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Oxalates
Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl oxalate (C2O4(CH3)2). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate. Relationship to oxalic acid The dissociation of protons from oxalic acid proceeds in a stepwise manner; as for other polyprotic acids, loss of a single proton results in the monovalent hydrogenoxalate anion . A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant ( ''K''a) for loss of the first proton is (p''K''a = 1.27). The loss of the second proton, which yields the oxalate ion, has an equilibrium constant of (p''K''a = 4.28). These values imply, in solutions with neutral pH, no oxalic acid and only trace am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Oxalate
Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula Na2C2O4. It is a white, crystalline, odorless solid, that decomposes above 290 °C. Disodium oxalate can act as a reducing agent, and it may be used as a primary standard for standardizing potassium permanganate (KMnO4) solutions. The mineral form of sodium oxalate is natroxalate. It is only very rarely found and restricted to extremely sodic conditions of ultra-alkaline pegmatites. Preparation Sodium oxalate can be prepared through the neutralization of oxalic acid with sodium hydroxide (NaOH) in a 1:2 acid-to-base molar ratio. Evaporation yields the anhydrous oxalateH. W. Foote and John E. Vance (1933), "The system; sodium iodate, sodium oxalate, water". ''American Journal of Science'', series 5, volume 26, issue 151, pages 16-18. that can be thoroughly dried by heating to between 200 and 250 °C. Half-neutralization can be accomplished with NaOH in a 1:1 ratio which produces NaHC2O4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxalic Acid
Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early investigators isolated oxalic acid from flowering plants of the genus '' Oxalis'', commonly known as wood-sorrels. It occurs naturally in many foods. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous. Oxalic acid has much greater acid strength than acetic acid. It is a reducing agent and its conjugate base, known as oxalate (), is a chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the formula . History The preparation of salts of oxalic acid (crab acid) from plants had been known, at least since 1745, when the Dutch botanist and physician Herman Boerhaave isolated a salt from wood sorrel. By 1773, François Pierre Savary of Fribourg, Switzerland had isolated oxalic acid fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogenoxalate
Hydrogenoxalate or hydrogen oxalate is an anion with chemical formula or , derived from oxalic acid by the loss of a single proton; or, alternatively, from the oxalate anion by addition of a proton. The name is also used for any salt containing this anion. Especially in older literature, hydrogenoxalates may also be referred to as bioxalates, acid oxalates, or monobasic oxalates. Hydrogenoxalate is amphoteric, in that it can react both as an acid or a base. Well characterized salts include sodium hydrogenoxalate (), potassium hydrogenoxalate (), ammonium hydrogenoxalate (), rubidium hydrogenoxalate () and dimethylammonium hydrogenoxalate (()). Structure Most hydrogenoxalate salts are hydrated. For example, potassium hydrogen oxalate crystallizes as 2·. These materials exhibit extended structures resulting from extensive hydrogen bonding and anion-cation interactions. The hydrates dehydrate upon heating: :2· → 2 + Proton transfe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pi Interaction
In chemistry, π-effects or π-interactions are a type of non-covalent interaction that involves π systems. Just like in an electrostatic interaction where a region of negative charge interacts with a positive charge, the electron-rich π system can interact with a metal (cationic or neutral), an anion, another molecule and even another π system. Non-covalent interactions involving π systems are pivotal to biological events such as protein-ligand recognition. Types The most common types of π-interactions involve: *Metal–π interactions: involves interaction of a metal and the face of a π system, the metal can be a cation (known as cation–π interactions) or neutral *Polar–π interactions: involves interaction of a polar molecule and quadrupole moment a π system. * Aromatic–aromatic interactions (π stacking): involves interactions of aromatic molecules with each other. **Arene–perfluoroarene interaction: electron-rich benzene ring interacts with electron-poor hexa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poppy Seed
Poppy seed is an oilseed obtained from the opium poppy ('' Papaver somniferum''). The tiny, kidney-shaped seeds have been harvested from dried seed pods by various civilizations for thousands of years. It is still widely used in many countries, especially in Central Europe and South Asia, where it is legally grown and sold in shops. The seeds are used whole or ground into meal as an ingredient in many foods – especially in pastry and bread – and they are pressed to yield poppyseed oil. History The poppy seed is mentioned in ancient medical text from many civilizations. For instance, the Egyptian papyrus scroll named Ebers Papyrus, written c. 1550 BC, lists poppy seed as a sedative. The Minoan civilization (approximately 2700 to 1450 BC), a Bronze Age civilization which arose on the island of Crete, cultivated poppies for their seed, and used a milk, opium and honey mixture to calm crying babies. The Sumerians are another civilization that are known to have grown poppy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parsley
Parsley, or garden parsley (''Petroselinum crispum'') is a species of flowering plant in the family Apiaceae that is native to the central and eastern Mediterranean region (Sardinia, Lebanon, Israel, Cyprus, Turkey, southern Italy, Greece, Portugal, Spain, Malta, Morocco, Algeria, and Tunisia), but has been naturalized elsewhere in Europe, and is widely cultivated as a herb, and a vegetable. Parsley is widely used in European, Middle Eastern, and American cuisine. Curly leaf parsley is often used as a garnish. In central Europe, eastern Europe, and southern Europe, as well as in western Asia, many dishes are served with fresh green chopped parsley sprinkled on top. Flat leaf parsley is similar, but it is easier to cultivate, some say it has a stronger flavor. Root parsley is very common in central, eastern, and southern European cuisines, where it is used as a snack or a vegetable in many soups, stews, and casseroles. It is believed to have been originally grown in S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Pepper
