Reactionary ability of the
saturated hydrocarbons
(alkanes, cycloalkanes).
Reactionary ability of the
unsaturated hydrocarbons
(alkenes, alkadienes, alkynes).
ass. Medvid I.I., ass. Burmas N.I.
Outline
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Concept of alkanes
Structure of alkanes
Nomenclature of alkanes
The isomery of alkanes
The methods of extraction of alkanes
Physical properties of alkanes
Chemical properties of alkanes
Structure of cycloalkanes
Nomenclature of cycloalkanes
Conformation of cycloalkanes
The methods of extraction of cycloalkanes
Chemical properties of cycloalkanes
Concept of alkenes
14. The nomenclature of alkenes
15. The isomery of alkenes
16. The methods of extraction of alkenes
17. Physical properties of alkenes
18. Chemical properties of alkenes
19. The nomenclature of dienes
20. Configurational isomers of dienes
21. The methods of extraction of dienes
22. Chemical properties of dienes
23. The nomenclature and isomery of alkynes
24. The nomenclature and isomery of alkynes
25. The methods of extraction of alkynes
26. Physical properties
27. Chemical properties
13.
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.
Alkanes:
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Undecane
Dodecane
Tridecane
Tetradecane
Pentadecane
CH4
C2H6
C3H8
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
C11H24
C12H26
C13H28
C14H30
C15H32
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.
CH3
H3C
CH
CH
CH2
H3C
CH
CH3
the longest main chain
(is the most branched,
has 3 substituents)
not the longest main chain
(is not the most branched,
has 2 substituents)
CH3
CH3
H3C
CH
CH
CH2
H3C
CH
CH3
CH3
2. To identify the substituent groups attached to the parent chain.
CH3
1
H3C
2
CH
3
CH2
4
CH2
5
CH3
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.
2
CH3
1,2,3,4,5 – primary;
6 – secondary;
7 – tertiary;
8 – quaternary.
1
H3C
7
CH
5
8
C
4
CH3 CH3
6
3
CH2 CH3
The Number of Constitutionally Isomeric Alkanes of Particular
Molecular Formulas
CH3
C
H3C H2C
H
CH2
CH2 CH3
R-3-methylhexane
CH3
H3C
H2C
H
H2C
C
CH2 CH3
S-3-methylhexane
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:
Fraction
Boiling
temperatu
re, C
Alkanes mixture (the
number of Carbon
atoms)
Petroleum ether
20-60
C5, C6
Benzine
60-180
C6 -C10
Kerosene
180-230
C11, C12
Diesel fuel
230-300
C13 - C17
Black oil
More than 300 C18 and more
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 180-300C. In this reaction catalysts are Fe
and Co). As the result the mixture of n-alkanes appears.
CO + 2H2
Fe (Co)
n-alkanes + H2O
This method is often used in industry for receiving of artificial benzine.
H3C
C
C
CH3 + H2
Pt (Pd, Ni)
H3C
C
H
C
C
CH3
butene-2
butyne-2
H
H3C
H
H
C
butene-2
CH3 + H2
Pt (Pd, Ni)
H3C H2C H2C
butane
CH3
H
2 H
C
I + 2Na
H3C H3C + 2NaI
ethane
H
iodomethane
4. Allowing of salts of carboxylic acids
and alkalis.
O
H3C
CH2 C
+ NaOH
ONa
H3C
CH3 + Na2CO3
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 oxidation;
-reactions of the destruction.
1. Halogenation of alkanes. Alkanes
react with halogens (except I2).
CH4 + Cl2
HCl + H3C
Cl
chlormethane
Cl
H3C
Cl + Cl2
HCl + H2C
Cl
dichlormethane
Cl
Cl
H2C
Cl + Cl2
HCl + Cl
C
H
Cl
trichlormethane
Cl
Cl
C
H
Cl
Cl + Cl2
HCl + Cl
C
Cl
Cl
tetrachlormethane
H3C
H 3C
CH2 CH3 +SO2+ Cl2
CH2 CH3 +HNO3
t, p
H3C
CH2 CH2 SO2Cl + HCl
H3C
CH2 CH2 NO2 + H2O
Alkanes can burn if oxygen is present. As
the result H2O and CO2 appear.
CH4 + 2O2 → CO2 + 2H2O
Cracking is the destroying of some −C−C−
and −C−H bonds in the molecule of
alkanes at high 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 atoms form the cycle and are in
the state of sp3-hybridization.
Cycloalkanes are saturated hydrocarbons.
