Transcript Document

SATURATED HIDROCARBONS
ALKANE
Alkane
= paraffin
= saturated hidrocarbons
= hydrocarbons with only single covalent
bonds between the carbon atoms
Definition
Acyclic branched or unbranched hydrocarbons
having the general formula CnH2n+2 , and
therefore consisting entirely of hydrogen
atoms and saturated carbon atoms.
IUPAC Gold Book
Sifat
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Sukar bereaksi
C1 – C4 pada tekanan & suhu normal fase gas
C5 – C17 pada tekanan & suhu normal fase cair
PC18 pada tekanan & suhu normal fase padat
Mudah larut pada pelarut non polar
Berat jenis naik dengan penambahan atom C
Pada alkana rantai lurus  semakin panjang
rantai maka titik didih & titik leleh semakin tinggi
Carbon Bonding in Alkane
Each carbon atom must have
4 bonds (either C–H or C–C
bonds),
and each hydrogen atom must
be joined to a carbon atom
(H–C bonds).
Straight-chain alkanes are sometimes indicated by the prefix
n- (for normal)
Name
Molecular
Formula
CnH2n+2
Structural Formula
Methane
CH4
CH4
Ethane
C2H6
CH3–CH3
Propane
C3H8
CH3–CH2–CH3
Butane
C4H10
CH3–CH2–CH2–CH3
Pentane
C5H12
CH3–CH2–CH2–CH2–CH3
Hexane
C6H14
CH3–CH2–CH2–CH2–CH2–CH3
Heptane
C7H16
CH3–CH2–CH2–CH2–CH2–CH2–CH3
Octane
C8H18
CH3–CH2–CH2–CH2–CH2–CH2–CH2–CH3
Nonane
C9H20
CH3–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH3
Decane
C10H22
CH3–CH2–CH2–CH2–CH2–CH2–CH2–CH2–CH2–
CH3
Isomerism
Alkanes with more than three carbon atoms
can be arranged in a multiple number of
ways, forming different structural isomers.
Isomers are compounds that have the same
molecular formula but different structural
formulas.
College Chemistry_ch.21.8_p.529
Practice 1 :
Write structural formulas and
condensed structural formulas of :
1.
2.
Pentane C5H12
Hexane C6H14
Pentane
Hexane
Alkyl
Number of carbons
1
2
3
4
5
6
7
8
9
10
11
12
Molecule name
methyl
ethyl
propyl
butyl
pentyl/amyl
hexyl
heptyl
octyl
nonyl
decyl
undecyl
dodecyl
sec-Butyl
Isopropyl
Isobutyl
tert-Butyl
IUPAC Nomenclature : Basic Principles
(1)
Select the longest continuous chain of carbon
atoms as the parent compound, and consider
all alkyl groups attached to it as side chains
that have replaced hydrogen atoms of the
parents hydrocarbon.
The name of the alkane consists of the name of
the parent compound prefixed by the names
of the side-chain alkyl groups attached to it.
IUPAC Nomenclature : Basic Principles
(2)
Number the carbon atoms in the parent carbon
chain starting from the end closest to the first
carbon atom that has an alkyl or other group
substitued for a hydrogen atom.
IUPAC Nomenclature : Basic Principles
(3)
Name each side-chain alkyl group and
designate its position on the parent
carbon chain by a number (for example,
2-methyl means a methyl group
attached to carbon number 2).
IUPAC Nomenclature : Basic Principles
(4)
When the same alkyl-group side chain occurs
more than once, indicate this by a prefix (di-,
tri-, tetra-, and si forth) written in front of the
alkyl-group name (for example, dimethyl
indicates two methyl groups).
The numbers indicating the positions of these
alkyl groups are separated by a comma and
followed by a hypen and are placed in front of
the name (for example, 2,3-dimethyl).
IUPAC Nomenclature : Basic Principles
(5)
When several different alkyl groups are
attached to the parent compound, list them in
alphabetical order; for example, ethyl before
methyl in 3-ethyl-4-methyloctane.
College Chemistry_ch.21.9_p.533
Practice 2 :
The following names are incorrect. Tell why the
name is wrong and gave the correct name.
1. 3-methylbutane
2. 2-ethylbutane
3. 2-dimethylpentane
4. 3-methyl-5-ethyloctane
5. 3,5,5-triethylhexane
1.
3-methylbutane
CH3 – CH2 – CH – CH3
CH3
2-methylbutane
2.
2-ethylbutane
CH3 – CH2 – CH – CH3
CH2
CH3
3-methylpentane
3.
2-dimethylpentane
CH3
CH3 – CH – CH – CH2 – CH3
CH3
2,2-dimethylpentane
4.
3-methyl-5-ethyloctane
CH3 – CH2 – CH – CH2 – CH – CH2 – CH2 – CH3
CH3
CH2
CH3
5-ethyl-3-methyloctane
5.
3,5,5-triethylhexane
CH2
CH3
CH3 – CH2 – CH – CH2 – C – CH3
CH2
CH2
CH3
CH3
3,5-diethyl-3-methylheptane
Reaction of Alkane :
Halogenation
Halogenation means substitution of halogens for hydrogen.
RH + X2  RX + HX
X = F, Cl, Br, I
Example :
CH3CH3 + Cl2  CH3CH2Cl + HCl
chloroethane
Reaction of Alkane :
Dehydrogenation
Dehydrogenation means removal of hydrogen.
CnH2n+2
700 – 900 oC
CnH2n + H2
Example :
CH3CH2CH3

