2. Objectives
describe the properties of
alkanes;
1
At the end
of the
lesson, you
should be
able to:
recognize the common
examples and uses of
alkanes;
2
write structural formulas
for alkanes; and
3
name alkanes based on
their structures.
4
3. Learn about It!
● These are a group of hydrocarbon compounds that contain
carbon-carbon single (C-C) bonds and carbon-hydrogen
(C-H) bonds only.
● It has a general formula of CnH2n+2 where n is the number of
carbon atoms (n=1, 2, 3, …).
● Their names end in -ane.
Alkanes
4. Learn about It!
● Alkanes are insoluble in water, but are soluble in organic
solvents such as toluene and chloroform.
● They are also less dense than water.
TOLUENE - colorless, water-insoluble liquid with the smell
associated with paint thinners.
CHLOROFORM - colorless, toxic, sweet-tasting liquid formed
by combining methane with chlorine.
Properties of Alkanes
5. Learn about It!
Alkanes may come into two forms: straight-chain and
branched-chain.
● Straight-chain alkanes can be seen as a continuous
row of carbons.
● Branched-chain alkanes are composed of a parent
chain and alkyl groups.
Naming Alkanes
6. Learn about It!
● In the case of nomenclature, straight-chain alkanes can be
easily named with the first part of its name representing
the number of carbon atoms and the suffix -ane
representing the hydrocarbon group, alkane.
● For example, methane can be analyzed with meth- defining
one carbon in the compound, and -ane signaling that the
compound is purely an alkane.
Naming Straight-Chain Alkanes
7. Learn about It!
Number of
Carbon Atoms
Name (Molecular
Formula)
Kekule Structures Condensed Structure
1 methane (CH4) CH4
2 ethane (C2H6) CH3CH3
3 propane (C3H8) CH3CH2CH3
Table 1. Some examples of straight-chain alkanes and their corresponding nomenclature, Kekule
structures, and condensed structures.
8. Learn about It!
Number of
Carbon Atoms
Name (Molecular
Formula)
Kekule Structures Condensed Structure
4 butane (C4H10) CH3CH2CH2CH3
5 pentane (C5H12) CH3CH2CH2CH2CH3
6 hexane (C7H14) CH3CH2CH2CH2CH2CH3
Table 1. Some examples of straight-chain alkanes and their corresponding nomenclature, Kekule
structures, and condensed structures.
9. Learn about It!
To illustrate straight-chain alkanes, we can make
use of the three main structural methods:
● Condensed
● Kekule,
● Skeletal structure.
Drawing Straight-Chain Alkanes
10. Learn about It!
● How to draw the skeletal structure (line angle formula):
− They are represented by line segments connected
through a zigzag direction.
− Endpoints represent carbon atoms.
− The symbols of carbon and hydrogen are not shown for
the purpose of simplification.
Drawing Straight-Chain Alkanes
11. Learn about It!
Number of Carbon Atoms Name (Molecular Formula) Skeletal structures
3 propane (C3H8)
4 butane (C4H10)
5 pentane (C5H12)
6 hexane (C6H14)
7 heptane (C7H16)
Table 2. Some examples of straight-chain alkanes and their corresponding nomenclature and skeletal
structures.
12. Learn about It!
● To name branched-chain alkanes, you may refer to the
order of naming below:
Naming Branched-Chain Alkanes
Basic technique in naming branched-chain alkanes
13. Learn about It!
● In naming and drawing alkanes, the following terms should be
considered:
− The parent chain is defined as the longest straight-chain alkane
present in the hydrocarbon structure.
− Substituents are alkyl groups attached to one or more non-
terminal carbon atoms belonging to parent chain.
− The locant represents the number of carbon where the
substituents are attached.
Naming Branched-Chain Alkanes
14. Learn about It!
● The order location-prefix-parent chain-suffix is followed.
Prefixes are used to denote the number of identical
substituents attached to the parent chain.
● In naming alkanes, two numbers are separated by a
comma, while a word and a number are separated by a
dash.
Naming Branched-Chain Alkanes
15. Learn about It!
Name the branched-chain alkane shown below.
Naming Branched-Chain Alkanes
16. Learn about It!
Step 1. Find the longest continuous chain in the molecule. This
will serve as the parent chain.
The longest chain is composed of
nine carbons. Thus, it shall have
the name, nonane.