Cycloalkanes have the general molecular
formula CnH2n.
Early chemists observed that cyclic
compounds found in nature generally had
five- or sixmembered rings. Compounds
with three- and fourmembered rings were
found much less frequently. This
observation suggested that compounds
with five- and sixmembered rings were
more stable than compounds with threeor fourmembered rings.
In 1885, the German chemist Adolf von Baeyer
proposed that the instability of three- and
fourmembered rings was due to angle strain. We
know that, ideally, an sp3-hybridized carbon has
bond angles of 109.5°. Baeyer suggested that the
stability of a cycloalkane could be predicted by
determining how close the bond angle of a planar
cycloalkane is to the ideal tetrahedral bond angle
of 109.5°. The angles in an equilateral triangle
are 60°. The bond angles in cyclopropane,
therefore, are compressed from the ideal bond
angle of 109.5° to 60°, a 49.5° deviation. This
deviation of the bond angle from the ideal bond
angle causes strain called angle strain.
The angle strain in a three-membered ring can be appreciated
by looking at the orbitals that overlap to form the σ-bonds in
cyclopropane. Normal σ-bonds are formed by the overlap of
two sp3-orbitals that point directly at each other. In
cyclopropane, overlapping orbitals cannot point directly at
each other. Therefore, the orbital overlap is less effective than
in a normal −C−C− bond. The less effective orbital overlap is
what causes angle strain, which in turn causes the −C−C−
bond to be weaker than a normal −C−C− bond. Because the
−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
to be compressed from 109.5° to 90°, the bond
angle associated with a planar four-membered
ring. Planar cyclobutane would then be expected
to have less angle strain than cyclopropane
because the bond angles in cyclobutane are only
19.5° away from the ideal bond angle.
Baeyer predicted that cyclopentane would be
the most stable of the cycloalkanes because
its bond angles (108°) are closest to the ideal
tetrahedral bond angle. He predicted that
cyclohexane, with bond angles of 120°, would
be less stable and that as the number of sides
in the cycloalkanes increases, their stability
would decrease.
Contrary to what Baeyer predicted, cyclohexane is
more stable than cyclopentane. Furthermore,
cyclic compounds do not become less and less
stable as the number of sides increases. The
mistake Baeyer made was to assume that all
cyclic molecules are planar. Because three
points define a plane, the carbons of
cyclopropane must lie in a plane. The other
cycloalkanes, however, are not planar.

Angle strain is the strain induced in a molecule
when the bond angles are different from the ideal
tetrahedral bond angle of 109.5°.
 Torsional strain is caused by repulsion between
the bonding electrons of one substituent and the
bonding electrons of a nearby substituent.
 Steric strain is caused by atoms or groups of
atoms approaching each other too closely.
Although planar cyclobutane would have less angle strain than
cyclopropane, it could have more torsional strain because it has
eight pairs of eclipsed hydrogens, compared with the six pairs of
cyclopropane. So cyclobutane is not a planar molecule—it is a
bent molecule. One of its methylene groups is bent at an angle of
about 25° from the plane defined by the other three carbon
atoms. This increases the angle strain, but the increase is more
than compensated for by the decreased torsional strain as a
result of the adjacent hydrogens not being as eclipsed, as they
would be in a planar ring.
If cyclopentane were planar, as Baeyer had
predicted, it would have essentially no angle
strain, but its 10 pairs of eclipsed hydrogens
would be subject to considerable torsional strain.
So cyclopentane puckers, allowing the
hydrogens to become nearly staggered. In the
process, however, it acquires some angle strain.
The puckered form of cyclopentane is called the
envelope conformation because the shape
resembles a squarish envelope with the flap up.
spiranic system
bridge system
condensed system
Cycloalkanes are almost always written as skeletal
structures. Skeletal structures show the carbon–
carbon bonds as lines, but do not show the
carbons or the hydrogens bonded to carbons.
Atoms other than carbon and hydrogens bonded
to atoms other than carbon are shown. Each
vertex in a skeletal structure represents a carbon.
It is understood that each carbon is bonded to the
appropriate number of hydrogens to give the
carbon four bonds.

In the case of a cycloalkane with an attached
alkyl substituent, the ring is the parent
hydrocarbon unless the substituent has more
carbon atoms than the ring. In that case, the
substituent is the parent hydrocarbon and the
ring is named as a substituent.
There is no need to number the position of a
single substituent on a ring.
 If
the ring has two different
substituents, they are cited in
alphabetical order and the number 1
position is given to the substituent
cited first.

