Carbon group

The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl).

In modern IUPAC notation, it is called Group 14. In the field of semiconductor physics, it is still universally called Group IV. The group was once also known as the tetrels (from the Greek word tetra, which means four), stemming from the Roman numeral IV in the group names, or (not coincidentally) from the fact that these elements have four valence electrons (see below).

Carbon group (group 14)
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
boron group  pnictogens
IUPAC group number 14
Name by element carbon group
Trivial name tetrels
CAS group number
(US, pattern A-B-A)
IVA
old IUPAC number
(Europe, pattern A-B)
IVB

↓ Period
2
Diamond and graphite, two allotropes of carbon
Carbon (C)
6 Reactive nonmetal
3
Purified silicon
Silicon (Si)
14 Metalloid
4
Polycrystallline germanium
Germanium (Ge)
32 Metalloid
5
Alpha- and beta-tin, two allotropes of tin
Tin (Sn)
50 Post-transition metal
6
Lead crystals
Lead (Pb)
82 Post-transition metal
7 Flerovium (Fl)
114 Unknown chemical properties

Legend
primordial element
synthetic element
Atomic number color:
black=solid

Characteristics

Chemical

Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior:

Z Element No. of electrons/shell
6 Carbon 2, 4
14 Silicon 2, 8, 4
32 Germanium 2, 8, 18, 4
50 Tin 2, 8, 18, 18, 4
82 Lead 2, 8, 18, 32, 18, 4
114 Flerovium 2, 8, 18, 32, 32, 18, 4 (predicted)

Each of the elements in this group has 4 electrons in its outer orbital (the atom's top energy level). The last orbital of all these elements is the p2 orbital. In most cases, the elements share their electrons. The tendency to lose electrons increases as the size of the atom increases, as it does with increasing atomic number. Carbon alone forms negative ions, in the form of carbide (C4−) ions. Silicon and germanium, both metalloids, each can form +4 ions. Tin and lead both are metals while flerovium is a synthetic, radioactive (its half life is very short), element that may have a few noble gas-like properties, though it is still most likely a post-transition metal. Tin and lead are both capable of forming +2 ions.

Carbon forms tetrahalides with all the halogens. Carbon also forms three oxides: carbon monoxide, carbon suboxide (C3O2), and carbon dioxide. Carbon forms disulfides and diselenides.[1]

Silicon forms two hydrides: SiH4 and Si2H6. Silicon forms tetrahalides with fluorine, chlorine, and iodine. Silicon also forms a dioxide and a disulfide.[2] Silicon nitride has the formula Si3N4.[3]

Germanium forms two hydrides: GeH4 and Ge2H6. Germanium forms tetrahalides with all halogens except astatine and forms dihalides with all halogens except bromine and astatine. Germanium bonds to all natural single chalcogens except polonium, and forms dioxides, disulfides, and diselenides. Germanium nitride has the formula Ge3N4.[4]

Tin forms two hydrides: SnH4 and Sn2H6. Tin forms dihalides and tetrahalides with all halogens except astatine. Tin forms chalcogenides with one of each naturally occurring chalcogen except polonium, and forms chalcogenides with two of each naturally occurring chalcogen except polonium and tellurium.[5]

Lead forms one hydride, which has the formula PbH4. Lead forms dihalides and tetrahalides with fluorine and chlorine, and forms a tetrabromide and a lead diiodide, although the tetrabromide and tetraiodide of lead are unstable. Lead forms four oxides, a sulfide, a selenide, and a telluride.[6]

There are no known compounds of flerovium.[7]

Physical

The boiling points of the carbon group tend to get lower with the heavier elements. Carbon, the lightest carbon group element, sublimates at 3825 °C. Silicon's boiling point is 3265 °C, germanium's is 2833 °C, tin's is 2602 °C, and lead's is 1749 °C. The melting points of the carbon group elements have roughly the same trend as their boiling points. Silicon melts at 1414 °C, germanium melts at 939 °C, tin melts at 232 °C, and lead melts at 328 °C.[8]

Carbon's crystal structure is hexagonal; at high pressures and temperatures it forms diamond (see below). Silicon and germanium have diamond cubic crystal structures, as does tin at low temperatures (below 13.2 °C). Tin at room temperature has a tetragonal crystal structure. Lead has a face-centered cubic crystal structure.[8]

The densities of the carbon group elements tend to increase with increasing atomic number. Carbon has a density of 2.26 grams per cubic centimeter, silicon has a density of 2.33 grams per cubic centimeter, germanium has a density of 5.32 grams per cubic centimeter. Tin has a density of 7.26 grams per cubic centimeter, and lead has a density of 11.3 grams per cubic centimeter.[8]

The atomic radii of the carbon group elements tend to increase with increasing atomic number. Carbon's atomic radius is 77 picometers, silicon's is 118 picometers, germanium's is 123 picometers, tin's is 141 picometers, and lead's is 175 picometers.[8]

