Sub-rules for IUPAC nomenclature 1)If there are two or more longest chains of equal length: Choose the one having the largest number of substituents. Choose the one having the simples substituents. 2)If both ends of the root chain have equidistant substituents. Begin numbering at the end nearest a third substituent,if one is present. Begin numbering at the end nearest the first cited group (alphabetical order). Chapter 3 10 2013 Pearson Education,Inc.© 2013 Pearson Education, Inc. Sub-rules for IUPAC nomenclature 1) If there are two or more longest chains of equal length: – Choose the one having the largest number of substituents. – Choose the one having the simples substituents. 2) If both ends of the root chain have equidistant substituents. – Begin numbering at the end nearest a third substituent, if one is present. – Begin numbering at the end nearest the first cited group (alphabetical order). Chapter 3 10