The stereochemical descriptors 'Erythro' and 'Threo' differentiate specific diastereomeric pairs. In — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Erythro and Threo nomenclature exclusively applies to diastereomers with two adjacent chiral centers. In a Fischer projection, if the two identical or similar functional groups (like $-OH$) are structurally positioned on the exact *same* side of the vertical carbon backbone, it is Erythro. If they are drawn strictly on *opposite* sides, the isomer is definitively classified as Threo.