Hexane, hexene, phenol, nitrobenzene and ethanol are identified by one reagent. What kind of reagent is this? And how to do this kind of problem.

Bromine water should be used. First of all, ethanol and bromine water are mutually soluble, while hexane, hexene and nitrobenzene are layered.

The density of hexene and hexane is lower than that of water, and the density of nitrobenzene is higher than that of water, so that the organic layer is above and below the water layer respectively.

Organic solvents can extract bromine from the water layer, so the organic layer will become colored and the water layer will become transparent.

However, hexene has a double bond and can react with bromine, so the hexene layer will become colorless.

So the phenomenon is,

Not layered, it is ethanol;

Layered, the upper and lower layers are colorless, hexene;

Layered, the upper layer is colored and hexane;

Layered, the lower layer is colored, nitrobenzene.

Let me talk about phenol again. If phenol is a pure compound, its melting point is 40.5 degrees Celsius, so it is a solid at room temperature. This is where this question is not rigorous. If it is made into dilute aqueous solution, phenol will react with water to produce white precipitate of tribromophenol.

This question is a bit irregular (phenol). This kind of problem, first consider the melting point, for example, if you add a butane, butane is a gas at room temperature, so don't worry at all. Third, it is miscible with water, and ethanol, acetic acid and water are infinitely miscible. Then there is density, which is lighter above the water layer and heavier below the water layer. There are not many organic compounds heavier than water, and halogenated compounds (especially bromide and iodide) are definitely heavier than water. Chlorinated compounds are not necessarily, such as chlorobenzene is heavier than water, chlorobutane is lighter than water, which needs to be understood by yourself) and nitro compounds (such as nitrobenzene). That's about it. This kind of problem is nothing more than bromine water and potassium permanganate solution, which has not changed much.