醇Alcohol (chemistry)

按羟基所连碳原子分为伯醇（RCH₂OH）、仲醇（R₂CHOH）和叔醇（R₃COH）。醇分子之间能形成氢键，沸点比相对分子质量相近的烷烃高得多：乙醇 78 °C，丙烷 −42 °C。低级醇能与水形成氢键而与水互溶，随碳链增长，溶解度降低。

By the carbon bearing –OH they are primary (RCH₂OH), secondary (R₂CHOH) or tertiary (R₃COH). Alcohol molecules hydrogen-bond to each other, so they boil far higher than alkanes of similar Mr: ethanol 78 °C, propane −42 °C. Small alcohols hydrogen-bond with water and mix with it completely; solubility falls as the chain lengthens.

燃烧：C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O。与钠反应放出氢气：2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂。氧化：酸化重铬酸钾把伯醇氧化为醛和羧酸，仲醇氧化为酮，叔醇不被氧化。脱水：浓硫酸或 Al₂O₃ 催化下加热生成烯烃。与羧酸酯化生成酯。与 HBr（或 NaBr + 浓 H₂SO₄）、PCl₅、SOCl₂ 反应生成卤代烃。

Combustion: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O. With sodium, hydrogen is given off: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂. Oxidation: acidified dichromate turns primary alcohols into aldehydes and carboxylic acids and secondary alcohols into ketones, but leaves tertiary alcohols unchanged. Dehydration: heating with concentrated sulfuric acid or over Al₂O₃ gives alkenes. Esterification with carboxylic acids gives esters. HBr (or NaBr with concentrated H₂SO₄), PCl₅ and SOCl₂ convert them to haloalkanes.

甲醇用作溶剂和化工原料，有毒，误饮可致失明甚至死亡。乙醇由糖类发酵或乙烯水合制得，用于饮料、燃料、溶剂和消毒（75% 乙醇溶液）。乙二醇用作汽车防冻液和聚酯原料。丙三醇（甘油）用于化妆品、食品和制造硝酸甘油。

Methanol is a solvent and feedstock; it is toxic, and drinking it can cause blindness or death. Ethanol, made by fermenting sugars or hydrating ethene, is used in drinks, fuels, solvents and disinfection (75% solution). Ethane-1,2-diol is antifreeze and a polyester raw material. Propane-1,2,3-triol (glycerol) is used in cosmetics and food and to make nitroglycerine.