Chemistry of Arenes
Arenes
The aromatic hydrocarbons also have the name arenes. They contain in their molecule one or more cycles made up from 6 carbon atoms. When the molecule is formed out of a single cycle, the hydrocarbons are mono nucleuses; when the molecule contains more than one cycle, the hydrocarbons are poly nucleuses. The simplest aromatic hydrocarbon, benzene, is compound out of just one such cycle; its formula is C6H6. The representation of benzene through a cycle of 6 carbon atoms with 3 double bounds was proposed by Kekule in 1865:
In some special conditions, benzene can be hydrogenated, the result being a cyclic hexane: | +3H2 | |
Under the influence of light, chlorine or bromine addition at the benzene’s molecule giving hexachlorocyclohexane: C6H6 + 3Cl2 C6H6Cl6. With ozone, the benzene gives a trizonide, which by decomposing (with water), passes in glycoxal. These addition reactions prove the following: benzene has a cycle of 6 carbon atoms; there are three double bounds in the cycle. Yet, the addition reactions at benzene take place only in special conditions, benzene usually giving substitution reactions, like:
With halogens: C6H6 + Cl2 C6H5Cl + HCl
With sulfuric acid: C6H6 + HO-SO3H C6H5-SO3H + H2O
With nitric acid: C6H6 + HO-NO2 C6H5-NO2 + H2O
The easy formation of the substitution products is a proof that benzene’s character is less unsaturated than the hydrocarbons with conjugated double bounds. Furthermore, benzene has a pronounced saturated character. Yet, this behavior does not correspond to Kekule’s structural formula, which says that three conjugated double bound should exist. Another critic brought to this formula is that she predicts the existence of for isomers than in reality.
If two hydrogen atoms in the benzene’s molecule are substituted with two bromine atoms, then, according tot Kekule’s rule, there should be two isomers containing two bromine atoms connected to two nearby carbon atoms (positions 1,2 and 1,6) at one
The aromatic hydrocarbons also have the name arenes. They contain in their molecule one or more cycles made up from 6 carbon atoms. When the molecule is formed out of a single cycle, the hydrocarbons are mono nucleuses; when the molecule contains more than one cycle, the hydrocarbons are poly nucleuses. The simplest aromatic hydrocarbon, benzene, is compound out of just one such cycle; its formula is C6H6. The representation of benzene through a cycle of 6 carbon atoms with 3 double bounds was proposed by Kekule in 1865:
In some special conditions, benzene can be hydrogenated, the result being a cyclic hexane: | +3H2 | |
Under the influence of light, chlorine or bromine addition at the benzene’s molecule giving hexachlorocyclohexane: C6H6 + 3Cl2 C6H6Cl6. With ozone, the benzene gives a trizonide, which by decomposing (with water), passes in glycoxal. These addition reactions prove the following: benzene has a cycle of 6 carbon atoms; there are three double bounds in the cycle. Yet, the addition reactions at benzene take place only in special conditions, benzene usually giving substitution reactions, like:
With halogens: C6H6 + Cl2 C6H5Cl + HCl
With sulfuric acid: C6H6 + HO-SO3H C6H5-SO3H + H2O
With nitric acid: C6H6 + HO-NO2 C6H5-NO2 + H2O
The easy formation of the substitution products is a proof that benzene’s character is less unsaturated than the hydrocarbons with conjugated double bounds. Furthermore, benzene has a pronounced saturated character. Yet, this behavior does not correspond to Kekule’s structural formula, which says that three conjugated double bound should exist. Another critic brought to this formula is that she predicts the existence of for isomers than in reality.
If two hydrogen atoms in the benzene’s molecule are substituted with two bromine atoms, then, according tot Kekule’s rule, there should be two isomers containing two bromine atoms connected to two nearby carbon atoms (positions 1,2 and 1,6) at one