Organic halides reactivity order

This generalized reaction sequence consumes the halide, the stannane, and the reactant X=Y, and effects addition to the organic radical and a hydrogen atom to the X=Y bond. The order of reactivity of organic halides toward stannyl radicals is iodides > bromides > chlorides. 

As usual, the reactivity order with respect to halogen in C=C-X is I > Br > Q. The organic halide in the couplings with alkynylzinc halides is usnaily an iodide, though also activated vinylic bromides (e.g. BrCH=CHCOOC2H5) have been found to react smoothly. We... 

The anionic hydrido carbonyls have been much studied because of their intermediacy in catalytic processes like the water gas shift reaction, reduction of organic substances, and other reactions. Thus chromium group hydrides [HM(CO)4PR3] are highly efficient H-transfer agents and for reactions with alkyl halides a reactivity order was established cii-[HW(CO)4PR3] > m-[HCr(CO)4PR3] > [HW(CO)5]... 

Castro et al. 44) found that the order of reactivity of various halides in coupling reactions with ethynylcopper compounds in DMF is ArSX, ArX > RCOX ArCHaX, RCH=CHCH2X, ArCOCHaX > RCH= CHX, Alkyl-X. A somewhat different order is observed for the reactivity of some organic halides towards perhaloarylcopper reagents in THF (97, 147) Allyl Aryl > Alkyl and perfluoroaryl, perfluoro-vinyl > aryl > perfluoroalkyl. Acid halides were also far more reactive than aryl iodides in ethereal solvents 146). The ease of halide displacement is I > Br > Cl. 

A listing of alkyne-nucleophile systems whose substitution kinetics have been studied is given in Table 24 for each of these systems. Rate constants and enthalpies and entropies of activation, if available, are tabulated. In order to compare the reactivity of haloalkynes with other organic halides we have also included in Table 24 related rate data for vinylic, aromatic and alkyl halides. 

By extension to cross-coupling with vinyl and aryl triflates, the scope of the Stille reaction has been expanded greatly. Almost all functional groups are tolerated without the need for protection. The reactivity order of organic halides is I>Br>OTf>>Cl, but the order between Br and OTf can be reversed by addition of LiCl. By addition of LiCl (2 or 3 equiv) to provide a more reactive Pd-intermediate (vinyl-PdCIl versus vinyl-PdOTfL ) [25] and/or stable tin by-product (RjSnCl versus R3SnOTf), the reaction proceeds smoothly at ambient temperature. 

Rapid and nearly complete alkylation of carboxylate salts with reactive organic halides has been demonstrated in nonpolar and polar solvents. With less reactive alkyl halides, the use of dipolar aprotic solvents for alkylation has been marginally successful. The rate of alkylation of potassium 2-methyl-2-propylpentanoate with 1-chlorohexane in four dipolar aprotic solvents at 60 °C decreased in the order HMPA > iV-methylpyrrolidone > DMSO > DMF. ... 

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