ass. Medvid I.I., ass. Burmas N.I.ass. Medvid I.I., ass. Burmas N.I.

Reactionary ability of the Reactionary ability of the saturated saturated hydrocarbons hydrocarbons (a(alkaneslkanes,, cycloalkanes cycloalkanes).).

Reactionary ability of the Reactionary ability of the unsaturated unsaturated hydrocarbons hydrocarbons ((aalkeneslkenes, a, alkadieneslkadienes, a, alkyneslkynes).).

1.1. Concept of alkanesConcept of alkanes

2.2. Structure of alkanesStructure of alkanes

3.3. Nomenclature of alkanesNomenclature of alkanes

4.4. The isomery of alkanesThe isomery of alkanes

5.5. The methods of extraction of alkanesThe methods of extraction of alkanes

6.6. Physical properties of alkanesPhysical properties of alkanes

7.7. Chemical properties of alkanesChemical properties of alkanes

8.8. Structure of cycloalkanesStructure of cycloalkanes

9.9. Nomenclature of cycloalkanesNomenclature of cycloalkanes

10.10. Conformation of cycloalkanesConformation of cycloalkanes

11.11. The methods of extraction of cycloalkanesThe methods of extraction of cycloalkanes

12.12. Chemical properties of cycloalkanesChemical properties of cycloalkanes

OutlineOutline

13.13. Concept of alkenesConcept of alkenes14.14. The nomenclature of alkenesThe nomenclature of alkenes15.15. The isomery of alkenesThe isomery of alkenes16.16. The methods of extraction of alkenesThe methods of extraction of alkenes17.17. Physical properties of alkenesPhysical properties of alkenes18.18. Chemical properties of alkenesChemical properties of alkenes19.19. The nomenclature of dienesThe nomenclature of dienes20.20. Configurational isomers of dienesConfigurational isomers of dienes21.21. The methods of extraction of dienesThe methods of extraction of dienes22.22. Chemical properties of dienesChemical properties of dienes23.23. The nomenclature and isomery of alkynesThe nomenclature and isomery of alkynes24.24. The nomenclature and isomery of alkynesThe nomenclature and isomery of alkynes25.25. The methods of extraction of alkynesThe methods of extraction of alkynes26.26. Physical propertiesPhysical properties27.27. Chemical propertiesChemical properties

Alkanes are the hydrocarbons of aliphatic row. Alkanes are hydrocarbons in which all the bonds are single covalent bonds (-bonds). Alkanes are called saturated hydrocarbons.

Alkanes have the general molecular formula CnH2n+2. The simplest one, methane (CH4), is also the most abundant. Large amounts are present in our atmosphere, in the ground, and in the oceans. Methane has been found on Jupiter, Saturn, Uranus, Neptune, and Pluto, and even on Halley's Comet.

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Pentane C5H12

Hexane C6H14

Heptane C7H16

Octane C8H18

Nonane C9H20

Decane C10H22

Undecane C11H24

Dodecane C12H26

Tridecane C13H28

Tetradecane C14H30

Pentadecane C15H32

Alkanes:

Alkanes can have either simple (unbranched) or branched Carbon chain. Alkanes with unbranched Carbon chain are called normal or n-alkanes.

In the molecules of alkanes all Carbon atoms are in the state of sp3-hybridization. The distance between two Carbon atoms is 0.154 nm, but the distance between two atoms of Carbon and Hydrogen is 0.110 nm. The rotation can take place around C—C bonds. As the result of this rotation the molecule have different conformations (spatial forms).

n-nonane

Some alkanes have trivial names. Methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and neopentane are trivial names. Other alkanes have IUPAC names in which the number of carbon atoms in the chain is specified by a Latin or Greek prefix preceding the suffix -ane, which identifies the compound as a member of the alkane family.

IUPAC Names of Unbranched Alkanes

1. To chose the longest Carbon chain in the molecule.

H3C CH

CH3

CH CH2

CH

CH3

H3C CH3

the longest main chain(is the most branched,has 3 substituents)

H3C CH

CH3

CH CH2

CH

CH3

H3C CH3

not the longest main chain(is not the most branched,has 2 substituents)

2. To identify the substituent groups attached to the parent chain.

H3C CH

CH3

CH2 CH2 CH31 2 3 4 5

If in molecule there are two and more similar substituents on the equal distance from the ends of the longest chain, it is necessary to begin the numbering from the end of Carbon chain where there are more substituents.

4-ethyl-3-methyloctane

In the molecules of organic compounds the atom of Carbon is connected with the atom of Carbon or the atom of Hydrogen. There are the primary, the secondary, the tertiary and the quaternary carbon atoms. The primary carbon atom is the atom which is connected only with one atom of carbon. The secondary carbon atom is the atom which is connected with two atoms of carbon. The tertiary carbon atom is the atom which is connected with three atoms of carbon. The quaternary carbon atom is the atom which is connected with four atoms of carbon.

1,2,3,4,5 – primary;6 – secondary;7 – tertiary;8 – quaternary.

