alkane1-student. matriculation

7/29/2019 ALKANE1-student. matriculation

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HYDROCARBONS


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Learning Outcome

Explain terms saturated and unsaturated HC

Describe alkanes

Drawing alkanes and its nomenclature-straight, branched chain, cyclic


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HYDROCARBONHydrocarbon are compoundswhich contain only carbonand

hydrogen atoms.


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ALKANES(saturated)

contain onlysingle bond

ALKENES(unsaturated)

containC=C

CYCLO-ALKANES (saturated)Alkanes which C atoms are

join in rings

ALKYNES(unsaturated)

contain

CC

CYCLO-ALKENES(unsaturated)

HYDROCARBONS

AROMATIC(contain one or more benzene ring)

ALIPHATIC(chain structure)


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Saturated hydrocarbons

- compound with C-C

- Example : alkanes and cycloalkanes

Contain the maximum number of hydrogen

atoms that the carbon compound canpossess.


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Unsaturated hydrocarbons

-compounds with multiple bonds

-Example : alkenes, cycloalkenes, alkynes

and aromatic hydrocarbons

They posses fewer than the maximum

number of hydrogen atoms.


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ALKANES

Alkanes are known as saturatedhydrocarbon which contain only singlecovalent bonds.

General formula for straight chain ofalkanes isCnH2n+2

where n

1General formula for cycloalkanes isCnH2nwhere n 3


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Each carbon atom in alkanes is

- sp3 hybridised- tetrahedral with four sigma bond (formed

by the four sp3 hybrid orbitals.)

- all bond angles are close to 109.5o

Alkanes IUPAC names have the ane

suffix.


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The First Ten Unbranched Alkanes

Molecular

formula

Structural formula No .of C

atoms

Name

CH4 CH4 1 Methane

C2H6 CH3CH3 2 Ethane

C3H8 CH3CH2CH3 3 Propane

C4H10 CH3(CH2)2CH3 4 Butane

C5H12 CH3(CH2)3CH3 5 Pentane

C6H14 CH3(CH2)4CH3 6 Hexane

C7H16 CH3(CH2)5CH3 7 Heptane

C8H18 CH3(CH2)6CH3 8 Octane

C9H20 CH3(CH2)7CH3 9 Nonane

C10H22 CH3(CH2)8CH3 10 Decane


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C C C

H

H

H

H

H

H

H

H

C C C C

H

H

H

H

H

H

H

H

H

H

C C C C

H

H

H

H

H

H

H

C

H

H

H

H

H

H

C

H

H H

C C

H

H

H

H

H

H


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Starting from C4H10 onwards,the alkanes show thephenomenon of chain

isomerism.

They can exist as linear OR

branched alkanes.


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Example

C4H10

CH3(CH2)2CH3 CH3CH(CH3)2

2-

isobutane


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C5H12


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IUPAC NOMENCLATURE

IUPAC International Union ofPure and Applied Chemistry

Branched - chain alkanes arenamed according to the following

rules:


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Choose the longest continuous chain ofcarbon atoms; this chain determines theparent name for alkanes.

Examples:

CH3CH2CH2CH2CH2CH3

Parent name: hexane


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Parent name : heptane

CH2CH2CH2CH2CH3

CH2

CH3


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Number the longest chain beginningwith the end of the chain nearer thesubstituent.

CH3CH2CH2CH2CHCH3

Example:

CH3 substituent

16 4 235


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CH3CH2CH2CH2CH|

CH2|CH3

substituentCH3

1

2

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Use rule number 2 to locate the positionof the substituent.

The position (that is number) and thename of the substituent must be

written in front of the parent chain.


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CH3CH2CH2CH2CHCH3

Examples:

CH3

2-methylhexane

16 4 235

Substituent

-methyl at C-2


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CH3CH2CH2CH2CHCH3|

CH2|CH3

3-methylheptane

1

2

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Substituent-methyl at C-

3


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butyl

isopropyl

propyl

ethyl

methyl

SubstituentName

CH3

CH2CH3

CH2CH2CH3

CHCH3

CH3

CH2CH2CH2CH3

Some Common Substituent Groups

Alkane

methane

propane

butane

ethane


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isobutyl

sec-butyl

tert-butyl

neopentyl

CH2CHCH3

CH3

CHCH2CH3

CH3CH3

CH3

CCH3

CH3

CH2CCH3

CH3


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cyclopropyl

cyclobutyl

phenyl

benzyl

C6H5 or

CH2


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Name Substituent

Bromo -Br

Chloro -Cl

Flouro -F

Iodo -I

Hydroxyl -OH

Amino -NH2

Cyano -CN

Nitro -NO2


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Iftwo ormore substituents are present,give each substituent a numbercorresponding to its location on the longest

chain.

the substituent should be listedalphabetically.

