For each of the following compounds, draw a structure and identify if it can show optical acitivity.
a. 2-bromobutane
b. cis-1,2-dichlorocyclohexane

Determine which of the given isomers of butane-2,3-diol is optically inactive. Justify your answer.

(S)-Amphetamine is a commercially available drug used as a CNS stimulant. Considering the fact that (S)-amphetamine rotates the plane-polarized light in the clockwise direction, answer the following questions:

(a) Should (S)-amphetamine be referred to as (d) or (l)?

(b) Should it be referred to as (+) or (−)?

(c) What would be the direction of rotation (d or l; + or −) for (R)-amphetamine?

Among the following structures, identify the stereoisomers which are optically inactive.

Determine whether (S)-(−)-2-methyl-1-butanol and (S)-(+)-2-methylbutanoic acid are dextrorotatory or levorotatory.