17. Learn about It!
Step 2. Identify the alkyl groups and their positions by looking at
which carbon atom they are attached. Make sure that the position
will yield the lowest number for the alkyl group.
In the example given, the alkyl group attached in the parent chain is methyl.
18. Learn about It!
● To locate its position, you can count either from left to right, or right to
left.
− If the counting starts at left, methyl will be connected to
carbon-4;
− If the counting starts at right, methyl will be connected to
carbon-6.
● Comparing the two, the first case gives the lowest number for methyl.
Step 3. Using the order location-prefix-parent chain-suffix, we write
the complete name of the molecule: 4-methylnonane.
19. Learn about It!
Draw the skeletal structure of the branched-chain alkane: 2,4-
diethylhexane.
Step 1. Draw the parent chain first.
Drawing Branched-Chain Alkanes
In the example given, the
parent chain is hexane.
20. Learn about It!
Step 2. Number the carbons in the molecule and draw and place
the alkyl groups based on the locations given by the name.
21. Learn about It!
● Alkanes are usually found in natural gas, petroleum deposits,
and coal.
● Methane (CH4), also known as natural gas, is a colorless,
odorless, and gaseous alkane that is mostly used as fuel for
heating homes, cooking, and electricity generation.
● Methane is commonly found together with other fossil fuels like
coal and oil
Uses of Alkanes
23. Try it! Solution
Step 1. Find the longest continuous chain in the molecule.
This will serve as the parent chain.
The longest chain is
composed of eight
carbons, thus shall
have the name octane.
24. Try it! Solution
Step 2. Identify the alkyl groups and their positions by looking at which
carbon atom they are attached. Make sure that the position will yield the
lowest number for the alkyl group.
The alkyl groups attached to the parent chain are both methyl groups.
25. Try it! Solution
● To locate its position, you can count either from left to right, or right to
left.
○ If the counting starts at left, methyl groups will be connected to
carbon-4;
○ If the counting starts at right, methyl groups will be connected to
carbon-5.
● Comparing the two, the first case gives the lowest number for the methyl
groups.
Step 3. Using the order location-prefix-parent chain-suffix, we write the
name of the molecule: 4,4-dimethyloctane.
26. Key Points
Alkanes are a group of hydrocarbons that contain carbon-
carbon single (C-C) bonds and carbon-hydrogen (C-H)
bonds only.
1
Alkanes have a general formula of CnH2n+2 where n is the
number of carbon atoms (n=1, 2, 3, …). Their names end in
-ane.
2
In a condensed structure, only the symbols for carbon
and hydrogen (and its subscripts) are shown while the line
bonds are absent.
3
27. Key Points
In a Kekule structure, the structure is drawn by explicitly
writing the symbols of each atom and the bonds that
exists between two atoms.
4
In a skeletal structure, the structure is represented by
line segments connected through a zigzag direction.
Endpoint represent carbon atoms.
5
28. Check Your Understanding
Fill up the table below.
Skeletal Structure of Alkane Name
2.
3.
4. 3,3,4,4-tetramethylheptane
5. 6-propyldecane
30. Objectives
describe the properties of
alkenes;
1
At the end
of the
lesson, you
should be
able to:
recognize the common
examples and uses of
alkenes;
2
write structural formulas
for alkenes; and
3
name alkenes based on
their structure.
4
31. Learn about It!
● These are a group of hydrocarbon compounds that contain carbon-
carbon double (C=C) bonds.
● They are also known as olefins.
● It has a general formula of CnH2n where n is the number of carbon
atoms (n=2, 3, 4, …).
● Their names end in -ene.
Alkenes
32. Learn about It!
● Alkenes are insoluble in water just like alkanes.
● They are also less dense than water.
● Alkenes are also highly flammable and very
reactive.
Properties of Alkenes
33. Learn about It!
● Simple alkenes can be easily named, with the first part of
its name representing the number of carbon atoms, and
the representing the hydrocarbon group, alkene.
● For example, ethene can be analyzed with eth- defining
two carbons in the compound, and -ene signaling that the
compound is an alkene.
Naming Alkenes
34. Learn about It!
Number of
Carbon Atoms
Name (Molecular
Formula)
Kekule Structure Condensed Structure
2 ethene (C2H4) CH2=CH2
3 propene (C3H6) CH3CH=CH2
4 1-butene (C4H8) CH2=CHCH2CH3
4 2-butene (C4H8) CH3CH=CHCH3
5 1-pentene (C5H10) CH2=CHCH2CH2CH3
5 2-pentene (C5H10) CH3CH=CHCH2CH3
35. Learn about It!
● It is also important to write down the position of the double
bond in the alkene..