In alphabetizing, the prefixes di, tri,tetra, sec-, tert- are ignoredexcept iso

and neo.


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Example:

1 2 3 4 5 6CH3CHCH2CHCH2CH3

| |

CH3 CH2|

CH3

4-ethyl-2-methylhexane


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Iftwo substituents are present on thesame carbon atom, use that numbertwiceExample:

CH3

|3 4 5 6CH3CH2CCH2CH2CH3

|2

CH2|

1CH3

3-ethyl-3-methylhexane


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~If two or more identical substituents arepresent, use prefixes di-(2 identical substituents),tri-(3 identical substituents), tetra-(4 identicalsubstituents).

~ Commas are used to separate numbers fromeach other.

Example:CH3CHCH CH3

| |

CH3

CH3

2,3-dimethylbutane


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If there are two chains of equal lengthas the parent chain, choose the chain

with the greater number ofsubstituents.


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7 6 5 4 3 2 1

2,3,5-trimethyl-4-propylheptane

(four substituents)

CH3CH

2-CH CH CH CHCH

3

| | | |CH

3CH

2CH

3CH

3

|

CH2

|

CH3

4 3 2 1

5

6

7

4-sec-butyl-2,3-dimethylheptane

(three substituents)


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If branching occurs at an equal distance fromeither end of the longest chain, choose the

name that gives the lower number at thefirst point of difference.

6 5 4 3 2 1CH

3CHCH

2CH CHCH

3

| | |

CH3 CH3 CH3

2,3,5-trimethylhexane

(NOT 2,4,5-trimethylhexane)

1 2 3 4 5 6


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CYCLOALKANES

Cycloalkanes

alkanes which carbon atomsare joined in rings.

Cycloalkanes are known as saturatedhydrocarbon, because it has the maximumnumber of bonded hydrogen ( only has single

bonds).

General formula:

CnH2n where n = 3, 4, 5,


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NOMENCLATURE OF

CYCLOALKANES

Cycloalkanes with only one ring arenamed with the prefix cyclo- to the names

of the alkanes (contain the same number

of carbon atoms)


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Monocyclic compounds

C3H6 cyclopropane

C4H8 cyclobutane

C5H10 cyclopentane


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If only one substituent is present, it is notnecessary to designate its position.

Examples:

CH3

Chlorocyclopropane

Methylcyclohexane

Cl


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Iftwo substituents are present, numbercarbon in the ring beginning with the

substituent according to the alphabeticalorder

and

number in the direction that gives the nextsubstituent the lowest number possible.


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Examples:

1-ethyl-2-methylcyclohexaneNOT

1-ethyl-6-methylcyclohexane

CH3

CH2CH31

23

4

5 6


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1,3-dichlorocyclopentane

(NOT 1,5-dichlorocyclopentane)

Cl Cl1

2

3

4 5


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When three ormore substituents arepresent, begin at the carbon with

substituent that leads to the lowest setof locants.


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Example:

CH2CH3

1-chloro-3-ethyl-4-methylcyclohexane

4- chloro-2-ethyl-1-methylcyclohexane

Cl CH3

Locants

chloroethyl

methyl

1

3

4 1

2

4

1

2 3

4

56

1

23

4

5 6


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1-ethyl-1,3-dimethylcyclopentane(NOT 3-ethyl-1,3-dimethylcyclopentane)

H3C CH2CH3

CH3


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When a single ring system is attachedto a single chain with a greater numberof carbon atoms

orwhen morethanone ring systemisattached to a single chain, then it is

appropriate to name the compounds as

cycloalkylalkane.

Number of C at ring

Number of C at

linear chain


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1,3-dicyclohexylpropane

1

2

3

cycloalkyl alkane


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Examples:

CH2CH

2CH

2CH

2CH

3

1-cyclobutylpentane


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CH CH3

CH3

CH2CH3

Name the following compounds according to IUPAC

nomenclature

CH3

CH2

CHCH2

CH3

CHCH

3CH3

CH3

C CH2

CH2

CH3

CH

CH3

CH3

CH3

CH3

CH CH2

CH CH

C2

H5

CH3

C2

H5

CH

CH3

CH3

CH3

CH2

CH3

CH3

CH3

CH2

CH3

CH3

Br

D th t t f h f th


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Draw the structure for each of the

following compounds

(a) 1,1-dichloro-3-methylcyclohexane(b) 2,2-dimethyl-3-cyclohexylbutane

(c) 1-bromo-5-chloro-3-ethyl-3-methylpentane]

(d) 5-sec-butyl-2,4-dimethylnonane

alkane1-student. matriculation

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