Question

Give the relationship of the two compounds: Different Compounds, Same compound, Constitutional (structural) isomers, Enantiomers, or Diastereomers

a) (4 pts) ОН HO- H2C Br H3C b) (4 pts) -OH NH2 NH2 c) (4 pts) OH

Answer 1

Three parts are given in the given problem.

(a) In the 1st part (a), the hydroxyl group is present at an equatorial position in one structure and in another structure, it is present at axial position. The stereochemistry around this carbon (-OH) is R in 1st structure and is 'S' in 2nd structure. Therefore, the given pair of isomer is diastereomer. They are diastereomers. Diastereomers are those isomers, in which at least one carbon has different stereochemistry around it.

(b) Similarly, in this set, both the NH2 and OH groups are oriented in a downward direction i.e. one adjacent axial-equatorial substituents are always either in the downward direction or in the upward direction in a chair conformation of cyclohexane. And when this chair conformation is drawn in a planar one, the direction of substituents will always remain same i.e. downward remain downward (below the plane) and upward remain upward (above the plane). But NH2 group is present downward in one conformation and above the plane in another one (upward). Therefore, the given pair is also a Diastereomer as the configuration around the Carbon atom attached to NH2 group changes.

(c) The isomers which have the same chemical formula but different connectivity of the groups are known as Constitutional isomers. In the 1st structure, the OH group is attached to the 5th carbon atom but attached to the 4th carbon atom in another one. Therefore, the given set of isomers is Constitutional isomers.

Hope it will help.