Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Isocyanates anhydrides

It has been estimated that 200 to 300 agents have been identified as inducers of occupational asthma [4], The LMW agents can be broadly classified by chemical class such as isocyanates, anhydrides, metals, dyes, amines, drugs, acrylates and other compounds. The HM W agents can be broadly classified as animal protein, plant protein and microbial byproducts. Table 33.1 shows apartial listing of LMW and HMW sensitizers along with the workplace environments where these agents can be encountered. [Pg.576]

The second group of activators are substances which react with the lactam or its anion to yield an A -substituted lactam [107, 113—116] in a sufficiently fast reaction e.g., isocyanates, anhydrides, esters, ketenimines. The activating effect of Af-substituted lactams was found to incresise with increasing electronegativity of substituents [84, 111, 117]. Another group of activating substances are precursors of compounds of the second group. For example, AT-2,2-trisubstituted j3-oxoamides [118—120] decompose at elevated temperatures very easily into ketone and isocyanate, which is a very effective activator. [Pg.406]

With use of appropriate catalysts, mixtures of dianhydrides and diisocyanates were directly converted to rigid foam products without use of foaming agents [105,106]. In situ formation of imide forms like the polyurethane process, was developed by Riccitiello et al. [107]. The system contains a unique furfuryl alcohol-acid mixture which generates heat to initiate the isocyanate-anhydride reaction. [Pg.21]

Numerous single chemicals are known to be sensitizers. These include isocyanates, anhydrides, amines, metals and metal compounds, and plastics and their monomers. A complete list of these, as well as of biological sensitizers, was compiled by van Kampen et alJ22 Table 17.4 contains a partial list of single chemical sensitizers. [Pg.268]

Many difunctional epoxides, isocyanates, anhydrides, or aldehydes are available for reaction. In general, the shorter the carbon chain is between the two functional reactive groups, the faster the reaction will occur. In many cases, once one functional group has reacted, the reactivity of the second is reduced. [Pg.428]

The nucleophilic reacbvity of the C-5 oxygen is well documented however, no quantitative data are available. A-2-Thiazoline-5-ones (212) react at oxygen with acetyl chloride or acetic anhydride (447. 452). benzoyl chloride (447). methyl or phenyl isocyanate (467). carbamoyl chloride (453, 467). or phosphorus derivatives (468, 428) in the presence of bases to give 213, 214, 215. or 216 (Scheme 109). Strong bases such as... [Pg.431]

Rea.ctlons, As with other tertiary alcohols, esterification with carboxyUc acids is difficult and esters are prepared with anhydrides (181), acid chlorides (182), or ketene (183). Carbamic esters may be prepared by treatment with an isocyanate (184) or with phosgene followed by ammonia or an amine (185). [Pg.112]

The Kleber-Colombes rigid PVC foam (253,254) is produced by compression mol ding vinyl plastisol to react and gel the compound, followed by steam expansion. The process involves mixing, mol ding, and expansion. The formulation consists of PVC, isocyanate, vinyl monomers such as styrene, anhydrides such as maleic anhydride, polymerization initiators, FC-11, and nucleators. The ingredients are mixed in a Wemer-Pfleiderer or a Baker Perkins... [Pg.420]

Carboxyhc acids react with aryl isocyanates, at elevated temperatures to yield anhydrides. The anhydrides subsequently evolve carbon dioxide to yield amines at elevated temperatures (70—72). The aromatic amines are further converted into amides by reaction with excess anhydride. Ortho diacids, such as phthahc acid [88-99-3J, react with aryl isocyanates to yield the corresponding A/-aryl phthalimides (73). Reactions with carboxyhc acids are irreversible and commercially used to prepare polyamides and polyimides, two classes of high performance polymers for high temperature appHcations where chemical resistance is important. Base catalysis is recommended to reduce the formation of substituted urea by-products (74). [Pg.452]

Poly(phenylene oxide)s undergo many substitution reactions (25). Reactions involving the aromatic rings and the methyl groups of DMPPO include bromination (26), displacement of the resultant bromine with phosphoms or amines (27), lithiation (28), and maleic anhydride grafting (29). Additional reactions at the open 3-position on the ring include nitration, alkylation (30), and amidation with isocyanates (31). [Pg.328]

Chemical Properties The formation of salts with acids is the most characteristic reaction of amines. Since the amines are soluble in organic solvents and the salts are usually not soluble, acidic products can be conveniendy separated by the reaction with an amine, the unshared electron pair on the amine nitrogen acting as proton acceptor. Amines are good nucleophiles reactions of amines at the nitrogen atom have as a first step the formation of a bond with the unshared electron pair of nitrogen, eg, reactions with acid anhydrides, haUdes, and esters, with carbon dioxide or carbon disulfide, and with isocyanic or isothiocyanic acid derivatives. [Pg.198]

It is possible to react an organic moiety to the hydroxyl groups on ceU waU components. This type of treatment also bulks the ceU with a permanently bonded chemical (68). Many compounds modify wood chemically. The best results are obtained by the hydroxyl groups of wood reacting under neutral or mildly alkaline conditions below 120°C. The chemical system used should be simple and must be capable of swelling the wood stmcture to facUitate penetration. The complete molecule must react quickly with wood components to yield stable chemical bonds while the treated wood retains the desirable properties of untreated wood. Anhydrides, epoxides, and isocyanates have ASE values of 60—75% at chemical weight gains of 20—30%. [Pg.330]

