Introduction
Classification of Hydrocarbon Hydrocarbon
Aromatic
Aliphatic
Hydrocarbon Chapter 2.0
Alkanes
Alkenes
Cycl Cycloa oalk lkan anes es
Alkynes
Cyclo Cycloal alk kenes enes
Unsaturated
Saturated
Introduction to Hydrocarbons Hydrocarbons Hydrocarbons
• Aliphatic Aliphatic
Aromatic
Hydrocarbons • simplest organic compounds • contain only only carbon and hydrogen hydrogen
Alkanes
Hydrocarbons
Aliphatic
• Alkanes Alkanes whose whose carbo carbon n atoms are joined in rings are called cycloalkanes. They have the general formula CnH2n where n = 3,4,
CycloAlkanes
Alkanes are hydrocarbons in which all of the bonds are single bonds. H H H
C
C
H
H
H
Hydrocarbons
• Aliphatic
Alkenes are hydrocarbons that contain a carboncarbon double bond. H H
Alkenes
C H
C H
1
Hydrocarbons
Hydrocarbons
• • Aliphatic
Alkynes are hydrocarbons that contain a carboncarbon triple bond. Alkynes HC
CH
The most common aromatic hydrocarbons are those that contain a H benzene ring.
Aromatic
H
H
H
H H
Alkanes Simplest members of hydrocarbon family
Hydrocarbon – Alkanes Chapter 2.1 Alkanes Alkanes nomenclature system Structural isomers Cycloalkanes Synthesis of alkanes Reaction of alkanes Sources of alkanes and cycloalkanes
• 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
Alkane Nomenclature
24.2
2
Alkyl Groups
Names of some common alkyl groups
Alkyl group is a group which is derived from
unbranched-chain alkanes by removing 1 H
Alkane
Alkyl Alkyl
Structure
methane
methyl
- CH 3
ethane
ethyl
- CH 2 CH3
atom from the end C atom
General formula : C nH2n + 1
Represented by “R” symbol
suffix : - yl
propyl
H
propane H
H
H
C
C
C
H
H
H
H
H
H
C
C
C
H
H
H
H
H
H
C
C
C
0
1
H
H
isopropyl
H
0
2
Alkane
Alkyl Alkyl
butane H
butyl
H
H
H
H
C
C
C
C
H
H
H
10
sec-butyl
isobutyl CH3 H
C
C
H
H
C
H 30
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
CH3 H
H
H
H
H
C
C
C
C
C
C
C
C
H
H
H
H
H
CH 3 H
H
H
H
H
H
H
C
C
H
tert-butyl
H
C
Structure
1
0
pentyl
H
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
C
C
C
C
H
CH3 H
H
10
H
H
CH3 H
C
C
H
CH3 H
C
H
H
Naming of organic compound according to IUPAC system. Step 1)
H
H
H
Alkyl Alkyl
pentane H
H
H
H
H
20
H
H
H
H
Alkane
Structure
H
H
H
isopentyl
neopentyl
H
H
CH3 H
C
C
H
CH3 H
C
Carbon Chain Length and Prefixes Used in the I.U. P.A.C Nomenclature System
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 substituents in in alphabetical order. order .
3
Naming Alkanes
Practice Exercise
C-C-C-C–C–C
(CH3)2CHCH(CH3)2
Six carbon atoms in longest chain used base name of
All carbon and hydrogen with single bonds use ending Name of compound is
Use replicating prefixes (di-, tri-, tetra-, etc.) according to the number of identical substituents attached to the main chain.
H C
1
H3C
H C
2
4
3
CH3
1 1 22 C
but
Parent name:
CH3 - on 2nd and 3rd carbon - di methyl 2,3-dimethylbutane
CH 2
Start by drawing the longest carbon chain: C–C–C–C–C–C–C
prefixes di, tri, tert … are ignored in
C–C–C–C–C–C–C 5
C
CH
methyl CH3
C 4
6
3
the substituents are listed alphabetically
except iso 55 and6 neo
11 alphabetising 22 33 44
Answer:
3
CH CH
When 2 or more of different kind of substituents present :
CH3
2
55
CH 2
Continuous C chain : Prefix : Suffix : Substituent : Locant :
1
44
CH3
Draw the structure of 3,5,5 - trimethyl heptane
C
CH 2 CH 3
33
H 3C
7 77
6
ane
All C and H with single bonds – use
IUPAC name:
Give IUPAC name for the following compound CH3
CH3 CH3 Longest C chain has 4 carbon – use
Practice Exercise
CH2
CH
CH2
CH2
CH3
ethyl
CH3
7
4-ethyl-2-methyl….
