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43-412: The word 'malic' is derived from Latin mālum , meaning 'apple'. The related Latin word mālus , meaning 'apple tree', is used as the name of the genus Malus , which includes all apples and crabapples; and is the origin of other taxonomic classifications such as Maloideae , Malinae , and Maleae . L -Malic acid is the naturally occurring form, whereas a mixture of L - and D -malic acid

86-403: A crop treatment in horticulture. Click on genes, proteins and metabolites below to link to respective articles. Acetyl-CoA Oxaloacetate Malate Fumarate Succinate Succinyl-CoA Citrate cis- Aconitate Isocitrate Oxalosuccinate 2-oxoglutarate Malus See text Malus ( / ˈ m eɪ l ə s / or / ˈ m æ l ə s / )

129-436: A 1:1 ratio. In his pioneering work, Louis Pasteur was able to isolate the isomers of sodium ammonium tartrate because the individual enantiomers crystallize separately from solution. To be sure, equal amounts of the enantiomorphic crystals are produced, but the two kinds of crystals can be separated with tweezers. This behavior is unusual. A less common method is by enantiomer self-disproportionation . The second strategy

172-561: A molecule as a whole or conformational change converts one chemical into its enantiomer. Chemical structures with chirality rotate plane-polarized light. A mixture of equal amounts of each enantiomer, a racemic mixture or a racemate , does not rotate light. Stereoisomers include both enantiomers and diastereomers . Diastereomers, like enantiomers, share the same molecular formula and are also nonsuperposable onto each other; however, they are not mirror images of each other. There are three common naming conventions for specifying one of

215-403: A pair of molecular entities which are mirror images of each other and non-superposable. Enantiomers of each other are much like one's right and left hands; without mirroring one of them, hands cannot be superposed onto each other. It is solely a relationship of chirality and the permanent three-dimensional relationships among molecules or other chemical structures: no amount of re-orientiation of

258-406: A racemic drug to an enantiopure drug is called a chiral switch . In many cases, the enantiomers have distinct effects. One case is that of Propoxyphene. The enantiomeric pair of propoxyphene is separately sold by Eli Lilly and company. One of the partners is dextropropoxyphene , an analgesic agent (Darvon) and the other is called levopropoxyphene , an effective antitussive (Novrad).  It

301-455: A serrated margin. The flowers are borne in corymbs , and have five petals , which may be white, pink, or red, and are perfect , with usually red stamens that produce copious pollen , and a half-inferior ovary ; flowering occurs in the spring after 50–80 growing degree days (varying greatly according to subspecies and cultivar ). Many apples require cross-pollination between individuals by insects (typically bees , which freely visit

344-528: A tart taste to wine ; the amount decreases with increasing fruit ripeness . The taste of malic acid is very clear and pure in rhubarb , a plant for which it is the primary flavor. It is also the compound responsible for the tart flavor of sumac spice. It is also a component of some artificial vinegar flavors, such as "salt and vinegar" flavored potato chips. The process of malolactic fermentation converts malic acid to much milder lactic acid . Malic acid occurs naturally in all fruits and many vegetables, and

387-646: Is Enantioconvergent synthesis , the synthesis of one enantiomer from a racemic precursor, utilizing both enantiomers. By making use of a chiral catalyist, both enantiomers of the reactant result in a single enantiomer of product. Enantiomers may not be isolable if there is an accessible pathway for racemization (interconversion between enantiomorphs to yield a racemic mixture) at a given temperature and timescale. For example, amines with three distinct substituents are chiral, but with few exceptions (e.g. substituted N -chloroaziridines), they rapidly undergo " umbrella inversion " at room temperature, leading to racemization. If

430-621: Is a genus of about 32–57 species of small deciduous trees or shrubs in the family Rosaceae , including the domesticated orchard apple , crab apples (sometimes known in North America as crabapples ) and wild apples . The genus is native to the temperate zone of the Northern Hemisphere . Apple trees are typically 4–12 metres (13–39 feet) tall at maturity, with a dense, twiggy crown. The leaves are 3–10 centimetres ( 1 + 1 ⁄ 4 –4 inches) long, alternate, simple, with

