chapter 2- alkane clb 10803 -student version
TRANSCRIPT
1
Hydrocarbon
Chapter 2.0
Introduction
Classification of Hydrocarbon Classification of Hydrocarbon Classification of Hydrocarbon Classification of Hydrocarbon
Hydrocarbon
Aliphatic Aromatic
Alkanes Alkenes Alkynes
Cycloalkanes Cycloalkenes
Saturated Unsaturated
HydrocarbonsHydrocarbons
AromaticAromaticAliphaticAliphatic
Hydrocarbons
• simplest organic compounds
• contain only carbon and hydrogen
Introduction to HydrocarbonsHydrocarbonsHydrocarbons
AliphaticAliphatic
AlkanesAlkanes
• Alkanes are
hydrocarbons in
which all of the
bonds are single
bonds.
CC CCHH HH
HH HH
HH HH
HydrocarbonsHydrocarbons
AliphaticAliphatic
CycloAlkanesCycloAlkanes
• Alkanes whose carbon
atoms are joined in rings
are called cycloalkanes.
They have the general
formula CnH2n where n =
3,4,'
HydrocarbonsHydrocarbons
AliphaticAliphatic
AlkenesAlkenes
• Alkenes are
hydrocarbons that
contain a carbon-
carbon double
bond.
CC CC
HH HH
HH HH
2
HydrocarbonsHydrocarbons
AliphaticAliphatic
AlkynesAlkynes
• Alkynes are
hydrocarbons that
contain a carbon-
carbon triple bond.
HCHC CHCH
HydrocarbonsHydrocarbons
AromaticAromatic
• The most
common aromatic
hydrocarbons are
those that contain a
benzene ring.
HH
HH
HH
HH
HH
HH
Alkanes
Alkanes nomenclature system
Structural isomers
Cycloalkanes
Synthesis of alkanes
Reaction of alkanes
Sources of alkanes and cycloalkanes
Hydrocarbon – Alkanes
Chapter 2.1
Alkanes
Simplest members of hydrocarbon family
• Contain only hydrogen and carbon
• Only have single bonds
• Saturated compound
All members have general formula of
CnH2n + 2
Twice as many
hydrogen as carbon + 2
24.2
Alkane Nomenclature
3
� Alkyl group is a group which is derived from
unbranched-chain alkanes by removing 1 H
atom
from the end C atom
� General formula : CnH2n + 1
� Represented by “R” symbol
� suffix : - yl
Alkyl GroupsAlkyl GroupsAlkyl GroupsAlkyl GroupsAlkaneAlkaneAlkaneAlkane AlkylAlkylAlkylAlkyl StructureStructureStructureStructuremethane methyl
Names of some common alkyl groups
ethane
propane
ethyl
propyl
isopropyl
- CH3
- CH2 CH3
H
H
C
H
H
H
C
H
C
H
H
C
H
H
H
C
H
H
C
H
H
C
H
H
H
C
H
C
H
H
H
10
20
AlkaneAlkaneAlkaneAlkane AlkylAlkylAlkylAlkyl StructureStructureStructureStructure
butanebutyl
isobutyl
sec-butyl
tert-butyl
H
H
C
H
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
H
C
H
C
H
H
H
C
H
H
H
C
CH3
C
H
H
H
H
C
H
H
H
C
CH3
H
C
H
H
C
H
H
H
C
CH3
C
H
H
H
C
H
H
H
C
H
H
C
H
C
H
H
10
20
10
30
AlkaneAlkaneAlkaneAlkane AlkylAlkylAlkylAlkyl StructureStructureStructureStructurepentane
pentyl
isopentyl
H
10 C
H
H
H
C
H
H
C
H
H
C
H
H
C
H
HC
H
H
H
C
H
H
C
H
H
C
H
H
C
H
H
C
H
H
H
C
H
CH3
C
H
H
C
H
H
H
C
H
H
H
C
CH3
CH3
C
H
H
H neopentyl C
H
H
H
C
CH3
CH3
C
H
H
Naming of organic compound according to IUPAC
system.
Step 1) Find the longest continuous carbon chain and use the
IUPAC name of the unbranched alkane as the basis.
Step 2) Add name of substituent as a prefix. Use base name
with yl ending. Use replicating prefixes (di-, tri-, tetra-,
etc.) according to the number of substituents attached
to the main chain.
Step 3) Number the chain from the end nearest the substituent,
and identify the carbon to which the substituent is
attached by number.
Step 4) List substituents in List substituents in alphabetical orderalphabetical order..