CH3CH=CH2 + H2
propene
Reaction of Alkane :
Cracking
Cracking means breaking up large molecules to
form smaller ones.
Example :
C16H34
alkane

C8H18 + C8H16
alkane
alkene
Reaction of Alkane :
Isomerization
Isomerization means rearrangement of molecular structures.
Example :
Chlorination Products of Methane
(1)
CH4 + Cl2  CH3Cl
CH3Cl + Cl2  CH2Cl2
CH2Cl2 + Cl2  CHCl3
CHCl3 + Cl2  CCl4 + HCl
Chlorination Products of Methane
(2)
Formula
IUPAC name
Common name
CH3Cl
CH2Cl2
CHCl3
CCl4
Chloromethane
Dichloromethane
Trichloromethane
Tetrachloromethane
Methyl chloryde
Methylene chloryde
Chloroform
Carbon tetrachloride
Cycloalkane/cycloparaffin/naphtane
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Cycloalkanes are types of alkanes which
have one or more rings of carbon atoms in
the chemical structure of their molecules 
struktur alisiklik.
Rumus: CnH2n
Contoh:
Cyclopropane
Cyclobutane
C3H6
C4H8
Cyclopentane
C5H10
Cyclohexane
C6H12
Sources of Alkanes
The two main sources of alkanes are
natural gas and petroleum / crude oil.
Natural gas consists of :
 Methane
 Other hydrocarbons
 Hydrogen
 Nitrogen
 Carbon monoxide
 Carbon dioxide
 Hydrogen sulfide (just in some location)
Petroleum is formed by the decomposition of plants
and animals over million of years.
Composition:
 Carbon
 Hydrogen
 Nitrogen
 Oxygen
 Sulfur
 Metals
Four different types of hydrocarbon molecules appear
in crude oil :
 Paraffins
 Naphthenes
 Aromatics
 Asphaltics
Fractional Distillation of
Crude Oil
Crude oil is separated into fractions by
fractional distillation. The fractions at the top
of the fractional column have lower boiling
points than the fractions at the bottom. The
heavy bottom fractions are often cracked into
lighter, more useful products. All of the
fractions are processed further in other
refining units.
Octane Rating
Octane CH3(CH2)6CH3
Octane has 18 structural isomers :
• Octane (n-octane)
• 2-Methylheptane
• 3-Methylheptane
• 4-Methylheptane
• 3-Ethylhexane
• 2,2-Dimethylhexane
• 2,3-Dimethylhexane
• 2,4-Dimethylhexane
• 2,5-Dimethylhexane
• 3,3-Dimethylhexane
• 3,4-Dimethylhexane
• 2-Methyl-3-ethylpentane
• 3-Methyl-3-ethylpentane
• 2,2,3-Trimethylpentane
• 2,2,4-Trimethylpentane (isooctane)
• 2,3,3-Trimethylpentane
• 2,3,4-Trimethylpentane
• 2,2,3,3-Tetramethylbutane
0
100
The octane rating was developed by chemist Russel Marker
at the Ethyl Corporation at 1926. The selection of n-heptane
as the zero point of the scale was due to the availability of
very high purity n-heptane, not mixed with other isomers of
heptane or octane, distilled from the resin of the Jeffrey
Pine. Other sources of heptane produced from crude oil
contain a mixture of different isomers with greatly differing
ratings, which would not give a precise zero point.
Higher octane ratings correlate to higher activation energies.
Activation energy is the amount of energy necessary to start
a chemical reaction. Since higher octane fuels have higher
activation energies, it is less likely that a given compression
will cause detonation.
The alternative method to boost octane rating and
minimize engine knocking is too add small
amounts of an additive to the fuel. One such
additive commonly used in gasoline was
tetraethyllead, (C2H5)4Pb.
The function of tetraethyllead is to prevent the
premature explosions that constitute knocking.
Use of tetraetthyllead additives poses a serious
enviromental hazard. Lead becomes pollutant in
air, water, and sovent.
Current additives in anleaded gasoline :
• Toluene
• Xylene
• Methyl tert-butyl ether (MTBE)