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Органическая химия = Organic Chemistry. Лабораторный практикум

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Reactivity of benzene homologs

	CH2Br Br	CH3 Br2	CH3Br	CH3
HBr +	2		+	+ HBr
HBr +	t	Fe	+	+ HBr
	t	Fe	o-bromotoluene	Br
	benzyl	KMnO4	o-bromotoluene	Br
	bromide	KMnO4	COOH	p -bromotoluene
		100°C	benzoic acid

Benzenehomologshavetworeactivecenters:benzenering and side-chain (alkyl groups). The reaction pathway depends on the nature of the reagent.

The side-chain reactions proceed via radical substitution mechanism, whereas reactions for benzene ring via electrophilic substitution mechanism.

Laboratory work №2.		Aromatic compounds
№	Procedure		Equations of reactions	Observations
Exp

1Interactions of toluene with bromine water

and potassium permanganate aqueous Br2 aq solution:

Take two test tubes.

Place about 1 ml of bromine water into the first test tube and about 1 ml of potassium

	permanganate aqueous solution into the	KMnO4
	second test tube.	KMnO4	o
		H2O, 20		C

	Into each test tube add about 1 ml of
	Into each test tube add about 1 ml of
	toluene (methylbenzene).
Accurately shake both test tubes.

2	Bromination of toluene:
	Place 2 ml of bromine water and 2 ml of	H3C	Br2
	toluene into a test tube. Put the obtained		Br2
			t

	mixture into a steam bath for 5 minutes.
	mixture into a steam bath for 5 minutes.
	Place 2 ml of bromine water and 2 ml of	H3C	Br2
	toluene into a test tube. Add some iron
	toluene into a test tube. Add some iron
	dust. Put the obtained mixture into a steam		Fe
	dust. Put the obtained mixture into a steam		Fe
	bath for 5 minutes.

3Nitration of toluene:

		Into a flask with plate bottom place 2 ml	H3C	HNO3 к
		(accurate amount) of concentrated sulfuric
				H2SO4 к

		acid and 1 ml (accurate amount) of
		acid and 1 ml (accurate amount) of
		concentrated nitric acid. The amounts of
		the acids should be measured by a
		cylinder!!!
		Add 1 ml of toluene to the obtained
		mixture of acids.
		Close the flask with a stopper and shake it
		vigorously for 5 minutes.
		Then pour out the mixture into a glass with
		cool water.

4	Combustion of toluene:		H3C	O2
		This experiment is carried out by a
				t °C

		laboratory assistant for the group.
		laboratory assistant for the group.

HALIDES

Halides are organic compounds in which one or several hydrogen atoms are substituted by halogen atoms (fluorine, chlorine, bromine and iodine). There are aliphatic, aromatic and unsaturated halides.

CH3-Cl	CH2=CH-Br		Cl		CH2Cl
CH3-Cl	CH2=CH-Br
chloromethane	vinyl bromide	chlorobenzene		benzyl chloride
methyl chloride		chlorobenzene		benzyl chloride

The most important reaction for alkyl halides is nucleophilic substitution. The carbon-halogen bond is polarized due to the greater electronegativity of the halogen atom. Thus, the carbon atom acquires a partial positive charge (δ-), the halogen atom – a partial negative charge(δ+). In the reactions with nucleophilic reagents the halogen atoms are substituted for nucleophile, so instead of the halogen atoms there will be other atoms or groups of atoms in the molecule.

R CH2

NO2

nitroalkane

R-CH2-CH2-R

AgNO2

NH3

alkane

amine

H2O

R-CH2-Mg-Hal

R CH2

Hal

CH2

Grignard reagent

KOH

CH3ONa

KCN

alcohol

alc.

CH2

R'-CH=CH2

R CH2 OCH3

nitrile

alkene

ether

Besides nucleophilic substitution reactions alkyl halides react with metals: reaction with sodium metal leads to the coupling of the alkyl radicals (Wurtz reaction), reaction with magnesium metal yields organomagnesium compounds (Grignard reagents).

