Which of the following will exhibit geometric isomerism?

Which of the following will exhibit geometric isomerism? Correct Answer Cinnamic acid

Concept: 

Functional isomers:

• It has the same chemical formula but different functional groups attached to them.
• e.g C3H6O 
• It has two functional isomers i.e 

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Metamerism:

• It is a form of structural isomerism.
• This isomerism is due to the presence of different alkyl chains on each side of the functional group.
• e.g C5H12O has two metamers i.e 
  • Pentan-2-one (CH3OC3H7)
  • Pentan-3-one (C2H5OC2H5)

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Geometrical:

• It is a type of stereoisomers.
• Isomers have different spatial arrangements of atoms in three-dimensional space.
• There are two three dimensional structures of but-2-ene.
• These two structures are named cis and trans.

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• Cis trans isomers are found in geometrical isomerism, so they are generally known as cis-trans isomerism.
• Cis - When higher priority groups are on the same side then the structure is named as cis.
• Trans - When higher priority groups are on the different side then it is known as trans

Explanation:

Cinnamic acid is the trans-isomer and hence is also known as trans - β-phenylacetic acid. The cis-isomer (cis - β- phenylacetic acid) is also known as allocinnamic acid.
trans-Cinnamic acid is the form that occurs naturally (free and as esters) in balsams.

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Each of the doubly bonded carbon atoms should be bonded to two different ligands.

Hence the correct option is Cinnamic acid.