Allotropes

Carbon has multiple allotropes. The most common is graphite, which is carbon in the form of stacked sheets. Another form of carbon is diamond, but this is relatively rare. Amorphous carbon is a third allotrope of carbon; it is a component of soot. Another allotrope of carbon is a fullerene, which has the form of sheets of carbon atoms folded into a sphere. A fifth allotrope of carbon, discovered in 2003, is called graphene, and is in the form of a layer of carbon atoms arranged in a honeycomb-shaped formation.[3][9][10]

Silicon has two known allotropes that exist at room temperature. These allotropes are known as the amorphous and the crystalline allotropes. The amorphous allotrope is a brown powder. The crystalline allotrope is gray and has a metallic luster.[11]

Tin has two allotropes: α-tin, also known as gray tin, and β-tin. Tin is typically found in the β-tin form, a silvery metal. However, at standard pressure, β-tin converts to α-tin, a gray powder, at temperatures below 13.2° Celsius/56° Fahrenheit. This can cause tin objects in cold temperatures to crumble to gray powder in a process known as tin pest or tin rot.[3][12]

Nuclear

At least two of the carbon group elements (tin and lead) have magic nuclei, meaning that these elements are more common and more stable than elements that do not have a magic nucleus.[12]

Isotopes

There are 15 known isotopes of carbon. Of these, three are naturally occurring. The most common is stable carbon-12, followed by stable carbon-13.[8] Carbon-14 is a natural radioactive isotope with a half-life of 5,730 years.[13]

23 isotopes of silicon have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay of actinides, and via spallation in the upper atmosphere. Silicon-34 also occurs naturally as the result of radioactive decay of actinides.[13]

32 isotopes of germanium have been discovered. Five of these are naturally occurring. The most common is the stable isotope germanium-74, followed by the stable isotope germanium-72, the stable isotope germanium-70, and the stable isotope germanium-73. The isotope germanium-76 is a primordial radioisotope.[13]

40 isotopes of tin have been discovered. 14 of these occur in nature. The most common is tin-120, followed by tin-118, tin-116, tin-119, tin-117, tin-124, tin-122, tin-112, and tin-114: all of these are stable. Tin also has four radioisotopes that occur as the result of the radioactive decay of uranium. These isotopes are tin-121, tin-123, tin-125, and tin-126.[13]

38 isotopes of lead have been discovered. 9 of these are naturally occurring. The most common isotope is lead-208, followed by lead-206, lead-207, and lead-204: all of these are stable. 4 isotopes of lead occur from the radioactive decay of uranium and thorium. These isotopes are lead-209, lead-210, lead-211, and lead-212.[13]

6 isotopes of flerovium (flerovium-284, flerovium-285, flerovium-286, flerovium-287, flerovium-288, and flerovium-289) have been discovered. None of these are naturally occurring. Flerovium's most stable isotope is flerovium-289, which has a half-life of 2.6 seconds.[13]

Occurrence

Carbon accumulates as the result of stellar fusion in most stars, even small ones.[12] Carbon is present in the earth's crust in concentrations of 480 parts per million, and is present in seawater at concentrations of 28 parts per million. Carbon is present in the atmosphere in the form of carbon monoxide, carbon dioxide, and methane. Carbon is a key constituent of carbonate minerals, and is in hydrogen carbonate, which is common in seawater. Carbon forms 22.8% of a typical human.[13]

Silicon is present in the earth's crust at concentrations of 28%, making it the second most abundant element there. Silicon's concentration in seawater can vary from 30 parts per billion on the surface of the ocean to 2000 parts per billion deeper down. Silicon dust occurs in trace amounts in earth's atmosphere. Silicate minerals are the most common type of mineral on earth. Silicon makes up 14.3 parts per million of the human body on average.[13] Only the largest stars produce silicon via stellar fusion.[12]

Germanium makes up 2 parts per million of the earth's crust, making it the 52nd most abundant element there. On average, germanium makes up 1 part per million of soil. Germanium makes up 0.5 parts per trillion of seawater. Organogermanium compounds are also found in seawater. Germanium occurs in the human body at concentrations of 71.4 parts per billion. Germanium has been found to exist in some very faraway stars.[13]

Tin makes up 2 parts per million of the earth's crust, making it the 49th most abundant element there. On average, tin makes up 1 part per million of soil. Tin exists in seawater at concentrations of 4 parts per trillion. Tin makes up 428 parts per million of the human body. Tin (IV) oxide occurs at concentrations of 0.1 to 300 parts per million in soils.[13] Tin also occurs in concentrations of one part per thousand in igneous rocks.[14]

