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Pyridinium
Pyridinium refers to the cation . It is the conjugate acid of pyridine. Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines. They are prepared by treating pyridine with acids. As pyridine is often used as an organic base in chemical reactions, pyridinium salts are produced in many acid-base reactions. Its salts are often insoluble in the organic solvent, so precipitation of the pyridinium leaving group complex is an indication of the progress of the reaction. Pyridinium cations are aromatic, as determined through Hückel's rule. They are isoelectronic with benzene. ''N''-Alkylpyridinium cations When the acidic proton is replaced by alkyl, the compounds are called ''N''-alkylpyridinium. A simple representative is ''N''-methylpyridinium (). These pyridinium intermediates have been used as electrophiles in synthetic organic chemistry to build dearomatized congeners called dihydropyridines, as demonstrated in one example from Smit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridine
Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated Polymer, polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide. Properties Physical properties Pyridine is diamagnetism, diamagnetic. Its critical point (thermodynamics), critical parameters are: pressure 5.63 MPa, temperature 619 K and volume 248 cm3/mol. In the temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylpyridinium
Methylpyridinium is an ion with the formula . It is the ''N''-methylated derivative of pyridine. It confers no color to its salts. The ion is classified as a quaternary ammonium ion. Preparation and occurrence Methylpyridinium is prepared by treating pyridine with dimethylsulfate: : It is found in some coffee products. It is not present in unroasted coffee beans, but is formed during roasting from its precursor chemical, trigonelline. Ionic liquid The chloride salt of ''N''-methylpyridinium behaves as an ionic liquid. Mixtures of that salt and zinc chloride have been characterised over the temperature range . See also * Pyridinium * 4-Caffeoyl-1,5-quinide 4-Caffeoyl-1,5-quinide (4-caffeoylquinic-1,5-lactone or 4-CQL) is found in roasted coffee beans. It is formed by lactonization of 4-''O''-caffeoylquinic acid during the roasting process. : It is reported to possess opioid antagonist properties i ... * References Pyridinium compounds Ionic liquids Cations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraquat
Paraquat ( trivial name; ), or ''N'',''N''′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is a toxic organic compound with the chemical formula C6H7N)2l2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. It is one of the most widely used herbicides worldwide. It is quick-acting and non-selective, killing green plant tissue on contact. Paraquat is highly toxic to humans and other animals. The toxicity and lethality depends on the dose and how the herbicide is absorbed by the body. In humans, paraquat damages the mouth, stomach, and intestines if it is ingested orally. Once absorbed in the body, paraquat causes particular damage to the lungs, kidneys, and liver. Paraquat's lethality is attributed to its enhancing production of superoxide anions and human lung cells can accumulate paraquat. Paraquat exposure has been strongly linked to the development of Parkinson's disease. Paraquat may be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridinium Chlorochromate
Pyridinium chlorochromate (PCC) is a yellow-orange salt (chemistry), salt with the chemical formula, formula [C5H5NH]+[CrO3Cl]−. It is a reagent in organic synthesis used primarily for organic redox reaction, oxidation of Alcohol (chemistry), alcohols to form carbonyls. A variety of related compounds are known with similar reactivity. PCC offers the advantage of the selective oxidation of alcohols to aldehydes or ketones, whereas many other reagents are less selective. Structure and preparation PCC consists of a pyridinium cation, [C5H5NH]+, and a tetrahedral chlorochromate anion, [CrO3Cl]−. Related salts are also known, such as 1-butylpyridinium chlorochromate, [C5H5N(C4H9)][CrO3Cl] and potassium chlorochromate. PCC is commercially available. Serendipity, Discovered by accident, the reagent was originally prepared via addition of pyridine into a cold solution of chromium trioxide in concentrated hydrochloric acid: :C5H5N + HCl + CrO3 → [C5H5NH][CrO3Cl] In one alternative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridinium Chloride
Pyridinium chloride is an organic chemical compound with a formula of C5H5NHCl. Preparation Pyridinium chloride can be produced by passing hydrogen chloride in pyridine dissolved in diethyl ether. The chemical formula is as follows: : Acidity Containing a pyridinium ion, pyridinium chloride has a pKa of approximately 5, slightly more acidic than that of typical amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...s. This is due to the hybridization of the nitrogen: the nitrogen is sp2 hybridized and more electronegative than those nitrogens in ammonium cations, which are sp3 hybridized. Hence they are stronger acids than amines and can be more easily deprotonated by bases. References {{reflist Pyridinium compounds Hydrochlorides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbicide
Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page for EPA reports on pesticide use ihere Selective herbicides control specific weed species while leaving the desired crop relatively unharmed, while non-selective herbicides (sometimes called "total weed killers") kill plants indiscriminately. The combined effects of herbicides, nitrogen fertilizer, and improved cultivars has increased yields (per acre) of major crops by three to six times from 1900 to 2000. In the United States in 2012, about 91% of all herbicide usage, was determined by weight applied, in agriculture. In 2012, world pesticide expenditures totaled nearly US$24.7 billion; herbicides were about 44% of those sales and constituted the biggest portion, followed by insecticides, fungicides, and fumigants. Herbicide is also used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salt (chemistry)
In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions ( anions), which results in a compound with no net electric charge (electrically neutral). The constituent ions are held together by electrostatic forces termed ionic bonds. The component ions in a salt can be either inorganic, such as chloride (Cl−), or organic, such as acetate (). Each ion can be either monatomic, such as sodium (Na+) and chloride (Cl−) in sodium chloride, or polyatomic, such as ammonium () and carbonate () ions in ammonium carbonate. Salts containing basic ions hydroxide (OH−) or oxide (O2−) are classified as bases, such as sodium hydroxide and potassium oxide. Individual ions within a salt usually have multiple near neighbours, so they are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insoluble
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubility of a substance in a specific solvent is generally measured as the concentration of the solute in a saturated solution, one in which no more solute can be dissolved. At this point, the two substances are said to be at the solubility equilibrium. For some solutes and solvents, there may be no such limit, in which case the two substances are said to be " miscible in all proportions" (or just "miscible"). The solute can be a solid, a liquid, or a gas, while the solvent is usually solid or liquid. Both may be pure substances, or may themselves be solutions. Gases are always miscible in all proportions, except in very extreme situations,J. de Swaan Arons and G. A. M. Diepen (1966): "Gas—Gas Equilibria". ''Journal of Chemical Physics'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precipitation (chemistry)
In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant. The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the supernate or supernatant. The notion of precipitation can also be extended to other domains of chemistry (organic chemistry and biochemistry) and even be applied to the solid phases (e.g. metallurgy and alloys) when solid impurities segregation (materials science), segregate from a solid phase. Supersaturation The precipitation of a compound may occur when its concentration exceeds its solubility. This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution. The formation of a pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cation
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 (e.g. K+ ( potassium ion)) while an anion is a negatively charged ion with more electrons than protons (e.g. Cl− ( chloride ion) and OH− ( hydroxide ion)). 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 ''monatomic ions'', ''atomic ions'' or ''simple ions'', while ions consisting of two or more atoms are termed polyatomic ions or ''molecular ions''. If only a + or − is present, it indic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
