Reactive amine catalysts

Polycat 15 (PC-15) Balanced reactive amine catalyst. APCI... 

Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity. 

All lene Oxides and Aziridines. Alkyleneamines react readily with epoxides, such as ethylene oxide [75-21-8] (EO) or propylene oxide [75-56-9] (PO), to form mixtures of hydroxyalkyl derivatives. Product distribution is controlled by the amine to epoxide mole ratio. If EDA, which has four reactive amine hydrogens, reacts at an EDA to EO mole ratio which is greater than 1 4, a mixture of mono-, di-, tri,-, and tetrahydroxyethyl derivatives of EDA are formed. A 10 1 EDA EO feed mole ratio gives predominandy 2-hydroxyethylethylenediamine [111-41-1], the remainder is a mixture of bis-(2-hydroxyethyl)ethylenediamines (7). If the reactive NH to epoxide feed mole ratio is less than one and, additionally, a strong basic catalyst is used, then oxyalkyl derivatives, like those shown for EDA and excess PO result (8,9). 

Step-growth polymerization processes must be carefully designed in order to avoid reaction conditions that promote deleterious side reactions that may result in the loss of monomer functionality or the volatilization of monomers. For example, initial transesterification between DMT and EG is conducted in the presence of Lewis acid catalysts at temperatures (200°C) that do not result in the premature volatilization of EG (neat EG boiling point 197°C). In addition, polyurethane formation requires the absence of protic impurities such as water to avoid the premature formation of carbamic acids followed by decarboxylation and formation of the reactive amine.50 Thus, reaction conditions must be carefully chosen to avoid undesirable consumption of the functional groups, and 1 1 stoichiometry must be maintained throughout the polymerization process. 

Addihon of primary and secondary amines to 1,3-butadiene and isoprene at 0 to 180°C over solid bases such as MgO, CaO, SrO, LajOj, Th02, and ZrOj has also been studied. CaO exhibits the highest achvity, while ZrOj is inachve. MejNH is the most reactive amine, giving primarily the 1,4-addihon product which undergoes iso-merizahon to the enamine N,N-dimethyl-l-butenylamine. It has been proposed that addihon of amines to 1,3-dienes on basic catalysts proceeds via aminoallyl carban-ion intermediates which result from addihon of amide ions to the dienes [169, 170]. 

Silk can be readily dyed with conventional high-reactivity dyes of the dichlorotriazine, dichloroquinoxaline or difluoropyrimidine classes. Exhaust dyeing at 60-70 °C and pH 5-6 gives satisfactory results, especially if a mildly alkaline aftertreatment is given to enhance fixation. Dichlorotriazine dyes can also be applied by pad-batch dyeing with bicarbonate and a batching time of 4-6 hours. The relatively low reactivity of aminochlorotriazine dyes, however, results in moderate to poor build-up on silk. Tertiary amine catalysts such as DABCO (7.66) can be used to accelerate the dye-fibre reaction and increase the fixation substantially [116], but it is difficult to achieve satisfactory compatibility in mixture dyeings by this method (section 7.4.2). 

Table 3.19 lists examples of the preparation of nitrogen-containing heterocycles by RCM. As mentioned in Section 3.2.5.3, free amines can partly deactivate metathesis catalysts. With the highly reactive molybdenum catalyst 1 it is, however, possible to cyclize dienes containing a basic amino group. If the less reactive catalysts 2 or 3 are to be used, protonation or acylation of the amine can be used to reduce their nucleophilicity. This will generally lead to higher yields with smaller amounts of catalyst. 

The first designed catalyst where there was some understanding of the relationship between structure and function was oxaldie 1, a 14-residue peptide that folds in solution to form helical bundles [11] (Fig. 12). Oxaldie 1 was designed to catalyze the decarboxylation of oxaloacetate, the a-keto acid of aspartic acid, via a mechanism where a primary amine reacts with the ketone carbonyl group to form a carbinolamine that is decarboxylated to form pyruvate. The reaction is piCj dependent and proceeds faster the lower the piC of the primary amine if the reaction is carried out at a pH that is lower than the piCj, of the reactive amine. The sequence contains five lysine residues that in the folded state form... 

The best reactivity and selectivity was illustrated with the binaphthol derived thiourea amine catalyst 277. The substrate scope was explored primarily with P-aryl-nitro-olefms of both electron-donating and electron-withdrawing natures. Yields and selectivities were high for the majority of substrates (Scheme 78). 

The two most common BF3 amine catalysts used commercially to cure epoxies are boron trifluoride monoethylamine, BF3 NH2C2H5, and boron trifluoride piperidine, BF3 NHCsHi0, complexes. Such complexes are latent catalysts at room temperature but enhance epoxide group reactivity at higher temperatures. 

Fully cured polyurethanes present no health hazard they are chemically inert and insoluble in water and most organic solvents. Dust can be generated in fabrication, and inhalation of the dust should be avoided. Polyether-based polyurethanes are not degraded in the human body, and are therefore used in biomedical applications. Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity. 

