Two acetylamino derivatives of 2,4-bis(trichloromethyl)-1,3-benzdioxin showing different types of hydrogen bonding: (a) (C13C)CH?O=C and (b) N-H?O=C

Abstract

8-Acetylamino-6-methyl-2,4-bis(trichloromethyl)-1,3-benzdioxin, (I), is monoclinic,P21/c,a=15.174(4),b=11.977(7),c=9.911(3)A,β=99.72(2)°. 6-Acetylamino-2,4-bis(trichloromethyl)-1,3-benzdioxin, (II), is monoclinic,P21/n,a=5.927(4),b=40.623(1),c =7.120(3)A,β=91.39(4)°. In compound (I) the imino hydrogen atom is locked in an intramolecular hydrogen bond to the proximate oxygen atom of the heterocyclic ring and is not available for intermolecular hydrogen bonding. Instead the weakly acidic hydrogen atom [Cl3C-C(2)]H takes part in a hydrogen bond to the carbonyl oxygen atom in another molecule. In compound (II) a “normal” intermolecular hydrogen bond of the type N-H⋯O=C occurs. The 6-acetylam-ino group is twisted about the (CAr-N) bond such that the angles N′H′⋯O=C, CArHAr⋯O=C, N′H′⋯O⋯HArCAr, at the carbonyl oxygen group total 360° (where N′H′ is in the related molecule). The packing in both compounds takes the form of infinite chains and in compound (II) partial overlap of the aromatic ring and the acetylamino group, with very little offset, also occurs.