H3C CH C

CH3

CH3

CH2

CH3

CH31

2

3

45

67 8

The Number of Constitutionally Isomeric Alkanes of Particular Molecular Formulas

C

CH3

H2CH

CH2H3C CH2 CH3

R-3-methylhexane

C

CH3

CH2H

H2C

S-3-methylhexane

CH3H2CH3C

FractionFraction Boiling Boiling temperatutemperatu

re, re, CC

Alkanes mixture (the Alkanes mixture (the number of Carbon number of Carbon

atoms)atoms)

Petroleum etherPetroleum ether 20-6020-60 CC55, C, C66

BenzineBenzine 60-18060-180 CC6 6 -C-C1010

KeroseneKerosene 180-230180-230 CC1111, C, C1212

Diesel fuel Diesel fuel 230-300230-300 CC13 13 - C- C1717

Black oilBlack oil More than 300More than 300 CC1818 and more and more

The main natural sources of alkanes are petroleum and gas. Petroleum is the complex mixture of organic compounds; the main components of petroleum are branched and normal alkanes. Gas consists of gaseous alkanes — methane (95%), ethane, propane, butane. For receiving alkanes from petroleum it is necessary to use fractional distillation. As the result several fractions are received:

This table lists that each fraction is the mixture of hydrocarbons which have equal points of boiling temperature. Gas is shared to its components by fractional distillation too.

1. Hydration of carbon (II) oxide. The mixture of CO and H2 is heated at temperature 180-300C. In this reaction catalysts are Fe and Co). As the result the mixture of n-alkanes appears.

CO 2H2Fe (Co)

H2O+ n-alkanes +

This method is often used in industry for receiving of artificial benzine.

H3C C C CH3 H2 H3C C C CH3

H H

+butyne-2

Pt (Pd, Ni)

butene-2

H3C C C CH3

H H

H2 H2CH2CH3C CH3+butane

Pt (Pd, Ni)

butene-2

H3C CH2 CO

ONaNaOH H3C CH3 Na2CO3+ +

C

H

I

H

H 2Na H3CH3C 2NaI+2

iodomethane

ethane

+

4. Allowing of salts of carboxylic acids and alkalis.

The first four alkanes in homological row are gaseous at room temperature. The unbranched alkanes pentane (C5H12) through heptadecane (C17H36) are liquids, whereas higher homologs are solids. The boiling points of unbranched alkanes increase with the number of carbon atoms. Branched alkanes have lower boiling points than their unbranched isomers. Isomers have the same number of atoms and electrons, but a molecule of a branched alkane has a smaller surface area than an unbranched one. The extended shape of an unbranched alkane permits more points of contact for intermolecular associations.

In normal conditions alkanes do not react with acids and alkalis because -bonds in their molecules are very strong. But alkanes take part in such reactions as:

-reactions of the substitution;-reactions of the substitution;-reactions of the oxidation; -reactions of the oxidation; -reactions of the destruction.-reactions of the destruction.

1. Halogenation of alkanes.1. Halogenation of alkanes. Alkanes Alkanes react with halogens (except Ireact with halogens (except I22). ).

CH4 Cl2 HCl H3C Cl+ +chlormethane

H3C Cl Cl2 HCl H2C Cl

Cl

+dichlormethane

+

CH

Cl

Cl

Cl Cl2 HCl C Cl

Cl

Cl

Cl

+

tetrachlormethane

+

H2C Cl

Cl

Cl2 HCl CH

Cl

Cl

Cl+

trichlormethane

+

H3C CH2 CH3 SO2 Cl2 H3C CH2 CH2 SO2Cl HCl+ + +

H3C CH2 CH3 HNO3 H3C CH2 CH2 NO2 H2O+ +t, p

Alkanes can burn if oxygen is present. As Alkanes can burn if oxygen is present. As the result Hthe result H22O and COO and CO22 appear. appear.

CH4 + 2O2 → CO2 + 2H2O

Cracking is the destroying of some −C−C− and Cracking is the destroying of some −C−C− and −C−H bonds in the molecule of alkanes at high −C−H bonds in the molecule of alkanes at high temperature.temperature.

CH3−CH3 → CH2=CH2 + H2

CH3−CH2−CH2−CH3 → CH4 + CH2=CH−CH3

CH3−CH3 + CH2=CH2

Cycloalkanes are hydrocarbons in which all Carbon Cycloalkanes are hydrocarbons in which all Carbon atoms form the cycle and are in the state of spatoms form the cycle and are in the state of sp33--hybridization. Cycloalkanes are saturated hybridization. Cycloalkanes are saturated hydrocarbons. Cycloalkanes have the general hydrocarbons. Cycloalkanes have the general molecular formula Cmolecular formula CnnHH2n2n..

Early chemists observed that cyclic Early chemists observed that cyclic compounds found in nature generally had compounds found in nature generally had five- or sixmembered rings. Compounds five- or sixmembered rings. Compounds with three- and fourmembered rings were with three- and fourmembered rings were found much less frequently. This found much less frequently. This observation suggested that compounds observation suggested that compounds with five- and sixmembered rings were with five- and sixmembered rings were more stable than compounds with three- more stable than compounds with three- or fourmembered rings.or fourmembered rings.

In 1885, the German chemist Adolf von Baeyer In 1885, the German chemist Adolf von Baeyer proposed that the instability of three- and proposed that the instability of three- and fourmembered rings was due to angle strain. We fourmembered rings was due to angle strain. We know that, ideally, an spknow that, ideally, an sp33-hybridized carbon has -hybridized carbon has bond angles of 109.5°. Baeyer suggested that the bond angles of 109.5°. Baeyer suggested that the stability of a cycloalkane could be predicted by stability of a cycloalkane could be predicted by determining how close the bond angle of a planar determining how close the bond angle of a planar cycloalkane is to the ideal tetrahedral bond angle cycloalkane is to the ideal tetrahedral bond angle of 109.5°. The angles in an equilateral triangle of 109.5°. The angles in an equilateral triangle are 60°. The bond angles in cyclopropane, are 60°. The bond angles in cyclopropane, therefore, are compressed from the ideal bond therefore, are compressed from the ideal bond angle of 109.5° to 60°, a 49.5° deviation. This angle of 109.5° to 60°, a 49.5° deviation. This deviation of the bond angle from the ideal bond deviation of the bond angle from the ideal bond angle causes strain called angle causes strain called angle strainangle strain..

