Chirality (chemistry)In chemistry, a molecule or ion is called chiral (ˈkaɪrəl) if it cannot be superposed on its by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (kaɪˈrælɪti). The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion.
StereoisomerismIn stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.
StereochemistryStereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which by definition have the same molecular formula and sequence of bonded atoms (constitution), but differ in the geometric positioning of the atoms in space. For this reason, it is also known as 3D chemistry—the prefix "stereo-" means "three-dimensionality".
Racemic mixtureIn chemistry, a racemic mixture or racemate (reɪˈsiːmeɪt,_rə-,_ˈræsɪmeɪt), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. He manually separated the crystals of a mixture by hand, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid.
Optical rotationOptical 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.
StereocenterIn stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups creates a new stereoisomer. Stereocenters are also referred to as stereogenic centers. A stereocenter is geometrically defined as a point (location) in a molecule; a stereocenter is usually but not always a specific atom, often carbon.
ThalidomideThalidomide, sold under the brand names Contergan and Thalomid among others, is an oral medication used to treat a number of cancers (e.g. multiple myeloma), graft-versus-host disease, and many skin disorders (e.g. complications of leprosy such as skin lesions). While thalidomide has been used in a number of HIV-associated conditions, such use is associated with increased levels of the virus. Common side effects include sleepiness, rash, and dizziness. Severe side effects include tumor lysis syndrome, blood clots, and peripheral neuropathy.
DiastereomerIn stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other. When two diastereoisomers differ from each other at only one stereocenter, they are epimers.
ChiralityChirality kaɪˈrælɪtiː 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. An object or a system is chiral if it is distinguishable from its ; that is, it cannot be superimposed onto it. Conversely, a mirror image of an achiral object, such as a sphere, cannot be distinguished from the object. A chiral object and its mirror image are called enantiomorphs (Greek, "opposite forms") or, when referring to molecules, enantiomers.
Tartaric acidTartaric 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.
