Question

Which‌ ‌configuration‌ ‌is‌ ‌erythro?‌
(A)
(B)
(C)
(D)

Answer 1

In the given question firstly we have to define the facts regarding the solution and the basic definition. Descriptors are the erythro and threo which are used to distinguish between the pair of diastereomers containing only two chiral centers, which are also adjacent and bearing two pairs of common ligands.

Complete step-by-step answer:
We can say that the descriptors is the erythro and threo which are used to distinguish between the pair of diastereomers containing only two chiral centers, which are also the adjacent and bearing two pairs of common ligands.
In the case of the erythro configuration, when all is drawn in Fischer projection the erythro configuration must have the two identical substituents on the same side of the structure. If the same groups are on the different side then it is known as threo isomer. So the configuration given in option A is the erythro configuration.
Therefore by the given facts we get that the correct option is the first one

So,the correct option is (A).

Note: If, in the case of the Fischer projection, like the ligands which are generally on the same side of the bond linking the chiral centers, the compound is identified as the erythro isomer. Also we can say that if they are on the opposite sides, then the compound is identified as the threo isomer for the case.