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Optical isomerism is a form of isomerism (specifically stereoisomerism) where the two different isomers are the same in every way except being non-superposable [1] mirror images of each other. Optical isomers are thus chiral (pronounced ki-rall). The study of chirality falls in the domain of stereochemistry. In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. ...
Main article: stereochemistry Stereoisomerism is the arrangement of atoms in molecules whose connectivity remains the same but their arrangement in space is different in each isomer. ...
In geometry, the mirror image of an object or two-dimensional figure is the virtual image formed by reflection in a plane mirror; it is of the same size as the original object, yet different, unless the object or figure has reflection symmetry (also known in the terminology of modern...
Chirality refers to several phenomena, all having to do with objects that differ from their mirror image. ...
The different types of isomers. ...
 The two enantiomers of bromochlorofluoromethane A molecule is chiral when it cannot be superimposed on its mirror image (see diagram). The two mirror image forms referred to as enantiomers. A mixture of equal amounts of the two enantiomers is said to be a racemic mixture. Chirality is of interest because of its application to stereochemistry in inorganic chemistry, organic chemistry, physical chemistry and biochemistry. The two chiral isomers of bromochlorofluoromethane. ...
The two chiral isomers of bromochlorofluoromethane. ...
In chemistry, two stereoisomers are said to be enantiomers if they are mirror images of each other. ...
In chemistry, a racemate is a mixture of equal amounts of left- and right-handed stereoisomers of a chiral molecule. ...
The different types of isomers. ...
Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ...
Organic chemistry is that part of chemistry concerned with the composition, structure, properties, reactions and synthesis of organic compounds. ...
Physical Chemistry is the combined science of physics, chemistry, thermodynamics, and quantum mechanics which functions to provide molecular-level interpretations of observed macroscopic phenomena. ...
Biochemistry is the study of the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ...
It is the symmetry of a molecule (or any other object) that determines whether it is chiral or not. Technically, a molecule is achiral (not chiral) if and only if it has an axis of improper rotation; that is, an n-fold rotation (rotation by 360°/n) followed by a reflection in the plane perpendicular to this axis which maps the molecule onto itself. (See chirality (mathematics).) A chiral molecule is not necessarily dissymmetric (completely devoid of symmetry) as it can have, for example, rotational symmetry. A simplified rule applies to tetrahedrally-bonded carbon, as shown in the illustration: if all four substituents are different, the molecule is chiral. Square with symmetry group D4 Symmetry is a characteristic of geometrical shapes, equations, and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...
In geometry, an improper rotation is the combination of an ordinary rotation of three-dimensional Euclidean space, that keeps the origin fixed, with a coordinate inversion (a vector x goes to −x). ...
In geometry, a figure is chiral (and said to have chirality) if it is not identical to its mirror image, or more particularly if it cannot be mapped to its mirror image by rotations and translations alone. ...
In a tetrahedral molecular geometry a central atom is located at the center with four substituents located at the corners of a tetrahedron. ...
General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...
In organic chemistry, a substituent is an atom or group of atoms subsituted in place of a hydrogen atom on the parent chain of a hydrocarbon. ...
History Via a magneto-optic effect, the (-)-form of an optical isomer rotates the plane of polarization of a beam of polarized light that passes through a quantity of the material in solution counterclockwise , the (+)-form clockwise. It is due to this property that it was discovered and from which it derives the name optical activity. The property was first observed by J.-B. Biot in 1815 [2], and gained considerable importance in the sugar industry, analytical chemistry, and pharmaceuticals. Louis Pasteur deduced in 1848 that the handedness of molecular structure is responsible for optical activity[3]. Artificial composite materials displaying the analog of optical activity but in the microwave regime were introduced by J.C. Bose in 1898 [4], and gained considerable attention from the mid-1980s [5]. Magneto-optic effect: Any one of a number of phenomena in which an electromagnetic wave interacts with a magnetic field, or with matter under the influence of a magnetic field. ...
Rotation of a plane, seen as the rotation of the terrain relative to the plane (exposure time 1. ...
This article treats polarization in electrodynamics. ...
Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. ...
Dissolving table salt in water In chemistry, a solution is a homogeneous mixture composed of one or more substances known as solutes that are dissolved in another substance known as a solvent. ...
A clockwise motion is one that proceeds like the clocks hands: from the top to the right, then down and then to the left, and back to the top. ...
A clockwise motion is one that proceeds like the clocks hands: from the top to the right, then down and then to the left, and back to the top. ...
When polarized light is passed through a substance containing chiral molecules (or nonchiral molecules arranged asymmetrically), the direction of polarization can be changed. ...
Louis Pasteur (December 27, 1822 – September 28, 1895) was a French microbiologist and chemist. ...
1848 is a leap year starting on Saturday of the Gregorian calendar. ...
