Introduction to Organic Chemistry: Nomenclature - Naming Organic Compounds

Question 1

Overview

Answer 1

• Count longest consecutive carbon chain and find prefix
• Look for functional groups and decide suffix
• Number functional groups if needed
• Look for side carbon branches and name them
• Number side carbon branches if needed
• Put name together

Question 2

Count longest consecutive carbon chain find prefix

Answer 2

• Remember you can go in up, down, left or right (even diagonally in skeletal formula) when counting carbons
• Number carbon chain so lowest number possible is assigned to most important functional group
• Number of carbons should tell you prefix: meth, eth, prop, but

Question 3

Look for functional groups and decide suffix

Answer 3

• Functional groups with higher priorities are put towards the end of the name of the compound
• Memorise priority list

Question 4

Number functional groups if needed

Answer 4

• If there is more than one of the same functional group, state number of the carbon they are attached to
• Typically, number goes before functional group name
• 1, 3 - dichlorobutane
• Numbers separated by commas; numbers and words are separated by hyphens
• Use multipliers before functional group name and after position number to indicate how many times the functional group appears: di, tri, tetra, penta, hexa

Question 5

Look for side carbon branches and name and number them

Answer 5

• If there are additional carbon branches that are not part of the longest consecutive chain, you must number and name them
• Branch or side chain is an alkyl group and have general formula of CnH2n+1
• Name them according to how many carbons are in a single side branch: methyl, ethyl, propyl
• Prefix same as alkanes but end in -yl instead of -ane
• Use multipliers if needed
• Provide which number carbon they are attached to
• 3 - methylpentane

Question 6

Put name together

Answer 6

• Functional groups with higher priorities are put towards the end of the name of the compound
• Numbers typically come before functional group name
• Numbers are separated by commas
• Words and numbers are separated by hyphens
• Use suffix for most important functional group (and alkanes/alkenes)
• Use prefix for every other functional group

Question 7

How do you add suffixes correctly?

Answer 7

• When using a suffix, add in the following way:

• If the suffix starts with a vowel- remove the –e from the stem alkane name
• e.g. Propan-1-ol, butan-1-amine, ethanoic acid, ethanoylchloride, butanamide

• If the suffix starts with a consonant or there are two or more of a functional group meaning di, or tri needs to be used then do not remove the the –e from the stem alkane name
- e.g. Propanenitrile, ethane-1,2-diol, propanedioic acid, propane-1,2,3-triol, Pentane-2,4-dione

Question 8

Which functional groups have position numbers go in between the prefix and suffix?

Answer 8

• Alcohols

• These have the ending -ol and if necessary the position number for the OH group is added between the name stem and the –ol
• Butan-2-ol

• Ketones
- These have the ending -one and if necessary the position number for the ketone group is added between the name stem and the –one