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Updated: Jun 1, 2026
06:44
From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
1-(2,5-Dichloro-3-thien-yl)ethanone: infinite sheets mediated by O⋯Cl halogen bonds
Abstract:
In the title compound, C(6)H(4)Cl(2)OS, the acetyl group is almost coplanar with the thio-phene ring [dihedral angle = 4.01 (2)°]. In the crystal, short inter-molecular O⋯Cl contacts [2.9494 (14) and 3.1191 (14) Å] link the mol-ecules into infinite (100) sheets and aromatic π-π stacking [centroid-centroid separation = 3.5422 (10) Å] consolidates the packing.
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Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
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Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
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Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
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