473-451: Is a racemate [1:1 mixture of ( S )-citalopram and ( R )-citalopram]; escitalopram [( S )-citalopram] is a pure enantiomer. The dosages for escitalopram are typically 1/2 of those for citalopram. Here, (S)-citalopram is called a chiral switch of Citalopram. Enantiopure compounds consist of only one of the two enantiomers. Enantiopurity is of practical importance since such compositions have improved therapeutic efficacy. The switch from

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516-487: Is a globose pome , varying in size from 1–4 cm ( 1 ⁄ 2 – 1 + 1 ⁄ 2  in) in diameter in most of the wild species, to 6 cm ( 2 + 1 ⁄ 4  in) in M. sylvestris sieversii , 8 cm (3 in) in M. domestica , and even larger in certain cultivated orchard apples. The centre of the fruit contains five carpels arranged star-like, each containing one or two seeds . 36 species and 4 hybrids are accepted. The genus Malus

559-409: Is asymmetric synthesis: the use of various techniques to prepare the desired compound in high enantiomeric excess . Techniques encompassed include the use of chiral starting materials ( chiral pool synthesis ), the use of chiral auxiliaries and chiral catalysts , and the application of asymmetric induction . The use of enzymes ( biocatalysis ) may also produce the desired compound. A third strategy

602-754: Is called a chirality center , a type of stereocenter . A chirality center is also called a chiral center or an asymmetric center . Some sources use the terms stereocenter , stereogenic center , stereogenic atom or stereogen to refer exclusively to a chirality center, while others use the terms more broadly to refer also to centers that result in diastereomers (stereoisomers that are not enantiomers). Compounds that contain exactly one (or any odd number) of asymmetric atoms are always chiral. However, compounds that contain an even number of asymmetric atoms sometimes lack chirality because they are arranged in mirror-symmetric pairs, and are known as meso compounds . For instance, meso tartaric acid (shown on

645-429: Is described by one of the chiral point groups : C n , D n , T, O, or I. For example, hydrogen peroxide is chiral and has C 2 (two-fold rotational) symmetry. A common chiral case is the point group C 1 , meaning no symmetries, which is the case for lactic acid. An example of such an enantiomer is the sedative thalidomide , which was sold in a number of countries around the world from 1957 until 1961. It

688-455: Is generated in fruit metabolism. Malic acid, when added to food products, is denoted by E number E296. It is sometimes used with or in place of the less sour citric acid in sour sweets. These sweets are sometimes labeled with a warning stating that excessive consumption can cause irritation of the mouth. It is approved for use as a food additive in the EU, US and Australia and New Zealand (where it

731-415: Is interesting to note that the trade names of the drugs, DARVON and NOVRAD, also reflect the chemical mirror-image relationship. In other cases, there may be no clinical benefit to the patient. In some jurisdictions, single-enantiomer drugs are separately patentable from the racemic mixture. It is possible that only one of the enantiomers is active. Or, it may be that both are active, in which case separating

774-449: Is listed by its INS number 296). Malic acid contains 10 kJ (2.39 kilocalories) of energy per gram. Racemic malic acid is produced industrially by the double hydration of maleic anhydride . In 2000, American production capacity was 5,000 tons per year. The enantiomers may be separated by chiral resolution of the racemic mixture. S -Malic acid is obtained by fermentation of fumaric acid . Self-condensation of malic acid in

817-487: Is not an important crop in most areas, being extremely sour due to malic acid (which like the genus derives from the Latin name mālum ), and in some species woody, so is rarely eaten raw. In some Southeast Asian cultures, they are valued as a sour condiment , sometimes eaten with salt and chilli or shrimp paste . Some crabapple varieties are an exception to the reputation of being sour, and can be very sweet, such as

860-491: Is produced synthetically. Malate plays an important role in biochemistry . In the C4 carbon fixation process, malate is a source of CO 2 in the Calvin cycle . In the citric acid cycle , ( S )-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions . Malate is also synthesized by

