Is the lowest sum rule still used in naming of organic compounds?

The "lowest sum rule" is not a valid or recommended rule in the IUPAC nomenclature for naming organic compounds. Here are the key points from the sources:

• The IUPAC recommendations do not include a "lowest sum rule." Instead, the correct approach is to use the "lowest set of locants" or the "rule of first point of difference," which involves comparing locant sets term by term to find the lowest number at the first point of difference134.

• Using the lowest sum of locants can lead to incorrect names, as illustrated by examples such as 2,7,8-trimethyldecane, where the correct name is not determined by the smallest sum of locants134.

• The correct method is to number the carbons in a way that gives the lowest numbers possible, but this is done by comparing each locant individually, not by summing them up4.

Therefore, the "lowest sum rule" should not be used in naming organic compounds according to IUPAC guidelines.