PYRIDINE
Updated 04-May-2020.
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Compound: PYRIDINE: Molecule Type: Small molecule, Molecular Formula: C5H5N, Molecular Weight: 79.10, Synonyms: Pyridine
Crystal structures of pyridine and pyridine trihydrate: The crystal structure of pyridine is orthorhombic with space group Pna21, a = 1752.4(3), b = 896.9(2), and c = 1135.2(2) pm at 153 K and Z = 16. A low melting crystalline hydrate of pyridine was found by DTA to be a trihydrate. It is orthorhombic, too, with space group Pbca, a = 1244.4(3), b = 1783.2(6), and c = 679.1(2) pm at 223 K and Z = 8. Both structures were determined from single crystal MoKα diffractometer data and refined to unweighted R values of 0.044 for 2769 and of 0.074 for 932 observed independent reflections. Most apparent in the anhydrous structure is an arrangement of the molecular noncrystallogrpahic twofold axes in layers perpendicular to the c-axis direction and separated by c/4. With the ring centers not far from the points of a bcc lattice a ”molecular coordination number” of 14 can be assigned to each of the four independent molecules. Their geometries are very similar and close to mm-C2v symmetry. In the structure of the trihydrate the water molecules are O-H ⋅ ⋅ ⋅ O hydrogen bonded in a new pattern of condensed four, five, and six-membered rings to form buckled layers, separated by b/2, which enclose the pyridine molecules. There is one hydrogen bond O-H ⋅ ⋅ ⋅ N from a water molecule to the pyridine molecule. All hydrogen atoms are ordered.
Pyridine: Chemsrc provides Pyridine(CAS#:110-86-1) MSDS, density, melting point, boiling point, structure, formula, molecular weight etc. Articles of Pyridine are included as well.
My botty best at summarizing from Wikipedia: Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N . it is colorless, but older or impure samples can appear yellow . the pyridine ring occurs in many important pyridine was originally produced from coal tar . it is synthesized on the scale of about 20,000 tonnes per year worldwide . the standard enthalpy of formation is 100.2 kJmol1 the critical parameters of pyridine are pressure 6.70 MPa, temperature 620 K and volume 229 cm3mol1 . the enthalpy of vaporization is 35.09 kJmol the difference is partly related to the lower symmetry of the individual pyridine molecule (C2v vs D6h for benzene) a trihydrate (pyridine3H2O) is known pyridine shows a triplet at (-C) = 150 ppm whereas benzene has a single line at 129 pm . all shifts are quoted for solvent-free pyridine is more prone to nucleophilic substitution, as evidenced by ease of metalation by strong organometallic bases . electrophiles, electrophilic substitution takes place where pyrine expresses the nitrogen center of pyridine features a basic lone pair of electrons . protonation gives pyridinium, C5H5NH+.The pKa of the conjugate acid is pyridinium p-toluenesulfonate (PPTS) is an illustrative salt . pyridine undergoes N-centered alkylation, acylation, nitrogen is involved in the -bonding aromatic system using its unhybridized p orbital . lone pair is in an sp2 orbital, projecting outward from the ring in in 1849, Anderson examined the contents of the oil obtained through high-temperature heating of animal bones . Anderson named the new substance pyridine, after Greek: (pyr) meaning fire. the suffix idine was added to indicate a cyclic compound containing a nitrogen atom . the chemical structure of pyridine was determined decades after its discovery . Wilhelm Körner (1869) and James De Emil Knoevenagel has shown that asymmetrically-substituted pyridine derivatives can be produced . the contemporary methods had a low yield, and the increasing demand for the new compound urged to search trace amounts of pyridine can be found in Beaufort cheese, vaginal secretions, black tea, saliva of those suffering from gingivitis, and sunflower honey . trace amounts are found in fried chicken, su in 1989, 26,000 tonnes of pyridine was produced worldwide . Among the largest 25 production sites, eleven are located in Europe . Pyridine production significantly increased in the early 2000s . vertellus is currently the world leader in pyridine production . unsubstituted is produced from formaldehyde and acetaldehlyde . acrolein is formed in a the recovered pyridine is separated from byproducts in a multistage process . practical application of the traditional Chichibabin synthesis are limited by its consistently low yield, typically about 20% . the catalyst is usually a low yield, high prevalence of byproducts render unmodified forms of Chichibabin’s method unpopular . modification of Reppe synthesis can be activated either by heat or by light . photoinduced cyclo when using acetonitrile as the nitrile, 2-methylpyridine is obtained . reaction of pyridine with -bromoesters gives the related pyridinium salt . nicotinic acid (vitamin B3) occurs in some bacteria, fungi, and mammals . mammals synthesize the acid through oxidation of the amino acid tryptophan . nic bacteria Mycobacterium tuberculosis and Escherichia coli produce nicotinic acid . pyridine more closely resembles nitrobenzene . direct nitration pyridine derivatives can be obtained by nitration with nitronium tetrafluoroborate (NO2BF4) . synthesis of 2,6-dibromopyridine followed by de addition of oxygen suppresses reactions at nitrogen atom and promotes substitution at 2- and 4-carbons . reactions usually proceed at the 2- or 4-position . oxygen atom can then be removed, e.g. using many nucleophilic substitutions occur more easily with pyridine modified with bromine, chlorine, fluorine, or sulfonic acid fragments . in general, the hydride ion is a nucleophilic substitutions to pyridine can result in the formation of pyridyne intermediates as heteroaryne . Radical dimerization yields 4,4′-bipyridine, or it can produce 2-tert-butylpyridine upon reacting pyridine with pivalic acid, silver nitrate and ammonium in sulfuric acid with a yield of 97% . reaction with al reduction with lithium aluminium hydride yields a mixture of 1,4-dihydropyridine . 1,2-dihydroxypyridine, and 2,5-dishydrophoridine are produced . ( Numerous square planar complexes are known, such as Crabtree’s catalyst . the pyridine ligand replaced during the reaction is restored after its completion . 6 coordination mode observed only in first synthesis step of insecticide chlorpyrifos consists of chlorination of pyridine . it is also the starting compound for pyrithione-based fungicides . cetylpyri pyridine is particularly suitable for the dehalogenation . it acts as the base of the elimination reaction and bonds the resulting hydrogen halide to form a pyridinium salt. pyridine has a flash point of 17 °C and is, therefore, highly flammable . it easily dissolves in water and harms both animals and plants in aquatic systems . external lobbying forced it to ban the permitted maximum allowable concentration of pyridine was 15–30 parts per million (ppm) in most countries in the 1990s, but was reduced to 5 ppm in the 2000s . one person died after accidental in pyridine has a narcotic effect and its vapor concentrations of above 3600 ppm pose a health risk . the oral LD50 in rats is 891 mgkg1. Pyridine pyridine might also have minor neurotoxic, genotoxic, and clastogenic effects . it is readily degraded by bacteria to ammonia and carbon dioxide . unsubstituted pyridine ring degrades more rapidly than picoline, lutidine, chloropyridine, or aminopyridines . minor amounts released into environment from some industrial processes systematic names for simple compounds are used very rarely . instead, heterocyclic nomenclature follows historically established common names . IUPAC discourages the use of azinine/azine in favor of pyridine the historical name pyridyl is encouraged by the IUPAC and used instead of the systematic name . cationic derivative formed by the addition of an electrophile to the nitrogen atom . Chichester: Blackwell Publishing. ISBN 978-1-4051-3300-5. Lide, D. R. (2009). Handbook of Chemistry and Physics (90th ed.). ISBN 978-1-4200-9084-0. Boca Raton: CRC Press. ISBN 1 978-1200-9094-0.