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MindMap Gallery Mind map of diphenyl, a compulsory course in high school chemistry

Mind map of diphenyl, a compulsory course in high school chemistry

High school chemistry compulsory course 2. Benzene (C₆H₆) is an organic compound and the simplest aromatic hydrocarbon. Its chemical formula is C₆H₆. It is a colorless, sweet and transparent liquid at room temperature. Its density is less than that of water and it has a strong The aromatic smell.

Edited at 2024-03-12 17:24:55

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Mind map of diphenyl, a compulsory course in high school chemistry

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Outline

benzene

1. learning target

Understand the physical properties and molecular composition of benzene;

Master the structural formula of benzene and understand the structural characteristics of benzene;

Understand the chemical properties of benzene.

2. Summary of key points

1. Molecular structure of benzene

1. Molecular composition and representation of benzene

Molecular formula Structural formula Simplified structure scale model ball and stick model C6H6

2. The spatial configuration of benzene:

The benzene molecule has a planar regular hexagonal structure. Six carbon atoms and six hydrogen atoms are on the same plane, The bond angle is 120°.

3. Structural characteristics of benzene

(1)

The bond lengths between the carbons in the six-membered ring are the same. The bond energy is also the same.

(2)

The bond between carbon and carbon on the benzene ring is not an ordinary carbon-carbon single bond. It’s not an ordinary carbon-carbon double bond either. Rather, it is a unique bond between a single bond and a double bond. Six carbon-carbon bonds are equivalent,

2. Properties of benzene

1. Physical properties of benzene

Benzene is a colorless liquid with a special odor. Toxic, insoluble in water, Less dense than water, The melting and boiling point is lower, It is a commonly used organic solvent.

2. Chemical properties of benzene

Due to the special structure of benzene, So that it has the properties of both saturated hydrocarbons and unsaturated hydrocarbons.

(1) Oxidation reaction

Interpretation:

Benzene burns in air, produce a bright flame, And with thick black smoke.

The reason for the thick smoke in combustion is that the benzene molecule contains a high carbon content. Due to insufficient combustion in air.

Benzene burns easily, But it is difficult to be oxidized by oxidants such as potassium permanganate. Therefore, benzene cannot discolor acidic potassium permanganate solution under normal conditions.

(2) Substitution reaction

The ring structure of the benzene molecule makes the hydrogen atoms in the ring Easily replaced by other atoms or atomic groups, Therefore, it has chemical properties similar to alkanes --Substitution reaction.

①Reaction of benzene and bromine

Under the action of FeBr3 catalyst, The hydrogen atoms in the benzene ring are replaced by bromine atoms, Generates bromobenzene.

Interpretation:

The bromine used in this experiment is liquid bromine. Benzene does not react with bromine water. Only extraction separation occurs.

This reaction does not require heating, It can react at room temperature. and releases a lot of heat, Fill the reactor with reddish-brown gas (bromine vapor), There is white mist at the mouth of the air tube.

Bromobenzene is a colorless liquid, Denser than water, Insoluble in water, During the experiment, bromobenzene turned brown due to dissolved unreacted bromine.

Purification of bromobenzene: Wash with NaOH solution (Br2 2NaOH=NaBr NaBrO H2O), Then separate the liquid.

In the presence of a catalyst, Benzene can also undergo substitution reactions with other halogens, Also called halogenation reaction.

Various hydrocarbons and liquid bromine, bromine water, bromine carbon tetrachloride solution, Comparison of reactions of acidic KMnO4 solutions

liquid bromine Bromine water Bromine in carbon tetrachloride solution Acidic KMnO4 solution Alkanes Substitution reaction with bromine vapor under light conditions No reaction, liquid alkanes can extract and discolor the bromine aqueous layer Non-reactive, miscible, non-fading No reaction Alkenes addition Additive fading Additive fading oxidation fading benzene Generally unreactive, catalytically replaceable No reaction, extraction occurs and the bromine aqueous layer fades Non-reactive, miscible, non-fading No reaction

②The reaction between benzene and nitric acid

Under the action of concentrated sulfuric acid, Benzene can also undergo a substitution reaction with concentrated nitric acid at 50-60°C Nitrobenzene is produced.

Interpretation:

The -NO2 atomic group in the nitric acid molecule is called nitro group. The reaction in which the hydrogen atoms in the benzene molecule are replaced by -NO2, It's called nitrification reaction. The essence of nitration reaction is a substitution reaction.

The main functions of concentrated sulfuric acid in the nitration reaction of benzene are catalyst and dehydrating agent.

The temperature of this reaction must be controlled at 50~60℃. Therefore, water bath heating is used (it is easy to control the temperature and is heated evenly), And you need to borrow a thermometer to control the water bath temperature.

The order of adding reagents during the experiment is to add concentrated nitric acid first, Add concentrated sulfuric acid, And stir continuously with a glass rod, Finally add benzene.

Nitrobenzene is colorless and has a bitter almond smell. An oily liquid that is denser than water and difficult to dissolve in water. Toxic, often appears yellow due to dissolved NO2. It can be purified by washing with water or NaOH solution multiple times.

(3) Addition reaction

Although benzene does not have the typical carbon-carbon double bonds like alkenes, However, under certain conditions, addition reactions can still occur. For example, benzene can react with hydrogen in the presence of nickel as a catalyst.

Comparison of ethane, ethylene and benzene

Ethane Ethylene benzene Molecular formula C2H6 C2H4 C6H6 Simplified structure CH3—CH3 CH2=CH2 Structural features C-C can rotate ①C=C cannot rotate ②One of the double bonds is easy to break ①The benzene ring is very stable ② A unique bond between single and double bonds Main chemical properties Substitution, oxidation (combustion) addition, oxidation Substitution, addition, oxidation (combustion)

3. The combustion rules of hydrocarbons

(1)

When the hydrocarbon CxHy with the same amount of material is completely burned, The amount of oxygen consumed depends on the value of "x y/4", The larger this value is, the more oxygen is consumed.

(2)

When equal masses of hydrocarbons are completely burned, The amount of oxygen consumed depends on the value of y/x in CxHy, The larger this value is, the more oxygen is consumed.

(3)

If the ratio of the number of carbon and hydrogen atoms in the composition of a hydrocarbon molecule is 1:2, The amounts of carbon dioxide and water produced after complete combustion are equal.

(4)

When various hydrocarbons of equal mass and the same simplest formula are completely burned The amount of oxygen consumed and the amount of carbon dioxide and water produced are equal.

(5)

The gaseous hydrocarbon CxHy is completely burned to produce CO2 and H2O.

①If the water produced after combustion is liquid

1(xy/4)x △V = V back - V front = - (1 y/4) < 0 (decrease)

Therefore, if the generated water is in a liquid state, The volume of gas after combustion must decrease, And the reduction value is only related to the number of hydrogen atoms in the hydrocarbon, It has nothing to do with the number of carbon atoms.

②If water becomes gaseous after burning

1 ( x y/4) x y/2 △V=Vback-Vfront=y/4-1

When y=4, △V=0, Gaseous hydrocarbons are mainly CH4, C2H4, and C3H4.

When y>4, △V>0 (increase), All gaseous hydrocarbons with N(H)>4 in the molecule are consistent.

When y<4, △V<0 (decrease), Among gaseous hydrocarbons, only C2H2 complies.