Erythro and Threo Nomenclature

source : oc hempal.org

Erythro and Threo Nomenclature-

This nomenclature is based on four carbon aldose sugars ; erythrose & threose.

Erythrose                                  Threose

Compounds having two different chiral or assymetric carbon atoms are named by using prefix- erythro or threo. When two same groups are on the same side of chiral carbon atom in fischer Projection formula then it is ‘ erythrose ‘. When two identical groups are on the opposite side of chiral carbon atom in Fischer Projection formula then it is ‘threose’

Ex.

(Erythrose)                            (Threose)