The IUPAC rules for naming alkenes are similar in many respects to those for naming alkanes Selecting the longest chain that contains the double bond 2. Number the chain 23 234 6 H2C=CHCH2 CH3 CH3CH=CHCH2 CH2CH3 32 654321 1-Butene 2-Hexene (not 3-butene) (not 4-hexeneThe IUPAC rules for naming alkenes are similar in many respects to those for naming alkanes 1. Selecting the longest chain that contains the double bond 2. Number the chain H2 C CHCH2 CH3 1-Butene (not 3-butene) 1 2 3 4 4 3 2 1 CH3 CH=CHCH2 CH2 CH3 1 2 3 4 5 6 6 5 4 3 2 1 2-Hexene (not 4-hexene)