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Hydrodefluorination
Hydrodefluorination (HDF) is a chemical transformation that converts a carbon–fluorine bond into a carbon–hydrogen bond, used to make partially fluorinated building blocks and break down persistent pollutants such as PFAS.
Hydrodehalogenation
Hydrodehalogenation (HDH) is a chemical reaction converting a carbon–halogen bond into a carbon–hydrogen bond; its deuterium counterpart is deuterodehalogenation (DDH). Both modify pharmaceuticals and detoxify pollutants.
Hydrodenitrogenation
Hydrodenitrogenation (HDN) is a catalytic refining process that removes organonitrogen compounds from petroleum by reaction with hydrogen over catalysts at 300 to 400 °C, converting nitrogen to ammonia.
Hydrodeoxygenation
Hydrodeoxygenation (HDO) is a catalytic process that removes oxygen from organic compounds by reaction with hydrogen, with oxygen leaving mainly as water. It is used to upgrade fast-pyrolysis bio-oil into transportation fuels.
Hydrodynamic dispersion
Hydrodynamic dispersion is the spreading and mixing of a solute as it moves through porous media, combining mechanical dispersion with molecular diffusion, and widening contaminant plumes in aquifers.
Hydrodynamic electron flow (Poiseuille flow)
Hydrodynamic electron flow, or Poiseuille flow, is the parabolic current profile electrons form when they collide mainly with each other, moving like a viscous fluid; it was first directly imaged in graphene in 2019.
Hydrodynamic electron flow in graphene
Hydrodynamic electron flow in graphene is a transport regime in which electrons collide with one another more often than with impurities, flowing collectively like a viscous fluid.
Hydrodynamic interaction
Hydrodynamic interaction is the influence suspended particles in a viscous fluid exert on each other's motion through their generated flows, central to sedimentation, colloidal suspensions, and microrheology.
Hydrodynamic stability
Hydrodynamic stability is the branch of fluid mechanics that studies whether laminar flows remain laminar under small disturbances or transition to turbulence, using tools like the Orr-Sommerfeld equation.
Hydrofluoric acid
Hydrofluoric acid (HF) is a solution of hydrogen fluoride in water, a weak but highly dangerous acid that binds calcium in the body and etches glass.
Hydrofluoroether
A hydrofluoroether (HFE) is a fluorinated ether developed by 3M in the 1990s as a replacement for ozone-depleting CFCs, used in precision cleaning, aerosols, and heat-transfer fluids.
Hydroformylation
Hydroformylation, also called the oxo process or oxo synthesis, is the catalytic addition of carbon monoxide and hydrogen to an alkene to form aldehydes, used industrially since 1938.
Hydrofunctionalization
Hydrofunctionalization is the addition of a hydrogen atom and a functional group across an unsaturated carbon–carbon bond, most often of an alkene or alkyne, an atom- and step-efficient strategy in organic synthesis.
Hydrogel bioelectronics
Hydrogel bioelectronics is a branch of bioelectronics in which water-rich hydrogels form the interface between soft biological tissue and rigid electronics, enabling neural recording, stimulation, and wearables.
Hydrogel microparticles
Hydrogel microparticles, also called microgels or hydrogel microspheres, are water-swollen, crosslinked polymer networks that can absorb several times their weight in water, used in drug delivery, tissue engineering, biosensing, and 3D bioprinting.
Hydrogel synthesis
Hydrogel synthesis is the set of chemical routes that form crosslinked hydrophilic polymer networks holding at least 10% water, used in contact lenses, drug delivery, and tissue engineering.
Hydrogen
Hydrogen, the lightest and simplest chemical element with atomic number 1, is the most abundant element in the universe and the fuel burned by stars like the Sun.
Hydrogen atom
The hydrogen atom, or atomic hydrogen, consists of a single proton and a single electron bound by Coulomb attraction, making it the simplest atom and the reference system of atomic physics.
Hydrogen atom transfer
Hydrogen atom transfer (HAT) is a chemical reaction in which a proton and an electron move together as a hydrogen atom between substrates in a single step.
Hydrogen atom transfer catalysis with thiols
Hydrogen atom transfer catalysis with thiols is a family of radical reactions in which thiol catalysts deliver or remove hydrogen atoms to generate radical intermediates.
Hydrogen atom transfer hydrofunctionalization
Hydrogen atom transfer (HAT) hydrofunctionalization adds a hydrogen atom and a functional group across an alkene, typically via cobalt metal hydride catalysis, giving Markovnikov products.
Hydrogen atom transfer photocatalysis
Hydrogen atom transfer (HAT) photocatalysis is a strategy in organic synthesis that uses light-absorbing catalysts to abstract hydrogen atoms, converting C–H bonds into C–C and C–heteroatom bonds.
Hydrogen atom transfer/nickel catalysis
Hydrogen atom transfer/nickel (HAT/nickel) catalysis is a cross-coupling method in which a HAT catalyst generates carbon radicals from C–H bonds and nickel couples them with aryl or alkyl halides, introduced in 2016 by David MacMillan.
Hydrogen bond
A hydrogen bond is an attractive interaction in which hydrogen attached to an electronegative atom is drawn toward an acceptor, proposed by Latimer and Rodebush in 1920.
Hydrogen bond network
A hydrogen bond network is the connected system of hydrogen bonds linking molecules or ions through a liquid, crystal, or biological structure, with liquid water as the archetype.
Hydrogen bromide
Hydrogen bromide (HBr) is a colorless, corrosive gas discovered by Antoine Jérôme Balard in 1826 that dissolves in water to form hydrobromic acid, one of the strongest mineral acids.
Hydrogen burning
Hydrogen burning is the set of thermonuclear reactions by which stars convert hydrogen into helium, the dominant energy source for most of a star's life.
Hydrogen chloride
Hydrogen chloride (HCl), also called anhydrous hydrochloric acid, is a colorless, corrosive, nonflammable gas with a pungent odor that dissolves in water to form hydrochloric acid, used in steel pickling.
Hydrogen cyanide
Hydrogen cyanide, also called prussic acid, is a colorless liquid or gas with a bitter almond odor that kills within minutes yet is produced industrially for nylon and gold mining.
Hydrogen embrittlement
Hydrogen embrittlement, also called hydrogen cracking, is the loss of ductility or load-bearing capacity in metals caused by atomic hydrogen, producing sudden brittle fracture below yield strength.