All articles starting with H

Hydroboration

Hydroboration is the addition of a boron–hydrogen bond, typically from borane (BH₃), across a carbon–carbon double or triple bond, discovered by H.C. Brown in 1959 and used to convert alkenes into alcohols with anti-Markovnikov regiochemistry.

Hydroboration–oxidation reaction

The hydroboration–oxidation reaction is a two-step organic reaction that converts alkenes into alcohols by anti-Markovnikov, syn addition of water, discovered by H.C. Brown in 1959.

Hydrocarbon

A hydrocarbon is an organic compound consisting of only carbon and hydrogen. Found in petroleum, coal, and natural gas, hydrocarbons serve mainly as fuels and as feedstocks for plastics.

Hydrocele

Hydrocele, also called hydrocele of the tunica vaginalis or canal of Nuck hydrocele in females, is serous fluid collection around the testis causing scrotal swelling; common in newborns, treated by hydrocelectomy or aspiration with sclerotherapy.

Oct 21, 2026

Hydrocele or spermatocele

Hydrocele or spermatocele (ICD-11 GB00; ICD-10 N43): scrotal fluid collections. Hydrocele is serous fluid in the tunica vaginalis or spermatic cord; spermatocele is an epididymal cyst containing dead sperm, usually painless and untreated.

Hydrocele testis

Hydrocele testis, fluid collection in the tunica vaginalis around the testis, causes painless scrotal swelling; common in newborns (at least 5%), often resolving by age 1, with communicating, noncommunicating, and filarial forms treated by observation, hydrocelectomy, or sclerotherapy.

Hydrocephalus

Hydrocephalus, "water on the brain," is abnormal CSF build-up in the brain's ventricles. Treated by shunt surgery or endoscopic third ventriculostomy (ETV), often with CPC; congenital, acquired, and NPH types.

Oct 20, 2026

Hydrocharitaceae

Hydrocharitaceae, the frog's-bit or tape-grass family (Najadaceae synonym), is a cosmopolitan family of 14 genera and about 136 fully aquatic monocot herbs in Alismatales, with 3 marine seagrass genera, water pollination, and an Asian Late Cretaceous origin.

Hydrochloric acid

Hydrochloric acid, also known as muriatic acid, is a strong corrosive acid that dissolves metals, pickles steel, and forms the gastric acid in the human stomach.

Hydrochlorothiazide

Hydrochlorothiazide (HCTZ) is a thiazide-type diuretic inhibiting the renal NCC transporter, used for hypertension and edema; the most prescribed US thiazide (~31.8 million 2023 prescriptions), with electrolyte, metabolic, and small skin-cancer risks.

Hydrocodone

Hydrocodone (dihydrocodeinone) is a semi-synthetic opioid analgesic and antitussive, a full mu-opioid agonist, sold mainly in combination products like Vicodin and Tussionex; DEA Schedule II since October 2014, with about 136 million US prescriptions in 2011.

Hydrocodone/paracetamol

Hydrocodone/paracetamol, also called hydrocodone/acetaminophen and formerly sold as Vicodin, is a prescription tablet combining the opioid hydrocodone with acetaminophen, prescribed in the United States for severe pain.

Hydrocolloid dressing

Hydrocolloid dressing, also called hydrocolloid wound dressing or patch (水胶体敷料), is a two-layer adhesive dressing of CMC, pectin, or gelatin with a polyurethane backing that gels with exudate to keep wounds moist, used for pressure injuries, minor burns, and acne.

Oct 21, 2026

Hydrocortamate

Hydrocortamate (CAS 76-47-1) is a synthetic glucocorticoid, a hydrocortisone diethylaminoacetate ester, glucocorticoid receptor agonist used topically for dermatoses; marketed as Magnacort 0.5% ointment, US-approved 1956, now discontinued.

Hydrocortisone

Hydrocortisone (cortisol) is the synthetic form of the adrenal glucocorticoid cortisol, used for cortisol replacement in adrenal insufficiency (15–25 mg/day divided) and as an anti-inflammatory; discovered as Compound F at Mayo Clinic, 1950 Nobel Prize context.

Oct 21, 2026

Hydrocotyle

Hydrocotyle (pennywort) is a cosmopolitan genus of creeping aquatic and wetland herbs in Araliaceae, transferred from Apiaceae after molecular work; about 130–180 species, with all annual species endemic to Australia.

Hydrocracker

A hydrocracker is a catalytic refinery unit that converts heavy gas oils into jet fuel, diesel, and gasoline by cracking heavy molecules with hydrogen and a catalyst.

Hydrocyanation

Hydrocyanation is a catalytic reaction that adds hydrogen cyanide across carbon–carbon double or triple bonds to form organonitriles, used industrially to make adiponitrile, the precursor to nylon-66.

Hydrocyclone

A hydrocyclone is a stationary separator with no moving parts that uses centrifugal force to split pressurized slurry into fine light overflow and coarse heavy underflow.

Hydrocynus goliath

Hydrocynus goliath, the giant or goliath tigerfish, is a large piscivorous African freshwater fish (Alestidae) of the Congo basin and Lake Tanganyika, reaching 133 cm and 50 kg, IUCN Least Concern.

Hydrodealkylation

Hydrodealkylation (HDA), also called hydrodemethylation for methyl groups, is an industrial petrochemical process that converts toluene and xylenes to benzene with hydrogen, in thermal and catalytic variants.

Oct 22, 2026

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.

Oct 22, 2026

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.

Hydrodesulfurization

Hydrodesulfurization is a catalytic refining process that removes sulfur from petroleum fractions by reacting organosulfur compounds with hydrogen over sulfided molybdenum catalysts, letting refineries meet ultra-low-sulfur diesel limits.

Hydrodynamic cavitation

Hydrodynamic cavitation (HC) is the formation, growth, and implosive collapse of vapor bubbles where liquid passes through a constriction, producing extreme conditions used in wastewater treatment.

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.