Question

Erythro and threo isomers

Answer 1

Answer:

1.Ephedrine exhibits optical isomerism and has two chiral centres, giving rise to four stereo isomers. By convention, the pair of enantiomers with the stereochemistry (1R,2S and 1S,2R) is designated ephedrine, while the pair of enantiomers with the stereochemistry (1R,2R and 1S,2S) is called pseudoephedrine. 

2.Again in order to distinguish threo from erythro.. Just memorize the word :TOES =Threo - Opposite Erythro - Same e. g., 

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