Ch02 Sec11to15 Lecture- Tatanama HC

8/11/2019 Ch02 Sec11to15 Lecture- Tatanama HC

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2.11

IUPAC Nomenclature of

Unbranched Alkanes


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Retained:

methane CH4

ethane CH3CH3

propane CH3CH2CH3

butane CH3CH2CH2CH3

Table 2.4

IUPAC Names of Unbranched Alkanes


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Note:

n-prefix is not part of IUPAC name of

any alkane.For example: n-butane is "common name"

for CH3CH2CH2CH3; butane is "IUPAC name."

Others:

Latin or Greek prefix for number of

carbons + ane suffix

Table 2.2



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Number of carbons Name Structure

5 pentane CH3(CH2)3CH3

6 hexane CH3(CH2)4CH3

7 heptane CH3(CH2)5CH3

8 octane CH3(CH2)6CH3

9 nonane CH3(CH2)7CH3

10 decane CH3(CH2)8CH3

Table 2.2



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11 undecane CH3(CH2)9CH3

12 dodecane CH3(CH2)10CH3

13 tridecane CH3(CH2)11CH3

14 tetradecane CH3(CH2)12CH3

15 pentadecane CH3(CH2)7CH3

16 hexadecane CH3(CH2)8CH3

Table 2.2



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17 heptadecane CH3(CH2)15CH3

18 octadecane CH3(CH2)16CH3

19 nonadecane CH3(CH2)17CH3

20 icosane CH3(CH2)18CH3

25 pentacosane CH3(CH2)22CH3

30 triacontane CH3(CH2)28CH3

Table 2.2



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2.12

Applying the IUPAC Rules:

The Names of the C6H14Isomers


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CH3CH2CH2CH2CH2CH3

(CH3)2CHCH2CH2CH3

(CH3CH2)2CHCH3

(CH3)2CHCH(CH3)2

(CH3)3CCH2CH3

The C6H14Isomers


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CH3CH2CH2CH2CH2CH3

The IUPAC name of the unbranched alkane

with a chain of 6 carbons is hexane.

Hexane

The C6H14Isomers


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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.

Step 3) Number the chain from the end nearest

the substituent, and identify the carbon towhich the substituent is attached by number.

IUPAC Nomenclature of Branched

Alkanes (Table 2.6)


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(CH3)2CHCH2CH2CH3

(CH3CH2)2CHCH3

2-Methylpentane

3-Methylpentane

The C6H14Isomers


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(CH3)2CHCH(CH3)2

(CH3)3CCH2CH3

2,3-Dimethylbutane

2,2-Dimethylbutane

Use replicating prefixes (di-, tri-, tetra-, etc.)

according to the number of identical substituents

attached to the main chain.

The C6H14Isomers


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2.13

Alkyl Groups


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Methyl and Ethyl Groups

Methyl

Ethyl C CH

H H

H H

CH3CH2

CH

H

H

CH3or

or


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Unbranched Alkyl Groups

If potential point of attachment is at the end

of the chain, take the IUPAC name of the

corresponding unbranched alkane and replace

the -aneending by -yl.

RHR


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Butyl

If potential point of attachment is at the end

of the chain, take the IUPAC name of the

corresponding unbranched alkane and replace

the -aneending by -yl.

RHR

CH3CH2CH2CH2C CH

H H

H H

C C

H H

H H

or



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HexylCH3(CH2)4CH2

CH3(CH2)5CH2

CH3(CH2)16CH2

Heptyl

Octadecyl



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The C3H7Alkyl Groups

CH3CH2CH2C CH

H H

H H

C

H

H

or

and

CH3CHCH3C CH

H H

H

HC

H

H

or


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CH3CH2CH2C CH

H H

H H

C

H

H

or

IUPAC name: Propyl

Common name: n-Propyl



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Naming Alkyl Groups (Table 2.7)

Step 1: Identify longest continuous chain starting at

point of attachment.

Step 2: Drop -aneending from name of unbranched

alkane having same number of carbons aslongest continuous chain and replace by -yl.

Step 3: Identify substituents on longest continuous

chain.

Step 4: Chain is always numbered starting at

point of attachment.


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IUPAC name: 1-Methylethyl

Common name: Isopropyl

CH3CHCH3C CH

H H

H

C

H

H

orH



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CH3CH2CH2C CH

H H

H H

C

H

H

or

Classification: Primary alkyl group

Alkyl groups are classified according to thedegree of substitution at the carbon that bears the

point of attachment. A carbon that is directly

attached to one other carbon is a primary carbon.



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Classification: Secondary alkyl group

Alkyl groups are classified according to the

degree of substitution at the carbon that bears the

point of attachment. A carbon that is directly

attached to two other carbons is a secondary carbon.

CH3CHCH3C CH

H H

H

C

H

H

orH



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IUPAC name: Butyl

Common name: n-Butyl


CH3CH2CH2CH2C CH

H H

H H

C C

H H

H H

or



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IUPAC name: 1-Methylpropyl

Common name: sec-Butyl

Classification: Secondary alkyl group

CH3CHCH2CH3C CH

H H

H

HC C

H H

H H

or1 2 3



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IUPAC name: 2-Methylpropyl

Common name: Isobutyl


123

C

H

CH2

CH3

CH3



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IUPAC name: 1,1-Dimethylethyl

Common name: tert-Butyl

Classification: Tertiary alkyl group

1 2

C CH3

CH3

CH3



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2.14

IUPAC Names of Highly

Branched Alkanes


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Branched alkanes

Octane


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4-Ethyloctane

Branched alkanes


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4-Ethyl-3-methyloctane

List substituents in alphabetical order.

Branched alkanes


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4-Ethyl-3,5-dimethyloctane

List substituents in alphabetical order.

But don't alphabetize di-, tri-, tetra-, etc.

Branched alkanes


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First Point of Difference Rule

The chain is numbered in the direction thatgives the lower locant to the substituent at the

first point of difference in the names.

Don't add locants!

2,2,6,6,7-Pentamethyloctane?


What is correct name?

12 3

45

67 8

87 6

54

32

1


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First Point of Difference Rule

The chain is numbered in the direction thatgives the lower locant to the substituent at the

first point of difference in the names.

Don't add locants!


What is correct name?

87 6

54

32

1


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CnH2n

2.15

Cycloalkane Nomenclature


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Cycloalkanes

Cycloalkanes are alkanes that contain a ring ofthree or more carbons.

Count the number of carbons in the ring, and

add the prefix cycloto the IUPAC name of the

unbranched alkane that has that number ofcarbons.

Cyclopentane Cyclohexane


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Ethylcyclopentane

Cycloalkanes

CH2CH3

Name any alkyl groups on the ring in the usualway.


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Name any alkyl groups on the ring in the usualway.

List substituents in alphabetical order and count

in the direction that gives the lowest numerical

locant at the first point of difference.

3 Eth l 1 1 di th l l h

CH2CH3

H3C CH3

Cycloalkanes

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Ch02 Sec11to15 Lecture- Tatanama HC