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Wize University Organic Chemistry Textbook > Intro to Orgo (Functional Groups, Drawing, Naming)

IUPAC Systematic Naming

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IUPAC Systematic Naming


General Naming Rules
  1. Identify and name the longest carbon chain
  2. If present, assign stereochemistry (R/S or E/Z)
  3. Identify and name any substituents on the carbon chain
  4. Give these substituents the appropriate 'address' - i.e. which carbon atom they are bonded to
  5. Add substituent names as a prefix to the carbon chain
  6. Change suffix of the carbon chain if necessary (for functional groups)

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Important Things to Consider
  • The length of the longest carbon chain (you may have to look for this!)
  • The types of C-C bonds in that chain
  • The functional groups incorporated in the chain
  • The priority of each of those functional groups
The Carbon Chain
The root of the name will always identified as number corresponding to the longest continuous chain of carbon atoms.
# carbon atoms = root1 = meth-6 = hex-2 = eth-7 = hept-3 = prop-8 = oct-4 = but-9 = non-5 = pent-10 = dec-\begin{array}{ll}\#\text{ carbon atoms = root}&\\ \text{1 = meth-} &\text{6 = hex-}\\ \text{2 = eth-} &\text{7 = hept-}\\ \text{3 = prop-} &\text{8 = oct-}\\ \text{4 = but-} &\text{9 = non-}\\ \text{5 = pent-} &\text{10 = dec-}\end{array}

This carbon chain must include any C-C multiple bonds present in the molecule, as this will complete the name of the carbon chain.


The Substituents



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Additional Considerations


Lower priority functional groups (alkyl groups, alkoxy groups and halides) that are attached to the carbon chain are listed before the name of the carbon chain.

Substituents that have similar priority as the ones listed above must be listed with the lowest possible numbering system, or 'address'. For example:

Going from left to right, the Cl has an address of 2. Going from right to left, the Cl has an address of 4. Since 2 < 4, we have a 2-chloro substituent - the name is 2-chloropentane.

Wize Concept
Note that each number and letter is separated by a hyphen (-).


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If there is more than one substituent, then the two numbers combined must give the lowest possible numbers. For example:


Going from left to right, the Cl is on 3 and the Br is on 4. Going from right to left, the Cl is on 3 and the Br is on 2. Since 2,3 <3,4, we have 2-bromo-3-chloro. The name is 2-bromo-3-chloropentane.


Wize Concept
Substituents are listed in alphabetical order.



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If there is more than one substituent of the same type, then we don’t list them separately, instead we combine them with a prefix. Each number is separated by a comma (,). Also notice that the prefixes used are as follows:
#= prefix1 = no prefix6 = hexa-2 = di-7 = hepta-3 = tri-8 = octa-4 = tetra-9 = nona-5 = penta-10 = deca-\begin{array}{ll}\#=\text{ prefix}&\\ \text{1 = no prefix} &\text{6 = hexa-}\\ \text{2 = di-} &\text{7 = hepta-}\\ \text{3 = tri-} &\text{8 = octa-}\\ \text{4 = tetra-} &\text{9 = nona-}\\ \text{5 = penta-} &\text{10 = deca-}\end{array}


Functional Groups

These are higher priority groups that occur along the carbon chain. These often result in a modification of the suffix of the carbon chain. These also effect the 'addressing' of the chain, as many of these groups are terminal and must start on Carbon-1.


Wize Tip
(Highest priority) Carboxylic Acids, Esters, Amides, Aldehydes, Ketones, Alcohols, Thiols, Alkenes, Alkynes, Alkyl Halides, Alkanes (Lowest priority)


Examples:





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Example: Converting Names to Structures

Draw the following molecules as line drawings.
  1. 4-methylpent-3-en-2-one
  2. 6-bromo-6-chloro-5-ethylheptan-3-ol

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Example: IUPAC Systematic Naming


Name the following molecule using IUPAC systematic naming.

4-bromo-2,4-dimethylpentanal
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Example: IUPAC Systematic Naming


Name the following molecules using IUPAC systematic naming.

5-ethyl-4,4-dimethylheptane-3-thiol

Practice: IUPAC Nomenclature


Name the following molecule using IUPAC systematic naming.



Practice: IUPAC Nomenclature


Name the following molecule using IUPAC systematic naming:



Summary Sheet: IUPAC Naming

General Naming Rules

  1. Identify and name the longest carbon chain
  2. If present, assign stereochemistry (R/S or E/Z)
  3. Identify and name any substituents on the carbon chain
  4. Give these substituents the appropriate 'address'
  5. Add substituent names as a prefix to the carbon chain
  6. Change suffix of the carbon chain if necessary (for functional groups)