Cyanuric acid readily dissolves in aqueous formaldehyde forming tris(hydroxymethyl)isocyanurate [10471-40-6] (THMIC) which can be isolated by evaporation (11). THMIC in turn reacts with acetic anhydride to yield tris(acetoxymethyl)isocyanurate [54635-07-3], either thionyl chloride or phosphoms pentachloride to give tris(chloromethyl)isocyanurate [63579-00-0], and phenyl isocyanate in pyridine to yield tris(A/-phenylcarbamoxymethyl) isocyanurate [21253-39-4] in 87% yield (65). Reaction of CA with paraformaldehyde and 2,6-dicyclohexylphenol yields... [Pg.419]

V-Acylation of oxaziridine (54) is of more importance, yielding 2-acyloxaziridines which were unaccessible otherwise until recently. Oxaziridines (54) derived from cyclohexanone, butanone or benzaldehyde are acylated readily by acetic anhydride, acid chlorides or isocyanates. Oxaziridines from aliphatic aldehydes, too unstable to be isolated, may be trapped in situ by benzoylation (67CB2593). [Pg.204]

H-Bond Acceptor (HBA) Acyl chlorides Acyl fluorides Hetero nitrogen aromatics Hetero oj gen aromatics Tertiary amides Tertiary amines Other nitriles Other nitros Isocyanates Peroxides Aldehydes Anhydrides Cyclo ketones Ahphatic ketones Esters Ethers Aromatic esters Aromatic nitriles Aromatic ethers Sulfones Sulfolanes... [Pg.1318]

Thermal reaction of affenyf azines derived from propargylphosphonium salts with ketenes, isocyanates. CS2 or phthallc anhydride to form bi and Incyclic fused pyrazolo heterocycles... [Pg.341]

In addition to the proteins discussed above, a large number of reactive chemicals used in industry can cause asthma and rhinitis. Hypersensitivity pneumonias have also been described. Isocyanates and acid anhydrides are industrial chemicals that cause occupational asthma. Acid anhydrides, such as phthalic anhydride, seem to cause mainly type I reactions, whereas the IgE-mediated mechanism explains only a part of the sensitizations to isocyanates. Several mechanisms have been suggested, but despite intensive research no models have been generally accepted. The situation is even more obscure for other sensitizing chemicals therefore, the term specific chemical hypersensitivity is often used for chemical allergies. This term should not be confused with multiple chemical sensitivity (MCS) syndrome, which is a controversial term referring to hypersusceptibility to very low levels of environmental chemicals. ... [Pg.310]

Q -Hydroxy-3Q (tetrahydropyran-2-yloxy)-2/3-(3Q -tetrahydropyran-2-yloxy-4-phenoxy-trans-1-buten-1 -yl)cyclopent-1Q -yl] -acetaldehyde a-hemiacetal Chromic anhydride Methanesulfonyl isocyanate Acetic acid... [Pg.1431]

Those involving the use of functionalized blend components that produce in situ compatibilizing interchain copolymers some common reactive functionalities include carboxyl, epoxy, isocyanate, and anhydride, etc. [Pg.654]

Acetylene works Acrylates works Aldehyde works Aluminum works Amines works Ammonia works Anhydride works Arsenic works Asbestos works Benzene works Beryllium works Bisulfate works Bromine works Cadmium works Carbon disulfide works Carbonyl works Caustic soda works Cement works Ceramic works Chemical fertilizer works Chlorine works Chromium works Copper works Di-isocyanate works Electricity works Fiber works Fluorine works Gas liquor works Gas and coke works Hydrochloric acid works Hydrofluoric acid works Hydrogen cyanide works Incineration works Iron works and steel works... [Pg.755]

ISOCYANIC ACID, ANHYDRIDE WITH CHIO ROACETIC ACID, 46, 16 ISOCYANIC ACID, ANHYDRIDF WITH CHLOROSULPONIC ACID, 46, 23 Isocyanides, preparation of volatile, 46, 77... [Pg.131]

Treatment of isatoic anhydrides with thionyl chloride furnishes the isocyanates 22, which react with methylhydrazine to yield Ihe benzotriazepinediones 23.362... [Pg.467]

Isocyanates react with carboxylic acids to form amides, ureas, anhydrides, and carbon dioxide, depending on reaction conditions and the structure of the starting materials (Scheme 4.13). Aliphatic isocyanates more readily give amides. Aromatic isocyanates tend to react with carboxylic acids to first generate anhydrides and ureas, which at elevated temperatures (ca. 160°C) may further react to give amides. In practice, the isocyanate reaction with carboxylic acid is rarely utilized deliberately but can be an unwanted side reaction resulting from residual C02H functionality in polyester polyols. [Pg.225]

Phosphorus ylids also react in a similar manner with the C=0 bonds of ketenes/ isocyanates, and certain anhydrides and imides, the N=0 of nitroso groups, and the C=N of imines, for example. [Pg.1237]


See other pages where Isocyanates anhydrides is mentioned: [Pg.10]    [Pg.581]    [Pg.155]    [Pg.10]    [Pg.56]    [Pg.398]    [Pg.1173]    [Pg.10]    [Pg.581]    [Pg.155]    [Pg.10]    [Pg.56]    [Pg.398]    [Pg.1173]    [Pg.135]    [Pg.103]    [Pg.126]    [Pg.361]    [Pg.403]    [Pg.336]    [Pg.107]    [Pg.67]    [Pg.159]    [Pg.788]    [Pg.74]    [Pg.286]    [Pg.135]    [Pg.230]    [Pg.94]    [Pg.5]    [Pg.24]   
See also in sourсe #XX -- [ Pg.32 , Pg.107 ]




SEARCH



Chlorosulfonyl isocyanate acid anhydride synthesis

Formic acid anhydride via chlorosulfonyl isocyanate

ISOCYANIC ACID, ANHYDRIDE WITH

Isocyanates reaction with cyclic anhydrides

Reaction of Isocyanates with Cyclic Anhydrides

© 2024 chempedia.info