Chemistry

Curium (Cm) — synthetic actinide element, atomic number 96 Curium Curium (Cm, Z=96) is a synthetic, radioactive actinide metal used mainly in research and as a neutron source; it was named for Marie and Pierre Curie and is produced in nuclear fac…

Cuvette: laboratory optical sample cell for spectroscopic measurements Cuvette A cuvette is a small optical sample cell used in spectroscopic instruments. This article explains its design, materials, common types, handling, and roles in measurements such as a…

Cyan (color) Cyan Cyan is a blue‑green hue midway between blue and green. It is a primary ink color in printing, a secondary color of light, and appears frequently in design, photography and nature.

Cyanide: chemistry, occurrence, toxicity and applications Cyanide Overview of cyanide chemistry, natural sources, toxic effects and medical/industrial uses, plus distinctions between cyanide ion, hydrogen cyanide and nitriles.

Cyclic compound (molecular ring structures) Cyclic compound A cyclic compound is a molecule in which a series of atoms bond to form a closed ring. This article covers structure, aromaticity, types, history, reactions, and common uses in che…

Cycloaddition: pericyclic ring-forming reactions in organic chemistry Cycloaddition Cycloadditions are pericyclic reactions that join unsaturated fragments to form rings. They include Diels–Alder and 1,3-dipolar cycloadditions and are central to synthesis, materia…

Cycloalkane: structure, properties, and common examples Cycloalkane Cycloalkanes are saturated ring hydrocarbons (general formula CnH2n) with distinctive conformations, ring strain and uses in solvents, fuels, and chemical synthesis.

Cyclohexane Cyclohexane is a colorless, flammable saturated cyclic hydrocarbon (C6H12) used as a solvent and as an industrial feedstock for producing adipic acid and caprolactam for nylon manu…

Cyclohexene: Structure, Properties, and Uses Cyclohexene Cyclohexene is a six-membered cyclic alkene (C6H10). This article summarizes its structure, common reactions, production routes, uses in synthesis, physical properties and safety c…

Cyclooctane — properties, structure, and applications Cyclooctane Cyclooctane (C8H16) is a colorless, nonpolar cycloalkane used mainly in research and as a solvent. It adopts multiple puckered conformations and undergoes typical alkane reactions;…

Cyclopropane: structure, properties, history and uses Cyclopropane Cyclopropane (C3H6) is the simplest cycloalkane: a three-membered, highly strained ring with distinctive bonding and reactivity; historically used as an anesthetic and valued in or…

Cysteine — sulfur-containing α‑amino acid Cysteine Cysteine is a sulfur-containing α-amino acid important in protein structure, enzyme catalysis and antioxidant biochemistry; it is semi‑essential and encoded by UGU and UGC.

D-block elements: the transition region of the periodic table D-block Overview of the d-block: location on the periodic table, electronic structure, chemical and physical properties, common uses, and distinctions such as Group 12 being classed as pos…

Dalton (unit) — unified atomic mass unit (Da, u, amu) Dalton (unit) The dalton (symbol Da), also called the unified atomic mass unit (u or amu), is the standard unit for atomic and molecular mass. It equals one twelfth the mass of a carbon‑12 atom,…

Darmstadtium (element 110) Darmstadtium Darmstadtium (Ds, Z=110) is a synthetic, highly radioactive transactinide first produced at GSI Darmstadt. It has no stable isotopes, short half-lives, and no practical uses beyond…

DDT (dichlorodiphenyltrichloroethane): history, properties, and impacts DDT DDT is a persistent organochlorine insecticide developed in the 20th century; effective against disease vectors but linked to environmental harm and human-health concerns, now larg…

Decaffeination: methods, history, and practical considerations Decaffeination Decaffeination is the removal of most caffeine from coffee, tea, cocoa and related products. Processes include solvent extraction, water-based methods and supercritical CO2. Residu…

Delocalized electron An electron not confined to a single atom or bond but spread over several atoms or an extended structure; central to resonance, aromaticity, conjugation and electrical conduction.

Depleted uranium: properties, uses, history and safety Depleted uranium Depleted uranium is the dense byproduct of uranium enrichment used in military munitions and civilian shielding. It is weakly radioactive, chemically toxic and the subject of envir…

Depolarizer (electrochemical cells) Depolarizer A depolarizer is a chemical agent used in primary electrochemical cells to prevent hydrogen buildup at the cathode, maintain voltage, and allow continued current flow; manganese di…

Deposition Deposition denotes placing, laying down, or removal: sworn out-of-court testimony in law; sediment accumulation in geology; material growth on surfaces in science; and removal from…

Deprotonation: removal of a proton in acid–base chemistry Deprotonation Deprotonation is the loss of a proton (H+) from a molecule. This article explains mechanisms, equilibrium (pKa), common bases and examples, roles in organic and biological chemistr…

Desiccation: drying, desiccants, effects and applications Desiccation Desiccation is extreme drying—the process or state of removing water. Covers mechanisms, common desiccants, industrial and biological roles, historical uses, and distinctions from…

Desublimation (deposition): gas-to-solid phase transition Desublimation Desublimation, also called deposition, is the direct transition from a vapor to a solid without passing through a liquid state; it occurs in nature (frost, snow) and in industrial…

