:Hans von Pechmann

{{Short description|German chemist (1850–1902)}}

{{Infobox scientist

| name = Hans von Pechmann

| image = Hans v Pechmann ca1899.jpg

| image_size =

| caption =

| birth_date = 1 April 1850

| birth_place = Nürnberg, Kingdom of Bavaria, German Empire

| nationality = German

| death_date = {{Death date and age|1902|4|19|1850|4|1|df=y}}

| death_place = Tübingen, Kingdom of Württemberg, German Empire

| field = organic chemistry

| work_institution = University of Munich University of Tübingen

| alma_mater = University of Greifswald

| doctoral_advisor = Heinrich Limpricht

| doctoral_students = William Hobson Mills Julius B. Cohen

| known_for = Pechmann condensation Diazomethane

| prizes =

| religion =

| footnotes =

}}Hans Freiherr{{efn|{{German title Freiherr}}}} von Pechmann (1 April 1850 – 19 April 1902) was a German chemist, renowned for his discovery of diazomethane in 1894.{{cite journal

| author= H. von Pechmann

| title = Ueber Diazomethan

| journal = Berichte der deutschen chemischen Gesellschaft

| year = 1894

| volume = 27

| issue = 2

| pages = 1888–1891

| doi = 10.1002/cber.189402702141| url = https://zenodo.org/record/1425744

}}{{cite journal

| author= H. von Pechmann

| title = Ueber Diazomethan

| journal = Berichte der deutschen chemischen Gesellschaft

| year = 1895

| volume = 28

| issue = 1

| pages = 855–861

| doi = 10.1002/cber.189502801189| url = https://zenodo.org/record/1425790

}} Pechmann condensation{{cite journal

| author= H. von Pechmann, Carl Duisberg

| title = Ueber die Verbindungen der Phenole mit Acetessigäther

| journal = Berichte der deutschen chemischen Gesellschaft

| year = 1883

| volume = 16

| issue = 1

| pages = 2119–2128

| doi = 10.1002/cber.188301602117| url = https://zenodo.org/record/1425297

}}{{cite journal

| author= H. von Pechmann

| title = Neue Bildungsweise der Cumarine. Synthese des Daphnetins

| journal = Berichte der deutschen chemischen Gesellschaft

| year = 1884

| volume = 17

| issue = 1

| pages = 929–936

| doi = 10.1002/cber.188401701248| url = https://zenodo.org/record/1425329

}} and Pechmann pyrazole synthesis.{{cite journal

| author= H. von Pechmann

| title = Pyrazol aus Acetylen und Diazomethan

| journal = Berichte der deutschen chemischen Gesellschaft

| year = 1898

| volume = 31

| issue = 3

| pages = 2950–2951

| doi = 10.1002/cber.18980310363| url = https://zenodo.org/record/1425922

}} He also first prepared 1,2-diketones (e.g., diacetyl), acetonedicarboxylic acid, methylglyoxal and diphenyltriketone; established the symmetrical structure of anthraquinone.

Von Pechmann also produced the first example of solid polyethylene serendipitously in 1898, via the decomposition of diazomethane.