醛和酮 Aldehydes and Ketones 急~

2010-12-12 3:19 am

有幾條問題想問(可以就用中文答,但係英文答都ok):

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1.普遍會用咩試劑做羰基化合物ge測試?
Generally, what reagent is used to test carbonyl compunds?

---------------------------------------------------------------------------------------------------------------2.NaOH, NaHSO3,C6H3(NO2)2NHNH2, K2Cr2O7/H+, Fehling's reagent, Tollen's reagent, CHI3

以上邊個/些反應和醛/酮有聚合物生成?
In which reaction(s) will a polymer be formed?
(可以就加埋/講一講個反應機理)

---------------------------------------------------------------------------------------------------------------仲有, Fehling's reagent, Tollen's reagent 其實係咩,用來做咩?

Thanks!

回答 (1)

己式庚辛

2010-12-12 8:17 am

✔ 最佳答案

1.
2,4-dinitrophenylhydrazine (2,4-DNP): test the presence of all carbonyl, both aldehydes and ketones.

2.
polymer? i'd bet NaOH.
except CHI3, all reagents above can react with aldehydes; NaHSO3 can also react with methylketones, such as propanone, butanone and pentane-2-one;
C6H3(NO2)2NHNH2 can react with all ketones too.

i've drawn a schematic mechanism for you:

圖片參考：http://imgcld.yimg.com/8/n/HA00075708/o/701012110120613873425660.jpg

carry on the reaction and stop by protonating the negative oxygen.

3.
Fehling's reagent is similar to Benedict's solution used in biology. it's to test for the presence of reducing agents (including reducing sugars, which contain aldehyde groups). aldehyde can reduce the copper(II)-containing solution to give red precipitate of copper(I) oxide.

Tollen's reagent is a solution of diamminesilver(I) ion, made by mixing excess ammonia solution with silver nitrate solution. aldehyde can reuce the silver complex into metallic silver. the silver formed often coat on the wall of container, thus nicknamed "silver mirror test".

both reagents can detect presence of reducing agents, specifically used to test for adehydes ---- ketones have no reactions toward them.

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