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Oxalate
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 tra ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethyl Oxalate
Dimethyl oxalate is the organic compound with the formula (CO2CH3)2. It is the dimethyl ester of oxalic acid. Dimethyl oxalate is a colorless or white solid that is soluble in water. Production Dimethyl oxalate can be obtained by esterification of oxalic acid with methanol using sulfuric acid as a catalyst: :\rm 2\ CH_3OH + (CO_2H)_2\ \xrightarrow\ (CO_2CH_3)_2 + 2\ H_2O Oxidative carbonylation route The preparation by oxidative carbonylation has attracted interest because it requires only C1 precursors: :\rm 4 \ CH_3OH + 4 \ CO + O_2 \xrightarrow\ 2 \ (CO_2CH_3)_2 + 2 \ H_2O The reaction is catalyzed by Pd2+.E. Amadio''Oxidative Carbonylation of Alkanols Catalyzed by Pd(II)-Phosphine Complexes'' PhD Thesis, Ca’Foscari University Venice, 2009 The synthesis gas is mostly obtained from coal or biomass. The oxidation proceeds via dinitrogen trioxide, which is formed according to (1) of nitrogen monoxide and oxygen and then reacts according to (2) with methanol forming meth ... [...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] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinach
Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either fresh, or after storage using preservation techniques by canning, freezing, or dehydration. It may be eaten cooked or raw, and the taste differs considerably; the high oxalate content may be reduced by steaming. It is an annual plant (rarely biennial), growing as tall as . Spinach may overwinter in temperate regions. The leaves are alternate, simple, ovate to triangular, and very variable in size: long and broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, in diameter, and mature into a small, hard, dry, lumpy fruit cluster across containing several seeds. In 2018, world production of spinach was 26.3 million tonnes, with China al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dianion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds. Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhubarb
Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of '' Rheum'' in the family Polygonaceae, which are cooked and used for food. The whole plant – a herbaceous perennial growing from short, thick rhizomes – is also called rhubarb. Historically, different plants have been called "rhubarb" in English. The large, triangular leaves contain high levels of oxalic acid and anthrone glycosides, making them inedible. The small flowers are grouped in large compound leafy greenish-white to rose-red inflorescences. The precise origin of culinary rhubarb is unknown. The species '' Rheum rhabarbarum'' (syn. ''R. undulatum'') and '' R. rhaponticum'' were grown in Europe before the 18th century and used for medicinal purposes. By the early 18th century, these two species and a possible hybrid of unknown origin, ''R.'' × ''hybridum'', were grown as vegetable crops in England and Scandinavia. They readily hybridize, and cul ... [...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 grass family. Buckwheat is related to sorrel, 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 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 PIE *''bhago''-) and ''weite'' (Mod. Dut. ''tarwe'', antiquated Dut. ' ... [...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 elsewhe ... [...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'' ssp. ' ... [...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] |
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