Additive versus Reactive Approaches

Ebdon, J. R., Hunt, B. J., Joseph, P., and Konkel, C. S., Flame-retarding thermoplastics Additive versus reactive approach, in Speciality Polymer Additives Principles and Applications, Al-Malaika, S., Golvoy, A., and Wilkie, C. A. (Eds.), 2001, Blackwell Science, Oxford, U.K., pp. 231-257. 

Aldehydes are generally more reactive than ketones in nucleophilic addition reactions for both steric and electronic reasons. Sterically, the presence of only one large substituent bonded to the C=0 carbon in an aldehyde versus two large substituents in a ketone means that a nucleophile is able to approach an aldehyde more readily. Thus, the transition state leadingto the tetrahedral intermediate is less crowded and lower in energy for an aldehyde than for a ketone (Figure 19.3). 

Apparently, analytical solution for these coupled equations is not feasible and we have to use numerical approaches. Model parameters are obtained similar to the single-site model. Additionally, since the adsorption experiments can only provide information on the total concentration of surface sites, we need to know the relative abundance of reactive versus nonreactive sites. That has not been determined unambiguously through experiments, so we simply assume that the reactive sites account for 10% of the total surface sites. 

This synthetic approach presents several advantages, such as an exact stoichiometry of addition of the two reagents is not required, since the two reactive groups are in the same molecule and only a catalytic amount of the activator K is needed. In both cases, the possibility of intramolecular versus inter-molecular reaction depends on their effective concentration. The probability of intramolecular reaction, i.e., of finding the co-end of a chain within a small reaction volume ve close to the a-end is given... 

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