Organic Chemistry Nomenclature

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Part 1. Hydrocarbon Nomenclature

From International Union of Pure and Applied Chemistry (IUPAC)

General Form of IUPAC Nomenclature
[branching substituent(s)] Root [Suffix]

Rules:
1.Identify the longest continuous chain of carbon atoms. This chain determines the parent name (root) of the alkane. The parent suffix for alkanes is, not surprisingly, -ane. For chains of equal length, pick the one with the most substituents.

(Note: I number all possibilities going from left to right – identify the longest chain)

2.Number the chain beginning at the end of the chain nearest any branching, thus obtaining the lower numbers in the same name.

(Note: I number going from left to right and right to left, then identify at which carbons there are substituents)

3.Use these numbers to designate the location of the substituent groups. Substituent alkyl groups are referred to with suffix “-yl”. (i.e., an alkane substituent is an alkyl)

4.If an alkyl group appears more than once, use the prefixes di, tri, tetra, penta, hexa (2, 3, 4, 5, 6, respectively) for each type of alkyl group.

5.List the groups alphabetically (note: you can ignore this rule in Chem 123)

6.Numbers are separated from letters by dash (-). Multiple numbers are separated by commas (,).

Linear chain hydrocarbon roots:
n = 1| meth| | n = 5| pent| | n = 8| oct|
n = 2| eth| | n = 6| hex| | n = 9| non|
n = 3| prop| | n = 7| hept| | n = 10| dec|
n = 4| but| | | | | | |

Hydrocarbon Suffixes
HydrocarbonSuffix
Alkaneane
Alkeneene
Alkyneyne

Common alkyl substituents
CH3-methyl
CH3CH2-ethyl
CH3CH2CH2-propyl
CH3CH2CH2CH2-butyl

Branched chains

Example 1

:

Rule 1.Identify the longest continuous chain of carbon atoms

SIX = hexane root

Rule 2.Number the chain beginning at the end of the chain nearest any branching

Substituent is at 2 position - lower number than the alternative

Rule 3.Substituent alkyl groups are referred to with suffix “-yl”

Rule 4.Not applicable
Rule 5.Not applicable
Rule 6.Not applicable

NAME: 2-methylhexane

Example 2

Rule 1.Identify the longest continuous chain of carbon atoms

FIVE = pentane root

Rule 2.Number the chain beginning at the end of the chain nearest any branching

Substituents at 2 and 3 positions - lower numbers than the alternative

Rule 3.Substituent alkyl groups are referred to with suffix “-yl”

Rule 4.2,3-dimethyl
Rule 5.Not applicable
Rule 6.As indicated in rule 4 in this case

NAME: 2,3-dimethylpentane

Practice question: Write the IUPAC name for the following hydrocarbon:

(in Order of Decreasing Priority for Citation as the Principal Function)

class| formula| principal name(suffix)| substituent name(prefix)| carboxylic acids| | -oic acid| carboxy|
esters| | -oate| R-oxycarbonyl|
amides| | -amide| amido|
nitriles| | -nitrile| cyano|
aldehydes| | -al| oxo|
ketones| | -one| oxo|
alcohols| -OH| -ol| hydroxy|
thiols| -SH| -thiol| mercapto (or sulfydryl)|
amines| -NH2| -amine| amino|
hydrocarbons| -H| -ane, -ene, -yne| |
ethers| R-O-R’| | R-oxy|
sulfides| R-S-R’| | R-thio|
halides| F, Cl, Br, I| (hal)-ide| halo|

Nomenclature for Functional Groups with Lower Priority Than Hydrocarbons (ethers, sulfides, halides)

Treat these functional groups like common alkyl branching substituents (i.e. as a prefix to the root rather than a suffix). Use the appropriate prefix name.

Example 1:

1-bromobutane

Example 2:

2-iodopentane

Example 3:

1-ethoxypropane

Example 4:

3-methoxypentane...
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