The straight chain consists of 4 Carbons. And there is a double bond between second and third Carbon atoms which means it is an alkene. So the IUPAC name will be But-2-ene or 2-Butene.

Structure:
The given structure is CH3-CH=CH-CH3.

IUPAC Name:
The IUPAC name of the given structure is 2-butene.

Explanation:
To determine the IUPAC name of the given structure, we need to follow the rules of IUPAC nomenclature for organic compounds.

Step 1: Identify the longest carbon chain
In the given structure, the longest carbon chain contains four carbon atoms. Therefore, it is a butene compound.

Step 2: Number the carbon chain
Number the carbon chain from the end that gives the lowest number to the double bond. In this case, we have a double bond between the second and third carbon atoms. Therefore, we start numbering from the end nearest to the double bond.

Step 3: Identify and name the substituents
In the given structure, there are no substituents attached to the carbon chain. The only groups present are methyl groups (CH3) at the ends of the chain.

Step 4: Determine the location of substituents
Since there are no substituents attached to the carbon chain, we do not need to specify their location in the name.

Step 5: Combine the names
Combine the names of the substituents and the carbon chain, while indicating the location of the double bond.

- The carbon chain is named as "but-" since it contains four carbon atoms.
- The double bond is indicated by the suffix "-ene".
- Since there are no substituents, we do not need to specify their location.

Therefore, the IUPAC name of the given structure CH3-CH=CH-CH3 is 2-butene.

Bute-2-ene.