Synthesis and crystal structures of (2E)-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione and (2E)-1,4-bis(4-bromophenyl)but-2-ene-1,4-dione

Abstract

The molecular structure of (2E)-1,4-bis(4-chlorophenyl)but-2-ene-1,4-dione [C16H10Cl2O2, (1)] is composed of two p-chlorophenyl rings, each bonded on opposite ends to a near planar 1,4-trans enedione moiety [–C(=O)—CH=CH—(C=O)–] [r.m.s. deviation = 0.003 (1) Å]. (2E)-1,4-Bis(4-bromophenyl)but-2-ene-1,4-dione [C16H10Br2O2, (2)] has a similar structure to (1), but with two p-bromophenyl rings and a less planar enedione group [r.m.s. deviation = 0.011 (1) Å]. Both molecules sit on a center of inversion, thus Z′ = 0.5. The dihedral angles between the ring and the enedione group are 16.61 (8) and 15.58 (11)° for (1) and (2), respectively. In the crystal, molecules of (1) exhibit C—Cl...Cl type I interactions, whereas molecules of (2) present C—Br...Br type II interactions. van der Waals-type interactions contribute to the packing of both molecules, and the packing reveals face-to-face ring stacking with similar interplanar distances of approximately 3.53 Å.

Keywords

• crystal structure
• synthesis
• 1,4-enedione moiety
• bis-halo-enedione
• NMR