Naming of Alkanes, Cycloalkanes, and Alkyl Halides

IUPAC Naming

Three portions to name:• Substitutents—what groups are off of the

main chain• Prefix—how many carbons in the main

chain of the molecule• Suffix—what functional groups are present,

if none or only halide use the ending “ane”

2-methyl-2-chloropropane

Parent

• Memorize the parent name for the following numbers of carbon atoms in the main chain

# carbons

1

2

3

4

5

6

7

8

9

10

11

12

prefix

meth

eth

prop

but

pent

hex

hept

oct

non

dec

undec

dodec

Identifying the Main Chain

F Cl

• Longest chain of bonded carbon atoms• If two chains have the same length, select the

chain with the most substituents as the main chain

Identifying the Main Chain

• Longest chain of bonded carbon atoms• If two chains have the same length, select the

chain with the most substituents as the main chain

F Cl F Cl

3 substituents 4 substituents

Main Chain with Rings• If a ring has more carbons in it than in an attached carbon

chain, the ring is the main chain• If the ring has fewer carbons, then the ring is a substituent

and the main chain is the carbon chain

C CH2

C

CH2

CH2

CH2CH3

H

Cl

H

CH

H2C CH2

CH3CH2CHCH3

Naming Substituents• Carbon-containing substituents are named as alkyl groups.• Halide groups are named as halo substituents• sec- and tert- are not alphabetized

CH3

CH2CH3

CH2CH2CH3

CH

CH2CH2CH2CH3 CH2

C

F

Cl

Br

I

CH3 CH3

CH

CH3 CH2CH3

CH

CH3CH3

CH3CH3

CH3

methyl propyl

ethyl

isopropyl("V")

butyl

sec-butyl ("L")

isobutyl("Y")

tert-butyl ("T")

fluoro

chloro

bromo

iodo

Complex Substituents• If there is not a common name for a substituent, you may

need to label the alkyl group as a complex substituent

CH2 CH2 CH2 CH CH3

CH3

Parent chain of molecule

1 2 3 4 5

#

#-(4-methylpentyl)

Numbering the Chain• Open chain compounds are numbered so that the first

substituent on either end receives the lowest number.• If the substituents that are first from either end are the

same distance, give the lowest number to the next substituent

• If only two substituents are present on the chain and they are equally distant, give the first in the alphabet the lowest number

ClBr

6-bromo-2-chloro-3-methyl

BrCl

2-bromo-6-chloro

Numbering Cycloalkanes• If there are only two substituents on the ring, the carbon in

the ring that has the substituent first in the alphabet = position #1

• Ignore di, tri, tetra, sec-, and tert-

Br

CH3

H

H

Number of Substituents• If there are more than one of a particular substituent,

indicate the number of that substituent using the below notation (di, tri, tetra, etc.)

• If you have two substituents, you need to indicate two position numbers for that pair of substituents.

# of substitutents

2

3

4

5

6

substituent prefix

di-

tri-

tetra-

penta-

hexa-“2,2,5-trimethyl”

Put the Name Together

#-Substituent + Parent + Suffix

• List substituents in alphabetical order, ignoring di, tri, tetra, sec-, and tert-

• Make sure that your substituent prefix matches the numbers you place in front of it, for example, 2-trimethyl is incorrect.

• If the molecule is a cycloalkane, you may need to include cis and trans at the front of the name