4-[2,4,6-tris(1-methylethyl)benzoyl]benzoic acid (S)-(-)-proline

The title compound, C23H28O3.C5H9NO2, is a 1:1 complex of the benzoic acid derivative and the (S)-proline zwitterion, with two formula units in the asymmetric unit (with pseudo-symmetry relationships between the separate components). The ketone carbonyl group in each benzoic acid molecule deviates slightly from a position normal to the plane of the triisopropylphenyl ring; the deviations (of about 16 degrees) are in opposite senses in the two molecules, so that the molecules have opposite conformational chiralities, leading to a nearly racemic photoproduct on solid-state photolysis.