Ab initio and DFT studies of hydrogen bond interactions in difluoroacetic acid dimer

Density functional theory (DFT) and ab initio calculations were performed for difluoroacetic acid (DFA). Eight theoretically possible conformers were considered and by using conformational analysis only three stable conformers were found. The hydrogen bonding interaction of DFA complex has been investigated using DFT and ab initio methods for cis conformers. Stabilization energies of dimers including basis set superposition error and ZPE were found in the range 8.89–13.08 kcal mol⁻¹. It was found that EFC dimer is slightly more stable. Red shift of O–H bond in the range −226.3 to 505.7 cm⁻¹ predicted for dimers. The natural bond orbital analysis was applied to characterize nature of the interaction.     

Nano-copper chromite (nano-CuCr2O4): a novel and efficient catalyst for the synthesis of biscoumarin and pyrano[c]chromene derivatives in water at room temperature

Research on Chemical Intermediates - A clean, efficient and eco-friendly procedure has been developed using nano-copper chromite (nano-CuCr2O4) as catalyst for the synthesis of biscoumarin and...     

Simple and efficient synthesis of 5‐substituted 1‐H‐tetrazoles using metal‐modified clay catalysts

The synthesis of 5‐substituted 1‐H‐tetrazoles based on reaction of a series of aromatic nitriles with sodium azide was investigated. The reaction was catalyzed by modified montmorillonite K‐10 including Cu²⁺, Fe³⁺, Ni²⁺, and Zn²⁺ metal ions. The best results obtained by Mont‐K10‐Cu catalyst. The catalysts were reused several times without loss of their activity. The present procedure offers advantages such as a shorter reaction time, simple workup, recovery, and reusability of the catalyst. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:168–173, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20672     

ClO<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack>/Al-MCM-41 nanoparticles as a solid acid catalyst for the synthesis of 2-amino-3-cyanopyridines

A one-pot four-component reaction of various types of aldehydes, acetophenone, malononitrile, and ammonium acetate was studied in the presence of perchlorated Al-MCM-41 (ClO ₄ ^? /Al-MCM-41) nanoparticles for the synthesis of 2-amino-3-cyanopyridines. Mesoporous Al-MCM-41 molecular sieves with the Si/Al molar ratios of 30, 40, and 50 were synthesized by the sol–gel method and ClO ₄ ^? /Al-MCM-41 with different calcination temperatures were prepared and characterized by SEM, TEM, XRD, FT-IR, potentiometric titration and, N₂ adsorption-desorption techniques. The characterization results show that ClO ₄ ^? /Al-MCM-41 with calcination temperature of 300 °C has the best catalytic activity for the synthesis of 2-amino-3-cyanopyridines. The catalyst is reusable many times with moderate loss in its activity.