformational differences via rotations about the acetic C(1)-C(2) an
d C(10)-C(11) bonds. Bond distances and angles for (S)-(+)-ibuprofen a
re in close agreement with those found for the structure of the racemi
c compound [McConnell (1974). Cryst. Struct. Commun. 3, 73-75].