0:00 / 0:00
Isomerism
Isomers are compounds that have the same molecular formula but their atoms are in a different arrangement
- Constitutional isomers possess a different connectivity from one another. This means while the molecular formulae are the same, there can be many possibilities for different functional groups or bonding patterns.
- Stereoisomers possess the same functional groups in the same connectivity (so they also have the same molecular formulae), but they have different 3D orientations of their atoms in space.
- Configurational isomers are a type of stereoisomer where the difference in spatial arrangement is not due to rotation or twisting about a single bond.
- 2a) Diastereomers (cis-trans isomers) are based on a double bond where different types of atoms or groups are bonded to each carbon atom in the double bond.
trans-but-2-ene cis-but-2-ene
Wize Tip
For the cis isomer: Both of the largest functional groups are on the same side
*Think cis are like sisters, so they are on the same side!
For the trans isomer: Both of the largest functional groups are on opposite sides.
Watch Out!
Diastereomers are not possible if two groups on one carbon are the same (see below for an example)
- 2b) Enantiomers a type of stereoisomer where molecules are mirror images of each other around a single carbon atom that is connected to 4 different types of atoms or groups
The alkane pentane, C5H12, has several structures (i.e. constitutional isomers, all of which are included in the set of molecules shown below.
Which of the following sets of structures presents the isomers of pentane without counting any isomer more than once?
Choose the compound below which is a structural isomer of 2,2-dimethylpentane
Which of the following drawings is cis – 5 – bromo – 6 – chlorooct-3-ene?
Which of the following molecules has both cis/trans isomers and has an enantiomer?