Triethylene diamine structure

Further reaction occurs with another BH molecule, and proceeds through the formation of hydrogen bonds between BH and either —O or —N— of one of the two resonance forms (it is not known which one). In a catalyzed reaction the catalyst can also take the place of the first BH molecule. Sterically unhindered amines such as triethylene diamine can thus catalyze the addition through the effect of the electron lone pairs on the nitrogen atom, which, because of the triethylene diamine structure, are particularly accessible. Metal salts such as di-n-butyl zinc diacetate are also very active. 

While most tertiary amine catalysts are effective approximately in proportion to their base strength, an exception is triethylene diamine, 4-diaza[2.2.2]bicyclo-octane). As shown by Farkas et al. [142,143] this catalyst is much more powerful than would be predicted from its base strength, being five times stronger as a catalyst than iV,JV -dimethyl-piperazine, which has slightly greater basicity. It was first suggested that the explanation may be the complete lack of steric hindrance in the structure. 

Reactions (1.4)-(1.10) and those of Figs 1.5 and 1.6 may be greatly influenced by use of appropriate catalysts, so that here, as in the choice of initial reactants, it is possible to affect both the rate and the direction of the polymer-forming process. The catalysts most widely used commercially in polyurethane processes are tertiary amines and organotin compounds. In the case of the amines, promotion of urethane links is related to the strength of the base but structural effects can be important and, as shown in Table 1.7 the relatively weakly basic triethylene diamine, where there is little or no steric hindrance, is an extremely powerful catalyst compared with triethylamine. 

Bases accelerate all the isocyanate reactions and in general their catalytic effect increases with increasing strength of the base. Table 4.7 compares the action of several amine catalysts at near ambient temperature. The significant increase in urethane reaction rate is apparent but particularly so in the case of triethylene diamine (l,4-diazo-[2,2,2]-bicyclo-octane), commonly known as DABCO. The reason for this is probably the complete lack of steric hindrance, given its cage-like structure. 

The structure of the metal coordination compounds with such aliphatic amines as ethylene diamine, diethylene triamine, triethylene tetramine, and so on is the combination of the closed chelate rings (Schemes 16-18)... 

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