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Benzene, Aromaticity, and Benzene Derivatives
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Halogenation is the replacement of a hydrogen atom on a benzene ring with a halogen atom. Benzene reacts with halogens, in the presence of a suitable Lewis acid, to give a halobenzene (chlorobenzene, bromobenzene, or iodobenzene). What is the product when diatomic bromine reacts with ferric bromide (FeBr3)? With aluminum chloride (AlCl3)?
Elastic and electro-optical properties of flexible fluorinated dimers with negative dielectric anisotropy
Published in Liquid Crystals, 2022
Greta Babakhanova, Hao Wang, Mojtaba Rajabi, David Li, Quan Li, Oleg D. Lavrentovich
Bromobenzene (30 mL, 287 mmol) is added to the flask of aluminium chloride (7.07 g, 53 mol) and rapidly stirred under nitrogen for 1 hour (Figure 2(a)). After the solution is cooled in an ice-water bath, pimeloyl dichloride (5 g, 25 mmol) is dissolved in bromobenzene (5 mL, 48 mmol) and is added dropwise to the previous flask for over one hour. The solution is then heated to 45°C and stirred for 48 hours. The reaction is cooled to ambient temperature and poured into a solution of concentrated hydrochloric acid (100 mL) in an ice-water bath and water (100 mL) is added. Subsequently, dichloromethane is added to the solution to extract the organic compound four times. The organic part is dried over magnesium sulphate overnight. Dichloromethane is evaporated with a rotatory evaporator. The crude solid is purified by silica gel chromatography column with the eluent of hexane: ethyl acetate (1:1 volume ratio) to get 1,7-bis(4-bromophenyl)heptane-1,7-dione as colourless crystal with yield 10.26 g, 92%. 1H NMR (400 MHz, CDCl3): δ 7.81 (d, J = 8.6 Hz, 4H), 7.59 (d, J = 8.6 Hz, 4H), 2.92 (t, J = 7.3 Hz, 4 H), 1.76–1.69 (m, 4 H), 1.42–1.35 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 199.10, 135.69, 131.89, 129.56, 128.10, 38.22, 28.82, 23.88.
2-(4-Biphenylyl)-1,3,4-oxadiazoles: synthesis and mesogenic studies
Published in Liquid Crystals, 2018
Farid Fouad, David R. Davis, Robert Twieg
In some cases the 2-biphenyl substituted 1,3,4-oxadiazole was built by addition of the oxadiazole ring to a preformed biphenyl unit bearing the appropriate functionalised terminus. This is most often the case for the alkoxy-substituted materials D for which 4-hydroxy-4ʹ-cyanobiphenyl is a readily available precursor (Scheme 2). In contrast, the alkyl substituted biphenyl oxadiazoles were prepared by creation of the biphenyl itself by means of a Suzuki reaction between the appropriate alkylphenylboronic acid and a bromobenzene derivative bearing functionality that permits elaboration of the oxadiazole ring (or even having an oxadiazole ring already intact). The later approach has also been used for some alkoxy-substituted targets (Schemes 1 and 3). Detailed synthetic procedures can be found in the Supplemental Data.
An efficient poly(amic acid) salt-stabilised palladium nanocatalyst with excellent recyclable performance for Suzuki–Miyaura coupling reactions under mild conditions
Published in Journal of Experimental Nanoscience, 2018
The applications of PdNPs/PAAS were explored for the synthesis of biphenyl compounds by Suzuki–Miyaura coupling reactions. Bromobenzene and phenylboric acid were chosen as model substrates to investigate the catalytic performance of the composites for Suzuki reaction. Subsequently, a series of experiments were carried out. The reaction did not proceed at 40 °C without catalyst used even after 3 h, the same situation to the reaction in blank PAAS and Na2B4O7·10H2O solution, ensuring that the reaction was not catalysed by PAAS or Na2B4O7·10H2O. However, when the supported PdNPs/PAAS were used as the catalyst, the desired products were detected within 0.5 h, indicating that Pd participated in the reaction.