Black pepper (''Piper nigrum'') is a flowering vine in the family Piperaceae, cultivated for its fruit, known as a peppercorn, which is usually dried and used as a spice and seasoning. The fruit is a drupe (stonefruit) which is about in diameter (fresh and fully mature), dark red, and contains a stone which encloses a single pepper seed. Peppercorns and the ground pepper derived from them may be described simply as ''pepper'', or more precisely as ''black pepper'' (cooked and dried unripe fruit), ''green pepper'' (dried unripe fruit), or ''white pepper'' (ripe fruit seeds). Black pepper is native to the Malabar Coast of India, and the Malabar pepper is extensively cultivated there and in other tropical regions. Ground, dried, and cooked peppercorns have been used since antiquity, both for flavour and as a traditional medicine. Black pepper is the world's most traded spice, and is one of the most common spices added to cuisines around the world. Its spiciness is due to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carambola
Carambola, also known as star fruit, is the fruit of '' Averrhoa carambola'', a species of tree native to tropical Southeast Asia. The mildly poisonous fruit is commonly consumed in parts of Brazil, Southeast Asia, South Asia, the South Pacific, Micronesia, parts of East Asia, the United States, and the Caribbean and contains the neurotoxin caramboxin. The tree is cultivated throughout tropical areas of the world. The fruit has distinctive ridges running down its sides (usually 5–6). When cut in cross-section, it resembles a star, giving it the name of ''star fruit''. The entire fruit is edible, usually raw, and may be cooked or made into relishes, preserves, garnish, and juices. Origins and distribution The center of diversity and the original range of ''Averrhoa carambola'' is tropical Southeast Asia, where it has been cultivated over centuries. It was introduced to the Indian Subcontinent and Sri Lanka by Austronesian traders, along with ancient Austronesian cult ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxalis
''Oxalis'' ( (American English) or (British English)) is a large genus of flowering plants in the wood-sorrel family Oxalidaceae, comprising over 550 species. The genus occurs throughout most of the world, except for the polar areas; species diversity is particularly rich in tropical Brazil, Mexico, and South Africa. Many of the species are known as wood sorrels (sometimes written "woodsorrels" or "wood-sorrels") as they have an acidic taste reminiscent of the sorrel proper (''Rumex acetosa''), which is only distantly related. Some species are called yellow sorrels or pink sorrels after the color of their flowers instead. Other species are colloquially known as false shamrocks, and some called sourgrasses. For the genus as a whole, the term oxalises is also used. Description and ecology These plants are annual or perennial. The leaves are divided into three to ten or more obovate and top-notched leaflets, arranged palmately with all the leaflets of roughly equal size. The m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sorrel
Sorrel (''Rumex acetosa''), also called common sorrel or garden sorrel, is a perennial herbaceous plant in the family Polygonaceae. Other names for sorrel include spinach dock and narrow-leaved dock ('dock' being a common name for the genus '' Rumex''). Sorrel is native to Eurasia and a common plant in grassland habitats. It is often cultivated as a leaf vegetable or herb. Description Sorrel is a slender herbaceous perennial plant about high, with roots that run deep into the ground, as well as juicy stems and arrow-shaped (sagittate) leaves. The lower leaves are in length with long petioles and a membranous ocrea formed of fused, sheathing stipules. The upper ones are sessile, and frequently become crimson. It has whorled spikes of reddish-green flowers, which bloom in early summer, becoming purplish. The species is dioecious, with stamens and pistils on different plants. Subspecies Several subspecies have been named. Not all are cultivated. * ''Rumex acetosa'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chenopodium Album
''Chenopodium album'' is a fast-growing weedy annual plant in the genus ''Chenopodium''. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach and fat-hen, though the latter two are also applied to other species of the genus ''Chenopodium'', for which reason it is often distinguished as white goosefoot.BSBIDatabase of names (xls file) ''Chenopodium album'' is extensively cultivated and consumed in Northern India, Nepal, and Pakistan as a food crop known as ''bathua''. Distribution Its native range is obscure due to extensive cultivation, but includes most of Europe,Flora Europaea''Chenopodium album''/ref> from where Linnaeus described the species in 1753.Linnaeus, C. (1753). ''Species Plantarum'' 1: 219Facsimile Plants native in eastern Asia are included under ''C. album'', but often differ from European specimens.Flora of China''Chenopodium album''/ref> It is widely naturalised elsewher ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buckwheat
Buckwheat (''Fagopyrum esculentum''), or common buckwheat, is a flowering plant in the knotweed family Polygonaceae cultivated for its grain-like seeds and as a cover crop. The name "buckwheat" is used for several other species, such as ''Fagopyrum tataricum'', a domesticated food plant raised in Asia. Despite its name, buckwheat is not closely related to wheat. It is not a cereal, nor is it even a member of the Poaceae, grass family. Buckwheat is related to sorrel, Polygonum, knotweed, and rhubarb, and is known as a pseudocereal because its seeds' culinary use is the same as cereals, owing to their high starch content. Etymology The name "buckwheat" or "beech wheat" comes from its triangular seeds, which resemble the much larger seeds of the beech nut from the beech, beech tree, and the fact that it is used like wheat. The word may be a translation of Middle Dutch ''boecweite'': ''boec'' (Modern Dutch ''beuk''), "beech" (see Proto-Indo-European language, PIE *''bhago''-) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
