|
Hindered Amine Light Stabilizers
Hindered amine light stabilizers (HALS) are chemical compounds containing an amine functional group that are used as stabilizers in plastics and polymers. These compounds are typically derivatives of tetramethylpiperidine and are primarily used to protect the polymers from the effects of photo-oxidation; as opposed to other forms of polymer degradation such as ozonolysis. They are also increasingly being used as thermal stabilizers, particularly for low and moderate level of heat, however during the high temperature processing of polymers (e.g. injection moulding) they remain less effective than traditional phenolic antioxidants. Mechanism of action HALS do not absorb UV radiation, but act to inhibit degradation of the polymer by continuously and cyclically removing free radicals that are produced by photo-oxidation of the polymer. The overall process is sometimes referred to as the Denisov cycle, after Evguenii T. Denisov and is exceedingly complex. Broadly, HALS react with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bis(2,2,6,6-tetramethyl-4-piperidyl) Sebacate
Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (abbreviated BTMPS) is a Hindered amine light stabilizers, hindered amine light stabilizer used to protect plastics and coatings such as paint from Redox, oxidation caused by sunlight weathering. Like most compounds of this class, the activated form is an aminoxyl radical. Synthesis It is produced by the diesterification of sebacic acid (decanedioic acid) with 4-Hydroxy-TEMPO, 4-hydroxy-TEMPO. Public health and medical concerns In 2024, it was detected as an adulterant in illicitly sold fentanyl in the United States. It is capable of inhibiting nicotinic acetylcholine receptors. Additionally, it is a potent Calcium channel blocker, blocker of L-type calcium channels. It is also able to induce Dose–response relationship, dose-dependent Hemodynamics, hemodynamic alterations. Similar to early calcium channel blockers, it can precipitate adrenergic release. See also * Antioxidant * Photodissociation, Photolysis (photodegradation) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrone
In organic chemistry, a nitrone is a functional group consisting of an Amine oxide, ''N''-oxide of an imine. The general structure is , where R3 is not a hydrogen. Their primary application is Chemical Intermediate, intermediates in chemical synthesis. A nitrone is a 1,3-dipole used in 1,3-dipolar cycloaddition, cycloadditions, and a Carbonyl group, carbonyl mimic. Structure Nitrones, as a tetrasubstituted double bond, admit Cis–trans isomerism, ''cis''–''trans'' isomerism. Generation of nitrones Typical nitrone sources are hydroxylamine oxidation or Alkylimino-de-oxo-bisubstitution, condensation with carbonyl compounds. Secondary hydroxylamines oxidize to nitrones in air over a timescale of several weeks, a process Copper compounds, cupric salts accelerate. The most general reagent used for the oxidation of hydroxylamines is aqueous mercuric oxide: However, a hydroxylamine with two Locant, α hydrogens may unsaturate on either side. Carbonyl condensation avoids this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steric Hindrance
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which dictate the shape and reactivity of molecules. Steric repulsive forces between overlapping electron clouds result in structured groupings of molecules stabilized by the way that opposites attract and like charges repel. Steric hindrance Steric hindrance is a consequence of steric effects. Steric hindrance is the slowing of chemical reactions due to steric bulk. It is usually manifested in ''intermolecular reactions'', whereas discussion of steric effects often focus on ''intramolecular interactions''. Steric hindrance is often exploited to control selectivity, such as slowing unwanted side-reactions. Steric hindrance between adjacent groups can also affect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BTMPS
Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (abbreviated BTMPS) is a hindered amine light stabilizer used to protect plastics and coatings such as paint from oxidation caused by sunlight weathering. Like most compounds of this class, the activated form is an aminoxyl radical. Synthesis It is produced by the diesterification of sebacic acid (decanedioic acid) with 4-hydroxy-TEMPO. Public health and medical concerns In 2024, it was detected as an adulterant in illicitly sold fentanyl in the United States. It is capable of inhibiting nicotinic acetylcholine receptors. Additionally, it is a potent blocker of L-type calcium channels. It is also able to induce dose-dependent hemodynamic alterations. Similar to early calcium channel blockers, it can precipitate adrenergic release. See also * Antioxidant * Photolysis (photodegradation) * Radical (chemistry) In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydrohalogenation
