Question

Give an IUPAC name for the following compound:

Answer 1

Answer) 1-[(E)-But-2-enyl]benzene

Explanation:

Identify the longest carbon chain. Benzene ring has 6 carbon while the alkenyl chain has 4 carbon atoms. Therefore, benzen is the parent group. Therefore the name ends with benzene and alkenyl substituent will be written in the beginning of the name .

The benzene ring carbon atoms are numbered. The numbering starts from the carbon atom of benzene ring directly attached to alkenyl chain.

2 2 5 L)

The alkenyl chain has a double bond and it has to be numbered( Numbering is done with red pen).

Numbering starts from the carbon directly attached to benzene ring. It has 4 cabons therefore name is butanyl. It has a double bond at 2nd carbon, therefore the an is replaced by -2-en .

Double bonds are of two types. When the higher priority (groups with higher molecular weight) are on the same side of the double bond, the stereochemistry of the double bond is Z and when the priority groups are on the opposite side of the double bond, the stereochemistry of the double bond is E.
The image of the molecule is drawn with the two types of double bonds to compare. Hence, the stereochemistry of the double bond of the given molecule is E.

3 4 6 5 and LD Z

Hence the name of alkenyl substituent is 1-[(E)-But-2-enyl]

IUPAC name is  1-[(E)-But-2-enyl]benzene