The angle strain in a three-membered ring can be appreciated The angle strain in a three-membered ring can be appreciated by looking at the orbitals that overlap to form the σ-bonds in by looking at the orbitals that overlap to form the σ-bonds in cyclopropane. Normal σ-bonds are formed by the overlap of cyclopropane. Normal σ-bonds are formed by the overlap of two sptwo sp33-orbitals that point directly at each other. In -orbitals that point directly at each other. In cyclopropane, overlapping orbitals cannot point directly at cyclopropane, overlapping orbitals cannot point directly at each other. Therefore, the orbital overlap is less effective than each other. Therefore, the orbital overlap is less effective than in a normal −C−C− bond. The less effective orbital overlap is in a normal −C−C− bond. The less effective orbital overlap is what causes angle strain, which in turn causes the −C−C− what causes angle strain, which in turn causes the −C−C− bond to be weaker than a normal −C−C− bond. Because the bond to be weaker than a normal −C−C− bond. Because the −C−C− bonding −C−C− bonding orbitals in cyclopropane can’t point directly at each other, they have shapes that resemble bananas and, consequently, are often called banana bonds. In addition to possessing angle strain, threemembered rings have torsional strain because all the adjacent −C−H bonds are eclipsed.

The bond angles in planar cyclobutane would have The bond angles in planar cyclobutane would have to be compressed from 109.5° to 90°, the bond to be compressed from 109.5° to 90°, the bond angle associated with a planar four-membered angle associated with a planar four-membered ring. Planar cyclobutane would then be expected ring. Planar cyclobutane would then be expected to have less angle strain than cyclopropane to have less angle strain than cyclopropane because the bond angles in cyclobutane are only because the bond angles in cyclobutane are only 19.5° away from the ideal bond angle.19.5° away from the ideal bond angle.

Baeyer predicted that cyclopentane would be Baeyer predicted that cyclopentane would be the most stable of the cycloalkanes because the most stable of the cycloalkanes because its bond angles (108°) are closest to the ideal its bond angles (108°) are closest to the ideal tetrahedral bond angle. He predicted that tetrahedral bond angle. He predicted that cyclohexane, with bond angles of 120°, would cyclohexane, with bond angles of 120°, would be less stable and that as the number of sides be less stable and that as the number of sides in the cycloalkanes increases, their stability in the cycloalkanes increases, their stability would decrease.would decrease.

Contrary to what Baeyer predicted, cyclohexane is Contrary to what Baeyer predicted, cyclohexane is more stable than cyclopentane. Furthermore, more stable than cyclopentane. Furthermore, cyclic compounds do not become less and less cyclic compounds do not become less and less stable as the number of sides increases. The stable as the number of sides increases. The mistake Baeyer made was to assume that all mistake Baeyer made was to assume that all cyclic molecules are planar. Because three cyclic molecules are planar. Because three points define a plane, the carbons of points define a plane, the carbons of cyclopropane must lie in a plane. The other cyclopropane must lie in a plane. The other cycloalkanes, however, are not planar.cycloalkanes, however, are not planar.

Angle strain Angle strain is the strain induced in a molecule is the strain induced in a molecule when the bond angles are different from the ideal when the bond angles are different from the ideal tetrahedral bond angle of 109.5°.tetrahedral bond angle of 109.5°.

Torsional strain Torsional strain is caused by repulsion between is caused by repulsion between the bonding electrons of one substituent and the the bonding electrons of one substituent and the bonding electrons of a nearby substituent.bonding electrons of a nearby substituent.

Steric strain Steric strain is caused by atoms or groups of is caused by atoms or groups of atoms approaching each other too closely.atoms approaching each other too closely.

Although planar cyclobutane would have less angle strain than Although planar cyclobutane would have less angle strain than cyclopropane, it could have more torsional strain because it has cyclopropane, it could have more torsional strain because it has eight pairs of eclipsed hydrogens, compared with the six pairs of eight pairs of eclipsed hydrogens, compared with the six pairs of cyclopropane. So cyclobutane is not a planar molecule—it is a cyclopropane. So cyclobutane is not a planar molecule—it is a bent molecule. One of its methylene groups is bent at an angle of bent molecule. One of its methylene groups is bent at an angle of about 25° from the plane defined by the other three carbon about 25° from the plane defined by the other three carbon atoms. This increases the angle strain, but the increase is more atoms. This increases the angle strain, but the increase is more than compensated for by the decreased torsional strain as a than compensated for by the decreased torsional strain as a result of the adjacent hydrogens not being as eclipsed, as they result of the adjacent hydrogens not being as eclipsed, as they would be in a planar ring.would be in a planar ring.

