Theoretical Studies On The Reaction Of Pentafulvenone With H₂O, HCN And HNC

In this paper, quantum chemistry methods were used to investigate the mechanism of reaction of pentafulvenone with H2O, HCN and HNC. CH2CO and its derivatives are interesting and useful substances for studying reactive molecules. As ketene′s derivative, pentafulvenone has attracted much attention. Pentafulvenone had been generated by photochemical Wolff rearrangement of the diazo ketone and in the 2- halogenphenols aqueous was produced by Wolff rearrangement after elimination of hydrogen halogen. There have been intensive theoretical and experimental studies on the additional and hydrated reactions of CH2CO and its derivatives, including the additional reactions of pentafulvenone with H2O, HCN and HNC.The results of this work show that:1. The mechanism for the reactions of pentafulvenone with monomeric water molecule and two water molecules are investigated at DFT (B3LYP) and MP2 levels with 6-311+G** basis set. The geometries and vibrational frequencies of stationary points on potential energy surface are obtained. The reaction of pentafulvenone with monomeric water molecule involves a complex, two intermediates, twelve products and twenty-nine transition states; the reaction of pentafulvenone with two water molecules involves four complexes, one intermediate, two products and three transition states. Our results show that the reactions of pentafulvenone with monomeric water molecule and two water molecules both have two attacking forms, which are H2O attacking C=O double bond and C=C double bond of pentafulvenone. The three kinds of cyclopentadienyl carboxylic acids can tautomerize to each other, and the most stable product is the b kind of cyclopentadienyl carboxylic acid.2. The effect of solvent of the reactions of pentafulvenone with water is studied using PCM-UAHF model. The results show that the structural parameters change slightly in going from gas phase to aqueous solvent, and after considering the solvation effect, the energies and barrier heights for the hydrations of pentafulvenone decrease.3. The mechanism for the reaction of pentafulvenone with HCN is investigated at DFT (B3LYP) and MP2 levels with 6-311+G** basis set. The geometries and vibrational frequencies of stationary points on potential energy surface are obtained. We found a complex, two intermediates, thirteen transition states and eight products. Our results show that the reaction has two attacking forms, which are HCN attacking C=O double bond and C=C double bond of pentafulvenone. Each kind of attacking form includes two reactive paths. The tautomerizations of products include two kinds of processes, which are the tautomerizations of the same kind and the different kinds of cyclopentadienyl cyanic acids. In the process, the b kind of cyclopentadienyl cyanic acids is the most stable products.4. The mechanism for the reaction of pentafulvenone with HNC is investigated in singlet and triplet states at DFT (B3LYP) and MP2 levels with 6-311+G** basis set. The geometries and vibrational frequencies of stationary points on potential energy surface are obtained. We found a complex, thirty-two transition states and twelve products. Our results show that the reaction has two attacking forms, which are HNC attacking C=O double bond and C=C double bond of pentafulvenone. The tautomerizations of products include two kinds of processes, which are the tautomerizations of the same kind and the different kinds of cyclopentadienyl isocyanic acids. In the process, the b kind of cyclopentadienyl isocyanic acids is the most stable products.