It has been suggested that left-handed be merged into this article or section. ...
Microwave image of 3C353 galaxy at 8. ...
Naming conventions
By optical activity: (+)- and (-)- An optical isomer can be named by the direction in which it rotates the plane of polarized light. If an isomer rotates the plane clockwise as seen by a viewer towards whom the light is traveling, that isomer is labeled (+). Its counterpart is labeled (-). The (+) and (-) isomers have also been termed d- and l-, respectively (for dextrorotatory and levorotatory). This labeling is easy to confuse with D- and L-.
By configuration: D- and L-
 An optical isomer can be named by the spatial configuration of its atoms. The D/L system does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself, and its two isomers are labeled D and L. Certain chemical manipulations can be performed on glyceraldehyde without affecting its configuration, and its historical use for this purpose (possibly combined with its convenience as one of the smallest commonly-used chiral molecules) has resulted in its use for nomenclature. In this system, compounds are named by analogy to glyceraldehyde, which generally produces unambiguous designations, but is easiest to see in the small biomolecules similar to glyceraldehyde. One example is the amino acid alanine: alanine has two optical isomers, and they are labeled according to which isomer of glyceraldehyde they come from. Glycine, the amino acid derived from glyceraldehyde, incidentally, does not retain its optical activity, since its central carbon is not chiral. Alanine, however, is essentially methylated glycine and shows optical activity. Wikipedia does not have an article with this exact name. ...
Fischer projection of D-glyceraldehyde Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. ...
In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...
Alanine is one of the 20 most common natural amino acids. ...
Glycine (Gly, G) is a nonpolar amino acid. ...
Chirality refers to several phenomena, all having to do with objects that differ from their mirror image. ...
In biochemistry, methylation refers to the replacement of a hydrogen atom (H) with a methyl group (CH3), regardless of the substrate. ...
The D/L labeling is unrelated to (+)/(-); it does not indicate which enantiomer is dextrorotatory and which is levorotatory. Rather, it says that the compound's stereochemistry is related to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde. Nine of the nineteen L-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and D-fructose is also referred to as levulose because it is levorotatory. Dextrorotation is the property of rotating plane polarized light to the right. ...
Levorotation (also spelled laevorotation) is the counterclockwise rotation of plane polarized light. ...
In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...
A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...
Fructose (or levulose) is a simple sugar (monosaccharide) found in many foods and one of the three most important blood sugars along with glucose and galactose. ...
The dextrorotatory isomer of glyceraldehyde is in fact the D isomer, but this was a lucky guess. At the time this system was established, there was no way to tell which configuration was dextrorotatory. (If the guess had turned out wrong, the labeling situation would now be even more confusing.)
A rule of thumb for determining the D/L isomeric form of an amino acid is the "CORN" rule. The groups: In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...
- COOH, R, NH2 and H (where R is an unnamed carbon chain)
are arranged around the chiral center carbon atom. If these groups are arranged counter-clockwise around the carbon atom, then it is the D-form. If clockwise, it is the L-form.
By configuration: R- and S- The R/S system is another nomenclature system for enantiomers which does not involve a reference molecule such as glyceraldehyde. It labels each chiral center R or S according to a system by which its ligands are each assigned a priority, according to the Cahn Ingold Prelog priority rules, based on atomic number. If the center is oriented so that the lowest-priority of the four is pointed away from a viewer, the viewer will then see two possibilities: a clockwise traversal of the remaining three may hit them in decreasing order, or in increasing order. In the first case, the center is labeled R; in the second, it is S. For compounds found in organic chemistry, the Cahn Ingold Prelog priority rules are used to determine the orientation of a molecule for purposes of assigning stereochemistry at a stereocenter and for assigning the name of isomers of molecules possessing double bonds such as alkenes. ...
This system labels each chiral center in a molecule (and also has an extension to chiral molecules not involving chiral centers). It thus has greater generality than the D/L system, and can label, for example, an (R,R) isomer versus an (R,S) — diastereomers. Diastereomers are stereoisomers that are not enantiomers, or mirror images of each other. ...
The R/S system has no fixed relation to the (+)/(-) system. An R isomer can be either dextrorotatory or levorotatory, depending on its exact ligands.
The R/S system also has no fixed relation to the D/L system. For example, one of glyceraldehyde's ligands is a hydroxy group, -OH. If a thiol group, -SH, were swapped in for it, the D/L labeling would, by its definition, not be affected by the substitution. But this substitution would invert the molecule's R/S labeling, due to the fact that sulfur's atomic number is higher than carbon's, whereas oxygen's is lower.
For this reason, the D/L system remains in common use in certain areas, such as amino acid and carbohydrate chemistry. It is convenient to have all of the common amino acids of higher organisms labeled the same way. In D/L, they are all L. In R/S, they are not, conversely, all S — most are, but cysteine, for example, is R, again because of sulfur's higher atomic number.
