Hydrocarbons Module 9: Hydrocarbons Alkanes Alkenes Alkynes Aromatic Hydrocarbons.

HydrocarbonsModule 9:

Hydrocarbons

Alkanes

Alkenes

Alkynes

Aromatic Hydrocarbons

Bonding

CH

H

H

H

two-dimensional structure of methane

Four bonds in Carbon

C C

4 single bonds 1 double bond and 2 single

bonds

2 double bonds

1 triple bond and

1 single bond

C

Types of Hydrocarbons

Saturated hydrocarbons - contain only single bonds

Example - alkanes

Unsaturated hydrocarbons – contain double or triple bonds between the carbon atoms.

Examples – alkenes, alkynes

Structural, Condensed, and Molecular Formulas for Simple Alkanes

HH

H

C - H

H HH

H

H

H

H

H

C - C - C

Carbon BackboneStructural Formula

Condensed Formula MolecularFormula

- C - CH4 CH4

C - C CH3-CH3 C2H6

C - C - C CH3-CH2-CH3

C3H8

C - C - C - C

CH3-CH2-CH2-CH3

C4H10

C - C - C - C - C CH3-CH2-CH2-CH2-CH3 C5H12

The Alkane Series# of C name # of C name

1 methane 6 hexane

2 ethane 7 heptane

3 propane 8 octane

4 butane 9 nonane

5 pentane 10 decane

Three-dimensional structures

methane ethane

http://www.chm.bris.ac.uk/pt/harvey/gcse/covalent.html

Structural isomers

http://www.chm.bris.ac.uk/pt/harvey/gcse/covalent.html

butane 2-methylbutane

Nomenclature of Alkanes

Alkyl GroupsCH3

- CH - CH3methyl ethyl propyl isopropyl

-CH3 -CH2-CH3 -CH2-CH2-CH3

CH3

-CH-CH3

Alkyl groups


Alkanes are named according to the number of carbon atoms in the longest continuous chain or parent chain.

To name an alkane, the parent chain must be located first.

If there Is branching then the chain is numbered so that the branch (or branches) get the lowest possible number.


Example: Name the following compound.

CH3CH2 CH2 CH CH3

CH3



The longest continuous chain consists of 5 carbon atoms, therefore the parent chain is pentane and the branch is attached to the second carbon in the chain.

CH2 - CH - CH 4

CH3

2 - CH33 2 1

CH -35



2 – methylpentane

CH2 - CH - CH 4

CH3

2 - CH33 2 1

CH -35

Haloalkanes or alkyl halides

fluoro = -F chloro = -Cl bromo = -Br iodo = -I

When a halogen is present in a compound, it is called a halogenated hydrocarbon


Example:

CH2 - CH2 - CH2 - CH2 - CH3

CH2 - CH2 - CH2 - CH3

5

9 106 7 8

4 3 1

I - C - CH2 - CH2 - CH3

2


Example:

Parent chain

Side chains

CH2 - CH2 - CH2 - CH2 - CH3

CH2 - CH2 - CH2 - CH3

5

9 106 7 8

4 3 1

I - C - CH2 - CH2 - CH3

2


Example:

Parent chain

decane

Side chains

CH2 - CH2 - CH2 - CH2 - CH3

CH2 - CH2 - CH2 - CH3

5

9 106 7 8

4 3 1

I - C - CH2 - CH2 - CH3

2

Haloalkanes or alkyl halidesExample:

Parent chain

decane

Side chainsPropyl groupIodo group

CH2 - CH2 - CH2 - CH2 - CH3

CH2 - CH2 - CH2 - CH3

5

9 106 7 8

4 3 1

I - C - CH2 - CH2 - CH3

2

Haloalkanes or alkyl halidesExample:

Parent chain

decane

Side chainsPropyl groupIodo group

CH2 - CH2 - CH2 - CH2 - CH3

CH2 - CH2 - CH2 - CH3

5

9 106 7 8

4 3 1

I - C - CH2 - CH2 - CH3

2

5-iodo-5-propyldecane

Cycloalkanes

C C

C C

H H

HH

H

H

H

H

C C

C C

C

C C

CC

HH

H

H

H H

H

H

HH

Carbon skeleton

Structural Formula

Geometric Formula

MolecularFormula

CYCLOPROPANE For cyclic compounds, each corner represents a

carbon atom and hydrogens are not shown. C3H6

CYCLOBUTANE

C4H8

CYCLOPENTANE

C5H10

Nomenclature of cycloalkanes

Example: Name the following cycloalkane.