4
Practice Exercise CH3 H3C
11 22
33 44 CH2 CH
C
CH
When 2 chains of equal length compete for selection as parent chain, choose the chain with
CH3
the greater number of substituents
6C hex
4-ethyl-2,2-dimethylhexane
- ane
dimethyl& ethyl
CH3 CH2
CH3
2
6
H3C
6
55 CH
CH3
Continuous C chain : Prefix : Suffix : Substituent :
55 CH2
CH
CH3
CH3
CH
CH
CH3
CH2 CH2
When first branching occurs at an equal distance
CH3
from either end of the longest chain, choose the CH3
H3C
CH
CH2
CH
CH3
CH3
CH
CH
name that gives the lower number at t he first point of different
CH3
CH2 CH2 CH3
CH3
6 55
H3C
CH
44
CH2
33
CH
22
CH
1 1
CH3
CH3
CH3
Polyfunctional organic compounds contain many different kinds of functional groups The proper suffix is determined by : CH3
1 1 22
H3C
CH CH3
33
CH2
44
CH CH3
55
CH
6 CH
3
i.
identifying all the functional groups present
ii.
then choose the principal group of
highest
priority
5
Name for polyfunctional groups consist of 4
Example of Polyfunctional Groups
parts: Suffix : identifies the principal functional
i.
parent
group class to which the molecule belongs ii.
Parent : identifies the size of the main
11
33
22
44
55 prefix
chain/ring iii.
Prefix : identifies what substituents are located
on the main chain/ring iv.
Higher priority ∴
Locants : tells where substituents are located on
the main chain/ring
suffix
5 55- amino pentan- 2 22-ol
@
5amino- 2pentanol 55- amino amino 22- pentanol
Practice Exercise suffix prefix
H3C CH CH3
CH2 CH3
CH3
Methylpropane
Ethyl cyclohexane
Structural Isomer
suffix
H3C CH CH2 CH3
Cyclopropyl butane
prefix
Structural Isomer
Structural Isomer All have same formula but different structures and properties
C4H10 H3C CH3
H C
CH3
H2 C
C H2
C5H12
CH3
butane
CH3 2-methylpropane
6
Number of Constitutionally Isomeric Alkanes CH4
1
C8H18
18
C2H6
1
C9H20
35
C3H8
1
C10H22
75
C4H10
2
C15H32
4,347
C5H12
3
C20H42
366,319
C6H14
5
C40H82
62,491,178,805,831
C7H16
9
Cycloalkanes
• Number Number of of isomeric isomeric alkanes alkanes increases as the number of carbons increase. • There There is is no simple simple way way to predict predict how many isomers there are for a particular molecular formula.
Naming of Cycloalkanes •
Name any alkyl groups on the ring in the usual way. CH2CH3
Ethylcyclopentane
List substituents in alphabetical order and count in the direction that gives the lowest number. •
H3C CH3 3-Ethyl Ethyl-- 1,1 1,1--dimethylcyclohexane CH2CH3
IUPAC Nomenclature of Cycloalkanes
Named by placing the prefix
If only one substituent present :
cyclo to the
to designate its position
corresponding alkanes
Example
Examples
suffix
CH 2
H 2C
not necessary
CH 2
Cyclopropane
H 2C
CH 2
H 2C
CH 2
prefix
6 C
1 1
CH3
hex ane Methyl cyclohexane
Cyclobutane
7
Example 1
Methyl
33
1-11 - ethyl ethyl-- 2 22-methyl cyclohexane
When 2 substituents present :
1 1
44
Numbered the C beginning with
i.
CH 3
22
55
substituent according to the
CH 2 CH 3 Ethyl
6
alphabetical order ii.
