JEE Main · 2020 · 09 Jan 2020 · Shift 2 · General Organic Chemistry

A racemic product forms when a reaction creates a new stereocentre through a planar, achiral intermediate that both faces can attack equally. Adding $\mathrm{HBr}$ to but-1-ene, for example, proceeds through a planar secondary carbocation and yields 2-bromobutane, whose $C2$ is a newly formed stereocentre generated as a $50:50$ mixture, so that route does give a racemate. The reaction that does not give a racemic product is instead the one that forms no new stereocentre through such a planar intermediate, the transformation whose product carries no newly generated chiral centre.