Racemic acid

Last updated
Tartaric acid in pen sketch Tartaric acid.svg
Tartaric acid in pen sketch
Computer-rendered image of right-handed molecule Tartaric-acid-3D-balls.png
Computer-rendered image of right-handed molecule
Racemic acid crystals drawn as if seen through an optical microscope TartrateCrystal.svg
Racemic acid crystals drawn as if seen through an optical microscope

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. It occurs naturally in grape juice.

Tartaric acid's 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 crystalline shapes are mirror images of each other. Thus, Louis Pasteur was able in 1848 to isolate each of the two enantiomers by laboriously separating the two kinds crystals using delicate tweezers and a hand lens. [1] Pasteur announced his intention to resolve racemic acid in:

while he presented his resolution of racemic acid into separate optical isomers in:

In the latter paper, Pasteur sketches from natural concrete reality chiral polytopes quite possibly for the first time. The optical property of tartaric acid was first observed in 1832 by Jean Baptiste Biot, who observed its ability to rotate polarized light. [4] [5] It remains unknown whether Arthur Cayley or Ludwig Schläfli, or other contemporary mathematicians who studied polytopes, knew of the French work.

In two modern-day re-enactments performed in Japan of the Pasteur experiment, [6] [7] 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

Related Research Articles

Louis Pasteur French chemist and microbiologist

Louis Pasteur was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation, and pasteurization. His research in chemistry led to remarkable breakthroughs in the understanding of the causes and preventions of diseases, which laid down the foundations of hygiene, public health and much of modern medicine. His works are credited to saving millions of lives through the developments of vaccines for rabies and anthrax. He is regarded as one of the founders of modern bacteriology and has been honoured as the "father of bacteriology" and as the "father of microbiology".

Optical rotation

Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror symmetry. Unlike other sources of birefringence which alter a beam's state of polarization, optical activity can be observed in fluids. This can include gases or solutions of chiral molecules such as sugars, molecules with helical secondary structure such as some proteins, and also chiral liquid crystals. It can also be observed in chiral solids such as certain crystals with a rotation between adjacent crystal planes or metamaterials.

Asparagine Chemical compound

Asparagine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, an α-carboxylic acid group, and a side chain carboxamide, classifying it as a polar, aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it. It is encoded by the codons AAU and AAC.

Picric acid Explosive chemical compound

Picric acid is an organic compound with the formula (O2N)3C6H2OH. Its IUPAC name is 2,4,6-trinitrophenol (TNP). The name "picric" comes from the Greek word πικρός (pikros), meaning "bitter", due to its bitter taste. It is one of the most acidic phenols. Like other strongly nitrated organic compounds, picric acid is an explosive, which is its primary use. It has also been used as medicine (antiseptic, burn treatments) and as a dye.

In chemistry, a racemic mixture, or racemate, is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. A sample with only a single enantiomer is an enantiomerically pure or enantiopure compound.

Jean-Baptiste Biot French physicist

Jean-Baptiste Biot was a French physicist, astronomer, and mathematician who co-discovered the Biot–Savart law of magnetostatics with Félix Savart, established the reality of meteorites, made an early balloon flight, and studied the polarization of light.

Tartaric acid C4-dihydroxy-dicarboxylic acid with different stereoisomers

Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of fermentation. It is commonly mixed with sodium bicarbonate and is sold as baking powder used as a leavening agent in food preparation. The acid itself is added to foods as an antioxidant E334 and to impart its distinctive sour taste. Naturally occurring tartaric acid is a useful raw material in organic chemical synthesis. Tartaric acid is an alpha-hydroxy-carboxylic acid, is diprotic and aldaric in acid characteristics, and is a dihydroxyl derivative of succinic acid.

Enantiomer Stereoisomers which are non-superposable mirror images of each other

In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable, much as one's left and right hands are mirror images of each other that cannot appear identical simply by reorientation. A single chiral atom or similar structural feature in a compound causes that compound to have two possible structures which are non-superposable, each a mirror image of the other. Each member of the pair is termed an enantiomorph ; the structural property is termed enantiomerism. The presence of multiple chiral features in a given compound increases the number of geometric forms possible, though there may still be some perfect-mirror-image pairs.

