Isobutene IUPAC naming [closed]

What is the correct name of an isomer of isobutene $\ce{C4H8}$: 1,1-dimethylethene or 2-methylprop-1-ene? I have done an exam recently and I'm just curious about what what would be correct.

closed as off-topic by Mithoron, Todd Minehardt, Jon Custer, bon, ronNov 23 '17 at 15:26

This question appears to be off-topic. The users who voted to close gave this specific reason:

If this question can be reworded to fit the rules in the help center, please edit the question.

1 Answer

It will be 2-methylprop-1-ene , as we need to select the longest carbon chain containing the functional group i.e. alkene here.