The configurations of the chirality centres i | vedclass

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(C) To determine the configuration of the chirality centers in $D$-threose,we assign priorities to the groups attached to each chiral carbon using Cah

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$2S, 3R$

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(C) To determine the configuration of the chirality centers in $D$-threose,we assign priorities to the groups attached to each chiral carbon using Cahn-Ingold-Prelog $(CIP)$ rules.For $C-2$ (the chiral carbon attached to the $CHO$ group):$1$. $-OH$ (priority $1$)$2$. $-CH(OH)CH_2OH$ (priority $2$)$3$. $-CHO$ (priority $3$)$4$. $-H$ (priority $4$)In the Fischer projection,the $-H$ is on the horizontal bond. The sequence $1$ $\rightarrow 2$ $\rightarrow 3$ appears clockwise $(R)$,but since the lowest priority group $(-H)$ is on a horizontal bond,we reverse the configuration to $S$. Thus,$C-2$ is $2S$.For $C-3$ (the chiral carbon attached to the $CH_2OH$ group):$1$. $-OH$ (priority $1$)$2$. $-CHO$ (priority $2$)$3$. $-CH_2OH$ (priority $3$)$4$. $-H$ (priority $4$)In the Fischer projection,the $-H$ is on the horizontal bond. The sequence $1$ $\rightarrow 2$ $\rightarrow 3$ appears counter-clockwise $(S)$,but since the lowest priority group $(-H)$ is on a horizontal bond,we reverse the configuration to $R$. Thus,$C-3$ is $3R$.Therefore,the configuration is $2S, 3R$.

The configurations of the chirality centres in $D$-threose (shown) are

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