Lead makes up 14 parts per million of the earth's crust, making it the 36th most abundant element there. On average, lead makes up 23 parts per million of soil, but the concentration can reach 20000 parts per million (2 percent) near old lead mines. Lead exists in seawater at concentrations of 2 parts per trillion. Lead makes up 1.7 parts per million of the human body by weight. Human activity releases more lead into the environment than any other metal.[13]

Flerovium only occurs in particle accelerators.[13]

History

Discoveries and uses in antiquity

Carbon, tin, and lead are a few of the elements well known in the ancient world, together with sulfur, iron, copper, mercury, silver, and gold.[15]

Silicon as silica in the form of rock crystal was familiar to the predynastic Egyptians, who used it for beads and small vases; to the early Chinese; and probably to many others of the ancients. The manufacture of glass containing silica was carried out both by the Egyptians – at least as early as 1500 BCE – and by the Phoenicians. Many of the naturally occurring compounds or silicate minerals were used in various kinds of mortar for construction of dwellings by the earliest people.

The origins of tin seem to be lost in history. It appears that bronzes, which are alloys of copper and tin, were used by prehistoric man some time before the pure metal was isolated. Bronzes were common in early Mesopotamia, the Indus Valley, Egypt, Crete, Israel, and Peru. Much of the tin used by the early Mediterranean peoples apparently came from the Scilly Isles and Cornwall in the British Isles,[16] where mining of the metal dates from about 300–200 BCE. Tin mines were operating in both the Inca and Aztec areas of South and Central America before the Spanish conquest.

Lead is mentioned often in early Biblical accounts. The Babylonians used the metal as plates on which to record inscriptions. The Romans used it for tablets, water pipes, coins, and even cooking utensils; indeed, as a result of the last use, lead poisoning was recognized in the time of Augustus Caesar. The compound known as white lead was apparently prepared as a decorative pigment at least as early as 200 BCE.

Modern discoveries

Amorphous elemental silicon was first obtained pure in 1824 by the Swedish chemist Jöns Jacob Berzelius; impure silicon had already been obtained in 1811. Crystalline elemental silicon was not prepared until 1854, when it was obtained as a product of electrolysis.

Germanium is one of three elements the existence of which was predicted in 1869 by the Russian chemist Dmitri Mendeleev when he first devised his periodic table. However, the element was not actually discovered for some time. In September 1885, a miner discovered a mineral sample in a silver mine and gave it to the mine manager, who determined that it was a new mineral and sent the mineral to Clemens A. Winkler. Winkler realized that the sample was 75% silver, 18% sulfur, and 7% of an undiscovered element. After several months, Winkler isolated the element and determined that it was element 32.[13]

The first attempt to discover flerovium (then referred to as "element 114") was in 1969, at the Joint Institute for Nuclear Research, but it was unsuccessful. In 1977, researchers at the Joint Institute for Nuclear Research bombarded plutonium-244 atoms with calcium-48, but were again unsuccessful. This nuclear reaction was repeated in 1998, this time successfully.[13]

Etymologies

The word "carbon" comes from the Latin word carbo, meaning "charcoal".The word "silicon" comes from the Latin word silex or silicis, which means "flint". The word "germanium" comes from the word germania, which is Latin for Germany, the country where germanium was discovered. The word "tin" derives from the Old English word tin. The word "lead" comes from the Old English word lead.[13]

Applications

Carbon is most commonly used in its amorphous form. In this form, carbon is used for steelmaking, as carbon black, as a filling in tires, in respirators, and as activated charcoal. Carbon is also used in the form of graphite is commonly used as the lead in pencils. Diamond, another form of carbon, is commonly used in jewelry.[13] Carbon fibers are used in numerous applications, such as satellite struts, because the fibers are highly strong yet elastic.[17]

Silicon dioxide has a wide variety of applications, including toothpaste, construction fillers, and silica is a major component of glass. 50% of pure silicon is devoted to the manufacture of metal alloys. 45% of silicon is devoted to the manufacture of silicones. Silicon is also commonly used in semiconductors since the 1950s.[12][17]

Germanium was used in semiconductors until the 1950s, when it was replaced by silicon.[12] Radiation detectors contain germanium. Germanium oxide is used in fiber optics and wide-angle camera lenses. A small amount of germanium mixed with silver can make silver tarnish-proof. The resulting alloy is known as argentium.[13]

Solder is the most important use of tin; 50% of all tin produced goes into this application. 20% of all tin produced is used in tin plate. 20% of tin is also used by the chemical industry. Tin is also a constituent of numerous alloys, including pewter. Tin (IV) oxide has been commonly used in ceramics for thousands of years. Cobalt stannate is a tin compound which is used as a cerulean blue pigment.[13]

80% of all lead produced goes into lead–acid batteries. Other applications for lead include weights, pigments, and shielding against radioactive materials. Lead was historically used in gasoline in the form of tetraethyllead, but this application has been discontinued due to concerns of toxicity.[18]