Numbered in the way that gives the
55
next substituent the lowest number possible
6
1 1
44 33
Practice Exercise
CH 3 CH 2 CH 3
22
1-11 - ethyl ethyl--6-methylcyclohexane
When single ring is attached to a chain
Give IUPAC names for the following cycloalkanes : CH3 HC 3
with greater no. of C atoms :
cycloalkyl alkane 5 C chain
named as
CH3
H3C
parent
CH2 CH2 CH2 CH2 CH3
11
4C chain
CH2CH3
22
33
44
55
1-11 - cyclobutyl pentane pentane
substituent CH3
When more than 1 ring is attached to a
Alkane
single
Physical Properties
chain : also named as
cycloalkyl alkane parent
straight chain
CH CH CH 11 2 22 2 33 2 1
22
Non – polar molecules Not – soluble in water Low density Low melting point
These goes up as the number of carbons increase
Low boiling point
substituent groups 1,31,3- di cyclo hexyl propane
8
Practice Exercise Arrange the following compounds in order of increasing boiling point CH3CH2CH3 propane
CH3CH2CH2CH2CH3 n-pentane
CH3( CH2)7 CH3 n-nonane
Hydrogenation of alkenes
An example of addition reaction
H
Synthesis of alkanes
H C
+
C
H
Pt / Pd / Ni
H2
H
H alkene
H
H
C
C
H
H
H
alkane
hydrogen
Example: C2H4 + H2
Ni
→
ethene
Hydrolysis of Grignard reagent (alkylmagnesium halide) RMgX + H2O
H+ →
alkylmagnesium halide
CH3CH2CH2MgCl + H2O Propylmagnesium chloride
ethane
Wurtz reaction (Reduction of alkyl halide)
RH + Mg(OH)X
2RX + Na
→
alkyl halide reducing agent
alkane
Example:
C2H6
R-R + 2NaX alkane
Example: H+
CH3CH2CH3 + Mg(OH)Cl Propane
2CH3CH2CH2Br + 2Na → CH3CH2CH2CH2CH2CH3 + 2NaBr bromopropane
hexane
9
Reaction of Alkanes
and cycloalkane Light/heat
Composition of Crude Oil Naphtha (bp 95-150 °C)
Kerosene (bp: 150-230 °C) CRUDE OIL
C5-C12 Light gasoline (bp: 25-95 °C)
C12-C15
HYDROCARBONS ALIPHATICS
Crude oil
25%
C15-C25
C1 - C60
NON-HYDROCARBONS
AROMATICS
NAPHTHENES
SULFURS
NITROGENS
17%
50%
<8%
<1%
(C6H5)n
CYCLOALKANES
OXYGENS <3%
METALLICS <100PPM
O
SH N
Gas oil (bp: 230-340 °C)
Refinery gas C1-C4
H
COOH
S
Residue
10
Industrial Fractioning Column
Petroleum refining •
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 Reforming
Petroleum Refining GAS
CRUDE
DESALTER
FURNACE
T O W E R
T O W E R
C5 - C?
LIGHT NAPHTHA
o
bp 50-200 F C? - C12
HEAVY NAPHTHA
bp 200-400oF
C12 - C16
KEROSENE
bp 400-500 oF C15 - C18
ATM. GAS OIL
TREATER
LIGHT NAPHTHA
GASOLINE HEAVY NAPHTHA
AROMATICS
HYDROTREATER
KEROSENE
ATM. GAS OIL
JET FUELS/KEROSENE
HYDROTREATER
CATALYTIC CRACKER
DIESEL & FUEL OILS
CATALYTIC CRACKER
VACUUM GAS OIL Vacuum Distillation
bp >650oF
AROMATIC EXTRACTION
REFORMER
HYDROTREATER
RESIDUUM
bp 500-650oC > C20
RESIDUUM
FUEL GAS
GAS
C1-C4 bp < 50 oF
LUBRICATING OIL ASPHALT COKE
COKER
Distillation – separation by boiling point
Catalytic Reforming – Conversion Reactions
Conversion Reactions
Dehydrogenation of cycloalkanes to aromatics
THERMAL
CRACK
CH3
C 7 H 15 .C 15 H 30 .C 7 H 15
C 7 H 16 gasoline
+
C 7 H 14
+
CH3
C 15 H 30
gasoline additive
recycle
3H2
CATALYTIC Dehydroisomerization of cyclopentanes to aromatics
ALKYLATION
CH
3 CH 2 CH 3
CH
2
CH
C H2 CH
3
CH 3 CH
2 CH 2
CH
2 CH 2 CH 2 CH 3
CH3
COMBINE
3H2 Isomerization of alkanes
POLYMERIZATION
CH3
REFORMIING
Dehydrogenation Dehydroisomerization
REARRANGE
CH3CH2CH2CH2 CH3 Dehdrocyclization of alkanes
H3C CH CH2 CH3
CH3
Isomerization ISOMERIZATION
Dehydrocyclization Hydrocracking
CH3 CH2CH2 CH2CH2 CH2CH3
4 H2
Hydrocrackingof alkanes
CH3CH2CH2CH2CH2 CH2CH3
CH3 CH2CH3
CH3CH2CH2 CH3
11
Catalytic cracking in laboratory scale
Conversion Reactions THERMAL
CRACK
C 7 H 15 .C 15 H 30 .C 7 H 15
C 7 H 16 gasoline
+
C 7 H 14
+
C 15 H 30
gasoline additive
recycle
CATALYTIC
ALKYLATION
CH
3 CH 2 CH 3
CH
2
CH
C H 2 CH
3
CH
3 CH 2 CH 2
CH
2 CH 2 CH 2 CH 3
COMBINE POLYMERIZATION
REFORMIING
Dehydrogenation Dehydroisomerization
REARRANGE
Isomerization ISOMERIZATION
Dehydrocyclization Hydrocracking
12
