Homologue of benzene

Chemical terminology

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The homologue of benzene is benzene ring On hydrogen atom cover alkyl Substituted products.^[1] Its general molecular formula is C n H 2n-6 (n ≥ 6, n ∈ N), its molecule contains only one benzene ring, benzene ring Of Side chain Is alkyl (- C n H 2n+1 ）, benzene ring and side chain interact.^[2]

Chinese name: Homologue of benzene

chemical formula: C n H 2n-6 （n≥6，n∈N）^[2]
Density: Smaller than water

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six physical property
seven application

definition

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The homologue of benzene is the hydrogen atom on the benzene ring alkyl Substituted products.^[1]

General molecular formula

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C n H 2n-6 (n≥6，n∈N)^[2]

name

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Benzene homologues are named with benzene as the parent, if there are two Substituent , which can be represented by "adjacent", "intermediate", and "opposite" respectively, or the six carbon atoms on the benzene ring can be numbered, with the position of the carbon atom where a methyl is located as No. 1, and the lowest position number can be selected to number another methyl.^[2]

Structural characteristics

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There is only one benzene ring in the molecule, and the side chain of the benzene ring is alkyl （—C n H 2n-6 ）, benzene ring and side chain interact.^[2]

chemical property

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Due to the influence of side chains on the benzene ring, the hydrogen atom on the benzene ring is active and easy to occur Substitution reaction

(1) Make benzene ring Adjacency And contrapuntal hydrogen atom Active, easily exposed to other atoms or Atomic cluster replace.

(2) Which makes the side chain directly connected with the benzene ring carbon atom The hydrogen atom on the is active and easy to be oxidized, and regardless of the side chain length Oxidation product Are Benzoic acid 。 as toluene 、 ethylbenzene Can make it acidic potassium permanganate The solution fades.

Two substitutions

toluene and bromine Can occur Substitution reaction , but the substitution position is different under different conditions.

(1) Occurs on benzene ring Upper, that is, the effect of side chain on benzene ring (Fe catalysis ）。

(2) Occurs on Side chain Up, i.e. similar alkane Of Substitution reaction , can continue. The conditions are the same alkane Substitution reaction (light).

Two kinds of fading

(1) Benzene homologues cannot Bromine water Fade (no reaction), but it can extract bromine in bromine water to fade the bromine water layer（ physical property ）。

(2) Benzene homologues can fade the acid potassium permanganate solution, while benzene cannot fade the potassium permanganate solution.^[2]

Explanation: Due to the interaction between benzene ring and side chain, the side chain connected to benzene ring can be oxidized by acid potassium permanganate solution, so that the purple red of acid potassium permanganate solution will fade, which can be used to identify benzene and benzene homologues. Because of the influence of the side chain on the benzene ring, the substitution reaction on the benzene ring is easier than the substitution reaction of benzene.^[2]

It can be summarized as: "Easy to replace easy oxidation hard Mark up 。”^[2]

Related reactions

⑴C seven H eight + 3HNO three →C seven H five N three O six (TNT)+3H2O (condition: concentrated sulfuric acid ,100 centigrade )

⑵C seven H eight +Br two →C seven H six Br ( benzene ring +Methyl+- Br)+ HBr (Condition: FeBr three As catalyst)

C seven H eight +Br2→C seven H six Br (benzene ring+CH two Br)+HBr (condition: light)

⑶C seven H eight + 3H two →C seven H fourteen (Name: Methylcyclohexane ）(Composition: cyclohexane +Methyl) (condition: catalyst, heating)

（4） oxidation reaction The common homologues of benzene can fade the acid potassium permanganate solution. If generated Benzoic acid 。

physical property

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I State of matter At room temperature, benzene and its homologues are mostly colorless liquids with aromatic smell. Its vapor is toxic, benzene is more toxic, and long-term inhalation is harmful to health.

2、 Boiling point and melting point follow relative molecular mass Increase. melting point Relative to molecular mass It is related to the shape of molecules. Molecular symmetry The higher, the higher the melting point. Same carbon Atomic number Of Isomer In, the shorter the side chain on the benzene ring, the more dispersed the side chain is distributed on the benzene ring, and the lower the melting and boiling point of the substance, usually the neighborhood> Interposition >Alignment. Generally speaking, the higher the melting point, the solubility The smaller it is, the easier it is to crystal 。

III relative density Less than 1, smaller than water.

IV Solubility Insoluble in water, Soluble to Organic solvent , which is also an organic solvent.

application

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Toluene and Concentrated nitric acid The reaction can take place under the catalysis of concentrated sulfuric acid (100 ℃) to generate Trinitrotoluene 。 Also known as TNT, it is a kind of yellow Acicular crystal 。 Insoluble in water. It is a kind of high explosive. It is used for national defense, mining, road construction, etc.

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