Medicine

Methodical instruction for students № 2

Methodical instruction for students № 5

 

Mononuclear arenas. The rules of orientation in benzene kernel.

 

The aim:

to form knowledge about the structure, classification, nomenclature, isomery, methods of receiving and chemical properties of arenes; to formulate knowledge about the structure, classification, isomery, methods of extraction of polynuclear arenes.

 

Practical skills:

а) to master the laboratory methods of receiving and study of chemical properties of the saturated hydrocarbons of aliphatic and alicyclic row; b) to be able to construct the devices and execute major operations which are used for determination of organic matters.

b) to be able to do the chemical reactions to polynuclear arenes.

 

 

Students independent study program.

1.    Mononuclear arenas, its concept.

2.    Nomenclature and isomery of arenes.

4.    Industrial and laboratory methods of receiving of arenes.

5.    Description of chemical connections in arenes:

Basic concepts of theme

Arenes

Sulfation

Nitration

Halogenation

Alkylation

Composition – Structure – Properties

Triphenyl radical

Triphenyl anion

Triphenyl kation

 

 Home tasks:

1.Name the compounds below:

2. Write the reactions through which you can make the following transformation:

3. What is the mass of trinitrotoluene is formed with 46.2 g of toluene, if output of reaction products is 80% of the theoretical?

4. Completion of benzene: a) 1.3-dinitro-4-hlorbenzene, b) 2.4-dihlorbenzonic acid, c) ethyl-p-tolilketon.
5. Through which reactions can distinguish toluene, benzene, styrene? Write the appropriate reactions and product names.

 

 

Practical part.

Experiment 1. The receiving of benzene and studying of its properties.

Reagents: sodium benzoate, natroncalc, concentrated HNO3, concentrated H2SO4, benzene, bromine water, KMnO4 (1% solution), H2SO4 (2N solution).

 

Technique of experiment.

а) receiving of benzene. Bring equal quantities of sodium benzoate and natroncalc in a dry test-tube. Close the test-tube by the cork with gas-pipeline. Dip the end of gas-pipeline in the test-tube with 2 drops of concentrated HNO3 and 3 drops of concentrated H2SO4. Heat it. Do it very carefully.

After the mixture is dark, stop heating. Add 8-10 drops of water and shake. As the result of reaction nitrobenzene formed (the smell of almond).

b) action bromine water and aqueous solution of potassium permanganate for benzene. In the two tubes to make 1 ml Benzene. To add another 1 ml of bromine water to another 1 ml of 1% solution of potassium permanganate and obtained mixture add 5 drops of 2 N. solution of sulfuric acid. The reaction mixture is mixed intensively in vitro and defend. Observed that bromine is dissolved in Benzene better than water, and because Benzene extracted from its aqueous solution. The top layer (benzenic) paint in brown colour. Decolouration of bromine of benzene bleaching does not occur. Does a bleaching solution and potassium permanganate. So Benzene is oxidation bromine water and aqueous solution of KMnO4, which distinguishes it in this case of unsaturated compounds, which are easily and quickly decolouration bromine water and aqueous solution of potassium permanganate.

Experiment 2. Toluene oxidation.

Reagents: toluen, potassium permanganate (5%  solution); sulfuric acid (2 n solution ).  Equipment: boiling water bath.

Methods of execution.  In 0.5 ml tube making toluenu, 1-2 ml of 5% of the first solution of potassium permanganate and 1 ml 2 n solution of sulfuric acid. The obtained reaction mixture is heated to the boiling water bath. Watched as decolouration solution of potassium permanganate. So toluen oxidation of potassium permanganate. Not subjected to oxidation benzenne core, which is resistant to action of potassium permanganate, and the side chain - alkilyne radical.  Potassium permanganate oxidation toluen in benzoic acid.

Experiment 3. Bromination of benzene, toluene.

Reagents: benzene; toluene; bromide (solution in CCl 4, 1:5); iron sawdust; litmus paper blue; ammonia (25% solution).

Equipment: boiling water bath.

 ( Experiment conducted under exhaust cabinets.)

Methods of execution.

a) the reaction in the presence of a catalyst. In the two dry test-tubes bring in 1 ml of bromine in carbon tetrachloride. Afterwards, at each tube is added to 0.1 g iron sawdust. Then, in one test- tube add 1 ml of benzene and the other - 1 ml toluene. Test tubes with reaction mixture put in the support and often mixed. Watched as decolouration bromine toluene. The mouth  test-tube with a reactionary mixture containing toluene, trays smeared with water blue litmus paper or a glass stick, soaked in concentrated (25% ) ammonia solution. Litmus blue, and in the case of the ammonia produced white smoke of ammonium bromide. So toluen proactive for benzene in response bromination. During bromination toluene catalyst in the presence of hydrogen of benzene nucleus  toluenu substituted for bromine, followed by separation HBr.

