2. 卤代烃的水解反应制备醇

2.1在碱性水溶液中，脂肪组卤代烃的卤原子被羟基取代生成醇

该类反应属于典型的亲核取代反应，按照反应历程分两种类型：单分子的亲核取代反应(SN1)和双分子的亲核取代反应(SN2)。

单分子的亲核取代反应(SN1)历程中反应速度只与反应底物卤代物的浓度有关，与碱的浓度无关。因此，从动力学上讲它是一个一级反应。例如溴代叔丁烷的水解：

此反应是分两步进行,第一步是反应物在溶剂中首先离解成叔丁基正离子和溴负离子:

第二步则是生成的叔丁基碳正离子再与HO-作用,生成叔丁醇:

另一类为双分子的亲核取代反应(SN2)，它的水解速度与卤代烃的浓度和碱的浓度成正比，因此该类反应是一个二级反应。例如溴甲烷的水解：

反应过程中C-Br键的断裂与C-O键的形成是同时进行的。当进攻试剂HO-从离去基团Br的背后进攻中心碳原子时(这是比较有利的进攻方式)。此时，HO-、Br和中心碳原子几乎处于同一直线上，形成一个“过渡态”。而中间碳上的三个H原子则处于垂直于这个直线的平面上，当HO-与中心碳原子进一步接近，最终形成一个稳定的C-O键时，C-Br也彻底断裂，生成Br-离子，同时中心碳上的三个H原子也向后翻转，使碳原子恢复成原来的sp3杂化状态。从立体化学上来看，在反应过程中发生了构型的转化，使得产物与原来的反应物构型正好相反，这也正是在1893年发现的瓦尔登(Walden)转化。另外许多反应，卤代物直接水解并不是太好，因此一般先用AcO－取代，而后再水解得到相应的醇。 2.1.1卤代烃的水解反应制备醇示例

Combined the material with 75% DMF,1.2 equiv of NaOH were stirred for 30min at room temperature. And recrystallized from MeOH to give the colourless needles (95% yield)1.

2.1.2 卤代烃的水解反应制备醇示例

Water (100mL) and CaCO3(18g, 180mmol) were added into a solution of 10.5g (35mmol) of 1-bromo-2-(bromomethyl)naphthalene in 100mL of p-dioxane ,and the mixture was refluxed for 10hrs. The solution was cooled and the dioxane removed under reduced pressure. Methylene chloride (200mL) was added followed by treatment with dilute HCl until all solid had dissolved .The organic phase was separated, washed with NaHCO3solution, dried over MgSO4, and filtered.Removal of the solvent left a white solid,which was recrystallized from hexane to give 7.9g of (1-bromonaphthalen-2-yl)methanol (95% yield)2.

2.1.3 卤代烃的 AcO－取代 示例

A 150 g portion of the thus obtained 1-chloro-(E,Z)-7,9-dodecadiene was admixed with 150 g of anhydrous potassium ace-tate and 100 g of acetic acid and the mixture was heated at 160 .deg.C for 6 hours under agitation in an atmosphere of nitrogen to convert the chloride into acetate.. After completion of the reaction, the reaction mixture was poured into a large volume of water and the organic phase taken by phase separation was distilled under reduced pressure to give 80 g of 7,9-dodecadienyl acetate of which the purity of the E,Z-isomer was at least 75percent.

2.1.4酯水解得到相应的醇 示例

2N sodium hydroxide (40 ml) was added to a solution of 5-(2-acetoxyethyl)-2-methyl-4-phenyloxazole (16.6 g) in methanol (40 ml) and the mixture was stirred for 30 minutes, diluted with water and extracted with ethyl acetate..The ethyl acetate layer was washed with water and dried over anhydrous magnesium sulfate.

The solvent was then distilled off and the residue wwas purified by silica gel chromatography (silica gel: 190 g, eluent: isopropyl ether) to give an oil of 5-(2-hydroxyethyl)-2-methyl-4-phenyloxazole, yield 11.7 g (84.8percent).NMR (CDCl3) d: 2.40 (3H, s), 3.07 (2H, t), 3.20 (1H, broad), 3.97 (2H, broad), 7.23-7.80 (5H, m).

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