Racemic acid
Racemic acid is an old name for an optically inactive or racemic form of tartaric acid. It is an equal mixture of two mirror-image isomers (enantiomers), optically active in opposing directions.
Its sodium-ammonium salt is unusual among racemic mixtures in that during crystallization it can separate out into two kinds of crystals, each composed of one isomer, and whose macroscopic shapes are mirror images of each other. Thus, Louis Pasteur was able to separate the two enantiomers by picking apart the crystals.[1][2]
In a modern-time re-enactment of the Pasteur experiment,[3][4] it was established that the preparation of crystals was not very reproducible. The crystals deformed, but they were large enough to inspect with the naked eye (microscope not required).
See also
References
- ↑ Pasteur announced his intention to resolve racemic acid in:
- Pasteur, Louis (1848) "Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et le sens de la polarisation rotatoire" (On the relations that can exist between crystalline form, chemical composition, and the sense of rotary polarization), Annales de Chimie et de Physique, 3rd series, 24 (3) : 442–459. [in French]
- Pasteur, Louis (1850) "Recherches sur les propriétés spécifiques des deux acides qui composent l'acide racémique" (Investigations into the specific properties of the two acids that compose racemic acid), Annales de Chimie et de Physique, 3rd series, 28 (3) : 56–99. See also Plate II. (See also the report of the commission that was appointed to verify Pasteur's findings, pp. 99–117.) [in French]
- ↑ George B. Kauffman & Robin Myers (1998). "Pasteur's Resolution of Racemic Acid: A Sesquicentennial Retrospect and a New Translation" (PDF). The Chemical Educator. 3. doi:10.1007/s00897980257a. Archived from the original (PDF) on 2006-01-17.
- ↑ Yoshito Tobe (2003). "The reexamination of Pasteur's experiment in Japan" (PDF). Mendeleev Communications Electronic Version (3). doi:10.1070/MC2003v013n03ABEH001803. Archived from the original (PDF) on August 31, 2005.
- ↑ Masao Nakazaki (1979). "Morphology of sodium ammonium tartrate: Pasteur's spontaneous resolution and its reexamination". Kagaku no Ryoiki. 33: 951–962.