2.1.4 Nomenclature (IUPAC Rules) 2. Number the chain so that the substituent gets the lowest possible number CH3CH2CHCH2 CHCH2 CH2CH3 5-ethyl-3-methyloctane CH3 CH2CH3 not 4-ethyl-6-methyloctane because 3<4 CHCH CH3CHCHCH2 CHCH3 3-ethyl-2, 6-dimethylheptane CH3 CH3 not 5-ethyl-2, 6-dimethylheptane because 3< 52.1.4 Nomenclature (IUPAC Rules) ◼ 2. Number the chain so that the substituent gets the lowest possible number. ◼ CH3CH2CHCH2CHCH2CH2CH3 5-ethyl-3-methyloctane ◼ CH3 CH2CH3 not 4-ethyl-6-methyloctane ◼ because 3 < 4 ◼ CH2CH3 ◼ CH3CHCHCH2CH2CHCH3 3-ethyl-2,6-dimethylheptane ◼ CH3 CH3 not 5-ethyl-2,6-dimethylheptane ◼ because 3 < 5