Document Type : Original Article

Authors

• Ayoub Kanaani
• Seyed Abdollah Seyedkatouli ¹
• Sahar Koukalani ²

¹ Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Iran

² Department of Computer Sciences, Faculty of Mathematical Sciences, University of Mazandaran, Babolsar, Iran

Abstract

The intramolecular hydrogen bond (IHB) strengths of 4-amino-3 penten-2-one (APO), 3-methyl-4-amino-3-penten-2-one (3-MeAPO) and 4-methylamino-3-penten-2-one (APO-NMe) were investigated using combined theoretical and experimental approaches. All geometry optimizations and frequency calculations were performed using density functional theory (DFT) at the B3LYP/6-31++G(d,p) level of theory, as implemented in the Gaussian 09 program package. Geometrical parameters (R, θ), spectroscopic data (IR, UV–Vis, NMR), natural bond orbital (NBO) analysis, and atoms-in-molecules (AIM) calculations were employed to evaluate and compare the IHB strength in both compounds. The most results, such as 1HNMR, NH stretching, and the E(2), associated with the lp(O6) → σ*N7–H9 interaction confirming that the strength in APO-NMe is greater than in 3-MeAPO. In contrast, the other results, especially the X-ray data and AIM results, show different trends. These comparisons provide a clearer understanding of the effects of CH3 substitution at the α-position and on the nitrogen atom on the strength of the intramolecular hydrogen bond (IHB). In addition, molecular electrostatic potential (MEP), frontier molecular orbital analysis (HOMO–LUMO), natural atomic charges, global reactivity parameters, and non-linear optical properties of the compound were studied using same theoretical calculations.

Graphical Abstract

Keywords

• Methyl-4-amino-3-penten-2-one
• 4-Methylamino-3-penten-2-one
• Intramolecular hydrogen bond