question about the preration of ester

2007-02-22 4:36 am

a mixture of ethanol , conc. sulphur acid and ethanoic acid was heated under reflux for some time .the final product is ester . poured the ester into a beaker containing saturated sodium chloride solution.

why is it necessary to use saturated sodium chloride solution , and the purpose?
any other solution can also used in this experiment (give examples)?
but the function is same as used saturated sodium chloride solution.
p.s. the solution cannot be copy from the internet or books

更新1:

after the ester cooled ,poured the ester into a beaker containing saturated sodium chloride solution.

更新2:

please answer in english.

回答 (2)

Bob C. L.

2007-02-22 5:59 pm

✔ 最佳答案

基本上，如果只是想去聞酯的香味，單用水是可以的。但用飽和食鹽水(saturated sodium chloride solution)是可以提高收率和防止乳化產生。雖說酯除甲酸甲酯(methyl methanoate)之外全不溶於水，但產物乙酸乙酯(ethyl ethanoate)都有一點點水溶性，加上有未反應的乙醇存在，乙酸乙酯的水溶性也會提高。用飽和食鹽水有鹽析(Salt-Out)作用，減低乙酸乙酯的水溶性，使乙酸乙酯更易分離，收率提高。
改用的Saturated Sodium hydrogencarbonate solution也可以，還加一好處，中和系統中的sulphur acid ，防止水解(hydrolysis)的發生。切勿使用NaOH，因乙酸乙酯會水解。

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rickygaogaigar

2007-02-22 5:20 am

Pruposes:
1) To dissolve all other substances that not yet reacted. For example, acids, alcohol and conc. sulphuric acid.
2) To let u to smell the ester easily.

Besides NaCl(aq), water can also be used for the same purpose.

參考: My Chemistry knowledge

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