Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides
The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (1H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(...
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doaj-3b070c4c4ee74d69b7f52864c45c20c22020-11-25T01:36:43ZengMDPI AGMolecules1420-30492017-01-012218310.3390/molecules22010083molecules22010083Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-AminobenzamidesMalose Jack Mphahlele0Marole Maria Maluleka1Lydia Rhyman2Ponnadurai Ramasami3Richard Mokome Mampa4Department of Chemistry, College of Science, Engineering and Technology, University of South Africa, Private Bag X06, Florida 1710, South AfricaDepartment of Chemistry, College of Science, Engineering and Technology, University of South Africa, Private Bag X06, Florida 1710, South AfricaComputational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Reduit 80837, MauritiusDepartment of Chemistry, College of Science, Engineering and Technology, University of South Africa, Private Bag X06, Florida 1710, South AfricaDepartment of Chemistry, University of Limpopo, Private Bag X1106, Sovenga 0727, South AfricaThe structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (1H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)–NH2 single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the 1H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar–NH2 single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer (A) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.http://www.mdpi.com/1420-3049/22/1/83halogenated 2-aminobenzamides1H-NMR spectravibrational spectraDFTXRD |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Malose Jack Mphahlele Marole Maria Maluleka Lydia Rhyman Ponnadurai Ramasami Richard Mokome Mampa |
spellingShingle |
Malose Jack Mphahlele Marole Maria Maluleka Lydia Rhyman Ponnadurai Ramasami Richard Mokome Mampa Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides Molecules halogenated 2-aminobenzamides 1H-NMR spectra vibrational spectra DFT XRD |
author_facet |
Malose Jack Mphahlele Marole Maria Maluleka Lydia Rhyman Ponnadurai Ramasami Richard Mokome Mampa |
author_sort |
Malose Jack Mphahlele |
title |
Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides |
title_short |
Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides |
title_full |
Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides |
title_fullStr |
Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides |
title_full_unstemmed |
Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides |
title_sort |
spectroscopic, dft, and xrd studies of hydrogen bonds in n-unsubstituted 2-aminobenzamides |
publisher |
MDPI AG |
series |
Molecules |
issn |
1420-3049 |
publishDate |
2017-01-01 |
description |
The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (1H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)–NH2 single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the 1H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar–NH2 single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer (A) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure. |
topic |
halogenated 2-aminobenzamides 1H-NMR spectra vibrational spectra DFT XRD |
url |
http://www.mdpi.com/1420-3049/22/1/83 |
work_keys_str_mv |
AT malosejackmphahlele spectroscopicdftandxrdstudiesofhydrogenbondsinnunsubstituted2aminobenzamides AT marolemariamaluleka spectroscopicdftandxrdstudiesofhydrogenbondsinnunsubstituted2aminobenzamides AT lydiarhyman spectroscopicdftandxrdstudiesofhydrogenbondsinnunsubstituted2aminobenzamides AT ponnadurairamasami spectroscopicdftandxrdstudiesofhydrogenbondsinnunsubstituted2aminobenzamides AT richardmokomemampa spectroscopicdftandxrdstudiesofhydrogenbondsinnunsubstituted2aminobenzamides |
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