Von Pechmann

The first polymer with a polymethylene stmcture was synthesized by von Pechmann in 1898 from diazomethane (1). Since then, there have been four milestones in the history of PE polymers as commercial plastics. 

Although polyethylene is virtually defined by its very name as a polymer of ethylene produced by addition polymerisation, linear polymers with the formula (CH2), have also been prepared by condensation reactions. For example in 1898 von Pechmann produced a white substance from an ethereal solution of... 

The procedure for preparing methyl coumalate is based on a method described by von Pechmann. Methyl coumalate has also been prepared by direct esterification of the reaction mixture from malic acid and fuming sulfuric acid and from comnalyl chloride and methanol. ... 

The procedure for preparing 6-hydroxynicotinic acid is also based on a method described by von Pechmann. 6-Hydroxynico-tinic acid has also been prepared by decarboxylation of 6-hy-droxy-2,3-pyridinedicarboxylic acid by heating 6-hydra-zinonicotinic acid or its hydrazide with hydrochloric acid by the action of carbon dioxide on the sodium salt of a-pyridone at 180-200 and 20 atmospheres by heating the nitrile of 6-chlo-ronicotinic acid with alcoholic sodium hydroxide or hydrochloric acid from 6-aminonicotinic acid and by the prolonged action of concentrated ammonium hydroxide on methyl cou-malate. ... 

Diazomothane, which was first prepared in 1894 by von Pechmann/ undergoes numerous reactions, In the heterocyclic series, its reactions can be divided into the following types ... 

The classical theory of methylation with diazomethane was developed by Arndt from a different basis. It depends on the postulate (which can be traced back to von Pechmann " 0 of direct methylation mobile hydrogen in an acid compound is directly replaced by the methyl group, i.e., the methyl group appears in the place which the hydrogen previously occupied. For the reaction of tautomeric substances with diazomethane, the following equation is applicable ... 

With alkoxide and phenoxide ions diazo ethers are formed. The latter played a considerable part in the classic controversy about diazo isomerism between Hantzsch and Bamberger at the turn of the 19th century (see Sec. 1.1). Von Pechmann and Frobenius (1894 a) showed that the most convenient synthesis for preparative pur-... 

John EVO, Israelstam SS (1961) Use of cation exchange resins in organic reactions. I. The von Pechmann reaction. J Org Chem 26 240-242... 

Ruhrmann, G. von Pechmann, E. 1989. Structural and hydrothermal modification of the Gaertner uranium deposit, Key Lake, Saskatchewan, Canada. IAEA TECDOC-500, 363-377. 

Preparation of Benzoyl Peroxide.1—Hydrogen peroxide (50 c.c. of about 10 per cent aqueous solution) kept well cooled in ice and continually shaken (preferably in a glass-stoppered bottle) is treated alternately with 4 A-sodium hydroxide solution and benzoyl chloride, added each a few drops at a time the solution is maintained faintly alkaline throughout. After about 30 c.c. of alkali and 15 g. of benzoyl chloride have been used up, the hydrogen peroxide has been decomposed and the benzoyl peroxide has separated in crystalline flocks, while the odour of the chloride has almost completely disappeared. The peroxide is filtered with suction, washed with water, and dried. Yield 10-12 g. Crystallised from a little alcohol, with which it should be boiled for a short time only, the substance forms beautiful colourless prisms. Melting point 106°-108° decomp. Heat a small quantity rapidly in a dry test tube over a naked flame. An especially pure product is obtained when a 1 von Pechmann and Vanino, Ber., 1894, 27, 1510. 

The preparative importance of the acyloins depends on the fact that they are intermediate products, from which many 1 2-diketones can be obtained. The simplest aromatic member of this group is benzil (anisil and furil are analogous) like its aliphatic prototype diacetyl CH3.CO.CO.CH3 (and like anhydrous glyoxal) it is yellow in colour. Diacetyl is obtained from methyl-ethyl ketone via the monoxime of the former compound (von Pechmann). It is remarkable that diacetyl condenses to p-xyloquinone. (Formulate). 

Our method proceeds absolutely parallel to von Pechmann s, but urea is used instead of urethane. 

V. Pechmann, H. Duisberg, C. Ber. Dtsch. Chem. Ges. 1883, 16, 2119. Hans von Pechmann (1850-1902) was bom in Niimberg, Germany. After his doctorate, he worked with Frankland and von Baeyer. Pechmann taught at Munich and Tubingen. He committed suicide by taking cyanide. 

Although this was not appreciated at the time, these compounds were first handled by Busch and Becker in 1896. Their study continued until a more extensive report by Busch and Schmidt was published in 1929,195 However, Busch and his co-workers were apparently unaware of some closely related work reported by von Pechmann in 1896. These earlier studies have been interpreted by Farrar, extended by Christopherson and Treppendahl, and brought to a definitive conclusion by the Sheffield group. This history is an interesting facet of the development of the chemistry of meso-ionic heterocycles. 

In the early investigation of the nitrosation of 1,4-diphenyl-thiosemicarbazide (279, R = R = Ph), the product was obtained as deep red needles, m.p. 110°, and was allocated the remarkable 1,3-endoxyhydrazomethylene structure (280). Treatment of this deep red compound with warm aqueous alkali gave a colorless isomer, m.p. 157°, which was formulated as having one of the equally unacceptable structures 281 or 282. Recent investigations have established that nitrosation of 1,4-diarylthiosemicarbazides (279) yield the meso-ionic 1,2,3,4-oxatriazol-5-imines (277), which are transformed by base into the meso-ionic isomers (278). These alkaline transformation products formulated as meso-ionic l,2,3,4-tetrazol-5-ones (278) are in fact identical (see Section VII, J, 1) with substances prepared, but not formulated, by von Pechmann many years ago. ... 

In the von Pechmann synthesis, originally used to prepare pyran-2-one-5-carboxylic acid (coumalic acid), 2-hydroxybutane-l,4-dioic acid is converted into 3-oxopropanoic acid by treatment with oleum (sulfur trioxide and cone, sulfuric acid), and this product then self-condenses in the acidic medium to give pyran-2-one-5-carboxylic acid (Scheme 4,8a). Pyran-2-one is obtained by decarboxylating coumalic acid by heating it over copper at 650 °C. 

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