Acidity of leaving groups

Leaving group Relative rate Conjugate acid of leaving group p Ka of conjugate acid... 

Carboxylic acid derivative Nucleophile Tetrahedral intermediate Product Conjugate acid of leaving group... 

Elimination of hydrogen halides from polyfluoroalkanes by bases also usually involves earbanion intermediates (ElcB mechanism) [<8/l, and orientation is there tore governed by relative C H acidities and leaving group mobility Some examples are shown in equations 16-18 [145]... 

Polar C=Y double bonds (Y = NR, O, S) with electrophilic carbon have been added to suifinic acids under formation of sulfones. As in the preceding section one must distinguish between carbonyl groups and their derivatives on the one hand, and carboxylic acids (possessing leaving groups at the electrophilic carbon) on the other. Aldehydes " of sufficient reactivity—especially mono-substituted glyoxals - —and their aryl or arylsulfonyl imines have been added to suifinic acids (in a reversible equilibrium) to yield a-hydroxy or a-amino sulfones the latter could also be obtained from the former in the presence of primary amines (equation 26). 

Nucleophilic substitution of leaving groups is probably the most important area in pyrimidine reactivity and, in particular, the differential reactivity of C-2 and C-4 is the most investigated topic. The displacement of 2- and 4-sulfide and sulfone groups is referred to in the synthesis section. The selective hydrolysis of 4-amino-2-chloropyrimidines under acidic conditions has been studied in great detail by a process research group <06OPRD921>. 

The SB-GA mechanism consists of a rapid equilibrium deprotonation of the ZH intermediate, followed by rate-limiting, general acid-catalysed leaving-group departure from the anionic cr-complex Z via the concerted transition state, 2. The derived expression for this mechanism is equation 4, where fctBH is the rate coefficient for acid-catalyzed expulsion of L from Z and K3 is the equilibrium constant for the reaction ZH Z- + BH. 

Inert metal complexes, 34 145-147 acid-catalyzed paths, 34 167 alteration of leaving group displacement rate, 34 150... 

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