【简答题】实验室可由苯甲醛和乙酐在无水碳酸钾的作用下,控制温度在160~180°C制备肉桂酸,该反应成为Perkin反应,已知肉桂酸的pKa=4,mp=133°C,难溶于冷水,可溶于热水。请回答: (1)请写出该反应的反应机理。 (2)分离提纯过程中,水蒸气蒸馏的目的是什么?蒸馏前为什么需向出产物溶液中加入碳酸钠? (3)如何进一步提纯肉桂酸,用什么简便方法可以判断其纯度? (4)肉桂酸的红外光谱中应该有哪...
【简答题】在乙酸正丁酯制备中,粗产品中通常会含有硫酸、过量的醋酸、正丁醇、水等杂质。
请写出将乙酸正丁酯纯化并得到产品的过程。
【简答题】写出 AgCl(s) 在 (1) 纯水中, (2) 0.01mol·dm -3 NaCl , (3) 0.01mol·dm -3 CaCl 2 , (4)0.01 mol·dm -3 NaNO 3 和 (5) 0.1 mol·dm -3 NaNO 3 溶液中溶解度由大到小的次序
【单选题】You go and see a doctor right now. Because you got a fever.
【判断题】If you want to go and see a doctor, it's a good idea to make an appointment before you go.
【判断题】同相求和电路跟同相比例电路一样,各输入信号的电流几乎等于零。()
【单选题】You'd better go and see a doctor if you ______.
A.
see a sleepwalker in action
D.
sleepwalk occasionally
【单选题】You’d better go and see a doctor if you
A.
see a sleepwalker in action.
C.
sleepwalk occasionally.
【判断题】When you feel ill and want to go and see a doctor, it is a good idea to make an appointment before you go.
【单选题】When you feel ill and want to go and see a doctor, it is a good idea to make an appointment before you go .