TY - JOUR
T1 - Molecular structure and intramolecular hydrogen bond strength of 3-methyl-4-amino-3-penten-2-one and its N-Me and N-Ph substitutions by experimental and theoretical methods
AU - Seyedkatouli , Seyedabdollah
AU - Vakili, Mohammad
AU - Tayyari , Sayyed Faramarz
AU - Hansen, Poul Erik
AU - Kamounah, Fadhil S.
PY - 2019/2/11
Y1 - 2019/2/11
N2 - In the present work, molecular structures and intramolecular hydrogen bonding (IHB) of 3-methyl-4-amino-3-penten-2-one, 3-MeAPO, 3-methyl-4-methylamino-3-penten-2-one, 3-Me-MeAPO, and the 3-methyl-4-phenylamino-3-penten-2-one, 3-Me-PhAPO have been investigated by means of density functional theory (DFT) calculations, at the B3LYP/6-311++G** level, and experimental investigations including NMR, IR, Raman, UV spectroscopy, and X-ray crystallographic methods. The mentioned results were compared to those of 4-amino-3-penten-2-one, APO. DFT calculations suggest a relatively strong intramolecular hydrogen bond in 3-MeAPO and its N–Me and N-Ph substituted derivatives with N⋯O distances of 2.597, 2.584, and 2.581 Å, and calculated hydrogen bond energies of about 10.9, 13.6, and 14.9 kcal/mol in 3-MeAPO, 3-Me-MeAPO, and 3-Me-PhAPO, respectively. While, the calculated N⋯O distances and hydrogen bond energies, of APO, 2.669 Å and 7.67 kcal/mol respectively, suggest a medium IHB strength. According to the NBO results, the steric effect is the dominant factor for changes of the IHBs. The calculated geometrical parameters of 3-MeAPO are in excellent agreement with the X-ray results. UV-Vis spectra of 3-MeAPO, 3-Me-PhAPO, and 3-Me-MeAPO were recorded in ethanol supporting the results mentioned above. According to the calculated results and deuterium isotope effects on ¹³ C chemical shifts, 3-MeAPO exists as a keto-amine. Comparison of the observed and theoretical IR and Raman spectra and the spectral behavior upon deuteration were used for assignment of the vibrational spectra of 3-MeAPO. The assigned normal modes were compared to those of APO. The theoretical results were in good agreement with the experimental data. The vibrational frequencies also confirmed that the IHB strength in 3-MeAPO is stronger than that in APO.
AB - In the present work, molecular structures and intramolecular hydrogen bonding (IHB) of 3-methyl-4-amino-3-penten-2-one, 3-MeAPO, 3-methyl-4-methylamino-3-penten-2-one, 3-Me-MeAPO, and the 3-methyl-4-phenylamino-3-penten-2-one, 3-Me-PhAPO have been investigated by means of density functional theory (DFT) calculations, at the B3LYP/6-311++G** level, and experimental investigations including NMR, IR, Raman, UV spectroscopy, and X-ray crystallographic methods. The mentioned results were compared to those of 4-amino-3-penten-2-one, APO. DFT calculations suggest a relatively strong intramolecular hydrogen bond in 3-MeAPO and its N–Me and N-Ph substituted derivatives with N⋯O distances of 2.597, 2.584, and 2.581 Å, and calculated hydrogen bond energies of about 10.9, 13.6, and 14.9 kcal/mol in 3-MeAPO, 3-Me-MeAPO, and 3-Me-PhAPO, respectively. While, the calculated N⋯O distances and hydrogen bond energies, of APO, 2.669 Å and 7.67 kcal/mol respectively, suggest a medium IHB strength. According to the NBO results, the steric effect is the dominant factor for changes of the IHBs. The calculated geometrical parameters of 3-MeAPO are in excellent agreement with the X-ray results. UV-Vis spectra of 3-MeAPO, 3-Me-PhAPO, and 3-Me-MeAPO were recorded in ethanol supporting the results mentioned above. According to the calculated results and deuterium isotope effects on ¹³ C chemical shifts, 3-MeAPO exists as a keto-amine. Comparison of the observed and theoretical IR and Raman spectra and the spectral behavior upon deuteration were used for assignment of the vibrational spectra of 3-MeAPO. The assigned normal modes were compared to those of APO. The theoretical results were in good agreement with the experimental data. The vibrational frequencies also confirmed that the IHB strength in 3-MeAPO is stronger than that in APO.
KW - Infra red sepctrosscopy
KW - hydrogne bond energy
KW - isotope effects
KW - 3-Methyl-4-amino-3-penten-2-one
KW - Intramolecular hydrogen bond
KW - Isotope effects on C chemical shifts
KW - Molecular spectroscopy
KW - Substitution effect
U2 - 10.1016/j.molstruc.2019.02.007
DO - 10.1016/j.molstruc.2019.02.007
M3 - Journal article
SN - 0166-1280
VL - 1184
SP - 233
EP - 245
JO - Journal of Molecular Structure: THEOCHEM
JF - Journal of Molecular Structure: THEOCHEM
ER -