Conventional and Unconventional Intramolecular Hydrogen Bonding in some Beta-diketones

V Darugar, M Vakili, R Afzali, S Tayyari
2017 Org. Chem. Res   unpublished
This study presents our view of unconventional and conventional intramolecular hydrogen bonds (HBs) for some beta-diketones theoretically and experimentally. According to our results, the groups such as phenyl and t-but in beta positions increase and CF 3 group decrease IHB strength, respectively. For better understanding of the substitution effects, the compounds with similar and different substitutions compared to each other experimentally and theoretically. Comparison between theoretical and
more » ... experimental results, E HB and OH, shows that these parameters change by adding one substitution. These changes are almost doubled by adding another similar substitution. This conclusion achieved for DMPD with phenyl and t-But groups in beta positions. Whereas, TFBA, with phenyl and CF 3 groups, and TFDMHD with CF 3 and t-But groups in beta positions do not follow this achievement. The 1 H NMR chemical shifts for the stable cis-enol forms of the mentioned compounds have been calculated at different levels with various basis sets in CHCl 3 as solvent using PCM method. For the most beta-diketones, the 6-311G** and 6-311++G** basis sets, in all our calculated levels, are in better agreement with the experimental results. According to AIM results, unconventional hydrogen bonding is created in some beta-diketones containing Ph group. The strength of this hydrogen bonding is the same for all these compounds and is about 2 kcal mol-1 .