If cyclopentane were planar, as Baeyer had If cyclopentane were planar, as Baeyer had predicted, it would have essentially no angle predicted, it would have essentially no angle strain, but its 10 pairs of eclipsed hydrogens strain, but its 10 pairs of eclipsed hydrogens would be subject to considerable torsional strain. would be subject to considerable torsional strain. So cyclopentane puckers, allowing the So cyclopentane puckers, allowing the hydrogens to become nearly staggered. In the hydrogens to become nearly staggered. In the process, however, it acquires some angle strain. process, however, it acquires some angle strain. The puckered form of cyclopentane is called the The puckered form of cyclopentane is called the envelope conformation envelope conformation because the shape because the shape resembles a squarish envelope with the flap up.resembles a squarish envelope with the flap up.

spiranic system

condensed system

bridge system

Cycloalkanes are almost always written as Cycloalkanes are almost always written as skeletal skeletal structuresstructures. Skeletal structures show the carbon–carbon . Skeletal structures show the carbon–carbon bonds as lines, but do not show the carbons or the bonds as lines, but do not show the carbons or the hydrogens bonded to carbons. Atoms other than carbon and hydrogens bonded to carbons. Atoms other than carbon and hydrogens bonded to atoms other than carbon are shown. hydrogens bonded to atoms other than carbon are shown. Each vertex in a skeletal structure represents a carbon. It is Each vertex in a skeletal structure represents a carbon. It is understood that each carbon is bonded to the appropriate understood that each carbon is bonded to the appropriate number of hydrogens to give the carbon four bonds.number of hydrogens to give the carbon four bonds.

In the case of a cycloalkane with an attached alkyl In the case of a cycloalkane with an attached alkyl substituent, the ring is the parent hydrocarbon substituent, the ring is the parent hydrocarbon unless the substituent has more carbon atoms than unless the substituent has more carbon atoms than the ring. In that case, the substituent is the parent the ring. In that case, the substituent is the parent hydrocarbon and the ring is named as a substituent.hydrocarbon and the ring is named as a substituent.

There is no need to number the position of a single There is no need to number the position of a single substituent on a ring.substituent on a ring.

If the ring has two different substituents, If the ring has two different substituents, they are cited in they are cited in alphabetical order alphabetical order and and the number 1 position is given to the the number 1 position is given to the substituent cited first.substituent cited first.

If there are more than two substituents on the ring, they are If there are more than two substituents on the ring, they are cited in alphabetical order. The substituent given the number cited in alphabetical order. The substituent given the number 1 position is the one that results in a second substituent 1 position is the one that results in a second substituent getting as low a number as possible. If two substituents have getting as low a number as possible. If two substituents have the same low number, the ring is numbered—either the same low number, the ring is numbered—either clockwise or counterclockwise—in the direction that gives clockwise or counterclockwise—in the direction that gives the third substituent the lowest possible number. For the third substituent the lowest possible number. For example, the correct name of the following compound is 4-example, the correct name of the following compound is 4-ethyl-2-methyl-1-propylcyclohexane, not 5-ethyl-1-methyl-2-ethyl-2-methyl-1-propylcyclohexane, not 5-ethyl-1-methyl-2-propylcyclohexane:propylcyclohexane:

The cyclic compounds most commonly found in nature contain The cyclic compounds most commonly found in nature contain sixmembered rings because such rings can exist in a sixmembered rings because such rings can exist in a conformation that is almost completely free of strain. This conformation that is almost completely free of strain. This conformation is called the conformation is called the chair conformation.chair conformation. In the chair In the chair conformer of cyclohexane, all the bond angles are 111°, conformer of cyclohexane, all the bond angles are 111°, which is very close to the ideal tetrahedral bond angle of which is very close to the ideal tetrahedral bond angle of 109.5°, and all the adjacent bonds are staggered.109.5°, and all the adjacent bonds are staggered.

Cyclohexane can also exist in a Cyclohexane can also exist in a boat conformationboat conformation. Like the . Like the chair conformer, the boat conformer is free of angle strain. chair conformer, the boat conformer is free of angle strain. However, the boat conformer is not as stable as the chair However, the boat conformer is not as stable as the chair conformer because some of the bonds in the boat conformer because some of the bonds in the boat conformer are eclipsed, giving it torsional strain. The boat conformer are eclipsed, giving it torsional strain. The boat conformer is further destabilized by the close proximity of conformer is further destabilized by the close proximity of the the flagpole hydrogens flagpole hydrogens (the hydrogens at the “bow” and (the hydrogens at the “bow” and “stern” of the boat), which causes steric strain.“stern” of the boat), which causes steric strain.

When the carbon is pulled down to the point When the carbon is pulled down to the point where it is in the same plane as the sides of the where it is in the same plane as the sides of the boat, the very unstable boat, the very unstable half-chair conformer half-chair conformer is is obtained. Pulling the carbon down farther obtained. Pulling the carbon down farther produces the produces the chair conformer. chair conformer. The graph in The graph in figure shows the energy of a cyclohexane figure shows the energy of a cyclohexane molecule as it interconverts from one chair molecule as it interconverts from one chair conformer to the other; the energy barrier for conformer to the other; the energy barrier for interconversion is 12.1 kcal/mol (50.6 kJ/mol). interconversion is 12.1 kcal/mol (50.6 kJ/mol). From this value, it can be calculated that From this value, it can be calculated that cyclohexane undergoes 10 ring flips per second cyclohexane undergoes 10 ring flips per second at room temperature. In other words, the two at room temperature. In other words, the two chair conformers are in rapid equilibrium. chair conformers are in rapid equilibrium.

