The document provides information about aliphatic hydrocarbons, specifically alkanes. It begins with learning outcomes which state that students will understand organic compound families, explain alkane structure and properties, name organic compounds using IUPAC rules, describe alkane isomers and synthesis reactions. The document then covers classes of organic compounds including hydrocarbons, alkane properties such as physical states and solubility, IUPAC nomenclature rules, cyclic alkane naming, and alkane reaction and synthesis methods like hydrogenation of alkenes.

1. 1
Aliphatic Hydrocarbons
Jully Tan
School of Engineering
Learning Outcome
At the end of the lecture, students will be able to:
„ Understand the family under organic compounds.
„ Explain the aliphatic hydrocarbon or alkanes specifically by its structure, physical
EP101 / EG101 2
and chemical properties.
„ Naming the organic compound especially for alkanes according to IUPAC method.
„ Explain the type of isomer in organic compound and draw the different isomer
structures of the compound.
„ Explain the different type of the synthesis of alkanes and reaction of alkanes
specifically:
… Halogenation
… Combustion
… Hydrogenation of alkenes
… Reaction of Alkyl Halides with organometals
… Reduction of Alkyl Halides

2. 2
Classes of Organic Compounds
Organic compound
Halogeneted HC HC with N
Amine Amide Nitrile
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Hydrocarbon
Alkane
Alkene
Alkyne
Hydrocarbon with O
Alcohol
(-OH)
Ether/epoxide
Aldehyde/
Ketone
Carboxylic
acid
Carboxylic
Acid derivatives
Ester Halide acids anydride
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Overview
¾ Hydrocarbon
… Composed entirely of C and H atoms.
… Has 3 main categories
„ Aliphatic - straight chain HC
„ Cyclic - ring shape HC
„ Aromatic – HC derived from benzene ring.
¾ Each C can form a maximum of four single bonds, OR two single and one double bond, OR
one single and triple bond.

3. 3
Some five-carbon skeletons
C
C
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C C C C C
C
C C C C
C
C C C
C
C C C C C
C C C C C
C C C C
C
C C C C
C
C C
C C
C
C C
C C
C C
C
C C
C
C
C
C C
C C
C
C C
C C C C
single
bonds
double
bond
ring
Adding the H-atom skin to the C-atom skeleton
C C C
A C atom single-bonded
to two other
atoms gets two H
atoms.
H
C C C
C
C H
H
C C C
C C
H
C C
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H
C C
A C atom single-bonded
to one other
atom gets three H
atoms.
H
A C atom single-bonded
to three other
atoms gets one H
atom.
H
H H
C C C
C
A C atom single-bonded
to four other
atom is already fully
bonded (no H atoms).
H
A double- and single-bonded
C atom or a
triple-bonded C atom
is treated as if it were
bonded to three other
atoms.
A double-bonded C
atom is treated as if it
were bonded to two
other atoms.

4. 4
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5. 5
„ carbon–carbon single bond: s (head–on) overlap of carbon sp3 orbitals
„ saturated hydrocarbons; only C-C and C-H bonds
„ Alkane: a saturated hydrocarbon whose carbons are arranged in a chain. Saturated
hydrocarbon: a hydrocarbon containing only single bonds.
„ Aliphatic hydrocarbon: another name for an alkane: aliphatic, “fat”
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Alkanes, CnH2n+2
C
H
H
H
H
1. Molecular Formula of Alkanes
Name No of C Molecular Formula
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Methane 1
Ethane 2
Propane 3
Butane 4
Pentane 5
Hexane 6
Heptane 7
Octane 8
Nonane 9
Decane 10

6. 6
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Structure
„ Shape
… tetrahedral about carbon
… all bond angles are approximately 109.5°
„ Isomer: same chemical formula, but different structure.
„ There are 2 isomeric butanes
… n-butane
… C4H10
… n means “normal” or in a straight chain
H
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… isobutane
… C4H10
C
C C C
H
H
H H
H
H
H
H
H H
C C C C H
H
H
H
H
H
H
H
H
Branching vs. No Branching

