Which of the following molecules is But-2-ene?
Which of the following molecules is
The prefix but- means that the
molecule contains a chain of four carbon atoms. As such, we can eliminate answer
choice (B) as this molecule only contains a three-carbon-atom chain. We can also eliminate answer choice
(C) as this molecule contains a five-carbon-atom chain. The suffix -ene indicates that the
molecule is an alkene, an unsaturated hydrocarbon that contains at least one
carbon–carbon double bond. This means that we can eliminate
answer choice (D), as this molecule contains a triple bond, called an alkyne,
instead of a double bond.
The number two is the position
number of the alkene in the carbon atom chain. This means that the double bond
begins with the second carbon atom of the chain and connects carbon atoms two and
three. The remaining answer choice with a
double bond between the second and third carbon atoms of the chain is answer choice
(E). The displayed formula that
correctly represents but-2-ene is answer choice (E).