酯Ester

中文按“某酸某酯”命名，酸在前、醇在后：CH₃COOC₂H₅ 为乙酸乙酯。英文顺序相反，醇的烃基在前、酸根名（-oate）在后：ethyl ethanoate（俗名 ethyl acetate）。HCOOCH₃ 为甲酸甲酯 methyl methanoate。

In Chinese an ester is named acid first, then alcohol: CH₃COOC₂H₅ is 乙酸乙酯. English reverses the order, giving the alkyl group from the alcohol first and then the acid-derived -oate name: ethyl ethanoate (common name ethyl acetate). HCOOCH₃ is methyl methanoate (甲酸甲酯).

羧酸与醇在浓硫酸催化下加热，生成酯和水，这一反应可逆。浓硫酸既是催化剂，又能吸水，使平衡向生成酯的方向移动；也可以用过量醇或把生成的酯蒸出来提高产率。同位素示踪表明，生成的水中的氧来自羧酸的 –OH，即“酸脱羟基、醇脱氢”。用酰氯与醇反应可以不可逆地得到酯。

A carboxylic acid heated with an alcohol and concentrated sulfuric acid gives an ester and water in a reversible reaction. The acid both catalyses the reaction and absorbs water, pushing the equilibrium towards the ester; excess alcohol or distilling off the ester also raises the yield. Isotope labelling shows the oxygen in the water comes from the acid's –OH: the acid loses OH and the alcohol loses H. Acyl chlorides react with alcohols to give esters irreversibly.

酯在稀酸中加热水解生成羧酸和醇，反应可逆。在 NaOH 溶液中加热水解生成羧酸盐和醇，因羧酸被转化为盐而不可逆，油脂的碱性水解用于制肥皂，称为皂化反应。

Heated with dilute acid, an ester hydrolyses reversibly to the carboxylic acid and alcohol. Heated with aqueous NaOH it gives the carboxylate salt and alcohol; this is irreversible because the acid is converted to its salt. Alkaline hydrolysis of fats is used to make soap and is called saponification.

乙酸乙酯是常用溶剂；乙酸异戊酯有香蕉气味，用作香料。油脂是甘油与高级脂肪酸形成的三酯。对苯二甲酸与乙二醇缩聚得到聚对苯二甲酸乙二醇酯（PET），用于饮料瓶和涤纶纤维。阿司匹林（乙酰水杨酸）的分子中也含酯基。

Ethyl ethanoate is a common solvent; 3-methylbutyl ethanoate smells of bananas and is used as a flavouring. Fats and oils are triesters of glycerol with long-chain fatty acids. Condensation of benzene-1,4-dicarboxylic acid with ethane-1,2-diol gives poly(ethylene terephthalate), PET, used for drinks bottles and polyester fibre. Aspirin (acetylsalicylic acid) also contains an ester group.