what is threo isomers?

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Detailed Solution

Threo isomers are a type of diastereomers that occur when a molecule has two or more asymmetric (chiral) carbon atoms. They differ in the spatial arrangement of groups around these chiral centers.

When there are two chiral centers, the isomer can have the same configuration at one carbon and opposite configuration at the other.

Threo is the name given to the isomer in which the substituents of interest are on opposite sides in a Fischer projection (i.e., anti to each other).

The other diastereomer where the substituents are on the same side is called the erythro isomer.

Example: Consider a molecule with the structure HO–CH–CH–OH (like in some sugars):

If the –OH groups are on opposite sides in the Fischer projection → Threo

If the –OH groups are on the same side → Erythro

Key Points:

Threo and erythro are diastereomers, not enantiomers.
Commonly used in sugar chemistry and amino acid derivatives.
Helps in distinguishing stereochemistry of compounds with multiple chiral centers.

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