Carbon Chain Length and Prefixes Used in the I.U.P.A.C
Nomenclature System
4
Naming Alkanes
C - C - C - C – C – C
Six carbon atoms in longest chain used base name of
All carbon and hydrogen with single bonds use
ending
Name of compound is
(CH(CH33))22CHCH(CHCHCH(CH33))22
Use replicating prefixes (di-, tri-, tetra-, etc.)
according to the number of identical substituents
attached to the main chain.
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
HC
HCH3C CH3
CH3CH3
CH3 - on 2nd and 3rd carbon - dimethyl
12 3 4
but
ane
2,3-dimethylbutaneIUPAC name:
Longest C chain has 4 carbon – use
All C and H with single bonds – use
Parent name:
1111 2222 3333 4444
6666 7777
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
Give IUPAC name for the following compound
5555H 3C C
CH3
CH3
CH 2 CH 2 CH CH 3
CH 2CH 3
Continuous C chain :Continuous C chain :Continuous C chain :Continuous C chain :
Substituent :Substituent :Substituent :Substituent :Locant : Locant : Locant : Locant :
Prefix :Prefix :Prefix :Prefix :Suffix :Suffix :Suffix :Suffix :
Draw the structure of 3,5,5 - trimethyl
heptane
C – C – C – C – C – C – C
Start by drawing the longest carbon chain:
C – C – C – C – C – C – C 1 2 3 4 5 6 7
C C
C
Answer:
When 2 or more of different kind of
substituents present :
� the substituents are listed alphabetically
� prefixes di, tri, tert … are ignored in
alphabetising exceptexceptexceptexcept iso and neoCH
3CH CH
2
CH3
CH CH2
CH3
CH2
CH3
methylethyl
1111 2222 3333 4444 5555 6666
4-ethyl-2-methyl….
5
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
H3C C
CH3
CH3
CH2
CH
CH2
CH3
CH2
CH3
1111 2222 3333 4444 5555 6666
5555
6666
6C 6C 6C 6C Continuous C chain :Continuous C chain :Continuous C chain :Continuous C chain :
Substituent :Substituent :Substituent :Substituent :
Prefix :Prefix :Prefix :Prefix :Suffix :Suffix :Suffix :Suffix :
dimethyl
hex
- ane
& ethyl
4-ethyl-2,2-dimethylhexane
When 2 chains of equal length compete for
selection as parent chain, choose the chain
with
the greater number of substituents
H3C CH
2
CH3
CH3
CH CH
CH2
CH2
CH CH
CH3
CH3
CH3
H3C CH
2
CH3
CH3
CH CH
CH2
CH2
CH CH
CH3
CH3
CH3
When first branching occurs at an equal distance
from either end of the longest chain, choose the
name that gives the lower number at the first
point of different
1111 2222 3333 4444 5555 6666
H3C CH CH
2CH
CH3
CH CH3
CH3
CH3
H3C CH CH
2CH
CH3
CH CH3
CH3
CH3
11112222333355556666 4444
Polyfunctional organic compounds contain
many different kinds of functional groups
The proper suffix is determined by :
i. identifying all the functional groups present
ii. then choose the principal group of highest highest highest highest
priority priority priority priority
6
Name for polyfunctional groups consist of 4
parts:
i. Suffix : identifies the principal functional
group class to which the molecule belongs
ii. Parent : identifies the size of the main
chain/ring
iii. Prefix : identifies what substituents are located
on the main chain/ring
iv. Locants : tells where substituents are located on
the main chain/ring
Example of Polyfunctional GroupsExample of Polyfunctional GroupsExample of Polyfunctional GroupsExample of Polyfunctional Groups
1111 2222 3333 4444 5555
5555----aminoaminoaminoamino----2222----pentanolpentanolpentanolpentanol
Higher priorityHigher priorityHigher priorityHigher priority
prefix
∴∴∴∴ suffix
----2222----ololololpentanpentanpentanpentanaminoaminoaminoamino5555---- @
parentparentparentparent
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
MethylpropaneMethylpropaneMethylpropaneMethylpropane EthylEthylEthylEthyl
CyclopropylCyclopropylCyclopropylCyclopropyl
CH2 CH
3
H3C CH CH
2 CH
3
H3C CH CH
3
CH3
cyclohexanecyclohexanecyclohexanecyclohexane
butanebutanebutanebutane
suffix
prefix
suffix
prefix
Structural Isomer
CH2
CH3
H2C
H3C
butane
HC CH3CH3
2-methylpropane
CH3
C4H10
Structural Isomer
All have same formula but different structures and properties
Structural Isomer
C5H12
7
Number of Constitutionally Number of Constitutionally
Isomeric AlkanesIsomeric Alkanes
CHCH44 11 CC88HH1818 1818
CC22HH66 11 CC99HH2020 3535
CC33HH88 11 CC1010HH2222 7575
CC44HH1010 22 CC1515HH3232 4,3474,347
CC55HH1212 33 CC2020HH4242 366,319366,319
CC66HH1414 55 CC4040HH8282 62,491,178,805,83162,491,178,805,831
CC77HH1616 99•• Number of isomeric alkanes Number of isomeric alkanes
increases as the number of increases as the number of
carbons increase.carbons increase.
