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Solvent effect on polar and spectroscopic properties of 2‐ N ‐methylamino‐5‐nitro‐6‐methylpyridine and 2‐ N ‐methylamino‐3‐nitro‐6‐methylpyridine
Author(s) -
Pawełka Zbigniew,
Palasek Barbara,
Puszko Aniela
Publication year - 1997
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199711)10:11<835::aid-pca946>3.0.co;2-f
Subject(s) - chemistry , intramolecular force , hydrogen bond , solvent , nitro , solvent effects , polarity (international relations) , computational chemistry , stereochemistry , molecule , organic chemistry , alkyl , biochemistry , cell
Dipole moments of 2‐ N ‐methylamino‐5‐nitro‐6‐methylpyridine ( I ) and 2‐ N ‐methylamino‐3‐nitro‐6‐methylpyridine ( II ) were determined in solvents of different polarity and basicity. The solvent effect is discussed in terms of the two‐parameter (π*–β) Kamlet–Taft expression. The solvent dependences of the energy of intramolecular charge‐transfer transition and the frequency of the ν(NH) stretching vibration are in keeping with the dielectric results. It was found that the solvent‐induced disturbance in the electronic structure of I is brought about by hydrogen bond interaction with the NH group. The strong intramolecular hydrogen bond in II is stable in weakly basic solvents and the electronic structure is insensitive to the environment. However, in more basic solvents the intramolecular hydrogen bond is partly broken and an N—H· · ·solvent hydrogen bond is formed, bringing about distinct changes in polarity and spectroscopic properties. © 1997 John Wiley & Sons, Ltd.