903-800: Is subdivided into eight sections (six, with two added in 2006 and 2008). The oldest fossils of the genus date to the Eocene ( Lutetian ), which are leaves belonging to the species Malus collardii and Malus kingiensis from western North America (Idaho) and the Russian Far East ( Kamchatka ), respectively. 36 species and four natural hybrids are accepted: After Crabapples are popular as compact ornamental trees, providing blossom in spring and colourful fruit in autumn. The fruits often persist throughout winter. Numerous hybrid cultivars have been selected. Some crabapples are used as rootstocks for domestic apples to add beneficial characteristics. For example,

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946-447: Is the main acid in many fruits, including apricots , blackberries , blueberries , cherries , grapes , mirabelles , peaches , pears , plums , and quince , and is present in lower concentrations in other fruits, such as citrus. It contributes to the sourness of unripe apples. Sour apples contain high proportions of the acid. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/L. It confers

989-399: Is used to make handles of hand saws ; in the early 1900s 2,000,000 board feet of applewood were used annually for this purpose. Enantiomer In chemistry , an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ih-NAN-tee-ə-mər ; from Ancient Greek ἐναντίος (enantíos) 'opposite', and μέρος (méros) 'part') – also called optical isomer , antipode , or optical antipode – is one of

1032-419: The carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential , allowing water to enter the cell and promote aperture of the stomata. Malic acid

1075-405: The pagan Anglo-Saxon Nine Herbs Charm , recorded in the 10th century. Applewood gives off a pleasant scent when burned, and smoke from an applewood fire gives an excellent flavour to smoked foods. It is easier to cut when green; dry applewood is exceedingly difficult to carve by hand. It is a good wood for cooking fires because it burns hot and slow, without producing much flame. Applewood

1118-399: The 'Chestnut' cultivar. Crabapples are an excellent source of pectin . Using sugar and spices such as ginger, nutmeg, cinnamon, and allspice, their juice can be made into ruby-coloured crab apple jelly with a full, spicy flavour. A small percentage of crabapples in cider makes a more interesting flavour. As Old English Wergulu , the crab apple is one of the nine plants invoked in

1161-438: The (−)-chlorosuccinic acid. The cycle is completed when silver oxide takes this compound back to (−)-malic acid. L -malic acid is used to resolve α-phenylethylamine , a versatile resolving agent in its own right. Soil supplementation with molasses increases microbial synthesis of malic acid. This is thought to occur naturally as part of soil microbe suppression of disease , so soil amendment with molasses can be used as

1204-529: The apple trees. In emergencies, a bucket or drum bouquet of crabapple flowering branches is placed near the beehives as orchard pollenizers. Because of the plentiful blossoms and small fruit, crabapples are popular for use in bonsai culture. These cultivars have won the Royal Horticultural Society 's Award of Garden Merit :- Other varieties are dealt with under their species names. The seeds contain cyanide compounds. Crabapple fruit

1247-429: The direction in which the polarization of light rotates as it passes through a solution containing the molecule. When a molecule is denoted dextrorotatory, it rotates the plane of polarized light clockwise and can also be denoted as (+). When it is denoted as levorotatory, it rotates the plane of polarized light counterclockwise and can also be denoted as (−). The Latin words for left are laevus and sinister , and

1290-428: The flowers for both nectar and pollen ); these are called self-sterile, so self-pollination is impossible, making pollinating insects essential. A number of cultivars are self-pollinating, such as 'Granny Smith' and 'Golden Delicious', but are considerably fewer in number compared to their cross-pollination dependent counterparts. Several Malus species, including domestic apples, hybridize freely. The fruit

1333-542: The mixture has no objective benefits, but extends the drug's patentability. In the absence of an effective enantiomeric environment ( precursor , chiral catalyst , or kinetic resolution ), separation of a racemic mixture into its enantiomeric components is impossible, although certain racemic mixtures spontaneously crystallize in the form of a racemic conglomerate , in which crystals of the enantiomers are physically segregated and may be separated mechanically. However, most racemates form crystals containing both enantiomers in

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1376-705: The molecule is reflected; however, an atom or group within the molecule is changed to a similar atom or group. Quasi -enantiomers can also be defined as molecules that have the potential to become enantiomers if an atom or group in the molecule is replaced. An example of quasi -enantiomers would ( S )-bromobutane and ( R )-iodobutane. Under normal conditions the enantiomers for ( S )-bromobutane and ( R )-iodobutane would ( R)- bromobutane and ( S )-iodobutane respectively. Quasi -enantiomers would also produce quasi-racemates, which are similar to normal racemates (see Racemic mixture ) in that they form an equal mixture of quasi -enantiomers. Though not considered actual enantiomers,