As indicated from computational studies, the catalyst-activated iminium ion MM3-2 was expected to form with only the (E)-conformation to avoid nonbonding interactions between the substrate double bond and the gem-dimethyl substituents on the catalyst framework. In addition, the benzyl group of the imidazolidinone moiety should effectively shield the iminium-ion Si-face, leaving the Re-face exposed for enantioselective bond formation. The efficiency of chiral amine 1 in iminium catalysis was demonstrated by its successful application in several transformations such as enantioselective Diels-Alder reactions [6], nitrone additions [12], and Friedel-Crafts alkylations of pyrrole nucleophiles [13]. However, diminished reactivity was observed when indole and furan heteroaromatics where used for similar conjugate additions, causing the MacMillan group to embark upon studies to identify a more reactive and versatile amine catalyst. This led ultimately to the discovery of the second-generation imidazolidinone catalyst 3 (Fig. 3.1, bottom) [14],... 

A notable feature in all these coupling protocols is that the coupling rates of iron-phosphorus systems, of the (salen)iron complex 5, the Fe(acac)3 catalyst, and catalyst 10 with respect to the alkyl halide are rather uncommonly bromide> iodide>chloride (entries 3, 4, 9, 13), whereas the reactivity order for iron-amine catalyst systems is iodide>bromide>chloride (entries 1, 5, 6). 

This in no way detracts from the proved ability of the cyclohepta-trienyl cation to oxidize reactive amines, and consequently there is always doubt as to the true nature of the reaction mechanism when tropylium ion initiates polymerization of N-vinylcarbazole. We have made a detailed kinetic study of this polymerization (34), using an adiabatic calorimetric technique. Some typical data are shown in Table VII. Initiation is instantaneous and complete, there is no termination, and kp is evaluated readily as 4.6 X 10+5M-1 sec. 1 at 0°C. with Ea = 6 kcal./mole. By comparing data for the ion pair dissociation constant of C7HT"SbCl 6 (Table I) with the catalyst concentrations employed (Table VII) it is apparent that free tropylium ions are the dominant initiating speices. It... 

The reactivity of the model phenols and benzyl alcohols with phenyl isocyanate was determined in the presence of a tertiary amine (DMCHA) and a tin catalyst (DBTDL) by measurement of the reaction kinetics. The experimental results based on initial equal concentrations of phenyl isocyanate and protic reactants showed that the catalyzed reactions followed second order reaction with respect to the disappearance of isocyanate groups (see Figure 1). It was also found that a linear relationship exists between the experimental rate constant kexp, and the initial concentration of the amine catalyst (see Figure 2). In the case of the tin catalyst, the reaction with respect to catalyst concentration was found to be one-half order (see Figures 3-4). A similar relationship for the tin catalyzed urethane reaction was found by Borkent... 

Model studies based on substituted phenols and benzyl alcohols showed that the presence of substituents in the ortho position in benzyl alcohol had a relatively small effect on the reactivity of the hydroxyl group with isocyanate in the presence of tertiary amine catalyst (DMCHA). In contrast, similar substitution in phenols significantly affected the reactivity of the... 

EFFECT OF TERTIARY AMINE CATALYST ON REACTIVITY OF PHENOL AND ETHYL ALCOHOL WITH PHENYL ISOCYANATE21... 

The presence of the electron donor (-0-) in the vicinity of the phenolic hydroxyl activated the -OH group through induced polarization due to hydrogen bonding and therefore, increased reactivity was observed. Similarly, the polarizability of the phenolic hydroxyl groups by the tertiary amine catalyst is responsible for the multi order (1200 x) increase in the reactivity compared to the non-catalyzed reaction with isocyanate (see Table IV)... 

The action of the tin catalyst was found to be quite different from the action of the tertiary amine catalyst. In the presence of the amine catalyst the reactivity of the phenol and benzyl alcohol was approximately equal (see Table IV). In the case of DBTDL, the reactivity ratio was similar to that of the non-catalyzed reaction, which indicates that the polarization of the isocyanate by the tin catalyst due to complex formation presumably played an important role in the reaction catalysis (see Table VI). 

Table 15-8. Rblatiyb Reactivities or Subbti-TtTFEn Phenols with Fobmaldehtde Using am Amine Catalyst...

The amorphous polymeric, polyaxial initiators (PPIs) used in these systems to produce crystalline absorbable copolymeric materials can be made by reacting a cyclic monomer or a mixture of cyclic monomers such as trimethylene carbonate, caprolactone, and l,5-dioxapane-2-one in the presence of an organometallic catalyst with one or more polyhydroxy, polyamino, or hydroxyamino compounds having three or more reactive amines and/or hydroxyl groups. Typical examples of the latter compounds are glycerol and ethane-trimethylol, propane-trimethylol, pentaerythritol, triethanolamine, and N-2-aminoethyl-l,3-propanediamine. 

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