Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. Part 4. 2,4,6-Triaryl-N-benzylpyridinium cations: rate variation with electronic effects in the leaving group

1982 ◽  
pp. 1041 ◽  
Author(s):  
Alan R. Katritzky ◽  
Jeffrey Adamson ◽  
E. Michael Elisseou ◽  
Giuseppe Musumarra ◽  
Ranjan C. Patel ◽  
...  
Keyword(s):  
Rate Variation ◽  
Electronic Effects ◽  
Leaving Group ◽  
Leaving Groups

Impact of Electronic Effects on the Nucleofugality of Leaving Groups

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3422-3432 ◽  
Author(s):  
Bernard Denegri ◽  
Mirela Matić ◽  
Olga Kronja
Keyword(s):  
Short Review ◽  
Linear Free Energy Relationship ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Linear Free Energy ◽  
Leaving Group ◽  
Negative Hyperconjugation ◽  
Leaving Groups ◽  
The Impact ◽  
Leaving Group Ability

A short review of the development of nucleofugality and electrofugality scales based on solvolysis rates of benzhydryl derivatives is presented. Accordingly, the rate of the heterolytic step in the SN1 displacement reaction and the leaving group ability (nucleofugality) in a given solvent are related with the special linear free-energy relationship (LFER) equation: log k = s f (N f + E f). The impact of electronic effects in the leaving group (nucleofuge) on the overall SN1 reactivity of the substrate is given. The importance of inductivity, resonance, polarity and field effects in the leaving group moiety in the transition state is analyzed. Also, the effect of the negative hyperconjugation and the influence of other electronic effects in the leaving group on the height of the reaction intrinsic barrier are considered.1 Introduction2 Development of the Nucleofugality Scale3 Inductive and Resonance Effects4 Negative Hyperconjugation5 Intrinsic Barrier6 Conclusions

Kinetics and mechanisms of nucleophilic displacements with heterocycles as leaving groups. 2. N-benzylpyridinium cations: rate variation with steric effects in the leaving group

1981 ◽  
Vol 46 (19) ◽  
pp. 3823-3830 ◽  
Author(s):  
Alan R. Katritzky ◽  
Azzahra M. El-Mowafy ◽  
Giuseppe Musumarra ◽  
Kumars Sakizadeh ◽  
Choudhry Sana-Ullah ◽  
...  
Keyword(s):  
Steric Effects ◽  
Rate Variation ◽  
Leaving Group ◽  
Leaving Groups

The effect of steric size of leaving group on rates of the competing syn- and anti-pathways in biomolecular elimination

1980 ◽  
Vol 45 (8) ◽  
pp. 2171-2178
Author(s):  
Jiří Závada ◽  
Magdalena Pánková
Keyword(s):  
Comparative Analysis ◽  
Homologous Series ◽  
Leaving Group ◽  
Leaving Groups

Approximate rates of the competing syn- and anti-pathways have been determined in t-C4H9OK-t-C4H9OH promoted elimination from two homologous series of tosylates: I-OTs trans-III (R = H, CH3, C2H5, n-C3H7, i-C3H7, t-C4H9) and II-OTs trans-IV (R = CH3, C2H5, n-C3H7, i-C3H7, t-C4H9). A comparison has been made with rates of the same processes in the (+) elimination of the corresponding trimethylammonium salts I-N(CH3)3 trans-III and (+) II-N(CH3)3 trans-IV. The title effect is demonstrated by a comparative analysis of the rate patterns obtained for the two leaving groups.

Copper(II) complexes with tridentate halogen‐substituted Schiff base ligands: synthesis, crystal structures and investigating the effect of halogenation, leaving group and ligand flexibility on antiproliferative activities

2021 ◽  
Author(s):  
Nazanin Kordestani ◽  
Hadi Amiri Rudbari ◽  
Alexandra R Fernandes ◽  
Luís R Raposo ◽  
André Luz ◽  
...  
Keyword(s):  
Schiff Base ◽  
Anticancer Activity ◽  
Crystal Structures ◽  
Copper Complexes ◽  
Schiff Base Ligands ◽  
Leaving Group ◽  
Leaving Groups ◽  
Tridentate Schiff Base ◽  
Antiproliferative Activities

To investigate the effect of different halogen substituents, leaving groups and the flexibility of ligand on the anticancer activity of copper complexes, sixteen copper(II) complexes with eight different tridentate Schiff-base...