In chemistry, dehydrohalogenation is an elimination reaction which removes a hydrogen halide from a substrate (chemistry), substrate. The reaction is usually associated with the synthesis of alkenes, but it has wider applications. Dehydrohalogenation from alkyl halides Traditionally, alkyl halides are substrates for dehydrohalogenations. The alkyl halide must be able to form an alkene, thus halides having no C–H bond on an adjacent carbon are not suitable substrates. Aryl halides are also unsuitable. Upon treatment with strong base, chlorobenzene dehydrohalogenates to give phenol#Hydrolysis of chlorobenzene, phenol via a benzyne intermediate. Base-promoted reactions to alkenes When treated with a strong base many alkyl chlorides convert to corresponding alkene. It is also called a β-elimination reaction and is a type of elimination reaction. Some prototypes are shown below: :\begin \ce\ &\ce \\ \ce\ &\ce \\ \ce\ &\ce \end Here ethyl chloride reacts with potassium hydroxide, ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrochloric Acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is a component of the gastric acid in the digestive systems of most animal species, including humans. Hydrochloric acid is an important laboratory reagent and industrial chemical. Etymology Because it was produced from halite, rock salt according to the methods of Johann Rudolph Glauber, hydrochloric acid was historically called by European alchemists ''spirits of salt'' or ''acidum salis'' (salt acid). Both names are still used, especially in other languages, such as , , , , , , , , , , (''ensan''), zh, 盐酸 (''yánsuān''), and (''yeomsan''). Gaseous HCl was called ''marine acid air''. The name ''muriatic acid'' has the same origin (''muriatic'' means "pertaining to brine or salt", hence ''muriate'' means hydrochloride), and this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyvinyl Chloride
Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons of PVC are produced each year. PVC comes in rigid (sometimes abbreviated as RPVC) and flexible forms. Rigid PVC is used in construction for pipes, doors and windows. It is also used in making plastic bottles, packaging, and bank or membership cards. Adding plasticizers makes PVC softer and more flexible. It is used in plumbing, electrical cable insulation, flooring, signage, phonograph records, inflatable products, and in rubber substitutes. With cotton or linen, it is used in the production of canvas. Polyvinyl chloride is a white, brittle solid. It is soluble in ketones, chlorinated solvents, dimethylformamide, THF and DMAc. Discovery PVC was synthesized in 1872 by German chemist Eugen Baumann after extended investigation and experimenta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyurethane
Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term does not refer to the single type of polymer but a group of polymers. Unlike polyethylene and polystyrene, polyurethanes can be produced from a wide range of starting materials resulting in various polymers within the same group. This chemical variety produces polyurethanes with different chemical structures leading to many List of polyurethane applications, different applications. These include rigid and flexible foams, and coatings, adhesives, Potting (electronics), electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016. A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol. Since a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bottles, cups, jars, etc.). , over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. Many kinds of polyethylene are known, with most having the chemical formula (C2H4)''n''. PE is usually a mixture of similar polymers of ethylene, with various values of ''n''. It can be ''low-density'' or ''high-density'' and many variations thereof. Its properties can be modified further by crosslinking or copolymerization. All forms are nontoxic as well as chemically resilient, contributing to polyethylene's popularity as a multi-use plastic. However, polyethylene's chemical resilience also makes it a long-lived and decomposition-resistant pollutant when disposed of improperly. Being a h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More specialized polyolefins include Polyisobutene, polyisobutylene and polymethylpentene. They are all colorless or white oils or solids. Many copolymers are known, such as polybutene, which derives from a mixture of different butene isomers. The name of each polyolefin indicates the olefin from which it is prepared; for example, polyethylene is derived from ethylene, and polymethylpentene is derived from 4-methyl-1-pentene. Polyolefins are not olefins themselves because the double bond of each olefin monomer is opened in order to form the polymer. Monomers having more than one double bond such as butadiene and isoprene yield polymers that contain double bonds (polybutadiene and polyisoprene) and are usually not considered polyolefins. Polyolefins are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cope Reaction
The Cope reaction or Cope elimination, developed by Arthur C. Cope, is the elimination reaction of an N-oxide to an alkene and a hydroxylamine.Typically, the amine oxide is prepared from the corresponding amine with a peroxy acid or comparable oxidant. The actual elimination requires just heat. Illustrative is a synthesis of methylenecyclohexane: Mechanism and related eliminations The reaction proceeds through the Ei pathway, with an intramolecular, cyclic 5-membered transition state. Consequently, the elimination product is always ''syn'' and rarely occurs with 6-membered rings. ( Rings with 5 or 7 or more members undergo the reaction just fine.) This organic reaction is closely related to the Hofmann elimination, but the base is a part of the leaving group. Sulfoxides can undergo an essentially identical reaction to produce sulfenic acids, which is important in the antioxidant chemistry of garlic and other ''allium''s. Selenoxides likewise undergo selenoxid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
