Answer :
work out how many Carbons are in the main chain CH3 - CH = C(CH2CH3)-CH2-CHCl - CHBr - CH3 There are 7 carbons (hept) so this is a heptene, not a hexene Start counting from the end closest to the double bond, this gives you 2-heptene List all the groups in alphabetical order 6-bromo-5-chloro-3-ethyl-2-heptene