Production

Carbon's allotrope diamond is produced mostly by Russia, Botswana, Congo, Canada, and South Africa. 80% of all synthetic diamonds are produced by Russia. China produces 70% of the world's graphite. Other graphite-mining countries are Brazil, Canada, and Mexico.[13]

Silicon can be produced by heating silica with carbon.[17]

There are some germanium ores, such as germanite, but these are not mined on account of being rare. Instead, germanium is extracted from the ores of metals such as zinc. In Russia and China, germanium is also separated from coal deposits. Germanium-containing ores are first treated with chlorine to form germanium tetrachloride, which is mixed with hydrogen gas. Then the germanium is further refined by zone refining. Roughly 140 metric tons of germanium are produced each year.[13]

Mines output 300,000 metric tons of tin each year. China, Indonesia, Peru, Bolivia, and Brazil are the main producers of tin. The method by which tin is produced is to head the tin mineral cassiterite (SnO2) with coke.[13]

The most commonly mined lead ore is galena (lead sulfide). 4 million metric tons of lead are newly mined each year, mostly in China, Australia, the United States, and Peru. The ores are mixed with coke and limestone and roasted to produce pure lead. Most lead is recycled from lead batteries. The total amount of lead ever mined by humans amounts to 350 million metric tons.[13]

Biological role

Carbon is a key element to all known life. It is in all organic compounds, for example, DNA, steroids, and proteins.[3] Carbon's importance to life is primarily due to its ability to form numerous bonds with other elements.[12] There are 16 kilograms of carbon in a typical 70-kilogram human.[13]

Silicon-based life's feasibility is commonly discussed. However, it is less able than carbon to form elaborate rings and chains.[3] Silicon in the form of silicon dioxide is used by diatoms and sea sponges to form their cell walls and skeletons. Silicon is essential for bone growth in chickens and rats and may also be essential in humans. Humans consume on average between 20 and 1200 milligrams of silicon per day, mostly from cereals. There is 1 gram of silicon in a typical 70-kilogram human.[13]

A biological role for germanium is not known, although it does stimulate metabolism. In 1980, germanium was reported by Kazuhiko Asai to benefit health, but the claim has not been proven. Some plants take up germanium from the soil in the form of germanium oxide. These plants, which include grains and vegetables contain roughly 0.05 parts per million of germanium. The estimated human intake of germanium is 1 milligram per day. There are 5 milligrams of germanium in a typical 70-kilogram human.[13]

Tin has been shown to be essential for proper growth in rats, but there is, as of 2013, no evidence to indicate that humans need tin in their diet. Plants do not require tin. However, plants do collect tin in their roots. Wheat and corn contain seven and three parts per million respectively. However, the level of tin in plants can reach 2000 parts per million if the plants are near a tin smelter. On average, humans consume 0.3 milligrams of tin per day. There are 30 milligrams of tin in a typical 70-kilogram human.[13]

Lead has no known biological role, and is in fact highly toxic, but some microbes are able to survive in lead-contaminated environments. Some plants, such as cucumbers contain up to tens of parts per million of lead. There are 120 milligrams of lead in a typical 70-kilogram human.[13]

Toxicity

Elemental carbon is not generally toxic, but many of its compounds are, such as carbon monoxide and hydrogen cyanide. However, carbon dust can be dangerous because it lodges in the lungs in a manner similar to asbestos.[13]

Silicon minerals are not typically poisonous. However, silicon dioxide dust, such as that emitted by volcanoes can cause adverse health effects if it enters the lungs.[12]

Germanium can interfere with such enzymes as lactate and alcohol dehydrogenase. Organic germanium compounds are more toxic than inorganic germanium compounds. Germanium has a low degree of oral toxicity in animals. Severe germanium poisoning can cause death by respiratory paralysis.[19]

Some tin compounds are toxic to ingest, but most inorganic compounds of tin are considered nontoxic. Organic tin compounds, such as trimethyl tin and triethyl tin are highly toxic, and can disrupt metabolic processes inside cells.[13]

Lead and its compounds, such as lead acetate are highly toxic. Lead poisoning can cause headaches, stomach pain, constipation, and gout.[13]