Because the chair conformers are the most Because the chair conformers are the most stable of the conformers, at any instant stable of the conformers, at any instant more molecules of cyclohexane are in more molecules of cyclohexane are in chair conformations than in any other chair conformations than in any other conformation. It has been calculated that, conformation. It has been calculated that, for every thousand molecules of for every thousand molecules of cyclohexane in a chair conformation, no cyclohexane in a chair conformation, no more than two molecules are in the next more than two molecules are in the next most stable conformation—the twist-boat.most stable conformation—the twist-boat.

Unlike cyclohexane, which has two equivalent chair Unlike cyclohexane, which has two equivalent chair conformers, the two chair conformers of a conformers, the two chair conformers of a monosubstituted cyclohexane such as monosubstituted cyclohexane such as methylcyclohexane are not equivalent. The methylcyclohexane are not equivalent. The methyl substituent is in an equatorial position in methyl substituent is in an equatorial position in one conformer and in an axial position in the one conformer and in an axial position in the other, because substituents that are equatorial in other, because substituents that are equatorial in one chair conformer are axial in the other.one chair conformer are axial in the other.

The petroleum contains such cycloalkanes as The petroleum contains such cycloalkanes as cyclopentane and cyclohexane. It is possible to extract cyclopentane and cyclohexane. It is possible to extract these cycloalkanes from petroleum. But there are many these cycloalkanes from petroleum. But there are many artificial methods of extraction of cycloalkanes.artificial methods of extraction of cycloalkanes.

1. The reaction of 1. The reaction of αα,,ωω--dihalogenalkanes and metallic dihalogenalkanes and metallic sodium or zinc.sodium or zinc.

CH2

CH2

CH2

CH2

Br

BrZn

H2C

H2C

CH2

CH2

ZnBr2+ +

2. Dry distillation of calcium and 2. Dry distillation of calcium and barium salts of dicarboxylic acids.barium salts of dicarboxylic acids.

H2C CH2 C

O

O

Ca

O

C

O

H2CH2C

-CaCO3H2C

H2C

H3C

C

CH2

O[H]

H2CH2C

H3C

CH2

CH2

cyclopentanon cyclopentane

3. The reactions of cyclojoining:3. The reactions of cyclojoining:

a) The reaction of alkenes and carbenes:a) The reaction of alkenes and carbenes:

H3C CH CH2 + CH2 H3C CH

H2C

CH2

methylcyclopropanepropene

b) Dimerization

H2C CH2

H3C CH2

+CH2

CH2

CH2

CH2

c) Diene synthesisc) Diene synthesis

+CH2

CH2

HC

HC

CH2

CH2

+ H2

butadiene-1,3cyclohexene cyclohexane

d) Electrocyclic reactions

[H]CH

CH

(Z)

HC

CH

CH2

CH2

CH

CH

HC

CH

CH

CH

1,3,5-hexatriene cyclohexadiene

cyclohexane

Hydrogenation of arenes.

Use of malonic esters to obtain Cycloalkane - get the number of cycles of carbon atoms n = 3 - 7:

CH2

CH2

CH2 Br

Br

CH2

COOC2H5

COOC2H5 CH2

CH2 C

CH2COOC2H5

COOC2H5

CH2

CH2 C

CH2COOH

COOH

CH2

CH2 CH

CH2

COOH

+ 2C2H5ONa

-2NaBr

Diethylether 1,1-cyclobutane-

dicarboxilyc acids2H2O

-2C2H5OH

1,1-cyclobutanedicarboxilyc acids

-CO2

Cyclobutane carboxilyc acids

1. The reactions of substitution (halogenation)1. The reactions of substitution (halogenation)

Cl2 ClHCl+ +

cyclopropanechlorcyclopropane

2. The reactions of joining. During these reactions −C−C− bonds are broken.

H2C CH2

H3C CH2

H3C CH2+ H2 CH2 CH3Ni (Pt), t

cyclobutane

butane

Joining reactions

CH3 CH2 CH3+ H2

800

Pt, Ni

CH3 CH2 CH2 CH3+ H2

2000

CH3 CH2 CH2 CH2 CH3+ H2

3000

3000

Pt

CH2 CH2 CH2X X+ X2 (äå Õ - Br, I)t

Cl

Cl

+ 2Cl2 +2HCl

h

Br CH2 CH2 CH2 CH2 Br+ Br2

Br

+ Br2 + HBrt0

Cl

+ Cl2 + HClt0

CH3 CH2 CH2 Br+ HBr

CH3 CH2 CH2 CH2 I+ HI

OHC

O

(CH2)4HOOC COOH[O] O2

-H2O

2O2

Cyclohexane Cyclohexanol Cyclohexanol Adipinic acid

3. The reaction of increase and reduction of 3. The reaction of increase and reduction of Carbon cycle.Carbon cycle.

CH2 CH3

CH3AlCl3, t

ethylcyclobutanemethylcyclopentane

1. Concept of alkenes1. Concept of alkenesAlkenes are unsaturated hydrocarbons which contain one Alkenes are unsaturated hydrocarbons which contain one

carbon–carbon double bond. Early chemists noted that carbon–carbon double bond. Early chemists noted that an oily substance was formed when ethene (Han oily substance was formed when ethene (H22C=CHC=CH22) )

the smallest alkene, reacted with chlorine. On the basis the smallest alkene, reacted with chlorine. On the basis of this observation, alkenes were originally called of this observation, alkenes were originally called olefins olefins (oil forming). The general formula of acyclic alkenes is (oil forming). The general formula of acyclic alkenes is CCnnHH22nn. The general formula of cyclic alkenes is C. The general formula of cyclic alkenes is CnnHH22nn-2-2..