● Consider the molecule below in naming an alkene.
Naming Alkenes
36. Learn about It!
Step 1. Find the longest continuous chain in the molecule. This
will serve as the parent chain.
Naming Alkenes
The longest chain is composed of
six carbons, thus shall have the
name hexene.
37. Learn about It!
Step 2. Identify the double bonds and their positions by looking at which
carbon atom they are attached. Since two carbon atoms participate during
double bond, the first carbon that you counted will provide the number for
the alkene.
Naming Alkenes
38. Learn about It!
Step 3. Identify the alkyl groups
and their positions by looking at
which carbon atom they are
attached. The direction we used
in determining the location of the
alkenes shall also be used in
locating the alkyl groups.
Naming Alkenes
39. Learn about It!
Step 4. Combining the name of the alkyl group and the
parent chain, we write now the complete name of the molecule:
3,4-dimethyl-1,4-hexadiene.
Alternately, the molecule can also be named
3,4-dimethylhex-1,4-diene.
Naming Alkenes
40. Learn about It!
● Consider the sample alkene, 2,4-dimethyl-1,3-hexadiene,
in drawing the skeletal structure of alkenes when given only
their names.
Step 1. Draw the parent chain first.
Drawing Alkenes
The parent chain is 1,3-hexadiene.
41. Learn about It!
Step 2. Number the carbons in the molecule and draw and
place the alkyl groups based on the locations given by the name.
Drawing Alkenes
42. Try it!
Draw the skeletal formula of the straight-chain
alkene, 2,4,6-octatriene.
43. Try it! Solution
Draw the skeletal formula of the straight-chain alkene,
2,4,6-octatriene.
Step 1. Identify the prefix and the number of carbon atoms
present in the straight-chain alkene.
The prefix used is oct-, which corresponds to eight carbon
atoms.
Step 2. Identify the position of the double bond.
The locants indicate that there are three double bonds which
are positioned at the second, fourth, and sixth carbon atoms.
44. Try it! Solution
Draw the skeletal formula of the straight-chain alkene,
2,4,6-octatriene.
Step 3. Draw the skeletal formula of the straight-chain alkene.
The parent chain contains eight carbon atoms, as shown
below, where the double bonds are positioned in the
second, fourth, and sixth carbon atoms.
45. Learn about It!
● Alkenes, under constitutional isomers, form positional isomers, or
molecules with very similar structure except for the location of their
functional groups.
● Below is an example of positional isomers of octene.
Positional Isomers
Positional isomers of octene
46. Learn about It!
● Alkenes serve an important role in most biological molecules.
● Linoleic acid (C18H32O2), also known as omega-6 fatty acid, is an alkene
that naturally exist in plants.
− It serves as an important biomolecule for their nutrition as they use it
as a starting material in the production of prostaglandins.
Examples of Alkenes and Its Uses
linoleic acid
47. Learn about It!
● β-carotene (C40H56).
− It serves as a precursor to the synthesis of vitamin A.
− When vitamin A undergoes an enzymatic reaction, a series of
reaction follows in the retina, which then enables our eyes to
sense vision in bright, dim, and colored light.
Examples of Alkenes and Its Uses
β-carotene
48. Key Points
Alkenes are a group of hydrocarbons that contain carbon-
carbon double (C=C) bonds. They are also known as
olefins.
1
Alkenes have a general formula of CnH2n where n is the
number of carbon atoms (n=2, 3, 4, …). Their names end in
-ene.
2
Alkenes are generally insoluble in water just like alkanes.
They are also less dense than water.
3
49. Check Your Understanding
Fill up the table below.
Skeletal Structure of Alkene Name
1.
2.
3.
4. 1,4,6-octatriene
5. 3-ethyl-3-heptene
51. Objectives
describe the properties of
alkynes;
1
At the end
of the
lesson, you
should be
able to:
recognize the common
examples and uses of
alkynes;
2
write structural formulas
for alkynes; and
3
name alkynes based on
their structure.
4
52. Learn about It!
● These are a group of hydrocarbon compounds that contain
carbon-carbon triple (C≡C) bonds.
● It has a general formula of CnH2n-2 where n is the number of
carbon atoms (n=2, 3, 4, …)
● Their names end in -yne.
