The Research On Preparing Poly-aromatic Hydrocarbons Through Coupling C-H Bonds Of Aromatic Hydrocarbons

The compounds of poly-aromatic hydrocarbons have great value in the field of lives andindustry. They are the basic structure of many natural products and play a vital role in thefield of guest-host chemistry and functional material synthetics, as well as in the field ofmaking the immediate of medicines. In this article, we found a simple and effective method ofpreparing poly-aromatic hydrocarbons through coupling C-H bonds of aromatic hydrocarbonswithout using transition metals and solvents, and in stand using the benzoyl peroxide to activethe C-H bond of aromatic ring and the C-H bond on the alkyl substituent through the freeradical mechanism. The advantages of the method developed in this article include the mildcondition required for the reaction and the direct usage of the reactants themselves as well asthe simply treatment of the reaction mixture before and after the reaction and environmentalfriendly. The main contents of the article include:Firstly, we have reviewed the research development of the methods for the preparing ofpoly-aromatic hydrocarbons.Secondly, the products of different substituted aromatic hydrocarbons with benzoylperoxide are qualitatively analyzed by using GC-MS and GC. We established the quantityanalysis method of the products of the reaction of toluene with benzoyl peroxide usingdichlorobenzene as internal substrate with the average recycling percentage of98.15%to99.08%, and the relative standard error RSD lower than2%. Similarly, we established thequantity analysis method of the products of the reaction of other different substituted aromatichydrocarbons with benzoyl peroxide.Thirdly, we studied the laws of the yield and product selectivity of the reaction with thesubstituent on the aromatic hydrocarbon used. And the optimized reaction condition lied asfollowing: the ratio of substrate with benzoyl peroxide was2.6:1, the temperature was90degree and the reaction time was7hours with the protection of N₂without any solvent andcatalyst. Among all of the substituted aromatic hydrocarbons used, nitrobenzene achieved thehighest yield of16.7%. The highest selectively of the products derived from aromatic C-Hbonds coupling reached73.1%when the substituent was methyl group, and the highestselectively of the products derived from alkyl C-H bonds coupling reached68.0%when thesubstituent was isopropyl.Fourthly, we investigated the effects of the reaction conditions such as temperature,reaction time, solvent, base and protection gas on the yield and the selectively of products derived from aromatic C-H bonds coupling and the products derived from the alkyl C-Hbonds coupling of the reaction between toluene and benzoyl peroxide.Finally, we studied the reaction mechanism using the free radical catching reagentCBrCl3to catching the benzyl radical group and the reagent TEMPO to block the reactionaccording the mechanism of generating free radicals from benzoyl peroxide in the literatures.And we proposed the reaction mechanism of the reaction of benzoyl peroxide with substitutedaromatic hydrocarbons to produce aromatic C-H bonds coupling related products and alkylC-H bonds coupling related products based on the experimental results.