Alkenes are characterized by sp2-hybridization and their double bond contains σ- and π-bonds.

Alkenes play many Alkenes play many important roles in important roles in

biology. Ethene, for biology. Ethene, for example, is a plant example, is a plant

hormone — a hormone — a compound that controls compound that controls the plant’s growth and the plant’s growth and other changes in its other changes in its

tissues. Ethene affects tissues. Ethene affects seed germination, seed germination,

flower maturation, and flower maturation, and fruit ripening.fruit ripening.

2. The nomenclature of alkenes2. The nomenclature of alkenesThe systematic (IUPAC) name of an alkene The systematic (IUPAC) name of an alkene

is obtained by replacing the “ane” ending of is obtained by replacing the “ane” ending of the corresponding alkane with “ene.” For the corresponding alkane with “ene.” For example, a two-carbon alkene is called example, a two-carbon alkene is called ethene and a three-carbon alkene is called ethene and a three-carbon alkene is called propene. Ethene also is frequently called propene. Ethene also is frequently called by its common name: ethylene.by its common name: ethylene.

Most alkene names need a number to indicate Most alkene names need a number to indicate the position of the double bond. The IUPAC the position of the double bond. The IUPAC

rules:rules:1. 1. The longest continuous chain containing the functional group The longest continuous chain containing the functional group (in this case, the carbon–carbon double bond) is numbered in (in this case, the carbon–carbon double bond) is numbered in a direction that gives the functional group suffix the lowest a direction that gives the functional group suffix the lowest possible number. For example, 1-butene signifies that the possible number. For example, 1-butene signifies that the double bond is between the first and second carbons of double bond is between the first and second carbons of butene; 2-hexene signifies that the double bond is between butene; 2-hexene signifies that the double bond is between the second and third carbons of hexene.the second and third carbons of hexene.

2. 2. The name of a substituent is cited before the The name of a substituent is cited before the name of the longest continuous chain containing name of the longest continuous chain containing the functional group, together with a number to the functional group, together with a number to designate the carbon to which the substituent is designate the carbon to which the substituent is attached. Notice that the chain is still numbered in attached. Notice that the chain is still numbered in the direction that gives the the direction that gives the functional group suffix functional group suffix the lowest possible number.the lowest possible number.

3. If a chain has more than one substituent, 3. If a chain has more than one substituent, the substituents are cited in alphabetical the substituents are cited in alphabetical order. The prefixes order. The prefixes didi, , tritri, , secsec, and , and tert tert are are ignored in alphabetizing, but ignored in alphabetizing, but isoiso, , neoneo, and , and cyclo cyclo are not ignored.are not ignored.

4. If the same number for the alkene 4. If the same number for the alkene functional group suffix is obtained in both functional group suffix is obtained in both directions, the correct name is the name directions, the correct name is the name that contains the lowest substituent number.that contains the lowest substituent number.

5. In cyclic alkenes, a number is not needed to denote the 5. In cyclic alkenes, a number is not needed to denote the position of the functional group, because the ring is always position of the functional group, because the ring is always numbered so that the double bond is between carbons 1 and 2.numbered so that the double bond is between carbons 1 and 2.

In cyclohexenes numbering is in the direction that puts the lowest substituent number, not in the direction that gives the lowest sum of the substituent numbers.

6. If both directions lead to the same 6. If both directions lead to the same number for the alkene functional group number for the alkene functional group suffix and the same low number(s) for one suffix and the same low number(s) for one or more of the substituents, then those or more of the substituents, then those substituents are ignored and the direction substituents are ignored and the direction is chosen that gives the lowest number to is chosen that gives the lowest number to one of the remaining substituents.one of the remaining substituents.

Two groups containing Two groups containing a carbon–carbon a carbon–carbon double bond are used double bond are used in common names — in common names — the the vinyl group vinyl group and and the the allyl groupallyl group..

The vinyl group is the smallest possible group that contains a vinylic carbon; the allyl group is the smallest possible group that contains an allylic carbon. When “allyl” is used in nomenclature, the substituent must be attached to the allylic carbon.

3. The isomery of alkenes3. The isomery of alkenesAlthough ethylene is the only two-carbon alkene, and Although ethylene is the only two-carbon alkene, and

propene the only three-carbon alkene, there are propene the only three-carbon alkene, there are four isomeric alkenes of molecular formula Cfour isomeric alkenes of molecular formula C44HH88::

1-butene, 2-methylpropene and 2-butene (cis- and trans-)are structural isomers of butene. cis-2-butene and trans-2-butene are geometrical isomers of butene.

When there are 3 or 4 different substituents near When there are 3 or 4 different substituents near 2 carbon atoms connected by double bond, the 2 carbon atoms connected by double bond, the EE,,ZZ-system is used to name the compound.  -system is used to name the compound.  

C CCH2

CH2

H3C

H2CH3C

CH3

CH2 CH3

Z-4-ethyl-3-methylheptene-3

C CCH2

CH2

H3C

H2CH3C

CH2

CH3

E-4-ethyl-3-methylheptene-3

CH3

4. The methods of extraction of 4. The methods of extraction of alkenesalkenes

Alkenes are in oil and gas in small amount. There are methods of their extraction from oil and gas.

