1 Important Developments in the History of Ionic Liquids …
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Leipzig (1891) as a professor of physical and analytical chemistry at the Riga Polytechnic Institute (1893/94). In 1899, already as an appointed professor, he received
the Russian doctoral degree in chemistry working on stereochemistry at Saint Petersburg. In 1910, Walden was given full membership in the Russian Imperial Academy
of Sciences. Among his many landmark discoveries in various fields, the so-called
Walden inversion in organic chemistry is generally considered his most outstanding
achievement [13]. He was nominated six times (Stradi¸ nš says seven times [14] but
according to Morachevskii only two times [11]) for the Nobel Prize [15]. In 1919,
Walden decided to leave for Germany and not continue his work in the capital of
independent Latvia. From 1919 until his retirement in 1934, he was professor of
chemistry at the University of Rostock. Walden remained active during his retirement, published works on the history of chemistry, and held—from 1934 on as a
member of the National Socialist German Workers’ Party—various influential positions in academic organizations, such as the vice president of the German Chemical
Society [15, 16]. After the war, he lived in the French-occupied zone of Germany
and was given a guest professorship at the University of Tübingen where he gave
lectures until the age of 90.
Contemporary German papers often refer to his name as “Paul von Walden,” [17]
and some Internet sources still use this name [18]. The tag “von” indicates nobility
in the German style of writing names, and this fact convinced many that Paul Walden
was a typical Baltic German (like his teacher and mentor Wilhelm Ostwald). Walden
(who was educated in German schools and later entered a university where German
was the language used, a peculiarity of the Baltic provinces) had opted for German
citizenship after his emigration but kept strong ties to his homeland and saw himself
primarily as a “chemist” [12]. In fact, Walden was granted hereditary peerage by the
Russian Emperor in 1907 [10]. He did not use the “von” in his own works. Walden’s
genuine origin from Latvian peasantry was investigated, published, promoted, as well
as popularized already in Soviet times by the academician J¯ anis Stradi¸ nš [14]. The
post-Soviet independent Latvia honored Walden by issuing a special commemorative
stamp in 2013 [12], and, initiated by Stradi¸ nš, a monument was erected near the
University of Riga showing the Walden inversion [19].
At the University of Rostock, the Ludwig group conducted a study of ethylammonium nitrate to honor Walden’s merits for the city and for the field of ionic liquids [20].
Walden had no conception of the ionic liquid as we have now. He was only interested
in conductivity and molecular constitution. The term “ionic liquid” in its present
sense was coined by Barrer in 1943, but he referred to classical high-temperature
molten salts mostly by the term “ionic melts [21].”
From the remarkable amount of literature, the reader can choose from many
detailed timelines that outline the development of ionic liquids. Four can be considered representative and give the reader almost all corresponding key references. The
paper by Wilkes in Green Chemistry was the first [22]. The most recently published
historical overviews were contributed by Welton in Biophysical Reviews [23] and by
Shiflett and Scurto as an introductory chapter of their book issued volume 1250 of
the Symposium Series of the American Chemical Society [24]. The chapter on the
5
Leipzig (1891) as a professor of physical and analytical chemistry at the Riga Polytechnic Institute (1893/94). In 1899, already as an appointed professor, he received
the Russian doctoral degree in chemistry working on stereochemistry at Saint Petersburg. In 1910, Walden was given full membership in the Russian Imperial Academy
of Sciences. Among his many landmark discoveries in various fields, the so-called
Walden inversion in organic chemistry is generally considered his most outstanding
achievement [13]. He was nominated six times (Stradi¸ nš says seven times [14] but
according to Morachevskii only two times [11]) for the Nobel Prize [15]. In 1919,
Walden decided to leave for Germany and not continue his work in the capital of
independent Latvia. From 1919 until his retirement in 1934, he was professor of
chemistry at the University of Rostock. Walden remained active during his retirement, published works on the history of chemistry, and held—from 1934 on as a
member of the National Socialist German Workers’ Party—various influential positions in academic organizations, such as the vice president of the German Chemical
Society [15, 16]. After the war, he lived in the French-occupied zone of Germany
and was given a guest professorship at the University of Tübingen where he gave
lectures until the age of 90.
Contemporary German papers often refer to his name as “Paul von Walden,” [17]
and some Internet sources still use this name [18]. The tag “von” indicates nobility
in the German style of writing names, and this fact convinced many that Paul Walden
was a typical Baltic German (like his teacher and mentor Wilhelm Ostwald). Walden
(who was educated in German schools and later entered a university where German
was the language used, a peculiarity of the Baltic provinces) had opted for German
citizenship after his emigration but kept strong ties to his homeland and saw himself
primarily as a “chemist” [12]. In fact, Walden was granted hereditary peerage by the
Russian Emperor in 1907 [10]. He did not use the “von” in his own works. Walden’s
genuine origin from Latvian peasantry was investigated, published, promoted, as well
as popularized already in Soviet times by the academician J¯ anis Stradi¸ nš [14]. The
post-Soviet independent Latvia honored Walden by issuing a special commemorative
stamp in 2013 [12], and, initiated by Stradi¸ nš, a monument was erected near the
University of Riga showing the Walden inversion [19].
At the University of Rostock, the Ludwig group conducted a study of ethylammonium nitrate to honor Walden’s merits for the city and for the field of ionic liquids [20].
Walden had no conception of the ionic liquid as we have now. He was only interested
in conductivity and molecular constitution. The term “ionic liquid” in its present
sense was coined by Barrer in 1943, but he referred to classical high-temperature
molten salts mostly by the term “ionic melts [21].”
From the remarkable amount of literature, the reader can choose from many
detailed timelines that outline the development of ionic liquids. Four can be considered representative and give the reader almost all corresponding key references. The
paper by Wilkes in Green Chemistry was the first [22]. The most recently published
historical overviews were contributed by Welton in Biophysical Reviews [23] and by
Shiflett and Scurto as an introductory chapter of their book issued volume 1250 of
the Symposium Series of the American Chemical Society [24]. The chapter on the