This is called 1,3-hexadien-5-yne. I know. You’re thinking, “that can’t be right.” But it is.

In the name, you might have noticed that the e on the “-ene” infix was left out. That was purposeful. When an alkane, alkene or alkyne suffix comes before a number, you drop the last “e” (check the table on the right for the appropriate infix in these situations).

You also might have noticed that we only included the alkyne’s suffix (-yne). Well, the first “hexa” already covers the six carbons; there’s no need to repeat ourselves with a cumbersome name like 1,3-hexadien-5-hexyne – only include the suffix. That goes for any functional group, by the way, not just alkynes.

In the molecule, there are two alkenes and one alkyne in a six-carbon molecule. Like with 1,4-hexadiene, we look for the carbon near the alkene (or alkyne) that gives the lowest number and start there. In cases where the alkene and alkyne both have the same number, like they would above, we give the alkene priority.

Substituents With the Same Length As a Parent Chain

We know that a parent chain is the longest chain of carbons. But what if there is a substituent that has the same amount of carbons as a parent chain?