Acetic aldehyde (ethyl aldehyde, ethanal) represents itself colourless liquid with a pungent smell. Its chemical formula CH3COH. Let's well dissolve in water, in a number of organic matter (alcohols, air). It is used as raw materials by production of acetic acid, butadiene and also some polymers. How it is possible to distinguish acetic aldehyde from other organic liquids?
It is required to you
- - three glass test tubes;
- - spirit-lamp;
- - solution of complex connection [Ag(NH3)2]OH (it turns out at compound of oxide of Ag2O c silver NH4OH liquid ammonia).
Instruction
1. At first it is necessary to notice that to resort to such way as definition of substance extended among the beginning chemists on its smell, categorically it is not recommended. First, it is very unreliable way as there are various substances with very similar smells. Secondly, vapors of many substances are poisonous.
2. There are much more exact, evident and rather safe ways of definition. Let's assume, you were given three tests: one of them for certain contains liquid saturated hydrocarbon, for example, a pentane or hexane, in another – some alcohol (standard, propyl alcohol), in the third – acetic aldehyde. Your task is to find it.
3. Carry out "reaction of a silver mirror". For this purpose serially add to a test tube with each sample a little solution of this connection and begin to heat on a spirit-lamp. If in the studied sample there was an acetic aldehyde, you will soon see how glass will become covered by the brilliant reflecting layer and will feel a characteristic unpleasant smell of ammonia because there will be such reaction: 2 [Ag(NH3)2]OH + CH3COH = 2Ag + 4NH3 + H2O + CH3COOH.
4. Acetic aldehyde will turn into acetic acid, and the emitted silver will accumulate the thinnest layer on test tube walls. Therefore this reaction also carries such name – "reaction of a silver mirror".
5. Considering that compounds of silver quite expensive, it is possible to carry out high-quality reaction of definition of acetic aldehyde with hydroxide of copper (II).
6. Also serially add to a test tube with each sample of a little freshly cooked deposit Cu(OH)2 and begin to heat on a spirit-lamp flame. If in the studied sample there was an acetic aldehyde, blue color of hydroxide of copper (II) pretty fast will become yellow, and then – pinkish-red because hydroxide of copper (II) at first will turn into CuOH - hydroxide of copper (I), and then this unstable substance will break up to oxide of copper and water: 2CuOH = Cu2O + H2O.