Benzene can be prepared by acetylene gas. When acetylene gas send through a heated pipe, benzene is be given as a one of the product. Before that we have to convert ethanol to acetylene.
We know, first we have to prepare acetylene from ethanol. Each steps of converting ethanol to benzene and acetylene (ethyne) to benzene is explaned below.
Ethanol reacts with concentrated sulfuric acid and heated to happen the reaction. Ethene (C2H4) is given as the product.
Liquid bromine is added to ethene. Br2 is dissolved in CCl4. Two bromine atoms are added through double bond and dibromoethane is given as the product. Dibromoethane is an alkyl halide compound.
Bromoethane - BrCH2CH2Br
Alkyl halides are treated and heated with alcoholic KOH to give alkenes or alkynes. When dibromoethane is treated and heated with alcoholic KOH, ethyne (acetylene) is given. Acetylene is an alkyne.
Acetylene / ethyne / C2H2
Ethyne (acetylene) is sent through a heated copper pipe. Cu is behaved as a catalyst. Acetylene polymerizes and give benzene as one product. In this reaction, aromatic compound is prepared by an aliphatic compound.
Ethene is prepared from ethanol as below reactions. Then ethene reacts with basic KMnO4. It gives diol compound (HO-CH2-CH2-OH). Then it is heated with concentrated H2SO4 to get acetylene.
We have already discussed the acetylene to benzene conversion.
When phenol is distilled with zinc dust, it gives benzene.