If there are more than two substituents on the ring, they are
cited in alphabetical order. The substituent given the number
1 position is the one that results in a second substituent
getting as low a number as possible. If two substituents have
the same low number, the ring is numbered—either
clockwise or counterclockwise—in the direction that gives
the third substituent the lowest possible number. For
example, the correct name of the following compound is 4ethyl-2-methyl-1-propylcyclohexane, not 5-ethyl-1-methyl-2propylcyclohexane:
The cyclic compounds most commonly found in nature contain
sixmembered rings because such rings can exist in a
conformation that is almost completely free of strain. This
conformation is called the chair conformation. In the chair
conformer of cyclohexane, all the bond angles are 111°,
which is very close to the ideal tetrahedral bond angle of
109.5°, and all the adjacent bonds are staggered.
Cyclohexane can also exist in a boat conformation. Like the
chair conformer, the boat conformer is free of angle strain.
However, the boat conformer is not as stable as the chair
conformer because some of the bonds in the boat
conformer are eclipsed, giving it torsional strain. The boat
conformer is further destabilized by the close proximity of
the flagpole hydrogens (the hydrogens at the “bow” and
“stern” of the boat), which causes steric strain.
When the carbon is pulled down to the point
where it is in the same plane as the sides of the
boat, the very unstable half-chair conformer is
obtained. Pulling the carbon down farther
produces the chair conformer. The graph in
figure shows the energy of a cyclohexane
molecule as it interconverts from one chair
conformer to the other; the energy barrier for
interconversion is 12.1 kcal/mol (50.6 kJ/mol).
From this value, it can be calculated that
cyclohexane undergoes 10 ring flips per second
at room temperature. In other words, the two
chair conformers are in rapid equilibrium.
Because the chair conformers are the most
stable of the conformers, at any instant
more molecules of cyclohexane are in
chair conformations than in any other
conformation. It has been calculated that,
for every thousand molecules of
cyclohexane in a chair conformation, no
more than two molecules are in the next
most stable conformation—the twist-boat.
Unlike cyclohexane, which has two equivalent chair
conformers, the two chair conformers of a
monosubstituted cyclohexane such as
methylcyclohexane are not equivalent. The
methyl substituent is in an equatorial position in
one conformer and in an axial position in the
other, because substituents that are equatorial in
one chair conformer are axial in the other.
The petroleum contains such cycloalkanes as
cyclopentane and cyclohexane. It is possible
to extract these cycloalkanes from petroleum.
But there are many artificial methods of
extraction of cycloalkanes.
1. The reaction of α,ω-dihalogenalkanes and
metallic sodium or zinc.
CH2 CH2 Br
+ Zn
CH2 CH2 Br
H2C
CH2
H2C
CH2
+ ZnBr2
2. Dry distillation of calcium and
barium salts of dicarboxylic acids.
O
H2C
CH2 C
O
Ca
O
H2C H2C
C
-CaCO3
H2C
H3C
H2
C
C
C
H2
cyclopentanon
O
O
[H]
H2C
H3C
H2
C
CH2
C
H2
cyclopentane
3. The reactions of cyclojoining:
a) The reaction of alkenes and
carbenes:
H3C
CH
CH2 +
H2
C
H3C
CH2
propene
C
H
CH2
methylcyclopropane
b) Dimerization
CH2
CH2
H2C
CH2
CH2
H3C
CH2
+
CH2
c) Diene synthesis
HC
CH2
CH2
+ H2
+
HC
CH2
CH2
cyclohexene
butadiene-1,3
cyclohexane
d) Electrocyclic reactions
H
C
H
C
CH
CH2
CH
CH
CH2
CH
CH
[H]
(Z)
CH
C
H
C
H
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:
CH 2 Br
H 2C
COOC 2H 5
+
H 2C
CH 2 Br
COOC 2H 5
2C2H5ONa
H 2C
-2NaBr
H 2C
CH 2
COOC 2H 5
C
COOC 2H 5
Diethylether 1,1-cyclobutane2H2O
H 2C
CH 2
H 2C
dicarboxilyc acids
CH 2
COOH
-2C2H5OH H 2C
C
-CO2
H 2C
CH
COOH
COOH
1,1-cyclobutane
dicarboxilyc acids
Cyclobutane carboxilyc
acids
1. The reactions of substitution
(halogenation)
+ Cl2
cyclopropane
Cl
+ HCl
chlorcyclopropane
2. The reactions of joining. During these reactions
−C−C− bonds are broken.
