A New Method Of Synthesising Of Dibenzoylmethane And Its Derivatives And Research Of Their Capability

Skin will be damged when exposed to high-energy ultraviolet ray for a long time, even it would result in skin cancer if skin is radiated seriously.With the rapid development of industry, the ozone layer was badly destroyed, so that more and more ultraviolet ray could cross through the aerosphere and arrived in the ground, and this has a bad influence on the human. Based on this, it is of great significance to develop an ultraviolet ray absorber which is anti-ultraviolet ray and could be applied to daily life. It is accepted that the kind of dibenzoylmethane ultraviolet ray absorber is proved to be safety.Recently, the concept of green chemistry is gradually accepted by many people. The sythesis methods that are enviromentally benign and show high atom efficiency has become a hot spot. With its special mechanism, microwave irradiation become an ideal heating method by accomplishing chemical reaction with high yield in short time and its easy handling. Under the guidance of green chemistry, the sythesis of the kind of dibenzoylmethane ultraviolet ray absorber was studied by using microwave radiation.(1) with p-tert-butyl toluene as feedstock, under microwave irradiation and using phase transfer catatysis, the sythesis of p-t-butylbenzoic acid was accomplished environment-friendly. Through a series of experiments, factors influencing oxidation were discussed. The optimum conditions were determined as follows : the yield of p-t-butylbenzoic acid was 82.6% when using BTEAC as phase transfer catatysis, the molar ratio of p-tert-butyl toluene and KMnO4 was 1:1.5, microwave irradiation power was 660W, the reaction time was 50min. The structure of product was confirmed by IR and 1HNMR.(2) using microwave irradiation, the preparation of p-tert-butylbenzoic-acid- methyl ester by the reaction of p-butyl-benzoic acid with methanol,by using H₂SO₄ as a catalyst. The single-factor test were used to optimize esterfication conditions.It is indicate that when using H₂SO₄ as a catalyst, under microwave irradidtion,the esterfication conditions get higher yield and purer product than unedr traditional heating method.The structure of product was confirmed by IR and ¹HNMR.(3) five dibenzoylmethane compounds were synthesised from aromatic ketone and ester by classical Claisen condensation usingstrong alkali as catalyst. The sythesis of compound(4-tert-butyl-4'-methoxy-dibenzoylmethane) were mainly studied .The factors of condensation were investigated by orthogonal test. The structure of products were confirmed by IR and ¹HNMR.(4) according to national standards, five products'UV - visible spectrum was determined. In accordance with their areas in UV absorption band, we mixed these compounds. Then we measure these mixtures'UV - visible spectrum.It was proved that, compared with traditional heating method, microwave irradiation could heat reactants completely, and the carbonization of reactants is not simple. This improved the efficience of atoms, greatly increased reaction rate, shotened reaction time and raised reaction efficiency. It is a green and highly efficient method.The results show that their absorptions in ultraviolet A and B were good, and the mixture absorb all kinds of ultraviolet rays including ultraviolet A and B. The kind of dibenzoylmethane ultraviolet ray absorber was fine.