MECHANISM OF THE BIMOLECULAR NUCLEOPHILIC DISPLACEMENT REACTION ON Α-Halocarbonyl COMPOUNDS

Abstract

T\\ o mechanisms ha\.e pre\-iously been p o s t~~l a t e d for the high reactivity of a-halocarbonyl compounds in the n~~cleophilic clisplacernent reaction. Kinetic data for a-halocarbonyl compounds and ~a r i o u s ~~~~c l e o p h i l e s (cyanqte, acetate, azide, and thiocyanate) in anhydrous methanol are presented. The new clatn, 111 colljunction with previously reported results, arc it1 better agreement with the concept of neighboring group overlap than \\.ith that of Pearsoli's electrostatic facilitation between the ~lucleophile and the a-carbonyl group.

Syntheses and transformations of α-azido ketones and related derivatives

“…Kinetic measurements proved second-order kinetics, first order in each component, and marked rate enhancement in comparison to the analogous alkyl halide. 88,104,105 To explain this increased reactivity several hypotheses have been proposed (see ref. 105 for a short overview).…”

The Chemistry of α-Haloketones and Their Utility in Heterocyclic Synthesis

“…Also, the more polar the C–X bond, the faster the reaction with nucleophiles [ 95 ]. The data shown in Table 5 summarize the enhanced reactivity of α-halo-genat-ed ketones relative to the corresponding alkyl halides in bimolecular nucleophilic substitution reactions [ 96 , 97 , 98 , 99 ].…”

Stereochemical and Steric Effects in Nucleophilic Substitution of α-Halo Ketones

“…For example, phenacyl chloride and chloroacetone were reported to react 97 000 and 33 000 times as fast, respectively, as n-propyl chloride with iodide ion in acetone at 50" (1). Somewhat smaller rate factors, lying between 10' and lo3, were reported for the same compounds reacting at 30" in methanol with acetate, azide, cyanate, and thiocyanate ions (2).…”