Catalyst tertiary amines

Sheng and Zajacek reported that in the presence of VO(acac)2 or Mo(CO)e catalysts tertiary amines are smoothly oxidized to the corresponding A-oxides with either TBHP... 

Generally, when used as a sole catalyst, tertiary amines are used only in specialty applications where short pot life can be tolerated and where maximum physical or chemical properties are not required. DMP-10 and DMP-30 are used at concentrations of 4 to lOpph with liquid DGEBA epoxy resins. They achieve fairly fast cures overnight, even at room temperatures since the hydroxyl groups present in the epoxy molecule enhance the catalytic activity of the tertiary amine groups. 

Auxiliary blowing agent - Fluorocarbon Catalyst - Organotin salt Catalyst - Tertiary amines Surfactant - Silicone copolymer... 

Catalyst - Tertiary amines Processing aid - Phosphate ester... 

The currently accepted mechanism of the Baylis-Hillman reaction involves a Michael addition of the catalyst (tertiary amine) at the (3-position of the activated alkene to form a zwitterionic enolate. This enolate reacts with the aldehyde to give another zwitterion that is deprotonated, and the catalyst is released. Proton transfer affords the final product. 

Literature data confirm the possibilities of complexation between reagents (isocyanate, alcohol) and catalyst (tertiary amine, organometallic compound) considered two by two. 

Figure 13.6 Flow diagram for rigid polyether polyol fabrication (catalyst tertiary amines)...

One disadvantage of this method is the very long time needed in the last part of the reaction to decrease the acidity number to less than 2 mg KOH/g (i.e., several hours). Sometimes, the esterification with PO of the last unreacted -COOH groups needs a catalyst such as KOH [20-22], sodium or potassium acetate [20-22], DMC catalysts, tertiary amines and so on. Another disadvantage is the presence of a discrete and characteristic odour, due to the formation of some side products in very small quantities (for example cyclic compounds). 

They generally use a combination of two synergistic catalysts tertiary amine and orga-notin. Tertiary amines such as triethylene diamine promote the isocyanate-water reaction. 

Resin components such as a-glycol content and chloride types and levels are known to influence certain formulation reactivity and rheology, depending on their interactions with the system composition snch as basic catalysts (tertiary amines) and/or amine curing agents. Knowing the types and levels of chlorides guides formulators in the adjustment of their formulations for proper reactivity and flow... 

In the industrial production of this PC, interfacial polycondensation is used. The bisphenol A is first dissolved in the aqueous phase as sodium salt, and the phosgene in the organic phase, which is not miscible with water, e.g. dichloromethane. The reaction occurs at the interface of the two phases to produce oligomers, which enter the organic phase. The hydrolysis product NaCl enters the aqueous phase. The addition of catalysts (tertiary amines) accelerates the polycondensation process. The chlorine leaves the process as sodium chloride, see Fig. 96. 

Catalysis is usually accompHshed through the use of tertiary amines such as triethylenediamine. Other catalysts such as 2,4,6-/m(/V,/V-dimethylaminomethyl)phenol are used in the presence of high levels of cmde MDI to promote trimerization of the isocyanate and thus form isocyanurate ring stmctures. These groups are more thermally stable than the urethane stmcture and hence are desirable for improved flammabiUty resistance (236). Some urethane content is desirable for improved physical properties such as abrasion resistance. 

CycHc carbonates are made by treating 1,2-diols with dialkyl carbonates using an alkyl ammonium and tertiary amine catalyst. The combination of propylene glycol and dimethyl carbonate has been reported to result in a 98% yield of propylene carbonate (21). 

Commercially, polymeric MDI is trimerized duting the manufacture of rigid foam to provide improved thermal stabiUty and flammabiUty performance. Numerous catalysts are known to promote the reaction. Tertiary amines and alkaU salts of carboxyUc acids are among the most effective. The common step ia all catalyzed trimerizations is the activatioa of the C=N double boad of the isocyanate group. The example (18) highlights the alkoxide assisted formation of the cycHc dimer and the importance of the subsequent iatermediates. Similar oligomerization steps have beea described previously for other catalysts (61). 

The reaction of dihalocarbenes with isoprene yields exclusively the 1,2- (or 3,4-) addition product, eg, dichlorocarbene CI2C and isoprene react to give l,l-dichloro-2-methyl-2-vinylcyclopropane (63). The evidence for the presence of any 1,4 or much 3,4 addition is inconclusive (64). The cycloaddition reaction of l,l-dichloro-2,2-difluoroethylene to isoprene yields 1,2- and 3,4-cycloaddition products in a ratio of 5.4 1 (65). The main product is l,l-dichloro-2,2-difluoro-3-isopropenylcyclobutane, and the side product is l,l-dichloro-2,2-difluoro-3-methyl-3-vinylcyclobutane. When the dichlorocarbene is generated from CHCl plus aqueous base with a tertiary amine as a phase-transfer catalyst, the addition has a high selectivity that increases (for a series of diolefins) with a decrease in activity (66) (see Catalysis, phase-TRANSFEr). For isoprene, both mono-(l,2-) and diadducts (1,2- and 3,4-) could be obtained in various ratios depending on which amine is used. 

Other Rea.ctions, The photolysis of ketenes results in carbenes. The polymeriza tion of ketenes has been reviewed (49). It can lead to polyesters and polyketones (50). The polymerization of higher ketenes results in polyacetals depending on catalysts and conditions. Catalysts such as sodium alkoxides (polyesters), aluminum tribromide (polyketones), and tertiary amines (polyacetals) are used. Polymers from R2C—C—O may be represented as foUows. 

Acetoiicetyliition Reactions. The best known and commercially most important reaction of diketene is the aceto acetylation of nucleophiles to give derivatives of acetoacetic acid (Fig. 2) (1,5,6). A wide variety of substances with acidic hydrogens can be acetoacetylated. This includes alcohols, amines, phenols, thiols, carboxyHc acids, amides, ureas, thioureas, urethanes, and sulfonamides. Where more than one functional group is present, ring closure often follows aceto acetylation, giving access to a variety of heterocycHc compounds. These reactions often require catalysts in the form of tertiary amines, acids, and mercury salts. Acetoacetate esters and acetoacetamides are the most important industrial intermediates prepared from diketene. 

Manufacture and Uses. Acetoacetic esters are generally made from diketene and the corresponding alcohol as a solvent ia the presence of a catalyst. In the case of Hquid alcohols, manufacturiag is carried out by continuous reaction ia a tubular reactor with carefully adjusted feeds of diketene, alcohol, and catalyst, or alcohol—catalyst blend followed by continuous purification (Fig. 3). For soHd alcohols, an iaert solvent is used. Catalysts used iaclude strong acids, tertiary amines, salts such as sodium acetate [127-09-3], organophosphoms compounds, and organometaHic compounds (5). 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Secondary and tertiary amines are preferentially produced when rhodium or palladium are chosen as catalyst. As in Method 3, reforming reactions do not normally compete with the hydrogenation reaction and high selectivities to the desired product are possible. 

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