Alkynes
53. Learn about It!
● Alkenes are insoluble in water and are slightly soluble in
some organic solvents.
● Most are less dense than water and some are explosives.
● Some are used in pharmacy, manufacturing of plastic, and
artificial ripening of fruits.
Properties of Alkynes
54. Learn about It!
● Simple alkynes can be easily named, with the first part of
its name representing the number of carbon atoms, and
the suffix -yne representing the hydrocarbon group,
alkyne.
● For example, ethyne can be analyzed with eth- defining
two carbons in the compound, and -yne signaling that the
compound is an alkyne.
Naming Alkynes
55. Learn about It!
Number of
Carbon Atoms
Name (Molecular
Formula)
Kekule Structure Condensed Structure
2 ethyne (C2H2) CH≡CH
3 propyne (C3H4) CH≡CCH3
4 1-butyne (C4H6) CH≡CCH2CH3
4 2-butyne (C4H6) CH3C≡CCH3
56. Learn about It!
● It is also important to write down the position of the triple bond
in the alkyne.
Consider the molecule below in naming an alkene.
Naming Alkynes
57. Learn about It!
Step 1. Find the longest continuous chain in the molecule. This
will serve as the parent chain.
Naming Alkynes
The longest chain is composed of
seven carbons, thus shall have the
name heptyne.
58. Learn about It!
Step 2. Identify the triple bonds and their position/s by looking at which
carbon atom they are formed. Since two carbon atoms participate during
triple bond, the first carbon that you counted will provide the number for
the alkyne.
Naming Alkynes
59. Learn about It!
Step 3. Identify the alkyl groups and their positions by looking at which
carbon atom they are attached. The direction we used in determining the
location of the alkynes shall also be used in locating the alkyl groups.
Step 4. Combining the name of the alkyl group and the parent chain, we
write now the name of the molecule:
2,6-dimethyl-3-heptyne.
Alternately, the molecule can also be named 2,6-dimethylhept-3-yne.
Naming Alkynes
60. Learn about It!
● Consider the sample alkyne, 4,4-diethyl-2-hexyne, in
drawing the skeletal structure of alkynes when given only
their names.
Step 1. Draw the parent chain first.
Drawing Alkynes
The parent chain is 2-hexyne.
61. Learn about It!
Step 2. Number the carbons in the molecule and draw and place the alkyl
groups based on the locations given by the name.
Drawing Alkynes
62. Try it!
Draw the skeletal formula of the straight-chain
alkyne, 1,3-heptadiyne.
63. Try it! Solution
Draw the skeletal formula of the straight-chain alkyne,
1,3-heptadiyne.
Step 1. Identify the prefix and the number of carbon atoms present
in the straight-chain alkyne.
The prefix used is hept-, which corresponds to seven carbon
atoms.
Step 2. Identify the positions of the triple bonds.
The locants indicate that there are two triple bonds which are
positioned at the first and third carbon atoms.
64. Try it! Solution
Draw the skeletal formula of the straight-chain alkyne,
1,3-heptadiyne.
Step 3. Draw the skeletal formula of the straight-chain alkyne.
The parent chain contains seven carbon atoms, as shown
below, where the triple bonds are positioned in the first and
third carbon atoms.
65. Learn about It!
● Alkynes are very rare hydrocarbons, and yet they still useful to metal
works and pharmacy.
● Ethyne (C2H2), also known as acetylene, is an alkyne.
− It exists as a colorless and flammable gas.
− During the 20th century, it is widely used in torches for metal
works, as well as in portable lamps and lanterns (water and
calcium carbide were used to produce acetylene in these devices)
where it produces bright flame.
Examples of Alkynes and Its Uses
66. Learn about It!
● Another example of an alkyne is methylpentynol (C6H10O).
− This sedative is used as an over-the-counter drug for
people who experiences insomnia.
● One unique compound which contains alkyne is
ichthyothereol (C14H14O2).
− This compound is naturally secreted by poison dart frogs.
Examples of Alkynes and Its Uses
67. Key Points
Alkynes are a group of hydrocarbons that contain carbon-
carbon triple (C≡C) bonds.
1
Alkenes have a general formula of CnH2n-2 where n is the
number of carbon atoms (n=2, 3, 4, …). Their names end in
-yne.
2
68. Check Your Understanding
Fill up the table below.
Skeletal Structure of Alkyne Name
2.
3.
4. 2-hexyne
5. 4-methyl-1-pentyne
