Question

What is each compound’s systematic name?

Short answer

1. 4-methyl-2-pentene
2. 2-chloro-3,4-dimethyl-3-hexene
3. 1-bromocyclopentene
4. 1-bromo-4-methyl-3-hexene
5. 1,5-dimethylcyclohexene
6. 1-butoxy-1-propene
7. 1-bromo-2-methyl-1,3-pentadiene
8. 8,8-dimethyl-1-nonene

Step-by-step solution

Steps for writing the nomenclature of alkene

A) The longest continuous chain containing the functional group (in this case, the carbon– carbon double bond) is numbered in the direction that results in the lowest possible number for the functional group suffix.

B) The "ne" ending of the corresponding alkane is replaced with "diene," "triene," "tetraene," and so on for a molecule with two or more double bonds, depending on the number of double bonds in the parent hydrocarbon.

C) A substituent's name appears before the name of the longest continuous chain containing the functional group, along with a number indicating the carbon to which the substituent is connected.

D) If a chain has more than one substituent, the substituents are listed in alphabetical order, following the same alphabetizing principles. Each substituent is then given the proper number.

E) If counting in either manner yields the same number for the functional group suffix, the name with the lowest substituent number is the right one.

F) The position of the double bond in a cyclic alkene does not require a number because the ring is always numbered so that the double bond lies between carbons 1 and 2. Count around the ring in the direction (clockwise or anticlockwise) that puts the lowest number into the name to assign numbers to any substituents.

G) If counting in either direction yields the same number for the alkene functional group suffix and the same lowest number or numbers for one or more substituents, disregard those substituents and choose the direction that yields the lowest number for one of the remaining substituents.