7. 7
Find the Isomers of C6H14
Draw the structures for C6H14 starting with the longest chain (6 in a row)
…next draw all structures with 5 carbons in the longest chain (substitute for the H s)
…then substitute for other H s
H
H
H
H
H
C C C C C C H
H
H
H
H
H
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H
H
H
C
C C C C C
H
H
H H
H
H
H
H
H
H
H
H
H H
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Classification of C & H
„ Primary (1°) C: a carbon bonded to one other carbon
… 1° H: a hydrogen bonded to a 1° carbon
„ Secondary (2°): a carbon bonded to two other carbons
… 2°H: a hydrogen bonded to a 2° carbon
„ Tertiary (3°) C: a carbon bonded to three other carbons
… 3° H: a hydrogen bonded to a 3° carbon
„ Quaternary (4°) C: a carbon bonded to four other carbons

8. 8
CONNECTED TO TWO
OTHER CARBONS
C
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C C
PRIMARY
C C C
CONNECTED TO ONE
OTHER CARBON
C C C
C C C C
C
SECONDARY
TERTIARY QUATERNARY
CONNECTED TO THREE
OTHER CARBONS
CONNECTED TO FOUR
OTHER CARBONS
Degree of Substitution
EP101 / EG101 19
2. Chemical Properties
„ Not reactive compound:
… Alkanes are the least reactive among all other organic comp. They do not usually react
with strong acids or bases, or with most oxidizing or reducing agents.
„ Highly combustible compound
… Alkanes can burn easily in combustion reactions and releasing high energy.
CH4 O2 CO2 H O 2 + +

9. 9
3. Physical Properties, Density & Solubility
„ Alkanes physical forms as gas, liquid and solid.
a. Both bp and mp increase with increasing carbon number for straight-chain
alkanes with formula CnH2n+2
b. Branching tends to raise the melting point and lower the boiling point. Why??
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… C1-C4 -Gas
… C5-C17 -Liquid
… C18 and above -Solid
„ Only dissolves in organic solvent, such as benzene, CCl4, but do not dissolve in
water (hydrophobic).
„ Alkane is less density than water. (near 0.7 g/mL)
Why do alkane do
not dissolve in
water?
4. Boiling Point
Hint: surface area of alkane.
b. Branching tends to lower the boiling point and raise the melting point
BP 60oC 58oC 50oC
MP -154oC -135oC -98oC
Explanation:
MP Branching reduces the flexibility of the molecule which reduces the entropy term
ΔS in the equation Tmp= ΔH/ΔS. Since ΔS is in the denominator, Tmp increases. The
structure of the alkane packed better into a compact 3D structure which is said the atom are
bonded more tightly and need higher T to transform the alkane from solid to liquid phase.
BP Branching reduces surface area (more compact structure), and therefore Van der Waals
dispersion forces which control boiling point for these molecules been reduces. Less energy
to overcome these reactions to transform liquid to gas phase.
Answer: Solubility – alkanes are nonpolar molecules and therefore insoluble in water, which
is polar. Alkanes are hydrophobic.
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10. 10
Boiling points of the first 10 unbranched
alkanes
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Boiling Points of Alkanes
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11. 11
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Sources
¾ 2 main sources are petroleum & natural gas

12. 12
International
Union of
Pure and
Applied
Chemistry
colloquially:
“eye-you-pac”
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Nomenclature
International Union of Pure and Applied Chemistry (IUPAC)
EP101 / EG101 27

