Physical world and mathematics

Phenanthrene

Phenanthrene is a polycyclic aromatic hydrocarbon with three benzene rings fused in an angular arrangement, isomeric with anthracene and found in coal tar from incomplete combustion.

Phenanthrol, also called hydroxyphenanthrene, is any of five monohydroxylated derivatives of the three-ring hydrocarbon phenanthrene, occurring chiefly as metabolites; 9-phenanthrol is widely used to inhibit the TRPM4 ion channel.

Phenazine

Phenazine is a planar, redox-active tricyclic aromatic heterocycle whose derivatives, more than 100 of them made naturally by bacteria, include the antibiotic pyocyanin and electrolytes for redox flow batteries.

Phenethylamine (β-phenylethylamine)

Phenethylamine (β-phenylethylamine, PEA) is a trace amine found naturally in the human brain, in chocolate, and in fermented foods, and is the structural parent of amphetamine.

Phenetidine

Phenetidine, also known as ethoxyaniline, refers to two aromatic amine isomers. The commercially important para isomer is used in dyes and pharmaceuticals and is a metabolite of phenacetin.

Phenformin

Phenformin is an oral biguanide antidiabetic drug used from the late 1950s to treat type 2 diabetes and withdrawn in 1977 after hundreds of fatal lactic acidosis cases.

Phenmetrazine

Phenmetrazine, sold under the brand name Preludin, is a morpholine-derived stimulant marketed from 1959 as an appetite suppressant for obesity, later controlled in Schedule II and no longer marketed.

PhenoFluor

PhenoFluor is a deoxyfluorination reagent developed in Tobias Ritter's laboratory at Harvard University that converts phenols and alcohols directly into aryl and alkyl fluorides, first reported in 2011 with better safety than DAST.

Phenol

Phenol, also known as carbolic acid or hydroxybenzene, is an aromatic organic compound made chiefly by the cumene process for resins, bisphenol A, and nylons.

Phenol formaldehyde resin

Phenol formaldehyde resin, also known as phenolic resin, is a thermosetting polymer made from phenol and formaldehyde, the first fully synthetic plastic, marketed from 1907 as Bakelite.

Phenol red

Phenol red, also called phenolsulfonphthalein (PSP), is a synthetic sulfonephthalein pH indicator dye that changes from yellow below pH 6.8 to bright pink above pH 8.2.

Phenols

Phenols, also called phenolic compounds, are organic compounds with one or more hydroxy groups attached directly to an aromatic ring, distinct from alcohols in acidity and reactivity.

Sep 29, 2026

Phenomenological analysis

Phenomenological analysis is a qualitative research method that analyzes participants' descriptions of lived experiences to identify their essential meanings, with descriptive and interpretive traditions used in health research.

Phenomenological quantum gravity

Phenomenological quantum gravity is the branch of physics that searches for observable signatures of a quantum theory of gravity in astrophysical observations, gravitational waves, and laboratory experiments, since Planck-scale effects lie beyond any accelerator.

Phenomenology of spacetime discreteness

Phenomenology of spacetime discreteness is the study of what observations would reveal, and what they already rule out, if spacetime has a smallest length scale near the Planck length.

Phenothiazine

Phenothiazine, also known as dibenzothiazine, is an aromatic tricyclic organic compound synthesized in 1883, parent of the first antipsychotic drugs like chlorpromazine and itself used as a veterinary anthelmintic.

Phenothiazine photocatalysts

Phenothiazine photocatalysts are metal-free organic photoredox catalysts derived from the phenothiazine heterocycle, whose strongly reducing excited states can reduce aryl chlorides that metal complexes cannot.

Phenoxazine photocatalysts

Phenoxazine photocatalysts are organic photoredox catalysts based on the phenoxazine scaffold, whose strongly reducing excited states drive single-electron chemistry under visible light as metal-free alternatives to iridium and ruthenium catalysts.

Phenoxy herbicide

Phenoxy herbicides are a family of synthetic auxin weed killers built on a phenoxyacetic acid backbone, selectively killing broadleaf plants while sparing grasses; 2,4-D was first synthesized in 1941.

Phenoxy-dioxetane chemiluminescent probes

Phenoxy-dioxetane chemiluminescent probes are synthetic molecules built on a phenoxy-substituted 1,2-dioxetane ring that emit light through chemical decomposition once a target enzyme removes the phenol's protective group.

Phenoxybenzamine

Phenoxybenzamine, sold as Dibenzyline, is a long-acting, irreversible alpha-adrenergic receptor blocker used to control hypertension and sweating in pheochromocytoma and to prepare patients before tumor removal surgery.

Phentolamine

Phentolamine is a reversible, non-selective alpha-1 and alpha-2 blocker sold in the United States since 1952 as Regitine, once used for hypertension and now mainly for pheochromocytoma surgery.

Phenyl glycidyl ether

Phenyl glycidyl ether, also called glycidyl phenyl ether or 1,2-epoxy-3-phenoxypropane, is a colorless liquid used mainly as a reactive diluent in epoxy resins and regulated as a potential occupational carcinogen.

Phenyl group

The phenyl group, also known as the phenyl ring, is the monovalent fragment C₆H₅–, formed by removing one hydrogen atom from benzene so the ring can bond to a molecule.

Phenyl isocyanate

Phenyl isocyanate, also called isocyanatobenzene, is the simplest aromatic isocyanate, a very toxic colorless liquid used as a reagent and as a model compound in urethane chemistry.

Phenylacetaldehyde

Phenylacetaldehyde, also called 2-phenylethanal or hyacinthin, is an aromatic aldehyde with a sweet, honey-like odor found in foods, wine, honey, and floral scents, used in flavorings and perfumery.

Phenylacetic acid

Phenylacetic acid (PAA) is a white crystalline carboxylic acid with a sweet, honey-like odor that occurs in plants and bacteria and serves as a natural auxin and penicillin G precursor.

Phenylacetone

Phenylacetone, also called phenyl-2-propanone or benzyl methyl ketone, is a colorless liquid ketone and amphetamine metabolite, best known as an illicit precursor controlled by the DEA.

Phenylacetylene

Phenylacetylene (ethynylbenzene) is the simplest aryl alkyne, a colorless liquid building block in organic synthesis, best known as the standard terminal alkyne substrate in Sonogashira cross-coupling.