1419-430: The molecule's geometry with respect to a chiral center. The R/S system is assigned to a molecule based on the priority rules assigned by Cahn–Ingold–Prelog priority rules , in which the group or atom with the largest atomic number is assigned the highest priority and the group or atom with the smallest atomic number is assigned the lowest priority. The (+) or (−) symbol is used to specify a molecule's optical rotation —

1462-401: The order of 10 eV or 10 kJ/mol or less) due to the weak neutral current mechanism. This difference in energy is far smaller than energy changes caused by even small changes in molecular conformation, and far too small to measure by current technology, and is therefore chemically inconsequential. In the sense used by particle physicists, the "true" enantiomer of a molecule, which has exactly

1505-504: The presence of fuming sulfuric acid gives the pyrone coumalic acid : Carbon monoxide and water are liberated during this reaction. Malic acid was important in the discovery of the Walden inversion and the Walden cycle , in which (−)-malic acid first is converted into (+)-chlorosuccinic acid by action of phosphorus pentachloride . Wet silver oxide then converts the chlorine compound to (+)-malic acid, which then reacts with PCl 5 to

1548-411: The racemization is fast enough, the molecule can often be treated as an achiral, averaged structure. For all intents and purposes, each enantiomer in a pair has the same energy. However, theoretical physics predicts that due to parity violation of the weak nuclear force (the only force in nature that can "tell left from right"), there is actually a minute difference in energy between enantiomers (on

1591-421: The right) has two asymmetric carbon atoms, but it does not exhibit enantiomerism because there is a mirror symmetry plane. Conversely, there exist forms of chirality that do not require asymmetric atoms, such as axial , planar , and helical chirality. Even though a chiral molecule lacks reflection (C s ) and rotoreflection symmetries (S 2 n ), it can have other molecular symmetries , and its symmetry

1634-422: The rootstocks of Malus baccata varieties are used to give additional cold hardiness to the combined plants for orchards in cold northern areas. They are also used as pollinizers in apple orchards . Varieties of crabapple are selected to bloom contemporaneously with the apple variety in an orchard planting, and the crabs are planted every sixth or seventh tree, or limbs of a crab tree are grafted onto some of

1677-449: The same mass-energy content as the original molecule, is a mirror-image that is also built from antimatter (antiprotons, antineutrons, and positrons). Throughout this article, "enantiomer" is used only in the chemical sense of compounds of ordinary matter that are not superposable on their mirror image. Quasi -enantiomers are molecular species that are not strictly enantiomers, but behave as if they are. In quasi -enantiomers majority of

1720-445: The two enantiomers (the absolute configuration ) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents d - and l -) is based on its optical rotation properties; and the D / L system is based on the molecule's relationship to enantiomers of glyceraldehyde . The R/S system is based on

1763-539: The word for right is dexter (or rectus in the sense of correct or virtuous). The English word right is a cognate of rectus . This is the origin of the D/L and R/S notations, and the employment of prefixes levo- and dextro- in common names . The prefix ar- , from the Latin recto (right), is applied to the right-handed version; es- , from the Latin sinister (left), to the left-handed molecule. Example: ketamine , arketamine , esketamine . The asymmetric atom

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1806-452: Was first isolated from apple juice by Carl Wilhelm Scheele in 1785. Antoine Lavoisier in 1787 proposed the name acide malique , which is derived from the Latin word for apple, mālum —as is its genus name Malus . In German it is named Äpfelsäure (or Apfelsäure ) after plural or singular of a sour thing from the apple fruit, but the salt(s) are called Malat(e) . Malic acid

1849-448: Was withdrawn from the market when it was found to cause birth defects. One enantiomer caused the desirable sedative effects, while the other, unavoidably present in equal quantities, caused birth defects. The herbicide mecoprop is a racemic mixture, with the ( R )-(+)-enantiomer ("Mecoprop-P", "Duplosan KV") possessing the herbicidal activity. Another example is the antidepressant drugs escitalopram and citalopram . Citalopram

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