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Current Organocatalysis

Author(s): Ladapborlang Mawrie, Fazlur Rahman and Sarifuddin Gazi*

DOI: 10.2174/2213337210666230808152832

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Understanding Nucleophilicity of Pyridine-N-oxides Towards 2,4,6-Trinitrophenylbenzoate Through Simple Absorption Spectroscopic Studies

Page: [44 - 59] Pages: 16

  • * (Excluding Mailing and Handling)

Abstract

Aims: Understanding nucleophilicity of poor nucleophiles like pyridine-N-oxides.

Background: Nucleophilicity plays a vital role in substitution reactions. It helps to determine the possibility and extent of the substitution reactions. The study of the nucleophilicity of poor nucleophiles is challenging, and it has limited substrate scope. Understanding the strength of nucleophilicity of such poor nucleophiles in a quantitative way is important.

Objective: Understanding the strength of nucleophilicity of such poor nucleophiles in a quantitative way. Selection of appropriate electrophile for the reactions with the poor nucleophilespyridine- N-oxides. Development of suitable methodology for kinetic studies of the reaction.

Methods: UV-Vis spectroscopic methods for monitoring the reactions.

Results: The kinetic studies revealed that the second-order rate constants of the nucleophilic reactions are 1.67× 102 L mol-1 min-1, 29.8 L mol-1 min-1, 2.51 L mol-1 min-1, where the nucleophiles are p-methylpyridine-N-oxide, pyridine-N-oxide, and p-nitropyridine-N-oxide, respectively. The UV-Vis spectroscopic analysis revealed the nucleophilicity of p-methylpyridine-N-oxide > pyridine- N-oxide > p-nitropyridine-N-oxide.

Conclusion: This comparative study suggests that the strength of nucleophilicity of the pmethylpyridine- N-oxide is 5.6 times and 66.53 times more than that of pyridine-N-oxide and pnitropyridine- N-oxide, respectively, whereas the strength of nucleophilicity of the pyridine-Noxide is 11.87 times more than that of p-nitropyridine-N-oxide.

Graphical Abstract

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