Question

How many stereoisomers can be drawn for a molecule with formula CH 3 ​ CH(OH)CH(OH)CH 3 ​ ? Multiple Choice 4 3 2 1

Answer 1

A molecule with the formula CH3CH(OH)CH(OH)CH3 has two chiral centers and thus can have up to 4 stereoisomers, which in this case are two pairs of enantiomers.

Step-by-step explanation:

The molecule CH3CH(OH)CH(OH)CH3 has two chiral centers because there are two carbon atoms each bonded to four different groups -- one bonded to an OH group, a hydrogen atom, a CH3 group, and the rest of the organic molecule. According to the formula 2n for calculating the maximum number of stereoisomers, where n is the number of chiral centers, a molecule with two chiral centers could have up to 22 = 4 stereoisomers.

In this case, the molecule does indeed have four stereoisomers, which are two pairs of enantiomers (mirror images that are not superimposable). Since enantiomers are a type of stereoisomer, the correct answer to the question "How many stereoisomers can be drawn for a molecule with formula CH3CH(OH)CH(OH)CH3?" would be 4 stereoisomers.

Answer 2

The molecule
`$\mathrm{CH}_3 \mathrm{CH}(\mathrm{OH}) \mathrm{CH}(\mathrm{OH}) \mathrm{CH}_3$` has two chiral centers, namely the carbons bonded to the two hydroxyl groups. Each chiral center can exist in two configurations, R and S, leading to a total of
`$2^2=4$` possible stereoisomers.

Chiral centers: A chiral center is a carbon atom that has four different substituents attached to it. In this molecule, both carbons bonded to the hydroxyl groups have four distinct substituents: a hydrogen, a methyl group, a hydroxyl group, and the rest of the carbon chain.

`$\mathrm{R}$` and
`$\mathrm{S}$` configurations: Each chiral center can be assigned an R or S configuration based on the priority of the substituents according to the Cahn-Ingold-Prelog (CIP) rules. These rules assign priorities based on atomic numbers and the presence of double bonds.

Combinations: Since each chiral center can have two configurations, there are
`$2 * 2=4$` possible combinations of configurations for the two chiral centers. This means there can be four different stereoisomers of the molecule.

Therefore, option A ( 4 stereoisomers) is the correct answer.