13. 13
1. Numerical Roots for Carbon Chains and Branches
PREFIX + ROOT (Parent) + SUFFIX
Roots/Parent Number of C atoms
1
2
3
4
5
6
7
8
9
1
0
EP101 / EG101 28
meth-eth-prop-but-hex-pent-hept-oct-non-dec-
STEP 1 : Find the parent hydrocarbon
1. Find longest continuous chain of carbons and use as parent name.
2. If 2 chains have same number of carbons, choose the one with the more branch points.
STEP 2 : Number the atoms in parent chain
1. Begin at the end nearer to the first branch point.
Which one is the
correct way of
longest chain?
Which one is the
correct way of
numbering the
atom of the chain?
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14. 14
2. If branching occurs at equal distance from both ends, begin numbering at the end nearer the
EP101 / EG101 30
second branch point.
Which one is the
correct way of
numbering the
atom of the chain?
2. Naming the Compound Types of Suffix
PREFIX + ROOT (Parent) + SUFFIX
„ Suffix is the type of the family of that specifics organic compound.
„ For example, alkanes, alkene and etc.
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15. 15
3. Identify Prefix of the Chain
-CH 2 CH 2 CH 2 CH 2 CH 3
-CH 2 CH 2 CHCH 3
CH 3
CH 3
pentyl
-CH 2 CCH 3 neopentyl
CH 3
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isopentyl
STEP 1 : Identify and number the substituents
1. Give each substituent a number that corresponds to its position on the parent chain.
C3 CH2CH3 3-ethyl
C4 CH3 4-methyl
C6 CH2CH3 6-ethyl
2. Two substituents on the same carbon gets the same number
Substituents
Substituents :
C2 CH3 2-methyl
C4 CH3 4-methyl
C4 CH2CH3 4-ethyl
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16. 16
STEP 2: Write the name as a single word (follow alphabetical order)
1. Use hyphens to separate prefixes and commas to separate numbers or more identical
substituents are present, use multipliers (di, tri, tetra)
„ Note : the multipliers are not use for alphabetizing.
Name a complex substituent as if it were a compound and put them in parentheses
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Naming & Drawing Cyclic Alkanes
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Name of branching
group or substitute (if
any)
Parent
name
+ Use Prefix “cyclo” +
Parent Name = longest continuous chain of carbon atoms
Cyclo = parent chain forms a ring
STEP 1: Find parent
„ If number of carbon atoms in the ring is larger than the number in the largest substituent, the
compound is an alkyl-substituted cycloalkane.
„ If the number of carbon atoms in the ring is smaller than the number in the largest substituent,
the compound is an cycloalkyl-substituted alkane.

17. 17
„ STEP 2: Number the substituents and write the name
1. Start at a point of attachment and number the substituents so that the second substituent has
EP101 / EG101 36
the lowest possible number.
2. If necessary, proceed to the next substituent until a point of difference is found.
3. If 2 or more substituents might potentially receive the same number, number them
alphabetical priority. Treat halogens as if they are alkyl groups.
Which one is the
correct way of
numbering the atom
of the chain?
Which one is the
correct way of
numbering the atom
of the chain?
CH2
H2C CH2
EP101 / EG101 37
1. What is the parent name?
Propane (Longest chain is 3 carbons)
2. Is the parent chain in a ring?
Yes
Correct name is: cyclopropane

18. 18
CH2
H2C CH
CH3
Parent name is cyclopropane.
What is the branching group? Methyl –CH3
Correct name is: methylcyclopropane
Note: The number (1) is not needed to identify the place of the substituent if
only one is present in the molecule.
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CH CH3
3 2
4
1
H2C CH
EP101 / EG101 39
H2C
CH3
Parent name is cyclobutane.
What is the branching group? Methyl –CH3
Correct name is: 1, 2-dimethylcyclobutane
Note: The first named substituent is arbitrarily given the number one (1) position

19. 19
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Reaction of Alkanes &
Synthesis of Alkanes
Reaction
„ Halogenation
„ Combustion
„ Cracking & hydrocracking
Synthesis
„ Hydrogenation of Alkenes
„ Reduction of Alkyl Halides
„ Reaction of Alkyl Halides with
organometals