DENSITY FUNCTIONAL STUDY OF SELECTED MONO-ZINC AND GEM-DIZINC RADICAL CARBENOID CYCLOPROPANATION REACTIONS: OBSERVATION OF AN EFFICIENT RADICAL ZINC CARBENOID CYCLOPROPANATION REACTION AND THE INFLUENCE OF THE LEAVING GROUP ON RING CLOSURE

2003 ◽  
Vol 02 (03) ◽  
pp. 357-369 ◽  
Author(s):  
CUNYUAN ZHAO ◽  
DONG-QI WANG ◽  
DAVID LEE PHILLIPS
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Radical Reaction ◽  
Ring Closure ◽  
Functional Study ◽  
Reaction Step ◽  
Leaving Group ◽  
Reaction Barriers ◽  
Leaving Groups ◽  
Zinc Carbenoid

We report a theoretical study of the cyclopropanation reactions of EtZnCHI, (EtZn)2CH EtZnCHZnI, and EtZnCIZnI radicals with ethylene. The mono-zinc and gem-dizinc radical carbenoids can undergo cyclopropanation reactions with ethylene via a two-step reaction mechanism similar to that previously reported for the CH2I and IZnCH2 radicals. The barrier for the second reaction step (ring closure) was found to be highly dependent on the leaving group of the cyclopropanation reaction. In some cases, the (di)zinc carbenoid radical undergoes cyclopropanation via a low barrier of about 5–7 kcal/mol on the second reaction step and this is lower than the CH2I radical reaction which has a barrier of about 13.5 kcal/mol for the second reaction step. Our results suggest that in some cases, zinc radical carbenoid species have cyclopropanation reaction barriers that can be competitive with their related molecular Simmons-Smith carbenoid species reactions and produce somewhat different cyclopropanated products and leaving groups.

scholarly journals Improvement in hydrolytic antibody activity by change in haptenic structure from phosphate to phosphonate with retention of a common leaving-group determinant: evidence for the ‘flexibility’ hypothesis

2003 ◽  
Vol 376 (3) ◽  
pp. 813-821 ◽  
Author(s):  
Sheraz GUL ◽  
Sanjiv SONKARIA ◽  
Surapong PINITGLANG ◽  
José FLOREZ-ALVAREZ ◽  
Syeed HUSSAIN ◽  
...  
Keyword(s):  
Structural Motif ◽  
Catalytic Antibody ◽  
Antibody Activity ◽  
Reaction Centre ◽  
Binding Characteristics ◽  
Leaving Group ◽  
Catalytic Mechanisms ◽  
Leaving Groups ◽  
Antibody Preparations ◽  
Ester Substrate

To investigate the hypothesis that decreased hapten flexibility may lead to increased catalytic antibody activity, we used two closely related immunogens differing only in the flexibility of the atomic framework around the structural motif of the haptens, analogous to the reaction centre of the corresponding substrates. Identical leaving-group determinants in the haptens and identical leaving groups in the substrates removed the ambiguity inherent in some data reported in the literature. Anti-phosphate and anti-phosphonate kinetically homogeneous polyclonal catalytic antibody preparations were compared by using carbonate and ester substrates respectively, each containing a 4-nitrophenolate leaving group. Synthetic routes to a new phosphonate hapten and new ester substrate were developed. The kinetic advantage of the more rigid anti-phosphonate/ester system was demonstrated at pH 8.0 by a 13-fold advantage in kcat/knon-cat and a 100-fold advantage in the proficiency constant, kcat/knon-cat·Km. Despite these differences, the pH-dependences of the kinetic and binding characteristics and the results of chemical modification studies suggest closely similar catalytic mechanisms. The possible origin of the kinetic advantage of the more rigid hapten/substrate system is discussed.

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