Leaving group effects nucleophilic substitution

Nickel(ii).—A number of variables were studied for substitution at square-planar bis-dithiolatonickel(ii) complexes. These variables included the reactivity of the incoming nucleophile, leaving-group effects, the trans effect, and the denticity of the incoming group. The rate law here is simple... 

To derive the maximum amount of information about intranuclear and intemuclear activation for nucleophilic substitution of bicyclo-aromatics, the kinetic studies on quinolines and isoquinolines are related herein to those on halo-1- and -2-nitro-naphthalenes, and data on polyazanaphthalenes are compared with those on poly-nitronaphthalenes. The reactivity rules thereby deduced are based on such limited data, however, that they should be regarded as tentative and subject to confirmation or modification on the basis of further experimental study. In many cases, only a single reaction has been investigated. From the data in Tables IX to XVI, one can derive certain conclusions about the effects of the nucleophile, leaving group, other substituents, solvent, and comparison temperature, all of which are summarized at the end of this section. 

Predict the effect of substrate, nucleophile, leaving group and solvent on substitution and elimination reactions. 

All these systems are susceptible to nucleophilic attack, particularly the oxadiazoles, which often undergo ring cleavage with aqueous acid or base unless both carbon positions are substituted. Similarly, leaving groups are generally displaced easily there is substantial differential positional reactivity in both 1,2,4-oxa- and -thiadiazoles a 5-chlorine is displaced much more easily than a 3-chlorine, no doubt due to the more effective stabilisation of the intermediate anionic adduct in the former situation. 

Azine substitution (nucleophilic)—cont. kinetics for bic clic azines, 331-361 kinetics for monoc3rclic azines, 269-285 leaving group, effect of, 196-215 leaving group, hydrogen bonding of, 201... 

Leaving group effects on the ratio of C- to O-alkylation can be correlated by reference to the hard-soft-acid-base (HSAB) rationale. Of the two nucleophilic sites in an enolate ion, oxygen is harder than carbon. Nucleophilic substitution reactions of the Sn2 type proceed best when the nucleophile and leaving group are either both hard or both soft. Consequently, ethyl iodide, with the very soft leaving... 

In Chapter 9, we introduced the basic principles of nucleophilic substitution and elimination reactions. We focused almost entirely upon the reactions of haloalkanes and alcohols. In this chapter, we will expand upon these reactions and consider a much wider range of nucleophiles, leaving groups, substrates, solvents, and their effects on nucleophilic substitution and elimination reactions. We will ask ... 

A series of binuclear pentacoordinated silicon complexes 85 of diketopiperazine have been synthesized and substituent (or leaving group) effects on the Si-O coordination have been studied for five analogues with X=F, Cl, OTf, Br, and I [226]. Variable-temperature NMR spectroscopy (supported by X-ray crystallography) shows, for the first time in binuclear pentacoordinated silicon complexes, a complex equilibrium with both nonionic (0-Si) and ionic (Si-X) dissociation of the axial bonds in the silicon-centered trigonal bipyramids. The two dissociation pathways are consistent with a model for nucleophilic substitution at the silicon atom in a binuclear pentacoordinated silicon compound (Scheme 21) [226]. 

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