•• There is no simple way to predict There is no simple way to predict
how many isomers there are for ahow many isomers there are for a
particular molecular formula.particular molecular formula.
Cycloalkanes
EthylcyclopentaneEthylcyclopentane
Naming of Cycloalkanes
CHCH22CHCH33
• Name any alkyl groups on the ring in the usual
way.
• List substituents in alphabetical order and count
in the direction that gives the lowest number.
33--EthylEthyl-- 1,11,1--dimethylcyclohexanedimethylcyclohexane
CHCH22CHCH33
HH33CC CHCH33
� Named by placing the prefix cyclocyclocyclocyclo to the
corresponding alkanes
H2C CH 2
CH 2
CyclopropaneCyclopropaneCyclopropaneCyclopropane CyclobutaneCyclobutaneCyclobutaneCyclobutane
IUPAC Nomenclature of CycloalkanesIUPAC Nomenclature of CycloalkanesIUPAC Nomenclature of CycloalkanesIUPAC Nomenclature of Cycloalkanes
ExamplesExamplesExamplesExamples
H2C CH2
H2C CH2
If only one substituent present : not necessarynot necessarynot necessarynot necessaryto
designate its position
cyclocyclocyclocyclo
CH3
ExampleExampleExampleExample
suffix
prefix
MethylMethylMethylMethyl
11116 C6 C6 C6 C
hexhexhexhexaneaneaneane
8
When 2 substituents present :
i. Numbered the C beginning with
substituent according to the
alphabetical order
ii. Numbered in the way that gives the
next substituent the lowest number
possible
cyclohexanecyclohexanecyclohexanecyclohexane1111----ethylethylethylethyl----2222----methylmethylmethylmethyl
1111----ethylethylethylethyl----6666----methylcyclohexanemethylcyclohexanemethylcyclohexanemethylcyclohexaneCH
2CH
3
CH3
1111
22223333
4444
5555 6666
CH2CH
3
CH3
1111
22223333
4444
5555 6666 Ethyl
MethylExample 1Example 1Example 1Example 1
Give IUPAC names for the following cycloalkanes :
CH3
CH3
CH3
CH3
CH2CH
3
CH3
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
butylbutylbutylbutyl
When single ring is attached to a chain
with
greater no. of C atoms :
named as cycloalkylcycloalkylcycloalkylcycloalkylalkane
CH2 CH
2 CH
2 CH
2 CH
3
5 C chain 5 C chain 5 C chain 5 C chain
4C4C4C4Cchainchainchainchain
parentparentparentparent
substituentsubstituentsubstituentsubstituent
1111 2222 3333 4444 5555
1111---- cyclocyclocyclocyclo pentanepentanepentanepentane
When more than 1 ring is attached to a
single
chain :
also named as cycloalkylcycloalkylcycloalkylcycloalkylalkane
1,31,31,31,3----
CH2CH
2CH
2
parentparentparentparent
substituent groupssubstituent groupssubstituent groupssubstituent groups
straight chain straight chain straight chain straight chain
1111 2222 3333
propanepropanepropanepropanehexylhexylhexylhexylcyclocyclocyclocyclodidididi
Alkane
Physical Properties
Non – polar molecules
Not – soluble in water
Low density
Low melting point
Low boiling point
These goes up as the number
of carbons increase
9
Arrange the following compounds in order of
increasing boiling point
CH3CH2CH3
CH3CH2CH2CH2CH3
CH3( CH2)7 CH3
propane
n-pentane
n-nonane
Practice ExercisePractice ExercisePractice ExercisePractice Exercise
Synthesis of alkanes+ H+ H22CC CC HH CC CC
HH HH
HH HH
HH
HH
HH
HH
HH