Artificial methods:1. Dehydration of saturated alcohols

H2C CH2

H OH

ethanol

H2SO4,tCH2 CH2

ethylene

+ H2O

When the molecule contain a long brunched When the molecule contain a long brunched carbon chain, not all carbon-hydrogen bonds carbon chain, not all carbon-hydrogen bonds

can be destroyed. If the atom of carbon is can be destroyed. If the atom of carbon is connected with only 1 hydrogen atom, it connected with only 1 hydrogen atom, it

gives the hydrogen atom more easily than gives the hydrogen atom more easily than the carbon atom which is connected with 2 or the carbon atom which is connected with 2 or

3 atoms of hydrogen. This rule is named 3 atoms of hydrogen. This rule is named Zajtsev rule. Zajtsev rule.

HC C

OH H

3-methylbutanol-2

H2SO4,t HC C + H2OH3C

H3CCH3

CH3

CH3CH3

2-methylbutene-2

2. Dehydrohalogenation of 2. Dehydrohalogenation of monohalogenalkanesmonohalogenalkanes

HC CH2

H Br

H3CNaOH

HC CH2H3C H2O NaBr

1-brompropane

propene+ +

3. Dehalogenation of dihalogenalkanes

HC CH

Br Br

H3C CH3

ZnKOH

HC CHH3C CH3 ZnBr2

2,3-dibrombutanebutene-2

+ +

4. Dehydrogenation of alkanes4. Dehydrogenation of alkanes

CH3 CH2 CH3Ni CH2 CH CH3 H2+

propane propene

5. Hydrogenation of alkynes

CH C CH3 H2Pt, Pd

CH2 CH CH3+

4. Dehydrogenation of alkanes4. Dehydrogenation of alkanes

CH3 CH2 CH3Ni CH2 CH CH3 H2+

propane propene

5. Hydrogenation of alkynes

CH C CH3 H2Pt, Pd

CH2 CH CH3+

5. Physical properties of 5. Physical properties of alkenesalkenesAlkenes resemble alkanes in most of their

physical properties. The lower molecular weight alkenes through C4H8 are gases at room temperature and atmospheric pressure. Alkenes which contain carbon atoms (C5 – C17) are liquids and alkenes with carbon chain (≥C18) are solids.All alkenes are not dissolvable in water but are dissolvable in some organic solvents.n-alkenes have higher boiling temperatures than their isomers with brunched carbon chain.

6. Chemical properties of 6. Chemical properties of alkenesalkenes

Alkenes are very active, they can react with many compounds, because of the presence of double bond in their molecule.I. Reactions of joining1. Halogenation (the joining of halogens).

CH2 CH2 Br2CH2 CH2

Br Br+

2. Hydrohalogenation

CH2 CH2 + HBr CH3 CH2 Brbromomethane

This reaction runs by Markovnikov rule: the atom of Hydrogen (from the molecule of hydrohalogen) joines to the atom of Carbon which is connected by double bond and which is connected with bigger amount of atoms of Hydrogen than another carbon atom.

C CH2 +HBr CH3 CH3C

CH3

CH3

Br

CH3

3. Joining of concentrated H3. Joining of concentrated H22SOSO44

CH

CH2H3C H2SO4 CH3 CH

CH3

OSO3H

+

4. Joining of water (hydration)

CH

CH2+ H2O CH3 CH

H3C CH3

OH

5. Joining of hypohalogenic acids

CH

CH2H3C HClO CH3 CH

CH2

OH

Cl+

II. Reactions of reduction II. Reactions of reduction and oxidationand oxidation

1. Reactions of reduction

CH

CH2H3C H2 CH3

H2C CH3+ Ni

2. Reactions of oxidation •Reactions of oxidation by KMnO4

H2C CH2 2KMnO4 4H2OCH2 CH2

OH OH

2KOH 2MnO2+ + ++

•Reactions of oxidation by ozone

HC CH2H3C O3 CH CH2

H3C

O

O

O

+

ozonide

•Reactions of oxidation by O2

2 H2C CH2 O2Ag, t=300 H2C CH2

O+

ethyleneethylenoxide

III. Reactions of III. Reactions of polymerization polymerization

CH2═CH2 + CH2═CH2 + CH2═CH2 + … →

−CH2−CH2− + −CH2−CH2− + −CH2−CH2− + … →

−CH2−CH2−CH2−CH2−CH2−CH2− …

7. The nomenclature of dienes7. The nomenclature of dienes

Dienes are unsaturated hydrocarbons that contain two double bonds. The general formula of dienes is C2H2n-2. There are 3 types of location of double bonds in molecule.

The systematic (IUPAC) name of an dienes is obtained by replacing the “ane” ending of the corresponding alkane with “diene.”

8. Configurational isomers 8. Configurational isomers of dienesof dienes

A diene such as 1-chloro-2,4-heptadiene has four configurational isomers because each of the double bonds can have either the E or the Z configuration. Thus, there are E-E, Z-Z, E-Z, and Z-E isomers.

9. The methods of 9. The methods of extraction of dienesextraction of dienes

1. Dehydrogenation of alkanes and alkenesCr2O3, Al2O3, t=650

H3C CH2 CH2 CH3 -2H2H2C CH CH CH2

2. Dehydration of diols (alcohols with 2 –OH groups)

Al2O3, t=280H2C CH2 CH CH3

-2H2OH2C CH CH CH2

OH OH

3. Dehydration of unsaturated alkoholscat.

H3C CH CH CH2 H2C CH CH CH2OH-H2O

10. Chemical properties of dienes

1. Hydrogenation

H2C CH CH CH2Ni,Pt

+H2H3C CH CH CH3

2. Halogenation

Ni,Pt

H2C CH CH CH2

H2C CH CH CH2

Br Br

H2C CH CH H3C

Br Br+Br2

3. Hydrohalogenation

4. The Diels–Alder reactionIf a Diels–Alder reaction creates an acymmetric carbon in the product, identical amounts of the R and S enantiomers will be formed. In other words, the product will be a racemic mixture.

