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