H2C
H3C
CH2
CH2
cyclobutane
+ H2
Ni (Pt), t
H3C
CH2
CH2
butane
CH3
Joining reactions
+ H2
800
H3C
Pt, Ni
CH2 CH3
2000
+ H2
H3C
CH2 CH2 CH3
3000
+ H2
H3C
CH2 CH2 CH2 CH3
3000
Pt
t
+ X2
CH2 CH2 CH2 X (äå Õ - Br, I)
X
h
Cl
+ 2Cl2
+2HCl
Cl
Br CH2 CH2 CH2 CH2 Br
+ Br2
Br
t0
+ Br2
+ HBr
Cl
t0
+ Cl2
+ HCl
+ HBr
CH3 CH2 CH2 Br
+ HI
CH3 CH2 CH2 CH2 I
OH
O2
[O]
O
C
-H2O
Cyclohexane
Cyclohexanol
Cyclohexanol
2O2
HOOC
(CH 2) 4
Adipinic acid
COOH
3. The reaction of increase and reduction of
Carbon cycle.
CH2 CH3
AlCl3, t
CH3
ethylcyclobutane
methylcyclopentane
1. Concept of alkenes
Alkenes are unsaturated hydrocarbons which
contain one carbon–carbon double bond. Early
chemists noted that an oily substance was
formed when ethene (H2C=CH2) the smallest
alkene, reacted with chlorine. On the basis of
this observation, alkenes were originally called
olefins (oil forming). The general formula of
acyclic alkenes is CnH2n. The general formula of
cyclic alkenes is CnH2n-2.
Alkenes are characterized by sp2-hybridization and
their double bond contains σ- and π-bonds.
Alkenes play many
important roles in
biology. Ethene, for
example, is a plant
hormone — a
compound that controls
the plant’s growth and
other changes in its
tissues. Ethene affects
seed germination,
flower maturation, and
fruit ripening.
2. The nomenclature of alkenes
The systematic (IUPAC) name of an alkene
is obtained by replacing the “ane” ending of
the corresponding alkane with “ene.” For
example, a two-carbon alkene is called
ethene and a three-carbon alkene is called
propene. Ethene also is frequently called
by its common name: ethylene.
Most alkene names need a number to indicate
the position of the double bond. The IUPAC
1. The longest continuous rules:
chain containing the functional
group (in this case, the carbon–carbon double bond) is
numbered in a direction that gives the functional group
suffix the lowest possible number. For example, 1-butene
signifies that the double bond is between the first and
second carbons of butene; 2-hexene signifies that the
double bond is between the second and third carbons of
hexene.
2. The name of a substituent is cited before the
name of the longest continuous chain containing
the functional group, together with a number to
designate the carbon to which the substituent is
attached. Notice that the chain is still numbered in
the direction that gives the functional group suffix
the lowest possible number.
3. If a chain has more than one substituent,
the substituents are cited in alphabetical
order. The prefixes di, tri, sec, and tert are
ignored in alphabetizing, but iso, neo, and
cyclo are not ignored.
4. If the same number for the alkene
functional group suffix is obtained in
both directions, the correct name is the
name that contains the lowest
substituent number.
5. In cyclic alkenes, a number is not needed to denote
the position of the functional group, because the ring
is always 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
number for the alkene functional group
suffix and the same low number(s) for
one or more of the substituents, then
those substituents are ignored and the
direction is chosen that gives the lowest
number to one of the remaining
substituents.
Two groups containing
a carbon–carbon
double bond are used
in common names —
the vinyl group and
the allyl 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 alkenes
Although ethylene is the only two-carbon
alkene, and propene the only three-carbon
alkene, there are four isomeric alkenes of
molecular formula C4H8:
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 2 carbon atoms connected by double
bond, the E,Z-system is used to name the
compound.
CH2 CH3
H3C
C C
H3C H2C
CH2 CH2 CH3
Z-4-ethyl-3-methylheptene-3
H3C
H3C
H2C
C
C
CH2 CH2 CH3
CH2 CH3
E-4-ethyl-3-methylheptene-3
4. The methods of extraction of
alkenes
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
H
CH2
OH
ethanol
H2SO4,t
CH2 CH2 + H2O
ethylene
When the molecule contain a long brunched
carbon chain, not all carbon-hydrogen bonds
can be destroyed. If the atom of carbon is
connected with only 1 hydrogen atom, it
gives the hydrogen atom more easily than
the carbon atom which is connected with 2 or
3 atoms of hydrogen. This rule is named
Zajtsev rule.
