Alfred Stock
Encyclopedia
Alfred Stock was a German
inorganic
chemist. He did pioneering research on the hydride
s of boron
and silicon
, coordination chemistry
, mercury
, and mercury poisoning
. The German Chemical Society's Alfred-Stock Memorial Prize is named after him.
) and educated at Berlin
, he was nine years assistant of Emil Fischer
before he became professor at the University of Breslau in 1900. In 1916 he succeeded Richard Willstätter
as director at the Kaiser Wilhelm Institute for Chemistry in Berlin. After a severe mercury poisoning he became the director of the Chemistry Department at the Technische Hochschule in Karlsruhe from 1926 to 1936. He was renowned for his pioneering research on boron hydrides.
s - the boron
hydrogen
chemical compound
s with general formula BxHy - since 1909 at Breslau. Due to their extreme reactivity and flammability in air, boron hydrides could not be purified until his development of methods for separation using high-vacuum manifolds around 1912. He performed similar work on the hydride
s of silicon. The hydrides of boron and silicon represented the first family of binary compounds to approach the richness of hydrocarbons in terms of structural diversity. Not only did the boron hydrides exhibit challenging properties, their structures were also unusual. Elucidation of the structures and the associated bonding models dramatically expanded the scope of inorganic chemistry. Boron hydrides such as diborane
later developed into a range of reagent
s for organic synthesis
as well as a source of diverse ligands and building blocks for researchers. With Henri Moissan
, Stock discovered silicon boride
by electrolyzing a fused mixture of sodium
and beryllium fluorides. This method made beryllium available for industrial use, as in special alloys and glasses and for making windows in X-ray tubes.
He was also influential in coordination chemistry
. The term "ligand
" (from ligare Latin
, to bind) was first used by Stock in 1916. H. Irving and R.J.P. Williams adopted the term in a paper published in 1948. Monodentate, bidentate, tridentate characterized the number of ligands attached to a metal. Given the introduction of ligand concept, he was also able to further derive the idea of bite angle
and other aspects of chelation
.
The "Stock system," first published in 1919, was a means of nomenclature on binary compound
s. In his own words, he considered the system to be "simple, clear, immediately intelligible, capable of the most general application." In 1924, a German commission recommended Stock system to be adopted with some accommodations. FeCl2, which would have been named iron(2)-chloride according to Stock's original idea, became iron(II) chloride in the revised proposal. In 1934 Stock agreed to the use of Roman numerals
but preferred keeping the hyphen and dropping the parentheses. Although this suggestion has not been followed, the Stock system remains in use worldwide.
and mercury poisoning
. He also introduced sensitive tests and devised improved laboratory techniques for dealing with mercury which minimized poisoning risk, possibly initiated by his chronic mercury poisoning in 1923. He became more vocal on protesting the mercury usage after realizing the toxicity of its organic derivatives. German dentists
abandoned his warning in 1928 against copper amalgam
usage. Nevertheless a paper from Fleischmann, in which removal of mercury in amalgam-related illness had led to complete recovery, supported his idea. (Deutsche Medizinische Wochenschrift 1928, No. 8). A committee was founded in Berlin to investigate cases of possible mercury intoxication and hence the term micromercurialism was first used.
, in August 1946 at the age of 70.
. The prize, consisting of a gold medal and money, is awarded every other year for "an outstanding independent scientific experimental investigation in the field of inorganic chemistry."
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
inorganic
Inorganic chemistry
Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...
chemist. He did pioneering research on the hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
s of boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
and silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, coordination chemistry
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
, mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, and mercury poisoning
Mercury poisoning
Mercury poisoning is a disease caused by exposure to mercury or its compounds. Mercury is a heavy metal occurring in several forms, all of which can produce toxic effects in high enough doses...
. The German Chemical Society's Alfred-Stock Memorial Prize is named after him.
Life
Born in Danzig (GdańskGdansk
Gdańsk is a Polish city on the Baltic coast, at the centre of the country's fourth-largest metropolitan area.The city lies on the southern edge of Gdańsk Bay , in a conurbation with the city of Gdynia, spa town of Sopot, and suburban communities, which together form a metropolitan area called the...
) and educated at Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, he was nine years assistant of Emil Fischer
Hermann Emil Fischer
Hermann Emil Fischer, Emil Fischer was a German chemist and 1902 recipient of the Nobel Prize in Chemistry. He discovered the Fischer esterification. He developed the Fischer projection, a symbolic way of drawing asymmetric carbon atoms.-Early years:Fischer was born in Euskirchen, near Cologne,...
before he became professor at the University of Breslau in 1900. In 1916 he succeeded Richard Willstätter
Richard Willstätter
Richard Martin Willstätter was a German organic chemist whose study of the structure of plant pigments, chlorophyll included, won him the 1915 Nobel Prize for Chemistry. Willstätter invented paper chromatography independently of Mikhail Tsvet.-Biography:Willstätter was born in to a Jewish family...
as director at the Kaiser Wilhelm Institute for Chemistry in Berlin. After a severe mercury poisoning he became the director of the Chemistry Department at the Technische Hochschule in Karlsruhe from 1926 to 1936. He was renowned for his pioneering research on boron hydrides.