References

  1. ^ Carbon compounds, retrieved January 24, 2013
  2. ^ Silicon compounds, retrieved January 24, 2013
  3. ^ a b c d e Gray, Theodore (2011), The Elements
  4. ^ Germanium compounds, retrieved January 24, 2013
  5. ^ Tin compounds, retrieved January 24, 2013
  6. ^ Lead compounds, retrieved January 24, 2013
  7. ^ Flerovium compounds, retrieved January 24, 2013
  8. ^ a b c d e Jackson, Mark (2001), Periodic Table Advanced
  9. ^ Graphene, retrieved January 2013 Check date values in: |accessdate= (help)
  10. ^ Carbon:Allotropes, archived from the original on 2013-01-17, retrieved January 2013 Check date values in: |accessdate= (help)
  11. ^ Gagnon, Steve, The Element Silicon, retrieved January 20, 2013
  12. ^ a b c d e f g h Kean, Sam (2011), The Disappearing Spoon
  13. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad Emsley, John (2011), Nature's Building Blocks
  14. ^ tin (Sn), Encyclopædia Britannica, 2013, retrieved February 24, 2013
  15. ^ Chemical Elements, retrieved January 2013 Check date values in: |accessdate= (help)
  16. ^ Online Encyclopædia Britannica, Tin
  17. ^ a b c Galan, Mark (1992), Structure of Matter, ISBN 0-809-49663-1
  18. ^ Blum, Deborah (2010), The Poisoner's Handbook
  19. ^ Risk Assessment (PDF), 2003, archived from the original on January 12, 2012, retrieved January 19, 2013
Amine N-methyltransferase

In enzymology, an amine N-methyltransferase (EC 2.1.1.49) is an enzyme that is ubiquitously present in non-neural tissues and that catalyzes the N-methylation of tryptamine and structurally related compounds.

The chemical reaction taking place is:

Thus, the two substrates of this enzyme are S-adenosyl methionine and amine, whereas its two products are S-adenosylhomocysteine and methylated amine. In the case of tryptamine and serotonin these then become the dimethylated indolethylamines N,N-dimethyltryptamine (DMT) and bufotenine.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:amine N-methyltransferase. Other names in common use include nicotine N-methyltransferase, tryptamine N-methyltransferase, indolethylamine N-methyltransferase, and arylamine N-methyltransferase. This enzyme participates in tryptophan metabolism.

A wide range of primary, secondary and tertiary amines can act as acceptors, including tryptamine, aniline, nicotine and a variety of drugs and other xenobiotics.

Betaine—homocysteine S-methyltransferase

In the field of enzymology, a betaine-homocysteine S-methyltransferase also known as betaine-homocysteine methyltransferase (BHMT) is a zinc metallo-enzyme that catalyzes the transfer of a methyl group from trimethylglycine and a hydrogen ion from homocysteine to produce dimethylglycine and methionine respectively:

Trimethylglycine (methyl donor) + homocysteine (hydrogen donor) → dimethylglycine (hydrogen receiver) + methionine (methyl receiver)

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. This enzyme participates in the metabolism of glycine, serine, threonine and also methionine.

Chalcogen

The chalcogens () are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po). The chemically uncharacterized synthetic element livermorium (Lv) is predicted to be a chalcogen as well. Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper (the term was also used for bronze/brass, any metal in the poetic sense, ore or coin), and the Latinised Greek word genēs, meaning born or produced.Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Their most common oxidation states are −2, +2, +4, and +6. They have relatively low atomic radii, especially the lighter ones.Lighter chalcogens are typically nontoxic in their elemental form, and are often critical to life, while the heavier chalcogens are typically toxic. All of the chalcogens have some role in biological functions, either as a nutrient or a toxin. The lighter chalcogens, such as oxygen and sulfur, are rarely toxic and usually helpful in their pure form. Selenium is an important nutrient but is also commonly toxic. Tellurium often has unpleasant effects (although some organisms can use it), and polonium is always extremely harmful, both in its chemical toxicity and its radioactivity.

Sulfur has more than 20 allotropes, oxygen has nine, selenium has at least five, polonium has two, and only one crystal structure of tellurium has so far been discovered. There are numerous organic chalcogen compounds. Not counting oxygen, organic sulfur compounds are generally the most common, followed by organic selenium compounds and organic tellurium compounds. This trend also occurs with chalcogen pnictides and compounds containing chalcogens and carbon group elements.

Oxygen is generally extracted from air and sulfur is extracted from oil and natural gas. Selenium and tellurium are produced as byproducts of copper refining. Polonium and livermorium are most available in particle accelerators. The primary use of elemental oxygen is in steelmaking. Sulfur is mostly converted into sulfuric acid, which is heavily used in the chemical industry. Selenium's most common application is glassmaking. Tellurium compounds are mostly used in optical disks, electronic devices, and solar cells. Some of polonium's applications are due to its radioactivity.

Cyclopropane-fatty-acyl-phospholipid synthase

In enzymology, a cyclopropane-fatty-acyl-phospholipid synthase (EC 2.1.1.79) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + phospholipid olefinic fatty acid S-adenosyl-L-homocysteine + phospholipid cyclopropane fatty acid

Thus, the two substrates of this enzyme are S-adenosyl methionine and phospholipid olefinic fatty acid, whereas its two products are S-adenosylhomocysteine and phospholipid cyclopropane fatty acid.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:unsaturated-phospholipid methyltransferase (cyclizing). Other names in common use include cyclopropane synthetase, unsaturated-phospholipid methyltransferase, cyclopropane synthase, cyclopropane fatty acid synthase, cyclopropane fatty acid synthetase, and CFA synthase.