5. Polymerization

nCH2=CH−CH=CH2 → −(−CH2−CH=CH−CH2−)−n

11.The nomenclature and 11.The nomenclature and isomery of alkynesisomery of alkynes

Alkynes are unsaturated hydrocarbons which contain only one triple (−C≡C−) bond. They conform to the general formula C2H2n-2, for one triple bond. The IUPAC system for naming alkynes employs the ending -yne instead of the -ane used for naming of the corresponding saturated hydrocarbons:

The numbering system for locating the triple bond and substituent groups is analogous to that used for the corresponding alkenes:

Hydrocarbons with more than one triple bond are called alkadiynes, alkatriynes, and so on, according to the number of triple bonds. Hydrocarbons with both double and triple bonds are called alkenynes (not alkynenes). The chain always should be numbered to give the multiple bonds the lowest possible numbers, and when there is a choice, double bonds are given lower numbers than triple bonds. For example,

12. The nomenclature and 12. The nomenclature and isomery of alkynesisomery of alkynes

Alkynes (or acetylenes) are hydrocarbons that contain one carbon-carbon triple bond. This bond consists of one σ-bond and two π-bonds. The carbon atoms which are connected by triple bond are characterized by sp-hybridization. The general formula of acyclic alkynes is CnH2n-2. The simplest

alkyne is acetylene (CH≡CH).The IUPAC system for naming alkynes employs the

ending -yne instead of the -ane used for naming of the corresponding saturated hydrocarbon:

The numbering system for locating the triple bond and substituent groups is analogous to that used for the corresponding alkenes:

Both acetylene and ethyne are acceptable IUPAC names for HC≡CH. The position of the triple bond along the chain is specified by number in a manner analogous to alkene nomenclature.

Hydrocarbons with more than one triple bond are called alkadiynes, alkatriynes, and so on, according to the number of triple bonds. Hydrocarbons with both double and triple bonds are called alkenynes (not alkynenes). The chain always should be numbered to give the multiple bonds the lowest possible numbers, and when there is a choice, double bonds are given lower numbers than triple bonds. For example,

The hydrocarbon substituents derived from alkynes are called alkynyl groups:

Alkynes are characterized by structural isomery: isomery of carbon chain and different location of triple bond (isomery of location).

13. The methods of extraction 13. The methods of extraction of alkynesof alkynes

1. Acetylene was first characterized by the French chemist P. E. M. Berthelot in 1862 and did not command much attention until its large-scale preparation from calcium carbide in the last decade of the nineteenth century stimulated interest in industrial applications. In the first stage of that synthesis, limestone and coke, a material rich in elemental carbon obtained from coal, are heated in an electric furnace to form calcium carbide. Calcium carbide is the calcium salt of the doubly negative carbide ion .

Carbide dianion is strongly basic and reacts with water to form acetylene:

2. Beginning in the middle of the twentieth century, alternative methods of acetylene production became practical. One of these is based on the dehydrogenation of ethylene. At very high temperatures most hydrocarbons, even methane, are converted to acetylene. Acetylene has value not only by itself but is also the starting material from which higher alkynes are prepared.

HC CHNaNH2 HC CNa

-NaBr

C2H5BrHC C CH3-NH3

HC CH

Br

H

H

Br

HC CH 2NaBr 2H2O2NaOH, t

+ +(C2H5OH)

3. Alkylation of acetylene

4. Dehydrohalogenation of dihalogenalkanes and halogenalkenes

Natural products that contain carbon–carbon triple bonds are numerous. Two examples are tariric acid, from the seed fat of a Guatemalan plant, and cicutoxin, a poisonous substance isolated from water hemlock.

14. Physical properties14. Physical propertiesThe most distinctive aspect of the chemistry of acetylenes

is their acidity. As a class, compounds of the type RC≡CH are the most acidic of all simple hydrocarbons.

In the homological row the first 3 alkynes (C2-C4) are

gases, alkynes with carbon chain C5-C15 are liquids and next

alkynes are solids.

15. Chemical propertiesI. The reactions of joining1. Halogenation

2. Hydrohalogenation

3. Hydration

II. The reactions of substitution 1. The formation of acetylenides. Because of

their acidity alkynes can react like acids. In these reactions the atoms of hydrogen are changed to the atoms of metal.

HC≡CH + 2Ag(NH3)2OH → Ag−C≡C−Ag + 4NH3 + 2H2OSilver acetylenide

2. The substitution of the atom of hydrogen in ≡C−H –radical to atom of halogen:

CH3−CH≡C−H + Br2 → CH3−CH≡C−Br + HBr

III. The reactions of the oxidation and reduction

1. The oxidation of alkynes. In this reaction the catalyst is KMnO4.

HC≡CH + 4[O] → COOH−COOH

2. The reduction of alkynes.

IV. The reactions of dimerisation, trimerisation and tetramerisation

2HC≡CH → HC≡C−CH=CH2vinilacetylene

3HC≡CH →

Thanks you for attention!