Original picture from the Bayer archives of Dr Hans Finkelstein conversing with colleagues in a laboratory at the Uerdingen site of I.G. Farben, recorded in 1932.

Dr. Hans Finkelstein

Exclusion of a jewish employee at I.G. Farben

Hans Finkelstein was born into a family of chemists in 1885. After finishing high school, he studied chemistry in Leipzig and Dresden. From 1906 to 1909 he completed his work on his doctoral thesis in Strasbourg under the supervision of Friedrich Karl Johannes Thiele, a German chemist and university lecturer. Hereinafter, Hans Finkelstein worked as Professor Thiele’s assistant. Within the research for his doctoral thesis, he developed the “Finkelstein reaction”, which is recognized to this day and has been cited thousands of times.

Dr. Hans Finkelstein

Dr. Hans Finkelstein as a child. Picture: Courtesy of his family

The Finkelstein reaction

The Finkelstein Reaction

An essential tool in preparative organic chemistry

The Finkelstein reaction by Dr. Hans Finkelstein was first described in an article in 1910. In the classical reaction, chlorine or bromine is exchanged for iodine on hydrocarbons. It is an efficient method for the synthesis of iodine compounds which are not directly accessible due to the low reactivity of iodine. Iodinated organic compounds are used, for example, as contrast agents in radiological examinations and play a role as building blocks in the synthesis of chemical molecules. The reaction was decisively developed after Hans Finkelstein's death, which underlines its importance. It became an essential tool in preparative organic chemistry and is still an integral part of curriculums at school and university in the field of organic chemistry. It is used in the chemical industry, amongst others at Bayer AG, and in the areas of pharmaceuticals, agriculture (fungicides and insecticides), dyes and liquid crystals. 

Discrimination and Ousting

Dr. Hans Finkelstein came from a liberal Jewish family

After his academic career, as a young scientist, Finkelstein joined the research department at “Chemische Fabriken, vorm. Weiler-ter Meer” in Uerdingen in 1911. Like “Farbenfabriken vorm. Friedr. Bayer & Co.” with its sites in Leverkusen, Elberfeld and Dormagen, it became part of the newly founded I.G. Farbenindustrie AG in 1925. After joining the company, Finkelstein was put in charge of the scientific laboratory and became an authorized signatory with full power of attorney. 


The biography of Dr. Hans Finkelstein typifies the fate of people from a Jewish background or who follow the Jewish religion. When the National Socialists came to power and passed the Nuremberg Race Laws, he was defined as a "Jew" and as “non-Aryan”. Finkelstein came from a liberal Jewish family and had converted to Protestantism at the age of ten. Despite this, and having already experienced discrimination, he was forced to leave the company in 1938 and had to surrender his passport. Embittered and thoroughly disillusioned, he took his own life on December 30th, 1938, by poisoning himself. He and his wife Annemarie had three children: Eva (*1919), Klaus-Peter (*1913), and Berthold (*1925). As a “half-Jew”, his son Berthold had to work as a forced laborer at his former company.

House of the Finkelsteins in Uerdingen

The house of the Finkelstein family in Uerdingen today. © Rüdiger Borstel