The test-tube with a reactionary mixture containing benzene, put on hot a water bath. After some time watching how decolouration bromide benzene, indicating the interaction of benzene with bromine. Interaction of benzene with bromine in the presence of iron sawdust also accompanied by a HBr, and it is a litmus test or a concentrated solution of ammonia, as in the case bromination toluene.

Select HBr during interaction benzene with bromine indicates substitution of hydrogen in its molecule of bromine.

b) the reaction in the absence of catalyst.

Reagents: benzene,toluene; bromide (solution in CCl 4, 1:5).

Equipment:  boiling water bath.

 (An experiment conducted under exhaust cabinets.)

Methods of execution. An experiment conducted in two dry test- tubes, each of which contribute to 1 ml of bromine in CCl 4 (1:5). Then make a test- tube 1 ml of benzene and the other - 1 ml toluenu. Both test-tubes with the reaction mixture left to stand in the support, often mixing their contents. Watched as the reduced intensity of coloration of bromine in vitro and toluene, whereas in vitro with benzene is not any change. Then, each obtained reaction mixture is divided into two parts. To do this, with each tube pour half of its contents into another dry test-tube. One portion of each reaction mixture left to stand in the support, and another put in a water bath hot. Please note that the reaction mixture with toluene decolouration quickly, which is a sign of reaction bromination toluene. The mouth test-tube  with a reactionary mixture containing toluene, trays smeared with water blue litmus paper or a glass stick, soaked in concentrated ammonia solution. Litmus paper becomes red, and ammonia forms a white smoke of ammonium bromide. Change the color of blue litmus and formation of ammonium bromide indicates that the process bromination toluene in the absence of catalyst released HBr. So bromination toluene in the absence of catalyst is also on the type of substitution reaction.

The reaction mixture of benzene decolouration not even in the case of long heating in a water bath. So benzene in these conditions does not react with bromine. A drop of the reaction mixture obtained during bromination  toluene, applied to the strip of filter paper and allow it to dry in the air. (Dry box!) This HBr, toluene evaporate and carbon tetrachloride, and the paper is product bromination toluene - benzyl bromide, which a sharp halls and a tear. (Sniff gently!)

So, in the absence of a catalyst for hydrogen atoms in benzene and its homologs benzenic nucleus of bromine is replaced. In these circumstances, react the hydrogen atom side chains (eg, hydrogen atoms CH 3-group molecules toluene).

Experiment 4. Sulfonation of benzene, toluene and xylene.

Reagents: Benzene; toluene, p-xylene; sulfuric acid (concentrated, r = 1,84 g / cm 3).

Equipment:  boiling water bath.

Methods of execution.

A study conducted in three dry test tubes. The first of them make 0.5 ml of benzene in the second - 0.5 ml toluene in third - 0.5 ml p-xylene. Then, to aromatic hydrocarbons in each test-tube is added to 3 ml of concentrated sulfuric acid. The reaction mixture in the mixing vial. Aromatic hydrocarbons with sulfuric acid forming emulsion that form two layers while standing. Reaction mixture obtained simultaneously asked for hot a water bath. During the heat content probirok frequently and intensively mixed. Pay attention to the fact that the upper oily layer in a test- tube over time decreases, then disappears completely and the reaction mixture don′t form two layers. Therefore, aromatic hydrocarbons are sulfonation and sulfoacids reaction that will occur at the same time, dissolve in sulfuric acid. Sulfonation happening fastest in the case of p-xylene, and slowest - of benzene. The reaction mixture in the test tubes cooled and poured into three other tubes, each of which contains 6 ml of water. Вихідні ароматичні вуглеводні не виділяються при цьому у вигляді маслянистих крапель. Weekend aromatic hydrocarbons while not highlighted in the form of oily drops. Therefore, aromatic hydrocarbons sulfonationed and sulfoacids to emerge at that dissolve well in water.

In response to the activity sulfuvannya studied aromatic hydrocarbons can be placed in a row:

p-xylene> toluene> benzene

Obtained during sulfonation toluene o- and p-tolilsulfoacids can be identified as their sodium salts. To do this, 2-3 ml of aqueous reaction mixture obtained during sulfonation toluene, poured into another tube, which then add 6.7 ml of saturated aqueous sodium chloride. Watched as the precipitate formed sodium salts and o-p-tolilsulfoacids white colour, whose solubility in the presence of a large number of sodium ions is very small.

sulfonation of arenes

 

 

A student must know:

the structure, nomenclature, methods of extraction and chemical properties of polynuclear arenes.

 

A student must be able:

      to be able to do the chemical reactions to polynuclear arenes.

 

Prepared by assist. Burmas N.I..

Adopted at the Chair Sitting Minutes № 5

19” June, 2008, Revised