Flerovium

Flerovium is a superheavy artificial chemical element with symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. The element is named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna, Russia, where the element was discovered in 1998. The name of the laboratory, in turn, honours the Russian physicist Georgy Flyorov (Флёров in Cyrillic, hence the transliteration of "yo" to "e"). The name was adopted by IUPAC on 30 May 2012.

In the periodic table of the elements, it is a transactinide element in the p-block. It is a member of the 7th period and is the heaviest known member of the carbon group; it is also the heaviest element whose chemistry has been investigated. Initial chemical studies performed in 2007–2008 indicated that flerovium was unexpectedly volatile for a group 14 element; in preliminary results it even seemed to exhibit properties similar to those of the noble gases. More recent results show that flerovium's reaction with gold is similar to that of copernicium, showing that it is a very volatile element that may even be gaseous at standard temperature and pressure, that it would show metallic properties, consistent with it being the heavier homologue of lead, and that it would be the least reactive metal in group 14. The question of whether flerovium behaves more like a metal or a noble gas is still unresolved as of 2018.

About 90 atoms of flerovium have been observed: 58 were synthesized directly, and the rest were made from the radioactive decay of heavier elements. All of these flerovium atoms have been shown to have mass numbers from 284 to 290. The most stable known flerovium isotope, flerovium-289, has a half-life of around 2.6 seconds, but it is possible that the unconfirmed flerovium-290 with one extra neutron may have a longer half-life of 19 seconds; this would be one of the longest half-lives of any isotope of any element at these farthest reaches of the periodic table. Flerovium is predicted to be near the centre of the theorized island of stability, and it is expected that heavier flerovium isotopes, especially the possibly doubly magic flerovium-298, may have even longer half-lives.

Germabenzene

Germabenzene (C5H6Ge) is the parent representative of a group of chemical compounds containing in their molecular structure a benzene ring with a carbon atom replaced by a germanium atom. Germabenzene itself has been studied theoretically, and synthesized with a bulky 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl or Tbt group. Also, stable naphthalene derivatives do exist in the laboratory such as the 2-germanaphthalene-containing substance represented below. The germanium to carbon bond in this compound is shielded from potential reactants by a Tbt group. This compound is aromatic just as the other carbon group representatives silabenzene and stannabenzene.

Germanium

Germanium is a chemical element with symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors silicon and tin. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature.

Because it seldom appears in high concentration, germanium was discovered comparatively late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties from its position on his periodic table, and called the element ekasilicon. Nearly two decades later, in 1886, Clemens Winkler found the new element along with silver and sulfur, in a rare mineral called argyrodite. Although the new element somewhat resembled arsenic and antimony in appearance, the combining ratios in compounds agreed with Mendeleev's predictions for a relative of silicon. Winkler named the element after his country, Germany. Today, germanium is mined primarily from sphalerite (the primary ore of zinc), though germanium is also recovered commercially from silver, lead, and copper ores.

Elemental germanium is used as a semiconductor in transistors and various other electronic devices. Historically, the first decade of semiconductor electronics was based entirely on germanium. Today, the amount of germanium produced for semiconductor electronics is one fiftieth the amount of ultra-high purity silicon produced for the same. Presently, the major end uses are fibre-optic systems, infrared optics, solar cell applications, and light-emitting diodes (LEDs). Germanium compounds are also used for polymerization catalysts and have most recently found use in the production of nanowires. This element forms a large number of organometallic compounds, such as tetraethylgermane, useful in organometallic chemistry.

Germanium is not thought to be an essential element for any living organism. Some complex organic germanium compounds are being investigated as possible pharmaceuticals, though none have yet proven successful. Similar to silicon and aluminium, natural germanium compounds tend to be insoluble in water and thus have little oral toxicity. However, synthetic soluble germanium salts are nephrotoxic, and synthetic chemically reactive germanium compounds with halogens and hydrogen are irritants and toxins.

Group 14 hydride

Group 14 hydrides are chemical compounds composed of hydrogen atoms and carbon group atoms (the elements of group 14 are carbon, silicon, germanium, tin, and lead).

Guanidinoacetate N-methyltransferase

Guanidinoacetate N-methyltransferase (EC 2.1.1.2) is an enzyme that catalyzes the chemical reaction and is encoded by gene GAMT located on chromosome 19p13.3.