Hydrogenation of alkenes
Pt / Pd / Ni
alkene hydrogen alkane
Example:
C2H4 + H2 → C2H6
Ni
ethene ethane
� An example of addition reaction
Hydrolysis of Grignard reagent
(alkylmagnesium halide)
CHCH33CHCH22CHCH22MgCl + HMgCl + H22OO CHCH33CHCH22CHCH3 3 + Mg(OH)Cl+ Mg(OH)ClH+
RMgX + H2O → RH + Mg(OH)XH+
alkylmagnesium
halidealkane
Example:
Propylmagnesium
chloridePropane
Wurtz reaction (Reduction of alkyl halide)
2RX + Na → R-R + 2NaX
alkyl halide reducing
agent
alkane
Example:
2CH3CH2CH2Br + 2Na → CH3CH2CH2CH2CH2CH3 + 2NaBr
bromopropane hexane
10
Reaction of Alkanes
Light/heat
and cycloalkane
Crude oil
Refinery gas
C1-C4
Light gasoline
(bp: 25-95 °C)
C5-C12
Naphtha
(bp 95-150 °C)
Kerosene
(bp: 150-230 °C)
C12-C15
Gas oil
(bp: 230-340 °C)
C15-C25
Residue
Composition of Crude Oil
CRUDE OIL
HYDROCARBONS NON-HYDROCARBONS
ALIPHATICS AROMATICS NAPHTHENES SULFURS NITROGENS OXYGENS METALLICS
25% 17% 50% <8% <1% <3% <100PPM
C1 - C60 (C6H5)n CYCLOALKANESSH
S
N
H
O
COOH
11
Industrial Fractioning
Column • Cracking– converts high molecular weight
hydrocarbons to more useful, low molecular
weight ones
i) thermal cracking (by heat)
ii) catalytic cracking (with the aid of catalyst)
• Reforming– increases branching of hydrocarbon chains
– branched hydrocarbons have better burning
characteristics for automobile engines
Petroleum refining
Petroleum Refining
GAS
LIGHT NAPHTHA
HEAVY NAPHTHA
KEROSENE
ATM. GAS OIL
RESIDUUM
CRUDE DESALTER FURNACE
C1-C4
bp < 50 oF
C5 - C?
bp 50-200oF
C? - C12
bp 200-400oF
C12 - C16
bp 400-500oF
C15 - C18
bp 500-650oC
> C20
bp >650oF
TOWER
Distillation – separation by boiling point
Petroleum Reforming
GAS
LIGHT NAPHTHA
HEAVY NAPHTHA
KEROSENE
ATM. GAS OIL
RESIDUUM
TOWER
FUEL GAS
TREATER
HYDROTREATER
HYDROTREATER
HYDROTREATER
REFORMER AROMATIC
EXTRACTION
CATALYTICCRACKER
JET FUELS/KEROSENE
DIESEL & FUEL OILS
GASOLINE
AROMATICS
VacuumDistillation
VACUUM GAS OIL
LUBRICATING OIL
COKER COKE
ASPHALT
CATALYTICCRACKER
Conversion Reactions
gasoline gasoline add itive recycle
C 7H1 5.C 15H3 0.C 7H1 5 C 7H16 + C 7H1 4 + C 1 5H3 0CRACK
COMBINE
REARRANGE
THERMAL
CATALYTIC
ALKYLATION
POLYMERIZATION
REFORMIING
ISOMERIZATION
C H 3 C H 2 C H 3 C H 2 C H C H 2 C H 3C H 3 C H 2 C H 2 C H 2 C H 2 C H 2 C H 3
Dehydrogenation
Dehydroisomerization
Isomerization
Dehydrocyclization
Hydrocracking
Catalytic Reforming – Conversion
ReactionsDehydrogenation of cycloalkanes to aromatics
Dehydroisomerization of cyclopentanes to aromatics
Isomerization of alkanes
Dehdrocyclization of alkanes
Hydrocracking of alkanes
CH3 CH3
3H2
CH3
3H2
CH3CH2CH2CH2CH3 CHH3C
CH3
CH2 CH3
CH3CH2CH2CH2CH2CH2CH3
CH3
4 H2
CH3CH2CH2CH2CH2CH2CH3 CH3CH2CH3 CH3CH2CH2CH3
12
Catalytic cracking in laboratory scale Conversion Reactions
gasoline gasoline add itive recycle
C 7H1 5.C 15H3 0.C 7H1 5 C 7H16 + C 7H1 4 + C 1 5H3 0CRACK
COMBINE
REARRANGE
THERMAL
CATALYTIC
ALKYLATION
POLYMERIZATION
REFORMIING
ISOMERIZATION
C H 3 C H 2 C H 3 C H 2 C H C H 2 C H 3C H 3 C H 2 C H 2 C H 2 C H 2 C H 2 C H 3
Dehydrogenation
Dehydroisomerization
Isomerization
Dehydrocyclization
Hydrocracking