Explanation of Hydrocabons

1. Hydrocarbons
(alkanes, alkenes,
alkynes).

2. 1. Concept of alkanes
2. Structure of alkanes
3. Nomenclature of alkanes
4. The isomers of alkanes
5. Physical properties of alkanes
6. Chemical properties of alkanes
7. Structure of cycloalkanes
8. Nomenclature of cycloalkanes
9. Chemical properties of cycloalkanes
Content

3. 12.Conceptof alkenes
13.Thenomenclature of alkenes
14.The isomers of alkenes
15.Physical properties of alkenes
16.Chemical properties of alkenes
21.The nomenclature and isomers of alkynes
22.Physical properties
23.Chemical properties

4. Alkanes are aliphatic hydrocarbons. Alkanes are called
saturated hydrocarbons.
the general molecular formula
CnH2n+2.
Methane has been found on
Jupiter, Uranus, Neptune.

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

6. n-nonane

7. 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

8. 1. To choose the longest Carbon chain in the molecule.
H3C CH
CH3
CH
CH
CH2 CH3
H3C CH3
the longest main chain
(is the most branched,
has 3 substituents)
H3C CH
CH3
CH
CH
CH2 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.

9. H3C CH
CH3
1 2 3 4 5
CH2 CH2 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.

10. 4-ethyl-3-methyloctane

11. C-C-C-C-C-C-C-C
CH3 CH2-CH3
4-ethyl-6-methyloctane(wrong)
5-ethyl-3-methyloctane(correct)
Number the chain so that substituents take lowest
possible number
Di, tri, tetra….are ignored in alphabetical order but
iso, neo & cyclo are not ignored

12. There are the primary, the secondary, the tertiary and the
quaternary carbon atoms.
1,2,3,4,5 – primary;
6 – secondary;
7 – tertiary;
8 – quaternary.
3
CH3
CH3
1
2
3
4
5
CH
6
7
H3C CH C CH2 CH3
8

13. • Boiling point of alkanes increase with increasing
the number of carbon atoms.
• B.pt. decreases with branching.

14. H3C C C 2
H H
CH3+H
Pt(Pd, Ni)
H3C C C CH3
butene-2
H
3 2 2
2
3
H C H C H C CH3
+
butane
Pt(Pd,Ni)
butyne-2
H H
H3C C C CH
butene-2

15. H3C CH2 C NaOH H3C
+
ONa
CH3 + Na2CO3
H
H3C
I + 2Na
2 H C
H
iodomethane
ethane
H3C +2NaI
4. Reactions of salts of carboxylic acids and
alkalis. (heat).
O

16.  The first four alkanes 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.

17. • Alkanes are isoluble in water but soluble in
organic solvents.
• Insolubility increase with increasing no of C.

18. • In normal conditions alkanes do not react with acids
and alkalis because -bonds in their molecules are
very strong. They undergo.
-reactions of the substitution;
-reactions of the oxidation;
-reactions of the destruction.

19. Cl
CH4 + Cl2 HCl + H3C
H3C Cl
chlormethane
Cl
Cl +Cl2
dichlormethane
HCl + H2C

20. Cl
Cl C
H
C Cl
Cl
Cl + Cl2
Cl
tetrachlormethane
HCl +Cl
Cl
C Cl
Cl
H2C Cl + Cl2
H
trichlormethane
HCl + Cl

21. Cycloalkanes are saturated hydrocarbons.
Cycloalkanes have the general molecular
formula CnH2n.

22. • 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.

23. • 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.

24. • 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.

25. 1. Concept of alkenes
Alkenes (Olefins) are unsaturated hydrocarbons which contain
one carbon–carbon double bond.The general formula of acyclic
alkenes is CnH2n.The general formula of cyclic alkenes isCnH2n-2.

26. 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.

27. 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.”

28. Most alkene names need a number to indicate the pos
of the double bond.The IUPAC rules:
1. The longest continuous 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.

29. 2. The name of a substituent is cited before the name of the
longest continuous chain containing the functional group.

30. 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.

31. 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.

32. 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.

33. 3.The isomers 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.

34. 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
H3C CH3
C C
H3C H2C CH2 CH2 CH3
Z-4-ethyl-3-methylheptene-3
CH2
H3C CH2
C C
H3C H2C CH2 CH3
E-4-ethyl-3-methylheptene-3
CH3

35. Dehydrohalogenation of monohalogenalkanes
H3C HC CH2 NaOH
2
3
H C HC CH 2 NaBr
H Br
1-brompropane
propene
+ H O +
Dehalogenation of dihalogenalkanes
HC CH
H3C CH3
3
H C 3 2
Br Br
2,3-dibrombutane
HC CH
butene-2
+ Zn
KOH
CH + ZnBr

36. Dehydrogenation of alkanes
CH3 CH2 CH3
Ni
CH2 CH H2
CH3 +
propane propene
Hydrogenation of alkynes
CH CH3
C H2
Pt,Pd
CH2 CH CH3
+

37. Physical properties of alkenes
Alkenes resemble alkanes in most of their physical
properties.
• The lower molecular weight alkenes throughC4H8 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 soluble in water but are soluble in some
organic solvents.
•n-alkenes have higher boiling temperatures than their
isomers with branched carbon chain.

38. 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
Br
CH2
Br
CH2 CH2 + Br2

39. 2. Hydrohalogenation
CH2 CH2 + HBr CH3 CH2 Br
CH3
H3C C CH2 +HBr C CH3
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 CH3

40. II. Reactions of reduction and oxidation
1. Reactions of reduction
3
H C C
H
CH3
H2
C CH3
CH2+ H Ni
2
2. Reactions of oxidation
•Reactions of oxidation by KMnO4
H2C
CH2
OH
CH2+2KMnO4+4H2O
CH2
+2KOH+2MnO
2
OH

41. 8. The nomenclature and isomers 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

42. 12.The nomenclature and isomers of alkynes
• The IUPAC system for naming alkynes employs the
ending -yne instead of the -ane used for naming of the
corresponding saturated hydrocarbon:

43. 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.

44. 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

45. 2. Hydrohalogenation
3. Hydration