Phthalic acid Chemical compound

Phthalic acid is an aromatic dicarboxylic acid, with formula C6H4(CO2H)2. It is an isomer of isophthalic acid and terephthalic acid. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale. Phthalic acid is one of three isomers of benzenedicarboxylic acid, the others being isophthalic acid and terephthalic acid.

In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic form. Half of the optically active substance becomes its mirror image (enantiomer) referred as racemic mixtures. If the racemization results in a mixture where the D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. Racemization can proceed through a number of different mechanisms, and it has particular significance in pharmacology as different enantiomers may have different pharmaceutical effects.

Meso compound

A meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereogenic centers, the molecule is not chiral. A meso compound is "superposable" on its mirror image. Two objects can be superposed if all aspects of the objects coincide and it does not produce a "(+)" or "(-)" reading when analyzed with a polarimeter.

Chirality (chemistry) Geometric property of some molecules and ions

In chemistry, a molecule or ion is called chiral if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality. The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property.

Polarimeter

A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance.

Theodore Nicolas Gobley

Theodore (Nicolas) Gobley was born in Paris on 11 May 1811 and died on 1 September 1876 in Bagneres-de-Luchon. He was the first to isolate and ultimately determine the chemical structure of lecithin, the first identified and characterized member of the phospholipids class. He was also a pioneer researcher in the study and analysis of the chemical components of brain tissues.

Chiral resolution, or enantiomeric resolution, is a process in stereochemistry for the separation of racemic compounds into their enantiomers. It is an important tool in the production of optically active compounds, including drugs. Another term with the same meaning is optical resolution.

Isomer Chemical compounds with the same molecular formula but different atomic arrangements

In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae — that is, same number of atoms of each element — but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.

Chirality Difference in shape from a mirror image

Chirality is a property of asymmetry important in several branches of science. The word chirality is derived from the Greek χειρ (kheir), "hand", a familiar chiral object.

Jules Henri Debray was a French chemist.

Bertrand Pelletier French pharmacist and chemist

Bertrand Pelletier was an 18th-century French pharmacist and chemist.

Germaine Benoit was a French chemical engineer, pharmacologist and biologist, best known for her contributions to the study of sympathomimetic drugs.

References

  1. George B. Kauffman & Robin Myers (1998). "Pasteur's Resolution of Racemic Acid: A Sesquicentennial Retrospect and a New Translation" (PDF). The Chemical Educator. 3 (6): 1–4. doi:10.1007/s00897980257a. S2CID   95862598. Archived from the original (PDF) on 2006-01-17.
  2. (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.
  3. (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. Especially see Plate II. and the report of the commission that was appointed to verify Pasteur's findings, pp. 99–117.
  4. Biot (1835) "Mémoire sur la polarization circulaire et sur ses applications à la chimie organique" (Memoir on circular polarization and on its applications to organic chemistry), Mémoires de l'Académie des sciences de l'Institut, 2nd series, 13 : 39–175. That tartaric acid (acide tartarique cristallisé) rotates plane-polarized light is shown in Table G following p. 168. (Note: This article was read to the French Royal Academy of Sciences on 1832 November 5.)
  5. Biot (1838) "Pour discerner les mélanges et les combinaisons chimiques définies ou non définies, qui agissent sur la lumière polarisée; suivies d'applications aux combinaisons de l'acide tartarique avec l'eau, l'alcool et l'esprit de bois" (In order to discern mixtures and chemical combinations, defined or undefined, which act on polarized light; followed by applications to combinations of tartaric acid with water, alcohol [i.e., ethanol], and spirit of wood [i.e., methanol]), Mémoires de l'Académie des sciences de l'Institut, 2nd series, 15 : 93–279.
  6. Yoshito Tobe (2003). "The reexamination of Pasteur's experiment in Japan" (PDF). Mendeleev Communications Electronic Version. 13 (3): 93–94. doi:10.1070/MC2003v013n03ABEH001803. Archived from the original (PDF) on August 31, 2005.
  7. Masao Nakazaki (1979). "Morphology of sodium ammonium tartrate: Pasteur's spontaneous resolution and its reexamination". Kagaku No Ryoiki. 33: 951–962.