ORGANIC CHEMISTRYCHP2 : HYDROCARBON

Prepared By:ARBANAH MUHAMMAD

CLD 10302

TOPICS COVERED

2.1 Introduction in Process Industry2.2 Natural Gas and Petroleum Resources2.3 Alkanes2.4 Alkenes, Addition Polymerization and The

Chemistry of Rubber 2.5 Alkynes2.6 Chlorinated Alkanes and Geometrical Isomers2.7 Aromatic Hydrocarbon

2.1 Introduction in Process Industry

• Petroleum Refining• Polyolefins• Olefins• Ammonia and Urea

2.2 Natural Gas and Petroleum Resources

Gas Processing Plant

Introduction

Classification of Hydrocarbon

Hydrocarbon

Aliphatic Aromatic

Alkanes Alkenes Alkynes

CycloalkanesCycloalkenes

Saturated Unsaturated

Alkane

1. Alkanes2. Alkanes Nomenclature System3. Structural Isomers4. Cycloalkanes5. Sources of Alkanes and Cycloalkanes6. Synthesis of Alkanes7. Reaction of Alkanes

1. Alkane

• Simplest member of hydrocarbon family

• General formula:• Contains only – C H• Saturated compound • Alkanes are hydrocarbons in

which all of the bonds are single bonds

• Alkanes whose carbon atoms are joined in rings are called cycloalkanes.

Ethane

C CH H

H H

H H22 nnHC

No of C

Molecular Formula

Condensed Formula

Structural Formula

Bond Line Formula

Boiling PointMelting Point

(C)

1 C1H4 -182.5 -161.6

2 C2H6 -183.3 -88.6

3 C3H8 -189.7 -42.1

4 C4H10 -138.7 -0.5

5 C5H12 -129.8 36.1

6 C6H18 -95.3 68.7

7 C7H16 -90.6 98.4

8 C8H18 -56.8 125.7

9 C9H20 -53.5 150.8

10 C10H22 -29.7 174.0

Substituent: Alkyl Groups

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 e.g: eth-yl

Substituent: Alkyl GroupsNo of C Name Structure

1 Methyl - CH3

2 Ethyl -CH2CH3

3 Propyl

Isopropyl

-CH2CH2CH3

CH3 – CH - CH3

4 Butyl

Sec-butyl

-CH2CH2CH2CH3

C

H

H

H

C

H

H

C

H

C

H

H

H

No of C Name Structure

4 Iso-butyl

Tert-butyl

5 Pentyl CH3(CH2)4CH2-

Iso-pentyl

Neo-pentyl

C

H

H

H

C

CH3

H

C

H

H

C

H

H

H

C

H

CH3

C

H

H

C

H

H

C

H

H

H

C

CH3

CH3

C

H

H

C

H

H

H

C

CH3

C

H

H

H

2. Alkanes Nomenclature 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 alphabetical order.

Base Name - sufixAlkane

CH2 - methane

C2H6 -ethane

C3H8 -propane

C4H10 -butane

C5H12 -pentane

C6H14 -hexane

C7H16 -heptane

C8H18 -octane

C9H20 - nonane

C10H22 - decane

The proper suffix is

determined by :

i. identifying all the

functional groups

present

ii. Polyfunctional organic

compounds contain

many different kinds of

functional groups.

Then choose the

principal group of

highest priority

HC

HCH3C CH3

CH3CH3

2,3-dimethylbutane

Example

Practice

Exercis

e

Give IUPAC name for the following compound

When 2 or more of different kind of substituents present :

the substituents are listed alphabetically

prefixes di, tri, tert … are ignored

in

alphabetising except iso and

neoCH3 CH CH2

CH3

CH CH2 CH3

CH2

CH3

methylethyl

1 2 3 4 5 6

4-ethyl-2-methyl….

H3C C

CH3

CH3

CH2 CH

CH2

CH3

CH2 CH3

4-ethyl-2,2-dimethylhexane

Example

Practice

Exercis

e

Give IUPAC name for the following compound

Practice

Exercis

e

H3C C

CH3

CH3

CH2 CH

CH2

CH3

CH2 CH3

1 2 3 4 5 6

5

6

6C Continuous C chain :

Substituent :

Prefix :

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 CH2

CH3

CH3

CH CH

CH2

CH2

CH CH

CH3CH3

CH3

H3C CH2

CH3

CH3

CH CH

CH2

CH2

CH CH

CH3CH3

CH3

2,3,5-trimethyl-4-propylheptane (4 substituents)

4-sec-butyl-2,3-dimethylheptane (3 substituents)