Detergent (cleaning agent) Detergent Detergents are chemical cleaning agents—typically synthetic surfactant mixtures—used for laundry, dishwashing, industrial cleaning and personal-care products; they differ from soap…

Detonation (explosive shock wave) Detonation Detonation is a rapid, supersonic combustion process in an explosive that produces a high-pressure shock wave. It underlies high explosives, demolition, propulsion concepts, and im…

Deuterium: Characteristics, Natural Occurrence, and Applications Deuterium Deuterium, a stable hydrogen isotope with one neutron, occurs sparsely in nature and forms heavy water. Explore its physical properties, natural abundance, and practical uses from…

Dew point — atmospheric moisture and its measurement Dew point Dew point: the temperature at which air becomes saturated and water vapor begins to condense. Explains physical basis, measurement methods, practical uses, differences from relativ…

Diamond (mineral, gem, and industrial material) Diamond Diamond, a crystalline form of carbon, is noted for extreme hardness, high thermal conductivity and gem-quality varieties; it is used in jewelry, industrial tools and technical app…

Diastase: the amylase enzymes that break down starch Diastase Diastase refers to enzymes (amylases) that hydrolyze starch into sugars. Discovered in malt in 1833, diastase includes alpha, beta and other amylases and is important in brewing, b…

Diastereomer: definition, properties, examples, and significance Diastereomer An overview of diastereomers: stereoisomers that are not mirror images. Definitions, counting principles, epimers, physical and biological differences, methods of separation, and e…

Diatomic molecules Diatomic molecules are chemical species made of exactly two atoms. This article explains their types, bonding and electronic features, common examples, occurrence, uses, and distin…

Dicalcium phosphate Dicalcium phosphate (CaHPO4) is a white crystalline calcium phosphate used in food, pharmaceuticals, dentistry, animal feed and biomaterials; available as anhydrous or dihydrate fo…

Dieldrin (organochlorine insecticide) Dieldrin Dieldrin is a persistent chlorinated insecticide developed in the mid-20th century. It is effective against many pests but bioaccumulates and is toxic to wildlife and humans; now l…

Diels–Alder reaction A pericyclic 4+2 cycloaddition between a conjugated diene and a dienophile that builds cyclohexene rings; central to synthesis, catalysis, and material chemistry.

Diene: structure, types, reactions and applications Diene A diene is an organic molecule with two carbon–carbon double bonds. This article explains types (conjugated, cumulated, isolated), properties, common reactions (Diels–Alder, polyme…

Dietary mineral: essential inorganic nutrients in food Dietary mineral Dietary minerals are chemical elements required in food for growth, structure, and metabolic processes. They include macrominerals like calcium and phosphorus and trace minerals su…

Diethyl ether (ether): properties, history, uses and safety Diethyl ether Diethyl ether (ethoxyethane) is a volatile, highly flammable organic solvent historically used as an anesthetic. This article summarizes its properties, production, historical uses…

Differential Scanning Calorimeter (DSC): Principles, Types, and Applications Differential scanning calorimeter Differential scanning calorimetry measures heat flow differences between a sample and reference during controlled temperature programs, revealing transitions, enthalpies, heat capa…

Diffusion: movement of particles from regions of high to low concentration Diffusion Diffusion is the spontaneous spread of particles from regions of higher to lower concentration driven by random thermal motion; it occurs in gases, liquids, colloids and solids and…

Dimethylmercury — properties, hazards, uses and history Dimethylmercury A concise overview of dimethylmercury (CH3)2Hg: its chemistry, extreme toxicity, historical incidents, laboratory precautions, and limited applications in research.

Dinitrogen pentoxide (N2O5): properties, preparation, uses and safety Dinitrogen pentoxide Dinitrogen pentoxide (N2O5) is the anhydride of nitric acid, an oxidizing and nitrating reagent used in synthesis and atmospheric chemistry; it is reactive, corrosive and releases…

Dinitrogen tetroxide (N2O4) Dinitrogen tetroxide Dinitrogen tetroxide (N2O4) is the colorless dimer of nitrogen dioxide, a reversible oxidizer used in rocketry and industry; it exists in equilibrium with NO2 and is a toxic, corro…

Dioxin (polychlorinated dibenzodioxins): persistent environmental pollutants Dioxin Dioxins are a group of persistent, halogenated organic pollutants (PCDDs) formed unintentionally by combustion and chemical processes; they bioaccumulate and can cause toxic effect…

Disaccharide: structure, types, digestion and roles Disaccharide Disaccharides are carbohydrates made of two monosaccharides joined by a glycosidic bond. This article explains formation, common examples (sucrose, lactose, maltose), digestion, us…

Disinfectant: types, uses, history and safe handling Disinfectant Overview of disinfectants: what they are, main chemical types, common applications, historical background, distinctions from antiseptics, and safety and regulatory considerations.

Disproportionation (dismutation): a redox process producing two oxidation states Disproportionation Disproportionation is a redox reaction in which a single chemical species is both oxidized and reduced to give two different products containing the same element in different oxida…

Distillation: principles, history, methods and common uses Distillation Overview of distillation: the physical separation of liquids by vaporization and condensation, its types, history, industrial and household uses, limits and notable practical point…