IUPAC Nomenclature of Unbranched Alkanes

Retained: methaneCH 4 ethaneCH 3 CH 3 propaneCH 3 CH 2 CH 3 butaneCH 3 CH 2 CH 2 CH 3 IUPAC Names of Unbranched Alkanes

Note: n-prefix is not part of IUPAC name of any alkane. For example: n-butane is "common name" for CH 3 CH 2 CH 2 CH 3 ; butane is "IUPAC name." Others: Latin or Greek prefix for number of carbons + ane suffix IUPAC Names of Unbranched Alkanes

Number of carbons NameStructure 5pentaneCH 3 (CH 2 ) 3 CH 3 6hexaneCH 3 (CH 2 ) 4 CH 3 7heptaneCH 3 (CH 2 ) 5 CH 3 8octaneCH 3 (CH 2 ) 6 CH 3 9nonaneCH 3 (CH 2 ) 7 CH 3 10decaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

Number of carbons NameStructure 11undecaneCH 3 (CH 2 ) 9 CH 3 12dodecaneCH 3 (CH 2 ) 10 CH 3 13tridecaneCH 3 (CH 2 ) 11 CH 3 14tetradecaneCH 3 (CH 2 ) 12 CH 3 15pentadecaneCH 3 (CH 2 ) 7 CH 3 16hexadecaneCH 3 (CH 2 ) 8 CH 3 IUPAC Names of Unbranched Alkanes

Number of carbons NameStructure 17heptadecaneCH 3 (CH 2 ) 15 CH 3 18octadecaneCH 3 (CH 2 ) 16 CH 3 19nonadecaneCH 3 (CH 2 ) 17 CH 3 20icosaneCH 3 (CH 2 ) 18 CH 3 25pentacosaneCH 3 (CH 2 ) 22 CH 3 30triacontaneCH 3 (CH 2 ) 28 CH 3 IUPAC Names of Unbranched Alkanes

Applying the IUPAC Rules: The Names of the C 6 H 14 Isomers

CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 (CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 (CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 The C 6 H 14 Isomers

CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 The IUPAC name of the unbranched alkane with a chain of 6 carbons is hexane. Hexane The C 6 H 14 Isomers

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 to which the substituent is attached by number. IUPAC Nomenclature of Branched

(CH 3 ) 2 CHCH 2 CH 2 CH 3 (CH 3 CH 2 ) 2 CHCH 3 2-Methylpentane 3-Methylpentane The C 6 H 14 Isomers

(CH 3 ) 2 CHCH(CH 3 ) 2 (CH 3 ) 3 CCH 2 CH 3 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 C 6 H 14 Isomers

Alkyl Groups

Methyl and Ethyl Groups Methyl Ethyl C C HHHH H CH 3 CH 2 C HHH CH 3 or or

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 -ane ending by -yl. R HR

Butyl R HR CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or Unbranched Alkyl Groups

Hexyl CH 3 (CH 2 ) 4 CH 2 CH 3 (CH 2 ) 5 CH 2 CH 3 (CH 2 ) 16 CH 2 Heptyl Octadecyl Unbranched Alkyl Groups

The C 3 H 7 Alkyl Groups CH 3 CH 2 CH 2 C C H HH H H C H H or and CH 3 CHCH 3 C C H HH H H C H H or

CH 3 CH 2 CH 2 C C H HH H H C H H or IUPAC name: Propyl Common name: n-Propyl The C 3 H 7 Alkyl Groups

Naming Alkyl Groups (Table 2.8) Step 1:Identify longest continuous chain starting at point of attachment. Step 2: Drop -ane ending from name of unbranched alkane having same number of carbons as longest 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.

IUPAC name: 1-Methylethyl Common name: Isopropyl CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

CH 3 CH 2 CH 2 C C HHHH H C H H or Classification: Primary 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 one other carbon is a primary carbon. The C 3 H 7 Alkyl Groups

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. CH 3 CHCH 3 C C HHHH C H H or H The C 3 H 7 Alkyl Groups

IUPAC name: Butyl Common name: n-Butyl Classification: Primary alkyl group CH 3 CH 2 CH 2 CH 2 C C HHHH H C C HH H H or The C 4 H 9 Alkyl Groups

IUPAC name: 1-Methylpropyl Common name: sec-Butyl Classification: Secondary alkyl group CH 3 CHCH 2 CH 3 C C H HH H H C C HH H H or12 3 The C 4 H 9 Alkyl Groups

IUPAC name: 2-Methylpropyl Common name: Isobutyl Classification: Primary alkyl group C H CH 2 CH 3 The C 4 H 9 Alkyl Groups

IUPAC name: 1,1-Dimethylethyl Common name: tert-Butyl Classification: Tertiary alkyl group 1 2 C CH 3 The C 4 H 9 Alkyl Groups

IUPAC Names of Highly Branched Alkanes

Branched alkanes Octane

4-Ethyloctane

4-Ethyl-3-methyloctane List substituents in alphabetical order. Branched alkanes

4-Ethyl-3,5-dimethyloctane List substituents in alphabetical order. But don't alphabetize di-, tri-, tetra-, etc. Branched alkanes

First Point of Difference Rule The chain is numbered in the direction that gives 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? 2,3,3,7,7-Pentamethyloctane? What is correct name?

First Point of Difference Rule The chain is numbered in the direction that gives 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?

CnH2nCnH2nCnH2nCnH2n Cycloalkane Nomenclature

Cycloalkanes Cycloalkanes are alkanes that contain a ring of three or more carbons. Count the number of carbons in the ring, and add the prefix cyclo to the IUPAC name of the unbranched alkane that has that number of carbons. CyclopentaneCyclohexane

Ethylcyclopentane Cycloalkanes CH 2 CH 3 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 numerical locant at the first point of difference. 3-Ethyl-1,1-dimethylcyclohexane CH 2 CH 3 H3CH3CH3CH3C CH 3 Cycloalkanes