H3C C

CH3

CH3

CH2 CH2 CH CH3

CH2CH3

5-ethyl-2,2-dimethylheptane

Example

Practice

Exercis

e

Give IUPAC name for the following compound

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

1 2 3 4 5 6

H3C CH CH2 CH

CH3

CH CH3

CH3

CH3

H3C CH CH2 CH

CH3

CH CH3

CH3

CH3

12356 4

2,3,5-trimethylhexane

2,4,5-trimethylhexane

1 2 3 4

6 7

2,2,5-trimethylheptane

Practice

Exercis

e

Give IUPAC name for the following compound

5H3C C

CH3

CH3

CH2 CH2 CH CH3

CH2CH3

7C Continuous C chain :

Substituent :

Locant :

Prefix :

Suffix :

trimethyl

2, 2, 5

hept

- ane

Structural Isomers Alkane

• Compounds with same number of atom and bonds but different arrangement

C4H10

CH2

CH3

H2C

H3C

butane

HC CH3CH3

2-methylpropaneCH3

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 • Number of isomeric alkanes increases as the number of carbons increase.

• There is no simple way to predict how many isomers there are for a particular molecular formula.

Cyclopropane cyclohexane

cyclobutane

cyclopentane

• Cyclic alkane with general formula: CnH2n• Parent name: alkane . Add cylco in front.

Cycloalkanes

If only one substituent present :

not necessary to

designate its position

cyclo

CH3

Example

suffix

prefix

Methyl

16 C

hexane

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

cyclohexane1-ethyl-2-methyl

1-ethyl-6-methylcyclohexaneCH2CH3

CH3

1

23

4

5 6

CH2CH3

CH3

1

23

4

5 6 Ethyl

MethylExample 1

Naming of Cycloalkane

CH2CH3

CH2CH3

H3C CH3

Ethylcyclopentane

3-Ethyl- 1,1-dimethylcyclohexane

Give IUPAC names for the following cycloalkanes :

1,4-dimethylcyclohexane

1-ethyl-3-methylcyclopentane

Isopropylcyclobutane

CH3

CH3

CH3

CH3

CH2CH3

CH3

Practice Exercise

butyl

When single ring is attached to a chain with

greater no. of C atoms :

named as cycloalkylalkane

CH2 CH2 CH2 CH2 CH3

5 C chain

4Cchain

parent

substituent

1 2 3 4 5

1-

cyclo

pentane

When more than 1 ring is attached to a single

chain :

also named as cycloalkylalkane

1,3-

CH2CH2CH2

parent

substituent groups

straight chain

1 2 3

propanehexylcyclodi

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

Arrange the following compounds in order of

increasing boiling point

CH3CH2CH3

CH3CH2CH2CH2CH3

CH3( CH2)7 CH3

propane

n-pentane

n-nonane

Boiling pointincreases

Practice Exercise

Sources of Alkanes and Cycloalkanes

Crude oil

Refinery gasRefinery gas

C1-C4C1-C4

Light gasoline(bp: 25-95 °C)Light gasoline(bp: 25-95 °C)

C5-C12C5-C12

Naphtha(bp 95-150 °C)

Naphtha(bp 95-150 °C)

Kerosene(bp: 150-230 °C)

Kerosene(bp: 150-230 °C)

C12-C15C12-C15

Gas oil(bp: 230-340 °C)

Gas oil(bp: 230-340 °C)

C15-C25C15-C25

ResidueResidue

• Crackingconverts high molecular weight hydrocarbons to more useful, low molecular weight onesi) 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

Synthesis of Alkanes

HydrogenationGeneral reaction : Addition

HydrogenationHydrolysisReduction

+ H2C C H C C

H H

H H

H

H

H

H

H

Pt / Pd / Ni

alkene hydrogen alkane

Example:

C2H4 + H2 C2H6

Ni

ethene ethane

Hydrolysis of Grignard reagent (alkylmagnesium halide)

CH3CH2CH2MgCl + H2O CH3CH2CH3 + Mg(OH)ClH+

RMgX + H2O RH + Mg(OH)XH+

alkylmagnesium halide

alkane

Example:

Propylmagnesium chloride

Propane

Wurtz reaction (Reduction of alkyl halide)

2RX + Na R-R + 2NaXalkyl halide reducing

agentalkane

Example:

2CH3CH2CH2Br + 2Na CH3CH2CH2CH2CH2CH3 + 2NaBr

bromopropane hexane

Reaction of alkanes

Combustion

Usage:Fuel

OHCOOalkane 222

CombustionHalogenation

Halogenation

Usage:Dichloromethane: Paint stripper1,2 Dichloroethane: Dry cleaning fluid

Light/heat