S-adenosyl-L-methionine + guanidinoacetate S-adenosyl-L-homocysteine + creatine

Thus, the two substrates of this enzyme are S-adenosyl methionine and guanidinoacetate, whereas its two products are S-adenosylhomocysteine and creatine.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:N-guanidinoacetate methyltransferase. Other names in common use include GA methylpherase, guanidinoacetate methyltransferase, guanidinoacetate transmethylase, methionine-guanidinoacetic transmethylase, and guanidoacetate methyltransferase. This enzyme participates in glycine, serine and threonine metabolism and arginine and proline metabolism.

The protein encoded by this gene is a methyltransferase that converts guanidoacetate to creatine, using S-adenosylmethionine as the methyl donor. Defects in this gene have been implicated in neurologic syndromes and muscular hypotonia, probably due to creatine deficiency and accumulation of guanidinoacetate in the brain of affected individuals. Two transcript variants encoding different isoforms have been described for this gene.

Hexaprenyldihydroxybenzoate methyltransferase

In enzymology, a hexaprenyldihydroxybenzoate methyltransferase (EC 2.1.1.114) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + 3-hexaprenyl-4,5-dihydroxybenzoate S-adenosyl-L-homocysteine + 3-hexaprenyl-4-hydroxy-5-methoxybenzoate

Thus, the two substrates of this enzyme are S-adenosyl methionine and 3-hexaprenyl-4,5-dihydroxybenzoate, whereas its two products are S-adenosylhomocysteine and 3-hexaprenyl-4-hydroxy-5-methoxybenzoate.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:3-hexaprenyl-4,5-dihydroxylate O-methyltransferase. Other names in common use include 3,4-dihydroxy-5-hexaprenylbenzoate methyltransferase, and dihydroxyhexaprenylbenzoate methyltransferase. This enzyme participates in ubiquinone biosynthesis.

Horex

Horex is a German motorcycle manufacturer. In 1920 Friedrich Kleemann (1868-1949), financial manager at the Rex Konservenglas Gesellschaft (preservative jar manufacturing company) in Bad Homburg (Germany) bought COLUMBUS MOTORENBAU AG, a small motor factory in Oberursel by Taunus, which was in the neighbourhood. The factory made the later Horex model and the name remained the same for almost 30 years. Fritz Kleemann, the son of Friedrich Kleemann, made the first cycles with a GNOM engine, delivered from the Columbus-Engine factory. In 1923 Fritz Kleemann (1901-1975), founded HOREX-FAHRZEUGBAU AG. He derived the name from his town HOmburg and his father's preservative jar company REX. He was also a motorcycle racer and was riding his own Horex machine. He built the first "real" Horex, a 248cc, OHV, that he tested himself on race. So, Horex was built for motorcycle riders by motorcycle riders. Horex built motorcycles with Columbus four-stroke engines from Oberursel. In 1925 Horex and Columbus merged. Horex developed a range of models with single-cylinder Columbus engines from 250 cc to 600 cc. In 1933 it added two parallel-twin models: the 600 cc S6 and 800 cc S8. Both twins have chain-driven OHC valvegear.

World War II interrupted motorcycle production, but Horex resumed in 1948 with a 350 cc single-cylinder model, the SB 35 Regina. In 1951, Horex added a 500 cc OHC parallel-twin engine called the Imperator. In 1954 it added a 400 cc version of this twin to its range. In 1955, the company replaced the Regina with the Resident.

Daimler-Benz took over the company in 1960 and motorcycle production was terminated.

1989 CK design in Japan developed Horex 644 OSCA with Fritz Roeth in Hammelbach, 644cc single cylinder sports, using Honda RFVC engine. made debut press conference in Berlin 1990 .

On June 15, 2010, it was announced that the brand would be revived and that a Horex motorcycle with a narrow-angle, six-cylinder supercharged engine would be available for sale in Germany, Austria and Switzerland at the end of the year 2011, with international sales to follow. Besides the new VR6 supercharged engine, an aluminum bridge frame with a steel steering head forms the chassis. A single swing arm controls the rear wheel, while the engine power is transferred by a belt drive system.The company filed for bankruptcy in September 2014, and in late 2014 announced that all employees had been let go and the factory was closed.3C-Carbon Group AG is going to be the new owner of motorcycle brand Horex

Last Thursday at the creditors' meeting, under the direction of the insolvency administrator, Rainer U. Müller from the law firm, Anchor Rechtsanwälte, the 3C-Carbon Group AG came out on top in the quest to purchase the Horex brand. (6 February 2015).

Hydroxide

Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. A hydroxide attached to a strongly electropositive center may itself ionize, liberating a hydrogen cation (H+), making the parent compound an acid.

The corresponding electrically neutral compound HO• is the hydroxyl radical. The corresponding covalently-bound group –OH of atoms is the hydroxy group.

Hydroxide ion and hydroxy group are nucleophiles and can act as a catalysts in organic chemistry.

Many inorganic substances which bear the word "hydroxide" in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups.

