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Pyrazine
Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2. It is a symmetrical molecule with point group D2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a ''"deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour"''. Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anions and decrease nitric oxide production in human granulocytes. Synthesis Many methods exist for the organic synthesis of pyrazine and its derivatives. Some of these are among the oldest synthesis reactions still in use. In the Staedel–Rugheimer pyrazine synthesis (1876), 2-chloroacetophenone is reacted with ammonia to the amino ketone, then condensed and then oxidized to a pyrazine. A variation is the Gutknecht pyrazine synthesis (1879) also based on this selfcondensation, but di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkylpyrazine
Alkylpyrazines are chemical compounds based on pyrazine with different substitution patterns. Some alkylpyrazines are naturally occurring highly Aroma compound, aromatic substances which often have a very low odor threshold and contribute to the taste and aroma of various foods including cocoa, baked goods, coffee and wines. Alkylpyrazines are also formed during the cooking of some foods via Maillard reactions. Examples File:2-Methylpyrazine.svg , 2-Methylpyrazine (found in roasted sesame) File:2,3-Dimethylpyrazine.svg , 2,3-Dimethylpyrazine (found in roasted sesame) File:2,5-Dimethylpyrazine.svg , 2,5-Dimethylpyrazine (asparagus, tea, crispbread, malt, shrimp, soy, squid, Swiss cheese, bread, roasted sesame) File:Tetramethylpyrazine v2.svg , 2,3,5,6-Tetramethylpyrazine (nattō, fermented cocoa beans) 2-Methylpyrazine 2-Methylpyrazine was the volatile odorant found at the highest concentration in roasted sesame seed oil. 2,3-Dimethylpyrazine 2,3-Dimethylpyrazine is a compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramethylpyrazine
Tetramethylpyrazine, also known as ligustrazine, is a chemical compound found in nattō and in fermented cocoa beans. In an observational study, tetramethylpyrazine was the dominant volatile organic compound in one sourdough starter. When purified, tetramethylpyrazine is a colorless solid. It is classified as an alkylpyrazine. Its biosynthesis involves amination of acetoin, the latter derived from pyruvate. It exhibits potential nootropic Nootropics ( or ) (colloquially brain supplements, smart drugs, cognitive enhancers, memory enhancers, or brain boosters) are chemical substances which purportedly improve cognitive functions, such as attention, memory, wakefulness, and self ... and antiinflammatory activities in rats. References Anti-inflammatory agents Pyrazines Fermented soy-based foods Components of chocolate {{heterocyclic-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrazines
Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2. It is a symmetrical molecule with point group D2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a ''"deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour"''. Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods. Tetramethylpyrazine (also known as ligustrazine) is reported to scavenge superoxide anions and decrease nitric oxide production in human granulocytes. Synthesis Many methods exist for the organic synthesis of pyrazine and its derivatives. Some of these are among the oldest synthesis reactions still in use. In the Staedel–Rugheimer pyrazine synthesis (1876), 2-chloroacetophenone is reacted with ammonia to the amino ketone, then condensed and then oxidized to a pyrazine. A variation is the Gutknecht pyrazine synthesis (1879) also based on this selfcondensation, but dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methoxypyrazines
Methoxypyrazines are a class of chemical compounds that produce odors. The odors tend to be undesirable, as in the case of certain wines, or as defensive chemicals used by insects such as ''Harmonia axyridis'' which produces isopropyl methoxy pyrazine (IPMP). They have also been identified as List of additives in cigarettes, additives in cigarette manufacture. Detection thresholds are very low, typically near 2 parts per trillion (1 ng/L). Examples of methoxypyrazines in wine grapes Cabernet Sauvignon has high levels of methoxypyrazines.Oz Clarke ''Encyclopedia of Grapes'' pg 223 Harcourt Books 2001 Two methoxypyrazine compounds, 3-isobutyl-2-methoxypyrazine (IBMP) and 3-isopropyl-2-methoxypyrazine (IPMP), are considered to be important determinants of "green" (i.e., herbal, grassy, or vegetal) flavours in Sauvignon blanc wines.Marais, J., Hunter, J.J., & Haasbroek, P.D. (1999). Effect of microclimate, season and region on Sauvignon blanc grape composition and wine qual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrimidine
