Two nitro-alpha-methoxy-trans-chalcones

The crystal structures of 2-methoxy-3-(3-nitrophenyl)-1-phenylprop-2-en-1-one, C16H13NO4, (Ia), and 2-methoxy-3-(2-nitrophenyl)-1-phenylprop-2-en-1-one, C16H13NO4, (Ib), are reported. These two molecules are constitutional isomers differing in the position of the nitro group attached to one of the phenyl rings. The central double bond has a trans configuration in both structures. The conformations of the two molecules are very similar, except that in compound (Ia), the phenyl ring with the nitro substituent is nearly coplanar with the nitro group and the double bond, while in (Ib), there are significant deviations from coplanarity of these moieties.