CH3
H3C
HC
C
CH3
CH3
OH H
3-methylbutanol-2
H2SO4,t
H3C HC
C
2-methylbutene-2
CH3 + H2O
2. Dehydrohalogenation of
monohalogenalkanes
H3C
HC
CH2
H
NaOH
Br
H 3C
HC
CH2 + H2O + NaBr
propene
1-brompropane
3. Dehalogenation of dihalogenalkanes
H3C HC
Br
CH CH3
Br
2,3-dibrombutane
+ Zn
KOH
H3C HC
CH CH3 + ZnBr2
butene-2
4. Dehydrogenation of alkanes
CH3 CH2 CH3
Ni
CH2 CH
CH3 + H2
propene
propane
5. Hydrogenation of alkynes
CH C
CH3 + H2
Pt, Pd
CH2 CH
CH3
4. Dehydrogenation of alkanes
CH3 CH2 CH3
Ni
CH2 CH
CH3 + H2
propene
propane
5. Hydrogenation of alkynes
CH C
CH3 + H2
Pt, Pd
CH2 CH
CH3
5. Physical properties of
alkenes
Alkenes 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
alkenes
Alkenes are very active, they can react with
many compounds, because of the presence of
double bond in their molecule.
I. Reactions of joining
1. Halogenation (the joining of halogens).
CH2 CH2 + Br2
CH2
CH2
Br
Br
2. Hydrohalogenation
CH2 CH2 + HBr
CH3
CH2
Br
bromomethane
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.
CH3
H3C
C
CH3
CH2 + HBr
CH3
C
Br
CH3
3. Joining of concentrated H2SO4
OSO3H
H3C
C
H
CH2 + H2SO4
CH3
C
H
CH3
4. Joining of water (hydration)
OH
H3C
C
H
CH2 + H2O
CH3
C
H
CH3
5. Joining of hypohalogenic acids
OH
H3C
C
H
CH2 + HClO
CH3
C
H
CH2
Cl
II. Reactions of reduction and
oxidation
1. Reactions of reduction
H3C
C
H
CH2 + H2
Ni
CH3
H2
C CH3
2. Reactions of oxidation
•Reactions of oxidation by KMnO4
H2C
CH2 + 2KMnO4 + 4H2O
CH2
CH2
OH
OH
+ 2KOH + 2MnO2
•Reactions of oxidation by ozone
O
CH2 + O3
HC
H3C
O
CH
H3C
CH2
O
ozonide
•Reactions of oxidation by O2
2 H2C
Ag, t=300
CH2 + O2
ethylene
H2C
CH2
O
ethylenoxide
III. Reactions of
polymerization
CH2═CH2 + CH2═CH2 + CH2═CH2 + … →
−CH2−CH2− + −CH2−CH2− + −CH2−CH2− + … →
−CH2−CH2−CH2−CH2−CH2−CH2− …
7. 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
of 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
extraction of dienes
1. Dehydrogenation of alkanes and alkenes
H3C
CH2 CH2 CH3
Cr2O3, Al2O3, t=650
H2C
-2H2
CH CH
CH2
2. Dehydration of diols (alcohols with 2 –OH groups)
H2C
CH2 CH
OH
OH
CH3 Al O , t=280
2 3
-2H2O
H2C
CH CH
CH2
3. Dehydration of unsaturated alkohols
H3C
CH
CH CH2 OH
cat.
-H2O
H2C
CH CH
CH2
10. Chemical properties of dienes
1. Hydrogenation
H2C
CH CH
Ni,Pt
CH2 +H2
H3C
CH
CH CH3
2. Halogenation
Br
H2C
H2C
CH CH
Ni,Pt
CH2 +Br2
Br
CH CH CH2
Br
H2C
Br
CH CH
H3C
3. Hydrohalogenation
4. The Diels–Alder reaction
If 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
isomery 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
isomery 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
of alkynes
1. Acetylene was first characterized by the French chemist P. E. M.
Berthelot in 1862 and did not command much attention until its largescale 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.
3. Alkylation of acetylene
HC
CH
NaNH2
-NH3
HC
CNa
C2H5Br
-NaBr
HC
C
CH3
4. Dehydrohalogenation of dihalogenalkanes and
halogenalkenes
H
HC
Br
Br
CH
H
2NaOH, t
(C2H5OH)
HC
CH + 2NaBr + 2H2O
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 properties
The 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 properties
I. The reactions of joining
1. 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 + 2H2O
Silver 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=CH2
vinilacetylene
3HC≡CH →
Thanks you for attention!