Conformational state of β-hydroxynaphthylamides: Barriers for the rotation of the amide group around CN bond and dynamics of the morpholine ring

Tomasz Kozlecki; Peter M Tolstoy; Agnieszka Kwocz; Mikhail A Vovk; Andrzej Kochel; Izabela Polowczyk; Peter Yu Tretyakov; Aleksander Filarowski

doi:10.1016/j.saa.2015.04.052

Conformational state of β-hydroxynaphthylamides: Barriers for the rotation of the amide group around CN bond and dynamics of the morpholine ring

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Oct 5:149:254-62. doi: 10.1016/j.saa.2015.04.052. Epub 2015 Apr 28.

Authors

Tomasz Kozlecki¹, Peter M Tolstoy², Agnieszka Kwocz³, Mikhail A Vovk⁴, Andrzej Kochel³, Izabela Polowczyk¹, Peter Yu Tretyakov⁵, Aleksander Filarowski⁶

Affiliations

¹ Wroclaw University of Technology, Faculty of Chemistry, Division of Chemical Engineering, 50-373 Wrocław, Poland.
² St. Petersburg State University, Center for Magnetic Resonance, 198504 St. Petersburg, Russia. Electronic address: peter.tolstoy@spbu.ru.
³ Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
⁴ St. Petersburg State University, Center for Magnetic Resonance, 198504 St. Petersburg, Russia.
⁵ University of Architecture and Civil Engineering, 625001 Tyumen, Russia.
⁶ Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland; The Joint Institute for Nuclear Research, Frank Laboratory of Neutron Physics, 141980 Dubna, Russia. Electronic address: aleksander.filarowski@chem.uni.wroc.pl.

PMID: 25965172
DOI: 10.1016/j.saa.2015.04.052

Abstract

Three β-hydroxynaphthylamides (morpholine, pyrrolidine and dimethylamine derivatives) have been synthesized and their conformational state was analyzed by NMR, X-ray and DFT calculations. In aprotic solution the molecules contain intramolecular OHO hydrogen bonds, which change into intermolecular ones in solid state. The energy barriers for the amide group rotation around the CN bond were estimated from the line shape analysis of (1)H and (13)C NMR signals. A tentative correlation between the barrier height and the strength of OHO bond was proposed. Calculations of the potential energy profiles for the rotations around CC and CN bonds were done. In case of morpholine derivative experimental indications of additional dynamics: chair-chair 'ring flip' in combination with the twisting around CC bond were obtained and confirmed by quantum chemistry calculations.

Keywords: Amide group rotation; Conformational isomerism; DNMR; Intramolecular hydrogen bond; Solvent effects; β-Hydroxynaphthylamides.

Publication types

Research Support, Non-U.S. Gov't