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Von Pechmann was born in Nürnberg, the only son of a doctor, who was also named Hans.The von Pechmanns had distinguished themselves as soldiers; in 1702, von Pechmann's ancestor Martin Günther von Pechmann, a general of artillery in the Bavarian army, had been raised to the rank of a baron of the Holy Roman Empire by Leopold I. [6]
1898: Synthesis of polyethylene, the most common plastic, by Hans von Pechmann [160] 1898: First synthesis of purine by Emil Fischer. He had also coined the word in 1884. [161] Early 20th century: Schlenk flask by Wilhelm Schlenk [162] 1900s: Haber process by Carl Bosch and Fritz Haber [134] 1902: Ostwald process by Wilhelm Ostwald [163]
High-density polyethylene bottles are introduced; they will replace glass bottles in most applications. [11] 1965: Kevlar is developed at DuPont by Stephanie Kwolek: 1980s: Polyester film stock replaces cellulose acetate for photographic film and computer tapes. 1988: The first polymer bank notes are issued in Australia
Adolf von Baeyer Otto Bayer demonstrated in 1952 his invention Polyurethan Friedrich Bergius Carl Bosch Eduard Buchner Robert Wilhelm Bunsen. Lambert Heinrich von Babo; Manfred Baerns
Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. [12] [a] [13] [b] When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long −CH 2 − chains and termed it polymethylene.
The Pechmann condensation as applied to 7-hydroxy-4-methylcoumarin For coumarins unsubstituted at the 4-position, the method requires the use of formylacetic acid or ester. These are unstable and not commercially available, but the acid may be produced in situ from malic acid and sulfuric acid above 100 °C.
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Two German chemists also preceded Schlotterbeck in discovery of the reaction, Hans von Pechmann in 1895 and Viktor Meyer in 1905. [4] [5] The reaction has since been extended to the synthesis of β-keto esters from the condensation between aldehydes and diazo esters. [6] The general reaction scheme is as follows: General Scheme for Buchner Reaction