20. 20
C H C H n n Pt Pd Ni n n+ ⎯⎯⎯⎯→ H2
2 , / 2 2
Alkene Alkane
( ) ( )
−C = C− + H − H ⎯⎯Pt→−C−C−
EP101 / EG101 42
Synthesis of Alkanes:
1. Hydrogenation of Alkenes
„ Catalytic hydrogenation of alkene to form alkanes.
„ General rxn eqn:
„ Its take place under heterogenous ( more than 1 phase) system, the alkane & H2 are adsorbed on the
metallic surface. Therefore they are weakened (both multiple bond and H-H bond).
„ The H2 will add to the same side of the multiple bond: cis-condition.
What is the
function of
the
catalyst??
Synthesis of Alkanes:
2. Reduction of Alkyl Halides
Ether
δ δ
RX Mg RMgX R Mg X
Grignard
reagent
R alkyl aryl group
EP101 / EG101 43
A: Hydrolysis by Grignard Reagent
ƒ Gridgnard reagent: prepared by treating an alkyl/aryl halide with magnesium mether in dry ether. General eqn. of
the preparing of Grignard reagent
: /
ƒ Grignard reagent is a XreactCivel : , reBagrenIt. ,
It can react with H2O to form Alkane.
− +
+ ⎯⎯⎯→ −
RMgX + H O ⎯⎯→ R − H +
Mg ( OH ) X
2 Grignard
reagent

21. 21
B: Reduction by metal & acid
ƒ General eqn.
RX ⎯⎯→
Zn
RH
CH 3
COOH
ƒ Eg. Reduction of Cloro-cyclohexane with Zn & acetic acid able to produce 83% of cyclohexane.
ƒ Alkyl halide as well react with Litium aluminium hydride (LiAlH4)
ƒ Tetrahydroaluminate ion will react with alkyl halide to produce alkane
EP101 / EG101 44
RX ⎯L⎯iAl⎯H4→ RH
H − Al−−H + H −C− X ⎯⎯→H − Al + H −C−H + X −
tetrahydroaluminate Alkyl Halide Alkane
3. Reaction of Alkyl Halides with organometals
ƒ Alkane can be synthesis via nucleophilic substitution reaction between alkyl halide and a negative nucleophile.
ƒ The carbon in the polar carbon-halogen bond is positive, therefore the negative nucleophile is attracted to it.
R CuLi + R'X ⎯⎯→R − R' + RCu + LiX
EP101 / EG101 45
2
Litium diaalkylCumprum
RX ⎯⎯Li→+ R − Li⎯C⎯⎯uX→R CuLi +⎯R⎯⎯'X→+R − R
2

22. 22
EP101 / EG101 46
Reaction of Alkane
1. Halogenation
• Radical halogenation has three distinct parts.
EP101 / EG101 47
Halogenation of Alkanes
• A mechanism such as radical halogenation that involves two or more
repeating steps is called a chain mechanism.
• The most important steps of radical halogenation are those that lead to
product formation—the propagation steps.

23. 23
Halogenation of Alkanes
• When a single hydrogen atom on a carbon has been
replaced by a halogen atom, monohalogenation has
taken place.
• When excess halogen is used, it is possible to
replace more than one hydrogen atom on a single
carbon with halogen atoms.
• Monohalogenation can be achieved experimentally
by adding halogen X2 to an excess of alkene.
• When asked to draw the products of halogenation of
an alkane, draw the products of monohalogenation
only, unless specifically directed to do otherwise.
EP101 / EG101 48
Halogenation of Alkanes
• In the presence of heat or light, alkanes react with
halogens to form alkyl halides.
• Halogenation of alkanes is a radical substitution
reaction.
• Halogenation of alkanes is only useful with Cl2 or Br2.
Reaction with F2 is too violent, and reaction with I2 is
too slow to be useful.
• With an alkane that has more than one type of
hydrogen atom, a mixture of alkyl halides may result.
EP101 / EG101 49

24. 24
EP101 / EG101 50
2. Combustion
CnH2n+2 + (xs) O2, flame Æ n CO2 + (n+1) H2O + heat
gasoline, diesel, heating oil…
3. Pyrolyis (cracking)
alkane, 400-600oC Æ smaller alkanes + alkenes + H2
Used to increase the yield of gasoline from petroleum. Higher
boiling fractions are “cracked” into lower boiling fractions that
are added to the raw gasoline. The alkenes can be separated and
used in to make plastics.
EP101 / EG101 51

25. 25
REVISION CHECK
What should you be able to do?
Recall and explain the physical properties of alkanes
Recall and explain the types of isomerism found in alkanes
Recall and explain why alkanes undergo chlorination free radical reaction
Write balanced equations representing the reactions taking place in this
section
CAN YOU DO ALL OF THESE? YES
EP101 / EG101 52
NO