Research on the hydrides of boron and silicon
Stock began studying the boron hydrideHydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
s - the boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s with general formula BxHy - since 1909 at Breslau. Due to their extreme reactivity and flammability in air, boron hydrides could not be purified until his development of methods for separation using high-vacuum manifolds around 1912. He performed similar work on the hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
s of silicon. The hydrides of boron and silicon represented the first family of binary compounds to approach the richness of hydrocarbons in terms of structural diversity. Not only did the boron hydrides exhibit challenging properties, their structures were also unusual. Elucidation of the structures and the associated bonding models dramatically expanded the scope of inorganic chemistry. Boron hydrides such as diborane
Diborane
Diborane is the chemical compound consisting of boron and hydrogen with the formula B2H6. It is a colorless gas at room temperature with a repulsively sweet odor. Diborane mixes well with air, easily forming explosive mixtures. Diborane will ignite spontaneously in moist air at room temperature...
later developed into a range of reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
s for organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
as well as a source of diverse ligands and building blocks for researchers. With Henri Moissan
Henri Moissan
Ferdinand Frederick Henri Moissan was a French chemist who won the 1906 Nobel Prize in Chemistry for his work in isolating fluorine from its compounds.-Biography:...
, Stock discovered silicon boride
Silicon boride
Silicon borides are lightweight ceramic compounds formed between silicon and boron. Several stoichiometric silicon boride compounds, SiBn, have been reported: silicon triboride, SiB3, silicon tetraboride, SiB4, silicon hexaboride, SiB6, as well as SiBn...
Research on other areas of inorganic chemistry
In 1921, he first prepared metallic berylliumBeryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
by electrolyzing a fused mixture of sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
and beryllium fluorides. This method made beryllium available for industrial use, as in special alloys and glasses and for making windows in X-ray tubes.
He was also influential in coordination chemistry
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
. The term "ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
" (from ligare Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
, to bind) was first used by Stock in 1916. H. Irving and R.J.P. Williams adopted the term in a paper published in 1948. Monodentate, bidentate, tridentate characterized the number of ligands attached to a metal. Given the introduction of ligand concept, he was also able to further derive the idea of bite angle
Bite angle
The bite angle is a geometric parameter used to classify chelating ligands in inorganic and organometallic chemistry. Together with ligand cone angle, this parameter is relevant to diphosphine ligands, which are used in industrial processes such as hydroformylation and hydrocyanation...
and other aspects of chelation
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....
.
The "Stock system," first published in 1919, was a means of nomenclature on binary compound
Binary compound
A binary compound is a chemical compound that contains exactly two different elements. Examples of binary ionic compounds include calcium chloride , sodium fluoride , and magnesium oxide , whilst examples of binary covalent compounds include water , carbon monoxide , and sulfur hexafluoride...
s. In his own words, he considered the system to be "simple, clear, immediately intelligible, capable of the most general application." In 1924, a German commission recommended Stock system to be adopted with some accommodations. FeCl2, which would have been named iron(2)-chloride according to Stock's original idea, became iron(II) chloride in the revised proposal. In 1934 Stock agreed to the use of Roman numerals
Roman numerals
The numeral system of ancient Rome, or Roman numerals, uses combinations of letters from the Latin alphabet to signify values. The numbers 1 to 10 can be expressed in Roman numerals as:...
but preferred keeping the hyphen and dropping the parentheses. Although this suggestion has not been followed, the Stock system remains in use worldwide.
Interests in mercury and mercury poisoning
He published over 50 papers on different aspects of mercuryMercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
and mercury poisoning
Mercury poisoning
Mercury poisoning is a disease caused by exposure to mercury or its compounds. Mercury is a heavy metal occurring in several forms, all of which can produce toxic effects in high enough doses...
. He also introduced sensitive tests and devised improved laboratory techniques for dealing with mercury which minimized poisoning risk, possibly initiated by his chronic mercury poisoning in 1923. He became more vocal on protesting the mercury usage after realizing the toxicity of its organic derivatives. German dentists
Dentistry
Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...
abandoned his warning in 1928 against copper amalgam
Amalgam (chemistry)
An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore.The...
usage. Nevertheless a paper from Fleischmann, in which removal of mercury in amalgam-related illness had led to complete recovery, supported his idea. (Deutsche Medizinische Wochenschrift 1928, No. 8). A committee was founded in Berlin to investigate cases of possible mercury intoxication and hence the term micromercurialism was first used.
Retirement and death
After retirement in 1936, he moved from Karlsruhe to Berlin. He died at Aken an der Elbe, a small town near DessauDessau
Dessau is a town in Germany on the junction of the rivers Mulde and Elbe, in the Bundesland of Saxony-Anhalt. Since 1 July 2007, it is part of the merged town Dessau-Roßlau. Population of Dessau proper: 77,973 .-Geography:...
, in August 1946 at the age of 70.
Posthumous recognition
In recognition of his contributions to the field of inorganic chemistry, the German Chemical Society (Gesellschaft Deutscher Chemiker) posthumously created in 1950 the Alfred Stock Memorial PrizeAlfred Stock Memorial Prize
The Alfred-Stock Memorial Prize or Alfred-Stock-Gedächtnispreis is an award for "an outstanding independent scientific experimental investigation in the field of inorganic chemistry." It is awarded annually by the German Chemical Society...
. The prize, consisting of a gold medal and money, is awarded every other year for "an outstanding independent scientific experimental investigation in the field of inorganic chemistry."