Constitutional (structural) isomers introduction
Constitutional (structural) isomers are compounds that have the same molecular formula but a different atom-to-atom bonding sequence. Since constitutional isomers have different physical properties, usually they can be separated easily from each other.
(1)
(2)
(3)
Constitutional isomers of C5H12O are used below to illustrate different atom-to-atom bonding sequences.
(1)
(2)
Constitutional (structural) isomers may have the same functional group and the same carbon skeleton (The carbon skeleton shows the arrangement of carbon atoms.), but the functional group is attached to a different carbon atom.
There are only three different constitutional isomers for this carbon skeleton because the two pairs of carbons at either end of the chain are equivalent. The third isomer has OH at the center of the chain.
Examples of this type are the constitutional isomers (1) and (2).
This type of constitutional isomerism is also known as positional isomerism.
This type of constitutional isomerism is also known as positional isomerism.
There are only three different constitutional isomers for this carbon skeleton because the two pairs of carbons at either end of the chain are equivalent. The third isomer has OH at the center of the chain.
(3)
Constitutional (structural) isomers may have the same functional group and different carbon skeletons.
Constitutional isomer (3) is a C5H12O isomer with a carbon skeleton different from that of (1) and (2).
Constitutional isomers that have different carbon skeletons are also known as chain isomers.
There are four different alcohol isomers for this carbon skeleton because the two methyl groups bonded to the same carbon are equivalent due to both being bonded to three hydrogens and a carbon.
Constitutional isomers that have different carbon skeletons are also known as chain isomers.
There are four different alcohol isomers for this carbon skeleton because the two methyl groups bonded to the same carbon are equivalent due to both being bonded to three hydrogens and a carbon.
CH3CH2CH2OCH2CH3
(4)
(4)
Constitutional (structural) isomers may have different functional groups.
Constitutional isomers that have different functional groups are also known as functional group isomers.
Constitutional isomer (4) is a functional group isomer of the constitutional isomers (1), (2) and (3).
Constitutional isomer (4) is a functional group isomer of the constitutional isomers (1), (2) and (3).