Pyrimidine (; ) is an aromatic, heterocyclic, organic compound similar to pyridine (). One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine (nitrogen atoms at the 1 and 4 positions) and pyridazine (nitrogen atoms at the 1 and 2 positions). In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U). Occurrence and history The pyrimidine ring system has wide occurrence in nature as substituted and ring fused compounds and derivatives, including the nucleotides cytosine, thymine and uracil, thiamine (vitamin B1) and alloxan. It is also found in many synthetic compounds such as barbiturates and the HIV drug zidovudine. Although pyrimidine derivatives such as alloxan were known in the early 19th century, a laboratory synthesis of a pyrimidine was not carried out until 1879, when Grimaux repor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridazine
Pyridazine is an aromatic, heterocyclic, organic compound with the molecular formula . It contains a six-membered ring with two adjacent nitrogen atoms. It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other diazine () rings, pyrimidine and pyrazine. Occurrence Pyridazines are rare in nature, possibly reflecting the scarcity of naturally occurring hydrazines, common building blocks for the synthesis of these heterocycles. The pyridazine structure is a popular pharmacophore which is found within a number of herbicides such as credazine, pyridafol and pyridate. It is also found within the structure of several drugs such as cefozopran, cadralazine, minaprine, pipofezine, and hydralazine. Synthesis In the course of his classic investigation on the Fischer indole synthesis, Emil Fischer prepared the first pyridazine via the condensation of phenylhydrazine and levulinic acid. The parent heterocycle was first prepared by oxidation of be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piperazine
Piperazine () is an organic compound with the formula . In term of its structure, it can be described as cyclohexane with the 1- and 4-CH2 groups replaced by NH. Piperazine exists as deliquescent solid with a saline taste. Piperazine is freely soluble in water and ethylene glycol, but poorly soluble in diethyl ether. Piperazine is commonly available industrially is as the hexahydrate, , which melts at 44 °C and boils at 125–130 °C.''The Merck index, 10th Ed.'' (1983), p. 1076, Rahway:Merck & Co. Substituted derivatives of piperazine are a broad class of chemical compounds. Many piperazines have useful pharmacological properties, prominent examples include viagra, ciprofloxacin, and ziprasidone. Origin and naming Piperazines were originally named because of their chemical similarity with piperidine, part of the structure of piperine in the black pepper plant (''Piper nigrum''). The -az- infix added to "piperazine" refers to the extra nitrogen atom, compared to piperidine. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridazine
Pyridazine is an aromatic, heterocyclic, organic compound with the molecular formula . It contains a six-membered ring with two adjacent nitrogen atoms. It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other diazine () rings, pyrimidine and pyrazine. Occurrence Pyridazines are rare in nature, possibly reflecting the scarcity of naturally occurring hydrazines, common building blocks for the synthesis of these heterocycles. The pyridazine structure is a popular pharmacophore which is found within a number of herbicides such as credazine, pyridafol and pyridate. It is also found within the structure of several drugs such as cefozopran, cadralazine, minaprine, pipofezine, and hydralazine. Synthesis In the course of his classic investigation on the Fischer indole synthesis, Emil Fischer prepared the first pyridazine via the condensation of phenylhydrazine and levulinic acid. The parent heterocycle was first prepared by oxidation of be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrimidine
Pyrimidine (; ) is an aromatic, heterocyclic, organic compound similar to pyridine (). One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring. The other diazines are pyrazine (nitrogen atoms at the 1 and 4 positions) and pyridazine (nitrogen atoms at the 1 and 2 positions). In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U). Occurrence and history The pyrimidine ring system has wide occurrence in nature as substituted and ring fused compounds and derivatives, including the nucleotides cytosine, thymine and uracil, thiamine (vitamin B1) and alloxan. It is also found in many synthetic compounds such as barbiturates and the HIV drug zidovudine. Although pyrimidine derivatives such as alloxan were known in the early 19th century, a laboratory synthesis of a pyrimidine was not carried out until 1879, when Grimaux repor ... [...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] |
Aromatic
In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugation alone. The earliest use of the term was in an article by August Wilhelm Hofmann in 1855. There is no general relationship between aromaticity as a chemical property and the olfaction, olfactory properties of such compounds. Aromaticity can also be considered a manifestation of cyclic delocalization and of Resonance (chemistry), resonance. This is usually considered to be because electrons are free to cycle around circular arrangements of atoms that are alternately single- and double-covalent bond, bonded to one another. This commonly seen model of aromatic rings, namely the idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds (cyclohexatriene), was developed by Friedrich August Kekulé ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