The word “racemic” is derived from the Latin word for grape; the term having its origins in the work of Louis Pasteur who isolated racemic tartaric acid from wine. Louis Pasteur (December 27, 1822 – September 28, 1895) was a French microbiologist and chemist. ...
Tartaric acid is a white crystalline organic acid. ...
Properties of optical isomers They are identical with respect to ordinary chemical reactions, but differences arise when they are in the presence of other chiral molecules. For example, spearmint leaves and caraway seeds respectively contain L-carvone and D-carvone - enantiomers of carvone. These smell different to most people because our taste receptors also contain chiral molecules which behave differently in the presence of different enantiomers. Binomial name Mentha spicata Crantz Spearmint (Mentha spicata, syn ), yields an aromatic and carminative oil, referred to as oil of spearmint. Many people use the name scotch spearmint for gingermint (Mentha x gracilis, syn ), a hybrid of spearmint and wild mint (Mentha arvensis). ...
Binomial name Carum carvi L. Caraway or Persian cumin (Carum carvi) is a biennial plant that belongs to the Apiaceae, or parsley, family. ...
In a sensory system, a sensory receptor is a structure that recognizes a stimulus in the internal or external environment of an organism. ...
D-form Amino acids tend to taste sweet, whereas L-forms are usually tasteless. This is again due to our chiral taste molecules. The smells of oranges and lemons are examples of the D and L enantiomers. In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...
Penicillin's activity is stereoselective. The antibiotic only works on peptide links of D-alanine which occur in the cell walls of bacteria - but not in humans. The antibiotic can kill only the bacteria, and not us, because we don't have these D-amino acids. Penicillin nucleus Penicillin refers to a group of β-lactam antibiotics used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms. ...
The electric and magnetic fields of polarized light oscillate in a geometric plane. An axis normal to this plane gives the direction of energy propagation. Optically active isomers rotate the plane that the fields oscillate in. The polarized light is actually rotated in a racemic mixture as well, but it is rotated to the left by one of the two enantiomers, and to the right by the other, which cancel out to zero net rotation. This article treats polarization in electrodynamics. ...
Two intersecting planes in R3 In mathematics, a plane is a fundamental two-dimensional object. ...
In chemistry, a racemate is a mixture of equal amounts of left- and right-handed stereoisomers of a chiral molecule. ...
In chemistry two stereoisomers are said to be enantiomers if one can be superimposed on the mirror image of the other, and vice versa. ...
Chirality in biology Many biologically-active molecules are chiral, including the naturally-occurring amino acids (the building blocks of proteins), and sugars. Interestingly, in biological systems most of these compounds are of the same chirality: most amino acids are L and sugars are D. The origin of this homochirality in biology is the subject of much debate. Many chiral drugs must be made with high enantiomeric purity due to potential side-effects of the other enantiomer. (The other enantiomer may also merely be inactive.) Consider a racemic sample of thalidomide. One enantiomer is effective against morning sickness while the other is teratogenic. Unfortunately, in this case administering just one of the enantiomers to a pregnant patient would still be very dangerous as the two enantiomers are readily interconverted in vivo. Thus, if a person is given either enantiomer, both the D and L isomers will eventually be present in the patient's serum. Steroid receptor sites also show stereoisomer specificity. Biology is a branch of science, dealing with the study of life. ...
In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...
A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...
Magnified view of refined sugar crystals. ...
In chemistry, a molecule is chiral if it is not superimposable on its mirror image regardless of how it is contorted. ...
Biology is a branch of science, dealing with the study of life. ...
Alan Pharmaceuticals is a key supplier of thalidomide worldwide. ...
Morning sickness, also called nausea and vomiting of pregnancy (NVP), or pregnancy sickness, affects between 50 and 95 percent of all pregnant women. ...
Teratogenesis is a medical term from the Greek, literally meaning monster-making. ...
A steroid is a lipid characterized by a carbon skeleton with four fused rings. ...
Main article: stereochemistry Stereoisomerism is the arrangement of atoms in molecules whose connectivity remains the same but their arrangement in space is different in each isomer. ...
Chiral objects have different interactions with the two enantiomers of other chiral objects. Enzymes, which are chiral, often distinguish between the two enantiomers of a chiral substrate. Imagine an enzyme as having a glove-like cavity which binds a substrate. If this glove is right handed, then one enantiomer will fit inside and be bound while the other enantiomer will have a poor fit and is unlikely to bind. Ribbon diagram of the enzyme TIM. TIM is catalytically perfect, meaning its conversion rate is limited, or nearly limited to its substrate diffusion rate. ...
