One Step Synthesis Of2,5-dimethylaniline(2,5-dimethylphenol) By The Reaction Of P-xylene With Hydroxylamine Salts

2,5-dimethylaniline and2,5-dimethylphenol is an important organic chemicals, with awide range of application in medicine, spices, dyes, etc. Traditional ways for producingthese compounds involve complex process route, suffering from the drawbacks like lowatomic utilization, environmental pollution and unsafe process, etc. Therefore, we proposeda new process which is the synthesis of2,5-dimethylaniline (2,5-dimethylphenol) directlywith the p-xylene and hydroxylamine salt as raw materials.2,5-dimethylaniline and2,5-dimethylphenol were produced through the regulation of the reaction medium andconditions in the process.Using ammonium molybdate as homogeneous catalyst, the influences of variousreaction parameters such as solvent, temperature, time, the amount of hydroxylamine andcatalyst were studied systematically on the synthesis of2,5-dimethylaniline(2,5-dimethylphenol) directly with p-xylene and hydroxylamine salt as raw materials. Theresults showed that2,5-dimethylaniline (2,5-dimethylphenol) would be formed fromp-xylene and hydroxylamine salts catalyzed by ammonium molybdate. The productdistribution can be regulated by the composition of the reaction medium. The suitablereaction conditions for synthesis of2,5-dimethylaniline were HOAc-H2SO4(v/v=10:5~13:2)two-component medium，0.200mmol of ammonium molybdate,1~1.2molar ratio ofhydroxylamine: p-xylene, conducted at85℃for4h. Under the optimized reactionconditions, high conversion of p-xylene and selectivity of2,5-dimethylaniline wereobtained，corresponding to18.7%and88.0%respectively. In addition, the optimizedreaction conditions for synthesis of2,5-dimethylphenol were HOAc-H2SO4-H2O(v/v/v=10:1:4) three-component medium，0.400mmol of ammonium molybdate,1~1.2molar ratio of hydroxylamine: p-xylene, conducted at80℃for4h.p-xylene conversionand2,5-dimethylphenol selectivity were7.20%and83.0%respectively under the optimizedreaction conditions.For the above-mentioned problem of using concentrated sulfuric acid inp-xylene-hydroxylamine salts reaction system, acidic ionic liquids were used to replacesulfuric acid as reaction media in the reaction of direct hydroxylation of p-xylene to2,5-dimethylphenol with hydroxylamine. The effect of the types and acidity of acidic ionic liquid, reaction environment (closed or open air system) and the reaction conditions(temperature, time, the amount of catalyst, the composition of material, additives) on thereaction was considered. The results showed that2,5-dimethylphenol can be formed underacidic ionic liquid media from p-xylene and hydroxylamine salts catalyzed by ammoniummolybdate. The suitable reaction conditions investigated were0.260mmol of ammoniummolybdate,1~1.2molar ratio of hydroxylamine: p-xylene,18.0g HOAc-H2O-IL(m/m/m=10:4:4) medium, conducted at90℃for3~4h. p-xylene conversion and2,5-dimethylphenol selectivity were5.92%and98.3%respectively. While in a closedsystem, the p-xylene conversion was8.00%and2,5-dimethylphenol selectivity was97.9%under the same reaction conditions. It was verified that the medium of concentrated sulfuricacid could be replaced by acidic ionic liquids, and it improved the selectivity for the desiredproduct.