meso-tartaric acid is

Meso-tartaric acid is a type of tartaric acid, which is a white crystalline organic acid that occurs naturally in many fruits, most notably in grapes. It is one of the isomers of tartaric acid, which means it has the same molecular formula but a different structure and configuration.

The "meso" prefix in meso-tartaric acid refers to its stereochemistry, indicating that it is a specific type of isomer called a meso compound. Meso compounds are achiral (not chiral) and have an internal plane of symmetry. This means that despite having chiral centers (carbon atoms bonded to four different groups), the compound as a whole is not chiral. This is because the molecule can be divided into two parts that are mirror images of each other.

In the case of meso-tartaric acid, it has two chiral centers, but it does not rotate plane-polarized light, a characteristic behavior of chiral molecules, because the two halves of the molecule cancel out this effect.

Meso-tartaric acid is less soluble in water than other isomers of tartaric acid and it does not crystallize as easily. It is used in some organic synthesis reactions and in the production of some pharmaceuticals.