Alkane+Nomenclature

Organic Chemistry Nomenclature Guide – Alkanes



= Naming Branched-chain and Cyclic Alkanes =

The following steps should be used to properly name branched-chain alkanes.

1)Find the longest continuous chain of carbons that has the most branch points. 2)Begin numbering from the end closest to the first branch point, using alphabetical order for priority in case of a tie.

3)Assign the number at the branch point to the side chain attached to it. 4)List the side chains alphabetically. 5)Write out the name of the compound as one word:


 * Start with the side chains, alphabetically and separated by hyphens.
 * Group same side chains together; use prefixes to quantize and commas to separate numbers.
 * End with the name of the longest chain.

The following steps should be used to properly name cycloalkanes.

For unsubstituted cycloalkanes: 1)Count the number of carbons in the ring and add ‘cyclo‘ to the corresponding name.

For monosubstituted cycloalkanes: 2)Treat the ring as the longest side chain – it gets priority no matter the size of the substituent. 3)Generate the name of the compound by writing the side chain name followed by the name of the cycloalkane it is attached to all in one word. 4)For side chains larger than 4 carbons:


 * Number the longer part of the side chain starting at the point of attachment to the ring;
 * Follow the steps for naming branched hydrocarbons to name the side chain;
 * Write the name of the side chain in parentheses before the name of the ring.

For multiple substitutions on a ring: 5)Start numbering the ring according to the following order of priority:


 * Number starting at the carbon with the __most substitutions__; in case of more than one site, use alphabetical priority for these sites.
 * For multiple monosubstitutions, use __alphabetical priority__.If two of the same side chains are present, number so as to have the least number of carbons between side chains.

6)Continue numbering the ring according to the following order of priority:


 * Number so as to have the __least number of carbons__ between side chains.
 * If the number of carbons is the same, number using __alphabetical priority__.