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The intramolecular hydrogen bond, molecular structure, and vibrational frequencies of 2,4-pentanedione and its seventeen derivatives have been investigated by means of density functional (DFT) method with 6-311++G** basis set. The nature of these interactions, known as resonance-assisted hydrogen bonds, has been discussed. The topological properties of the electron density distributions for O–H···O intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). The results of calculations show that the Q-parameter describing the degree of π-electron delocalization within the O=C–C=C–O–H keto–enol group correlates with the strength of the H-bond. Correlations between the H-bond strength and topological parameters have been also studied. Natural population analysis data, the electron density and Laplacian properties, as well as, ν(O–H) and γ(O–H) have been used to evaluate the hydrogen-bonding interactions. Furthermore, calculated 1H NMR chemical shifts (δH) correlate well with the hydrogen-bond distance as well as electron density at the bond and ring critical points in the molecular electron density topography.

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This article presents, effects of fractional order derivative and magnetic field on double convection flow of viscous fluid over a moving vertical plate with constant temperature and general concentration. The model is fractionalized by using Caputo-Fabrizio derivative operator. Closed form solutions of the fluid velocity, concentration and temperature are obtained by means of the Laplace transform. Numerical computations and graphical illustrations are used in order to study the effects of the Caputo-Fabrizio time-fractional parameter , magnetic parameter , Prandtl and Grashof numbers on velocity field.