Calculate the numbers of optical isomers in th3 following compound CH3-CH-OH-CH-OH-CH3?
Answers
The number of optical isomers in a compound is determined by the number of chiral centres in it. A chiral centre is a carbon atom that is bonded to four different molecules or atoms. Each chiral centre will result in two different optical isomers.
So, to work out the number of chiral centres, draw out the displayed formula of the compound, and circle/highlight any carbons in the compound that have four different molecules attached to them (to check this, try drawing the molecule as a tetrahedral shape around your chosen chiral centre; each bond from the central C atom should go to a unique compound). Then, just multiply the number of chiral centres by two to give the number of optical isomers.
To work out which carbons are chiral, you just have to check each one separately. A chiral carbon is usually not on a branched group, or on the end of a chain, so often you can eliminate those pretty quickly. Below is the molecule with the chiral centres highlighted in yellow:
Theory of optical isomerism:
Stereoisomers are compounds that have the same structural formulae, but due to the lack of rotation around a double carbon bond (aka
π
-bond) will form slightly different compounds where a structure is above the molecular plane in one isomer, and below in the other.
Optical isomers (aka enantiomers) follow a similar principle, except instead of thinking about differences in location above and below a double bond, we are thinking about the orientation around tetrahedral carbon centre.
Answer:
3
Explanation: