SEMI HYDROGENATION OF ALKYNES
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Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula H2, called dihydrogen, or sometimes hydrogen gas, molecular hydrogen, or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas H2 (dihydrogen) and in molecular forms, such as in water and organic compounds. The most common isotope of hydrogen (1H) consists of one proton, one electron, and no neutrons. Hydrogen gas was first produced artificially in the 17th century by the reaction of acids with metals. Henry Cavendish, in 1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned; hence its name means 'water-former' in Greek. Understanding the colors of light absorbed and emitted by hydrogen was a crucial part of developing quantum mechanics. Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid-base reactions, which mainly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively charged anion, where it is known as hydride, or as a positively charged cation, H+, called a proton. Although tightly bonded to water molecules, protons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH. Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding H2. In the early universe, neutral hydrogen atoms formed about 370,000 years after the Big Bang as the universe expanded and plasma had cooled enough for electrons to remain bound to protons. Once stars formed most of the atoms in the intergalactic medium re-ionized. Nearly all hydrogen production is done by transforming fossil fuels, particularly steam reforming of natural gas. It can also be produced from water or saline by electrolysis, but this process is more expensive. Its main industrial uses include fossil fuel processing and ammonia production for fertilizer. Emerging uses for hydrogen include the use of fuel cells to generate electricity.
In connection with: Hydrogen
Description combos: in and reactions the molecules water Hydrogen 1H Dihydrogen
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.: 620 Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases (such as methane and propane), liquids (such as hexane and benzene), low melting solids (such as paraffin wax and naphthalene) or polymers (such as polyethylene and polystyrene). In the fossil fuel industries, hydrocarbon refers to naturally occurring petroleum, natural gas and coal, or their hydrocarbon derivatives and purified forms. Combustion of hydrocarbons is the main source of the world's energy. Petroleum is the dominant raw-material source for organic commodity chemicals such as solvents and polymers. Most anthropogenic (human-generated) emissions of greenhouse gases are either carbon dioxide released by the burning of fossil fuels, or methane released from the handling of natural gas or from agriculture.
In connection with: Hydrocarbon
Description combos: hydrocarbons coal such and group similar entirely be Hydrocarbons
Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons.
In connection with: Hydrogenation
Description combos: only catalytic reaction compounds often in be for atoms
Semiheavy water is the result of replacing one of the protium (normal hydrogen, 1H) in normal water with deuterium (2H; or D). It exists whenever there is water with 1H and 2H in the mix. This is because hydrogen atoms (1,2H) are rapidly exchanged between water molecules. Water with 50% 1H and 50% 2H, is about 50% H2HO and 25% each of H2O and 2H2O, in dynamic equilibrium. In normal water, about 1 molecule in 3,200 is HDO (1H2HO) (one hydrogen in 6,400 is 2H). By comparison, heavy water D2O or 2H2O occurs at a proportion of about 1 molecule in 41 million (i.e., 1 in 6,4002). This makes semiheavy water far more common than "normal" heavy water. The freezing point of semiheavy water is close to the freezing point of heavy water at 3.81°C compared to the 3.82°C of heavy water.
In connection with: Semiheavy water
Title combos: water Semiheavy
Description combos: makes is far atoms H2O is D2O about molecule
In chemistry, catenation is the bonding of atoms of the same element into a series, called a chain. A chain or a ring may be open if its ends are not bonded to each other (an open-chain compound), or closed if they are bonded in a ring (a cyclic compound). The words to catenate and catenation reflect the Latin root catena, "chain".
In connection with: Catenation
Description combos: to The and series of chain chain chemistry bonding
Nanomaterial-based catalysts are usually heterogeneous catalysts based upon metal nanoparticles. Metal nanoparticles have high surface area, which can increase catalytic activity. Nanoparticle catalysts can be easily separated and recycled. They are typically used under mild conditions to prevent decomposition or agglomeration of the nanoparticles. In many cases they are supported on substrates, sometimes they are not.
In connection with: Nanomaterial-based catalyst
Title combos: Nanomaterial based Nanomaterial catalyst based
Description combos: Metal and catalytic supported substrates on are based nanoparticles
Semi/partial hydrogenation of alkynes refers to the reduction of alkyne by one equivalent of hydrogen gas (H2) to give alkene rather than the fully reduced alkane. This process is a valuable transformation in organic synthesis and industrial chemistry, enabling selective conversion of alkynes to either cis (Z) or trans (E) alkenes. A variety of methods have been developed for this purpose, including classical approaches like Lindlar's catalyst and the Birch reduction, as well as modern techniques involving transition metal catalysis. Each method offers distinct advantages in terms of stereoselectivity, functional group tolerance, and scalability, allowing chemists to tailor reductions to specific synthetic goals.
In connection with: Semi-hydrogenation of alkynes
Title combos: hydrogenation Semi Semi hydrogenation of alkynes Semi hydrogenation of
Description combos: hydrogen Lindlar method developed specific functional for reduction including
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