Lead

Lead is a chemical element with symbol Pb (from the Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes each include a major decay chain of heavier elements.

Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form chains and polyhedral structures.

Lead is easily extracted from its ores; prehistoric people in Western Asia knew of it. Galena, a principal ore of lead, often bears silver, interest in which helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.

In the late 19th century, lead's toxicity was recognized, and its use has since been phased out of many applications. However, many countries still allow the sale of products that expose humans to lead, including some types of paints and bullets. Lead is a toxin that accumulates in soft tissues and bones, it acts as a neurotoxin damaging the nervous system and interfering with the function of biological enzymes, causing neurological disorders, such as brain damage and behavioral problems.

List of EC numbers (EC 2)

This list contains a list of EC numbers for the second group, EC 2, transferases, placed in numerical order as determined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology.

Methylamine—glutamate N-methyltransferase

In enzymology, a methylamine-glutamate N-methyltransferase (EC 2.1.1.21) is an enzyme that catalyzes the chemical reaction

methylamine + L-glutamate NH3 + N-methyl-L-glutamate

Thus, the two substrates of this enzyme are methylamine and L-glutamate, whereas its two products are NH3 and N-methyl-L-glutamate.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is methylamine:L-glutamate N-methyltransferase. Other names in common use include N-methylglutamate synthase, and methylamine-glutamate methyltransferase. This enzyme participates in methane metabolism.

Onium ion

In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table), chalcogen (group 16), or halogen (group 17). The oldest-known onium ion, and the namesake for the class, is ammonium, NH+4, the protonated derivative of ammonia, NH3.The name onium is also used for cations that would result from the substitution of hydrogen atoms in those ions by other groups, such as organic radicals, or halogens; such as tetraphenylphosphonium, (C6H5)4P+. The substituent groups may be divalent or trivalent, yielding ions such as iminium and nitrilium.A simple onium ion has a charge of +1. A larger ion that has two onium ion subgroups is called a double onium ion, and has a charge of +2. A triple onium ion has a charge of +3, and so on.

Compounds of an onium cation and some other negative ion are known as onium compounds or onium salts.

Onium ions and onium compounds are inversely analogous to -ate ions and ate complexes:

Lewis bases form onium ions when the central atom gains one more bond and becomes a positive cation.

Lewis acids form -ate ions when the central atom gains one more bond and becomes a negative anion.

Organolead compound

Organolead compounds are chemical compounds containing a chemical bond between carbon and lead. Organolead chemistry is the corresponding science. The first organolead compound was hexaethyldilead (Pb2(C2H5)6), first synthesized in 1858. Sharing the same group with carbon, lead is tetravalent.

Going down the carbon group the C–X (X = C, Si, Ge, Sn, Pb) bond becomes weaker and the bond length larger. The C–Pb bond in tetramethyllead is 222 pm long with a dissociation energy of 49 kcal/mol (204 kJ/mol). For comparison the C–Sn bond in tetramethyltin is 214 pm long with dissociation energy 71 kcal/mol (297 kJ/mol). The dominance of Pb(IV) in organolead chemistry is remarkable because inorganic lead compounds tend to have Pb(II) centers. The reason is that with inorganic lead compounds elements such as nitrogen, oxygen and the halides have a much higher electronegativity than lead itself and the partial positive charge on lead then leads to a stronger contraction of the 6s orbital than the 6p orbital making the 6s orbital inert; this is called the inert pair effect.By far the most important organolead compound is tetraethyllead, formerly used as an anti-knocking agent. The most important lead reagents for introducing lead are lead tetraacetate and lead chloride.

The use of organoleads is limited partly due to their toxicity.

Tetrahydrocannabivarin

Tetrahydrocannabivarin (THCV, THV) is a homologue of tetrahydrocannabinol (THC) having a propyl (3-carbon) side chain instead of a pentyl (5-carbon) group on the molecule, which makes it produce very different effects from THC.

Thymidylate synthase (FAD)

In enzymology, a thymidylate synthase (FAD) (EC 2.1.1.148) is an enzyme that catalyzes the chemical reaction

5,10-methylenetetrahydrofolate + dUMP + FADH2 dTMP + tetrahydrofolate + FAD

The 3 substrates of this enzyme are 5,10-methylenetetrahydrofolate, dUMP, and FADH2, whereas its 3 products are dTMP, tetrahydrofolate, and FAD.

This enzyme belongs to the family of transferases, to be specific those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is 5,10-methylenetetrahydrofolate,FADH2:dUMP C-methyltransferase. Other names in common use include Thy1, and ThyX. This enzyme participates in pyrimidine metabolism and one carbon pool by folate.

Most organisms, including humans, use the thyA- or TYMS-encoded classic thymidylate synthase whereas some bacteria use the similar flavin-dependent thymidylate synthase (FDTS) instead.

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