In the presence of alcoholic solution of sodium hydroxide elimination of hydrogen halide (dehydrohalogenation) occurs providing alkenes as products.

Compounds having halogen atom attached to a sp2-hybridized carbon atom or to a double bond are less reactive. The lack of reactivity can be explained by the conjugation of the lone pair of the halogen atom and the π-electron system of benzene ring or the double bond. As a result the carbon-halogen bond becomes stronger and unreactive in the in nucleophilic substitution under the ordinary conditions.

	Cl		OH
	Cl	KOH solid
KOH		KOH solid	+ KCl
KOH			+ KCl
H O
2
2		300 C	phenol
			phenol

For the detection of halogen atom in halides there is Beilstein’s test. A copper wire is cleaned and heated in a Bunsen burner flame. It is then dipped in the sample to be tested and once again heated in a flame. A positive test is indicated by a green flame. The test does not detect fluorine/fluorides.

Laboratory work №3.		Alkyl halides
№	Procedure			Equations of reactions	Observations
Exp
1	Preparation of ethyl bromide:
	Theexperimentiscarriedoutbythelaboratory			H2SO4
	assistant for the group.		CH3CH2OH	H2SO4
	assistant for the group.		CH3CH2OH	KBr
	Place 3 ml of ethanol and 3 ml of sulfuric
	acid into a Wurts flask. Cool it down. Add
	2 ml of water and 3 g of potassium
	bromide.
	Place 5 ml of water into a test tube and put
	it into a glass with ice. Put the end of
	delivery tube of the Wurts flask in to the
	test tube with ice.
	Close the flask with a stopper and heat it
	on a gas-burner.

2Beilstein’s test:

Put into the flame the copper wire and temper it until there is no color flame.

Cool it to the room temperature and put the wire into flask with alkyl halide.

Put the wetted wire into the flame and pay your attention to the color of the

flame.

Bromine contained in alkyl halide reacts with copper, forming copper bromide (II). On evaporation copper halides paint the flame green.

3Hydrolysis of benzyl chloride and

chlorobenzene:	Cl
Take two test tubes.			HOH		AgNO3
Take two test tubes.			HOH		AgNO3
Place 1 ml of chlorobenzene into the				....		....


first test tube and 1 ml of benzyl
chloride into the second one.		CH2Cl
Add 5 ml of water into each test tube		CH2Cl
and heat it.			HOH		AgNO3
To the hot solutions add 1 drop of silver				....		....
				....		....

nitrate solution.

ALCOHOLS. PHENOL

Alcohols are compounds which molecules have a hydroxyl group attached to a saturated (sр3-hybridized) carbon atom. In phenols a hydroxyl group is attached directly to an aromatic ring. Compounds which contain more than one –OH group are called

polyhydric alcohols or polyols.
Nomenclature: functional group – hydroxyl – ОH; suffix							- ol.
CH -OH	H	C-CH-CH		CH2-CH2		CH2-CH-CH2		OH

3	3	3		OH OH		OH OH OH
methanol		OH					phenol
	propan-2-ol		ethandiol		pronan-1,2,3-triol

		R-CH2-Hal + H2O
		alkyl halide
R-CH2-O-Na	Na	HHal		H2SO4		R-CH2-O-SO3H + H2O
R-CH2-O-Na				H2SO4		R-CH2-O-SO3H + H2O
alcoxide					0°C	alkyl hydrogen sulfonate
O	Cu				R-CH2-O-H
O	Cu				R-CH2-O-H
R-C		R-CH2-O-H				R-CH2-O-CH2-R + H2O
R-C	3000C	R-CH2-O-H			H2SO4	R-CH2-O-CH2-R + H2O
H	3000C				H2SO4	ether
aldehyde	[O]				140 °C
					140 °C
			R-COOH		H2SO4

O
O			H+		180 °C	R'-CH=CH2 + H2O
R-C OH			O			alkene
carboxylic acid		R-C		ester
			OCH R	ester
		2

Typical reactions for alcohols proceed both through a breaking of О-Н bond (formation of alcoxides, esterification, oxidation, dehydrogenation), and through abreakingofС-Оbond(nucleophilicsubstitutionofOH group, formation of ethers, dehydration).

