ChemInform Abstract: Base Catalysis in Nucleophilic Aromatic Substitution Reactions: Evidence for Cyclic Transition State Mechanism Over the Dimer Mechanism in a Non-polar Aprotic Solvent.

1986 ◽  
Vol 17 (31) ◽  
Author(s):  
O. BANJOKO ◽  
C. EZEANI
Keyword(s):  
Transition State ◽  
Aprotic Solvent ◽  
Base Catalysis ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Substitution Reactions ◽  
Cyclic Transition ◽  
Polar Aprotic Solvent ◽  
Cyclic Transition State

scholarly journals Rationalization of the effects of hydrogen bond donor solvent and nucleofugicity of fluoride ion on nucleophilic aromatic substitution reactions in non-polar aprotic solvent: reaction of 2,4-dinitrofluorobenzene with cyclohexylamine in toluene and toluene

2021 ◽  
Vol 46 (2) ◽  
Author(s):  
A. D. Adesina ◽  
I. A Babatunde
Keyword(s):  
Hydrogen Bond ◽  
Nucleophilic Aromatic Substitution ◽  
Fluoride Ion ◽  
Aromatic Substitution ◽  
Hydrogen Bond Donor ◽  
Substitution Reactions ◽  
Cyclic Transition ◽  
Polar Aprotic Solvent ◽  
Donor Solvent ◽  
Kinetics Of

The kinetics of the reaction of 2,4-dinitrofluorobenzene with cyclohexylamine were studied at different concentrations in toluene and toluene-alkanol mixtures. The reaction was not base-catalysed in toluene. Addition of small amounts of hydrogen-bond donor solvent, alkanol (ranging from methanol to hexanol) to the toluene medium of the reactions produced a different effect in comparison to uncatalysed reactions — slight increase in rate of reaction. The results are rationalized in terms of the effect of amine-solvent interaction on the nucleophilicity of the amine in addition to some other factors operating through cyclic transition states leading to products. It is also attributed to the peculiar nature of fluoride ion as a leaving group.

Hydrazinolysis of aryl cinnamates and related esters: the α-effect arises from stabilization of five-membered cyclic transition state

2019 ◽  
Vol 97 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Ik-Hwan Um ◽  
Ae-Ri Bae ◽  
Julian M. Dust
Keyword(s):  
Transition State ◽  
Linear Correlation ◽  
Primary Amines ◽  
Substitution Reactions ◽  
Cyclic Transition ◽  
Concerted Mechanism ◽  
Bonding Interaction ◽  
Leaving Group ◽  
Cyclic Transition State ◽  
Electron Withdrawing Group

A kinetic study is reported for nucleophilic substitution reactions of Y-substituted-phenyl cinnamates (1a–1h) with a series of primary amines including hydrazine in H2O containing 20 mol % DMSO at 25.0 °C. The Brønsted-type plot for the reaction of 2,4-dinitrophenyl cinnamate (1a) is linear with βnuc = 0.57 except hydrazine, which exhibits positive deviation from the linear correlation (i.e., the α-effect). The Brønsted-type plots for the reactions of 1a–1h with hydrazine and glycylglycine (glygly) are also linear with βlg = –0.71 and –0.87, respectively, when 1a is excluded from the linear correlation. Thus, the reactions have been concluded to proceed through a concerted mechanism on the basis of the linear Brønsted-type plots and magnitudes of the βnuc and βlg values. The α-effect shown by hydrazine is dependent on electronic nature of the substituent Y in the leaving group, e.g., it increases as the substituent Y becomes a weaker electron-withdrawing group (or as basicity of the leaving aryloxide increases), indicating that the α-effect is not due to destabilization of the ground state but mainly due to stabilization of the transition state. A five-membered cyclic TS structure, which could increase nucleofugality of the leaving aryloxide through H-bonding interaction, has been proposed to account for the leaving-group dependent α-effect found in this study. The theories suggested previously to rationalize the α-effect found for the related systems are also discussed.

scholarly journals The use of bisphthalonitriles in the synthesis of side-strapped 1,11,15,25-tetrasubstituted phthalocyanines

1996 ◽  
Vol 74 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Clifford C. Leznoff ◽  
David M. Drew
Keyword(s):  
Key Words ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Substitution Reactions ◽  
Pure Compounds

Nucleophilic aromatic substitution reactions of 3-nitrophthalonitrile yield 3-hydroxyphthalonitrile and 3-neopentoxyphthalonitrile, the latter of which condensed to 1,8,15,22-tetraneopentoxyphthalocyanine as a mixture of isomers. Bisphthalonitriles such as 1,3-bis(2′,3′-dicyanophenoxy)-2,2-dipentylpropane, 1,3-bis(2′,3′-dicyanophenoxy)-2,2-diethylpropane, 1,3-bis(2′,3′-dicyanophenoxy)-2,2-dioctylpropane, and 1,3-bis(2′,3′-dicyanophenoxy)-2-methyl-2-trityloxymethylpropane all gave bis-crown-like 1,11,15,25-tetrasubstituted phthalocyanines as pure compounds when treated with lithium octoxide in 1-octanol at 196 °C. A host of nine other bisphthalonitriles including 1,5-bis(2′,3′-dicyanophenoxy)-3-oxapentane, 1,1-bis(2′,3′-dicyanophenoxymethyl)cyclohexane, 1,2-bis(2′,3′-dicyanophenoxymethyl)benzene, and 2,5-bis(2′,3′-dicyanophenoxymethyl)furan did not dimerize to mononuclear phthalocynaines. The "gem dimethyl" effect was suggested as a reason for the successful macrocyclizations. Key words: nucleophilic aromatic substitution, phthalonitriles, bisphthalonitriles, 1,11,15,25-tetrasubstituted phthalocyanines.

Sign in / Sign up

Export Citation Format

Share Document