Types Most commonly, chiral molecules have point chirality, centering around a single atom, usually carbon, which has four different substituents. The two enantiomers of such compounds are said to have different absolute configurations at this center. This center is thus stereogenic (i.e., a grouping within a molecular entity that may be considered a focus of stereoisomerism), and is exemplified by the α-carbon of amino acids. A molecule can have multiple chiral centers without being chiral overall then called a meso compound if there is a symmetry element (a mirror plane or inversion center) which relates the two (or more) chiral centers. It is also possible for a molecule to be chiral without having actual point chirality. Commonly encountered examples include 1,1'-bi-2-naphthol (BINOL) and 1,3-dichloro-allene which have axial chirality, and (E)-cyclooctene which has planar chirality. Meso compound is a chemical compound whose molecules contain asymmetric centers but which is optically inactive due to overall symmetry. ...
1,1-bi-2-naphthol or 1,1-binaphthol or 1,1-binaphthalene-2,2-diol or BINOL is an organic compound that is often used as a ligand for transition-metal catalysed asymmetric synthesis. ...
Term used to refer to stereoisomerism resulting from the non-planar arrangement of four groups in pairs about a chirality axis. ...
Planar chirality is a special case of chirality in which a molecule does not posess a asymmetric chiral carbon atom but perpendicular disymmetric planes due to restricted rotation around a chemical bond in the molecule. ...
It is important to keep in mind that molecules which are dissolved in solution or are in the gas phase usually have considerable flexibility and thus may adopt a variety of different conformations. These various conformations are themselves almost always chiral. However, when assessing chirality, one must use a structural picture of the molecule which corresponds to just one chemical conformation - the one of lowest energy [6]. In chemistry, a chemical conformation is the spatial arrangement of atoms in a molecule. ...
Chirality in inorganic chemistry Many coordination compounds are chiral; for example the well-known [Ru(2,2'-bipyridine)3]2+ complex in which the three bipyridine ligands adopt a chiral propeller-like arrangement [7]. In this case, the Ru atom may be regarded as a stereogenic centre, with the complex having point chirality. The two enantiomers of complexes such as [Ru(2,2'-bipyridine)3]2+ may be designated as Λ (left-handed twist of the propeller described by the ligands) and Δ (right-handed twist). Hexol is a chiral cobalt complex which was first investigated by Alfred Werner. A complex in chemistry is a reversible association of molecules, atoms, or ions through weak non-covalent chemical bonds. ...
Hexol is a cobalt compound that was first prepared by Alfred Werner in 1914 and represented the first non-carbon-containing chiral compound. ...
See also The different types of isomers. ...
The two optical isomers of bromochlorofluoromethane Chiral synthesis (also called asymmetric synthesis) is organic synthesis which preserves or introduces a desired chirality. ...
Chirality is a manga by Satoshi Urushihara Chirality (Greek handedness, derived from the word stem χειÏ~, ch[e]ir~ - hand~) is an asymmetry property important in several branches of science. ...
In chemistry, two stereoisomers are said to be enantiomers if they are mirror images of each other. ...
References & notes - ↑ Ernest L. Eliel and Samuel H. Wilen (1994). The Sterochemistry of Organic Compounds, Wiley-Interscience.
- ↑ The term non-superposable distinguishes mirror images which are superposable, such as the mirror image of the letter "A", on the original, from those that aren't. The classic example of this are human hands. The left hand is a non-superposable mirror image of the right hand: No matter how the two hands are oriented relative to one another, one cannot line up all the major features of one hand with the other, whereas such an operation is trivial for a non-chiral mirror image (e.g., the letter "A").
- ↑ Lakhtakia, A. (ed.) (1990). Selected Papers on Natural Optical Activity (SPIE Milestone Volume 15), SPIE.
- ↑ Pasteur, L. (1848). "Researches on the molecular asymmetry of natural organic products, English translation of French original, published by Alembic Club Reprints (Vol. 14, pp. 1-46) in 1905, facsimile reproduction by SPIE in a 1990 book"
- ↑ Bose, J. C. (1898). "On the rotation of plane of polarisation of electric waves by a twisted structure, Proc. R. Soc. Lond. (Vol. 63, pp. 146-152), facsimile reproduction by Wiley in a 2000 book"
- ↑ Alex von Zelewsky (1996). Stereochemistry of Coordination Compounds, Wiley.
- ↑ Lakhtakia, A. (1994). Beltrami Fields in Chiral Media, World Scientific.
External links - http://www.chemguide.co.uk/basicorg/isomerism/optical.html#top
- http://www.chemistry.mcmaster.ca/berti/3f03/special_stereochemistry.pdf
- http://www.nature.com/horizon/chemicalspace/highlights/s5_nonspec1.html
- IUPAC nomenclature for amino acid configurations.
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