Practice Problem 16.14 Dihydropyran reacts readily with an alcohol in the presence of a trace of anhydrous HCl or H2SO4 to form a tetrahydropyranyl (THP) ether: 二氢吡喃与醇在无水 HCl 或 H2SO4 催化下能四氢吡喃醚 (THP) : (a)Write a plausible mechanism for this reaction. 写出该合理的反应机理。 (b)Tetrahydropyranyl ethers are stable in aqueous base but hydrolyze rapidly in aqueous acid to yield the original alcohol and another compound. Explain. (What is the other compound?) 四氢吡喃醚 (THP) 在碱性水溶液中稳定,但在酸性水溶液中迅速水解生成原来的醇和另一化合物,另一化合物是什么? (c) The tetrahydropyranyl group can be used as a protecting group for alcohols and phenols. Show how you might use it in a synthesis of 5-methyl-1,5-hexanediol starting with 4-chloro-1- butanol. 四氢吡喃基常用于保护醇和酚。如何利用这一方法以 4- 氯 -1- 丁醇为原料合成 5- 甲基 -1,5- 己二醇?