Reactivity profile

The industrial value of furfuryl alcohol is a consequence of its low viscosity, high reactivity, and the outstanding chemical, mechanical, and thermal properties of its polymers, corrosion resistance, nonburning, low smoke emission, and exceUent char formation. The reactivity profile of furfuryl alcohol and resins is such that final curing can take place at ambient temperature with strong acids or at elevated temperature with latent acids. Major markets for furfuryl alcohol resins include the production of cores and molds for casting metals, corrosion-resistant fiber-reinforced plastics (FRPs), binders for refractories and corrosion-resistant cements and mortars. 

Cyclohexanediamine is marketed by Milliken Chemical as an epoxy curative, Millamine 5260. It may be adducted with epichlorohydrin to generate solventiess low viscosity curatives for varnishes and surface coatings (76). Other cycloaHphatic diamines have long been modified as epoxy curatives to modify their reactivity profile (77). 

Sdieire 3.2. Reactivity profile of ctarryIcupratec with carbor electrophllec [16b, d]. 

The relative reactivity profile of the simple alkenes toward Wacker oxidation is quite shallow and in the order ethene > propene > 1-butene > Zi-2-butene > Z-2-butene.102 This order indicates that steric factors outweigh electronic effects and is consistent with substantial nucleophilic character in the rate-determining step. (Compare with oxymercuration see Part A, Section 5.8.) The addition step is believed to occur by an internal ligand transfer through a four-center mechanism, leading to syn addition. 

There are many ways to categorize the oxidation of double bonds as they undergo a myriad of oxidative transformations leading to many product types including epoxides, ketones, diols, endoperoxides, ozonides, allylic alcohols and many others. Rather than review the oxidation of dienes by substrate type or product obtained, we have chosen to classify the oxidation reactions of dienes and polyenes by the oxidation reagent or system used, since each have a common reactivity profile. Thus, similar reactions with each specific oxidant can be carried out on a variety of substrates and can be easily compared. 

In this author s opinion, the influence of chain length on the ease of cyclisation of bifunctional chains is the most relevant and fascinating aspect in intramolecular reactions. An illustrative example is provided by the reactivity profile (Fig. 7) related to the lactonisation of co-bromoalkanoate anions (44), which is the first ring-closure reaction series for which a complete set of... 

An alternative strategy for selective intermolecular G-H insertions has been the use of rhodium carbenoid systems that are more stable than the conventional carbenoids derived from ethyl diazoacetate. Garbenoids derived from aryldiazoacetates and vinyldiazoacetates, so-called donor/acceptor-substituted carbenoids, have been found to display a very different reactivity profile compared to the traditional carbenoids.44 A clear example of this effect is the rhodium pivalate-catalyzed G-H insertion into cyclohexane.77 The reaction with ethyl diazoacetate gave the product only in 10% yield, while the parallel reaction with ethyl phenyldiazoacetate gave the product in 94% yield (Equation (10)). In the first case, carbene dimerization was the dominant reaction, while this was not observed with the donor/acceptor-substituted carbenoids. 

It can be noted that solvent has only marginal effect on the Fukui functions and hence local site selectivity. A systematic investigation has been made to study the effect of solvation on the local philicity indices of carbonyl compounds using B3LYP scheme employing direct calculation method [55], It is possible to observe from the results that solvation marginally influences the local reactivity profiles. 

The main human AKRs have been cloned, expressed, and their substrate reactivity profiles and tissue and organ distribution determined. 

In a recent publication, Schafer and coworkers point out the utility of the electrode as a reagent which is effective in promoting bond formation between functional groups of the same reactivity or polarity [1]. They accurately note that reduction at a cathode, or oxidation at an anode, renders electron-poor sites rich, and electron-rich sites poor. For example, reduction of an a, -un-saturated ketone leads to a radical anion where the )g-carbon possesses nucleophilic rather than electrophilic character. Similarly, oxidation of an enol ether affords a radical cation wherein the jS-carbon displays electrophilic, rather than its usual nucleophilic behavior [2]. This reactivity-profile reversal clearly provides many opportunities for the formation of new bonds between sites formally possessing the same polarity, provided only one of the two groups is reduced or oxidized. Electrochemistry provides an ideal solution to the issue of selectivity, given that a controlled potential reduction or oxidation is readily achieved using an inexpensive potentiostat. 

Scheme 3.1. Reactivity profile of silylcuprates with carbon electrophiles [14ej.

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