	OH			OH			OH	OH
Br	Br		Br
					HNO3 dil.		NO2
			2				+	+ H2O
			H2O		0 °C
	Br							NO2
						о-nitrophenol
2,4,6-tribromophenol				NaOH				p -nitrophenol
(white precipitate)								O
	OCH3					O
				ONa	CH3-C		O C CH3
		CH3Cl
						Cl
methoxybenzene			sodium phenolate				phenyl acetate
(anisole)

Specific reactions for phenols are based on two reactive centers, which are hydroxyl group and aromatic ring. Phenols are more acidic in comparison with aliphatic alcohols due to the conjugation of OH group with the benzene ring. Moreover, this conjugation makes substitution of OH group almost impossible thus in case of phenols esterification reaction and substitution reaction of OH group for halogen do not occur.

Laboratory work №4.		Alcohols. Phenols
№	Procedure		Equations of reactions	Observations
Exp
1	Solubility of alcohols and phenols in water:		Draw the structures of the used alcohols.
	Take three test tubes.
	Place about 1 ml of ethanol into the first
	test tube, butyl alcohol into the second
	one, amylic alcohol into the third one.
	Add 1 ml of water into each test tube.
	Shake the test tubes accurately.

2Preparation of sodium phenolate:

Take phenol from the laboratory	OH	NaOH
assistant.		NaOH
assistant.

Add 1 ml of water to the test tube with phenol. (You must obtain a dull solution)

Into the obtained mixture of phenol with	ONa	H2SO4
Into the obtained mixture of phenol with	ONa	H2SO4
water add 10% solution of NaOH
water add 10% solution of NaOH
dropwise until you get a clear solution.
Shake well the test tube after the each	ONa	CO2
drop of NaOH solution.	ONa	CO2

		H2O
Divide the obtained mixture into two test		H2O
tubes.

Into the first test tube add several drops of sulfuric acid.

Bubble carbon dioxide into the second test tube.

3Preparation of sodium ethanolate:

Take from the laboratory assistant about 1 CH CH OH Na
ml of ethanol.	3	2
ml of ethanol.
Add a piece of sodium metal to it.

4Bromination of phenol:

Take from the laboratory assistant about 1

ml of phenol aqueous solution.		OH Br2 aq
Add about 1 ml of bromine water to it.
Add about 1 ml of bromine water to it.

5Copper glycerate preparation:

Place into a test tube 1 ml of 2% copper sulfate solution.

Add 2 ml of 10% sodium hydroxide solution into the test tube. You see the formation of the blue precipitate of Cu(OH)2.

Into the same test tube add 8 drops of glycerol. Shake well.

Add about 1 ml of HCl to the obtained copper glycerate.

CuSO4 + NaOH Cu(OH)2 + Na2SO4

H2C	OH Cu(OH)2	.....	HCl

HC	OH



H2C OH

ALDEHYDES AND KETONES

Aldehydes and ketones are compounds which molecules have carbonyl group (C=O). So, the other name for them is carbonyl compounds.

Nomenclature

In aldehydes the carbonyl group is bonded to one alkyl group and to one hydrogen atom.

The suffix –al is appended to the name of the hydrocarbon corresponding to the longest carbon chain that includes the carbonyl (aldehyde) carbon. The numbering of the carbon chain always starts from the aldehyde carbon atom.

H-C O	CH -C	O	CH3-CH2-C O	OCH
H	3	H	H

methanal	ethanal		propanal

formadehyde	acetadehyde			benzadehyde

In ketones the carbonyl group is bonded to two alkyl radicals.

The suffix –one is appended to the name of the hydrocarbon corresponding to the longest carbon chain that includes the carbonyl carbon. The chain is numbered to give the carbonyl group the lowest possible number.

CH3-C-CH3	CH3-C-CH2CH3
O	O
propanone, acetone,	butanone
dimethylketone	ethylmethylketone

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