CH3

CH2CH3

CH31

2

4



CH3

CH2CH3

CH31

2

4

Ethyl comes before methyl alphabetically



CH3

CH2CH3

CH31

2

4


The numbering results in the lowest branch locations (1,2,4) rather than 1,3,4)



CH3

CH2CH3

CH31

2

4





CH3

CH2CH3

CH31

2

4

4-ethyl-1,2-dimethylcyclohexane



Reactions of Alkanes

CxHy + O2 → CO2 + H2O

Combustion of Hydrocarbons

Reactions of Alkanes

Halogenation of Alkanes and Alkyl Halides

X + HXuv or

2X+ C C H

Nomenclature of Alkenes

CH - C - CH - CH3

CH

23CH -

2

22 3 4

1

Example: Name the following alkene.


CH - C - CH - CH3

CH

23CH -

2

22 3 4

1 Find the longest continuous carbon chain that contains the double bond



CH - C - CH - CH3

CH

23CH -

2

22 3 4


An ethyl group is attached to carbon 2.



CH - C - CH - CH3

CH

23CH -

2

22 3 4


An ethyl group is attached to carbon 2.

2-ethyl-1-butene


Cis-trans Isomerism of Alkenes

CH3

Br

H

Br

CH3

Br

Br

H

Br Br

Br's are on opposite side of double bond

Br's are on same side of double bond

CH3 - C = CH

trans-1,2-dibromopropenecis -1,2-dibromopropene

C = CC = C

Cis-trans Isomerism of Alkenes

No cis-trans isomers occur if either carbon atom in the double bond is attached to identical groups or atoms.

H

H

Br

CH3

no cis-trans isomers are possible because twoof the same atom (i.e., H's) are present on thesame indicated carbon.

C = C

Nomenclature of Cycloalkenes

1

CH3

CH3

CH3

2

34

Example: Name the following cycloalkene.


1

CH3

CH3

CH3

2

34

The double bond must be in positions 1 and 2.



1

CH3

CH3

CH3

2

34


The numbering is placed so that the branches have the lowest possible numbers.



1

CH3

CH3

CH3

2

34


The numbering is placed so that the branches have the lowest possible numbers.

3,3,4-trimethylcyclopentene


General Reaction for Alkenes

A B

The double bond is brokenand atoms A and B are added,

one to each carbon.C - C+ A - BC = C

Hydrogenation

Halogenation

Hydrohalogenation

Hydration

Hydrogenation of Alkenes

Addition of hydrogen

H H

catalystC = C + H2 C - C

Halogenation of Alkenes

Addition of halogen (usually Cl2 and Br2

X X

C = C + X2 C - C

Hydrohalogenation of AlkenesAddition of hydrohalogen, such as:

HF, HCl, HBr and HI

H X

C = C + H-X C - C

Hydrohalogenation of Alkenes

CH3 H

H H

CH3 H

H H

Cl HH was added to C

having the most H's

C - C+ H-Cl

This carbon has 2 HThis carbon has only 1 H

C = C

Markovnikov's Rule states that the H is added to the carbon that has the most H's

Hydration of Alkenes

Addition of water (H-OH)

H OH

H+

C = C + H-OH C - C

Hydration of Alkenes

Markovnikov addition

CH3CH3

OHH+

+ H-OH

This carbon has 1 H

This carbon has no H

H

CH3OH

Nomenclature of Alkynes

The rules are basically the same as those for naming alkenes; however, the parent chain name is changed to end in "yne".

C C - CH CH3 -

CH3

- CH2 - CH

CH3

2

7

3 4 5 621


Find the longest chain that contains the triple bond.

heptyne

C C - CH CH3 -

CH3

- CH2 - CH

CH3

2

7

3 4 5 621


Number from the end of the chain that gives the triple bond the lower numbers.

C C - CH CH3 -

CH3

- CH2 - CH

CH3

2

7

3 4 5 621


Then identify and name the side chains (branches)

methyl group

C C - CH CH3 -

CH3

- CH2 - CH

CH3

2

7

3 4 5 621


4-methyl-2-heptyne

C C - CH CH3 -

CH3

- CH2 - CH

CH3

2

7

3 4 5 621

Hydrogenation Reaction of Alkynes

H

H

H

H

- C - C -catalyst- C C - + 2 H2


Most aromatic hydrocarbons are derivatives of benzene



Examples:



Examples:

ClCl

Cl

Br

I

CH2-CH3

1-ethyl-4-iodobenzenep-ethyliodobenzene

1-bromo-3-chlorobenzenem-bromochlorobenzene

1,2-dichlorobenzeneo-dichlorobenzene



Examples:

ClCl

Cl

Br

I

CH2-CH3

1-ethyl-4-iodobenzenep-ethyliodobenzene

1-bromo-3-chlorobenzenem-bromochlorobenzene

1,2-dichlorobenzeneo-dichlorobenzene

Hydrocarbons

THE END

Hydrocarbons Module 9: Hydrocarbons Alkanes Alkenes Alkynes Aromatic Hydrocarbons.

Documents

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