In this research, molecular structures and character of the intramolecular hydrogen bonding (IHB) of 2,6- dimethylheptane-3,5-dione, C 9 H 16 O 2 , (DMHD) has been studied by the helping of experimental methods such as NMR, IR, Raman, and UV spectroscopic and using density functional theory (DFT) estimations such as optimized geometrical parameters, AIM results, and natural bond orbital (NBO). The outcomes were compared to those of 2,2,6,6-tetramethyl-3,5-heptanedione (TMHD), heptane-3,5-dione (HD), and acetylacetone (AA). Outstanding solidarities were got among experimental and theoretical results with the IHB strength. The results show that the trend of the IHB strength is: TMHD > DMHD > HD > AA. The vibrational frequencies of title compound were also obviously assigned. Several correlations between ge- ometrical, topological parameters, 1 HNMR chemical shift, and vibrational wavenumbers with the number of methyl groups were obtained. Fukui functions, frontier molecular orbital analysis, and reactivity de- scriptors were found and discussed. Also, according to calculate global reactivity parameters, the AA and DMHD show the highest and lowest hardness between the mentioned molecules, while DMHD and TMHD have the highest and lowest toxicity, respectively.

Keywords