Improvement and Innovation of Experiment Preparation and Characterization of Benzoin and Benzil
The preparation and characterization of benzoin and benzil is a classic experimental project involving organic synthesis in comprehensive chemical experiments.However,there are some shortcomings in the existing experimental scheme,such as the purification of reaction raw materials by vacuum distillation,low yield of benzoin,long synthesis time of benzil.To this end,the innovative design and improvement were carried out.The raw material benzaldehyde was purified with saturated sodium bicarbonate solution instead of vacuum distillation,and the dropping speed and dropping temperature of sodium hydroxide were regulated.Benzoin was optimized and synthesized using a stepwise warming method,and then benzil was synthesized with benzoin as precursor by microwave irradiation.The results showed that the raw material benzaldehyde can be purified with saturated sodium bicarbonate.The dropping time of sodium hydroxide solution was controlled at room temperature for 20 min.The yield of benzoin by heating to 70 ℃ gradually and holding for 60 min was about 50％,which was 15％higher than that by conventional method.Taking as-prepared benzoin as raw material,the synthesis conditions of benzil were optimized.When microwave irradiation for 16 min,the yield of benzil was about 90％,the reaction time was significantly shortened.The experimental design has become more reasonable through improvement and innovation,which enhances students'comprehensive experimental skills and independent exploration ability.
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