Prochirality

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An sp2-hybridized carbon atom, with re and si faces

In stereochemistry, prochiral molecules are those that can be converted from achiral to chiral in a single step.[1][2] An achiral species which can be converted to a chiral in two steps is called proprochiral.[2]

If two identical substituents are attached to a sp3-hybridized atom, the descriptors pro-R and pro-S are used to distinguish between the two. Promoting the pro-R substituent to higher priority than the other identical substituent results in an R chirality center at the original sp3-hybridized atom, and analogously for the pro-S substituent.

A

Cahn-Ingold-Prelog priority order (1 to 2 to 3) in a clockwise order, and si if the priorities increase in anti-clockwise order; note that the designation of the resulting chiral center as S or R depends on the priority of the incoming group.[3][4]

The concept of prochirality is necessary for understanding some aspects of enzyme

citrate as a possible intermediate in the tricarboxylate cycle
was mistaken.

References

  1. ^ John McMurry (2008). Organic Chemistry (6th ed.). Brooks/Cole. pp. 301–303.
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