Functional group, reactivity with

Sometimes, in the disconnection process, it may be convenient to interconvert functional groups (FGI) with the aim of modifying either some highly reactive or... 

The independence of functional group reactivity of molecular size is contrary to the general impression that was widely held in the early years of polymer science. There was a general misconception of decreased reactivity with increased molecular size. This was due... 

The failure to fit the data over the complete conversion range from 0 to 100% to a third-order plot has sometimes been ascribed to failure of the assumption of equal functional group reactivity, but this is an invalid conclusion. The nonlinearities are not inherent characteristics of the polymerization reaction. Similar nonlinearities have been observed for nonpolymerization esterification reactions such as esterifications of lauryl alcohol with lauric or adipic acid and diethylene glycol with caproic acid [Flory, 1939 Fradet and Marechal, 1982b]. 

Compare the gel points calculated from the Carothers equation (and its modifications) with those using the statistical approach. Describe the effect of unequal functional groups reactivity (e.g., for the hydroxyl groups in glycerol) on the extent of reaction at the gel point. 

Polymerization reactions of multifunctional monomers such as those used in dental restorations occur in the high crosslinking regime where anomalous behavior is often observed, especially with respect to reaction kinetics. This behavior includes auto acceleration and autodeceleration [108-112], incomplete functional group conversion [108,109,113-116], a delay in volume shrinkage with respect to equilibrium [108, 117,118], and unequal functional group reactivity [119-121]. Figures 3 and 4 show a typical rate of polymerization for a multifunctional monomer as a function of time and conversion, respectively. Several distinctive features of the polymerization are apparent in the rate profiles. 

Guibe and co-workers took advantage of this high reactivity to use N,N -dimethylbarbituric acid 231 (Scheme 47) as an efficient nucleophilic reagent in the deprotection of functional groups protected with allyl radicals. The recovery of benzylamine from its diallyl derivative 232 is one example (93JOC6109). 

What are the alternatives There are two main ones, and both involve functional group interconversion, with the reactive amine being converted to a less reactive derivative before disconnection. The first solution is to convert the amine to an amide and then disconnect that. The reduction of amide to amine is quite reliable, so the FGI is a reasonable one. 

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