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Abstract: Two series of dyes have been designed and theoretically characterized through density functional theory and timedependent density functional theory to systematically explore the structure--property relationship of dyes with D-A-π-A [...]

Some exercises to introduce students to the concept of green chemistry are given. By doing these exercises, students develop an appreciation for the role of green chemistry on feedstock substitution, milder reaction conditions, reduced environmental exposure, and resource conservation.

Some exercises to introduce students to the concept of green chemistry are given. By doing these exercises, students develop an appreciation for the role of green chemistry on feedstock substitution, milder reaction conditions, reduced environmental exposure, and resource conservation.

Allyl alcohol could provide an interesting model for chemocontrol in transition metal-catalyzed insertion of carbenoid into O H bond and olefin cyclopropanation. The chemoselectivity of PtCl 2 - and PtCl 4 -catalyzed (compared to Rh and Cu) reactions between methyl α-diazophenylacetate and unsaturated allyl alcohol has been carried out by DFT calculations. The potential energy profiles confirm that the intermediate free enol formed by intramolecular proton transfer is more favorable compared to the formation of the free ylide and cyclopropanation. The [1,3]-proton shift of the enol readily provides the final O H insertion product, which has a barrier of 4.5 and 6.9 kcal/mol using metal-assisted two-allyl-alcohol clusters as a proton shuttle. Calculations provide a good explanation for the O H insertion vs cyclopropanation of platinum, copper and rhodium catalysts have been used in these reactions. This study is expected to improve the understanding of platinum-catalyzed reactions for the C X bond construction and provide guidance for the future design of new catalysts and new reactions. [ABSTRACT FROM AUTHOR]

The dehydrogenation reaction mechanism of cyclohexane catalyzed by dimer transition metal cluster V2+ has been investigated at the B3LYP/6-31G (d, p) level of density functional theory. Density of states (DOS) graph is used to understand more deeply the roles of the front molecular orbital of the initial complexes. After the first molecular dehydrogenation, the reaction mainly consists of two competition mechanisms. First, the C-H bonds of cyclohexane can be effectively activated by the V2+ cation, yielding the same-face dehydrogenation products. Second, the C-C bonds are activated, forming the different-face dehydrogenation products. Our calculations indicate that the reaction takes place more easily along the low-spin potential energy surface on the same-face and is a low-barrier or even barrier-free transformation. Carbon-carbon single bonds are nonpolar and generally far less reactive. A comparison of the reaction mechanism of V2+ and congener Ti2+ with cyclohexane has been presented. The bond dissociation energies (BDEs) of V2+ are greater than that of Ti2+, leading to difficulties in forming sandwich complexes in the different-face dehydrogenation of cyclohexane, and the same-face dehydrogenation is an important reaction channel. [ABSTRACT FROM AUTHOR]

The first thorough theoretical mechanism analysis of heteronuclear bimetallic cation NiAl + with cyclohexane has been investigated on singlet and triplet potential energy surfaces (PESs) by using density functional theory. Our calculated results show that NiAl + can assist in the decomposition of cyclohexane to form benzene through two types of reaction channel: C H bond activation and H 2 formation; C C bond activation and HD formation. The most important conclusion is that NiAl + exhibits high efficiency and also high regioselectivity for C H bond oxidation. However, the high zero-point vibrational energy (ZPVE) value for the cleavage of inert C C bond is also the origin of its failure to form HD. In the process of the first C H and C C bond activations, crossing points (CPs) have been appeared between the two adiabatic surfaces, respectively. The minimum energy crossing points (MECPs) are gotten using the algorithmin Harvey method. Density of states (DOS) is used to obtain a deeper understanding for the roles of the front molecular orbital of the initial complexes. The bonding properties of the special intermediates involved in the process of C C bond activations are discussed by the IR spectrum methods. [ABSTRACT FROM AUTHOR]

In this paper, the reaction mechanism for N 2 O with CO on the surface of Ni 5 cluster was investigated by the B3LYP method of density functional theory (DFT). Ni atom of various species was calculated using B3LYP/ LANL2DZ basis set, and C, N, O atoms at B3LYP/6-31G ∗ level. In the temperature range of 100–1000 K, the statistical thermodynamics and Eyring transition state theory with Winger correction were used to study the kinetic characters of reaction. The calculation results indicated that the reaction of N 2 O with CO on Ni 5 cluster had two major reacting processes: (1) O atom first dissociated from N 2 O on Ni 5 cluster, and then reacted with CO on Ni 5 and (2) on the surface of Ni 5 catalyst, O atom of N 2 O direct interacted with C atom of CO, resulting into the dissociation of N 2 O and the form of CO 2 . The direct O extraction channel was the main channel due to its low potential energy and high rate constant. [ABSTRACT FROM AUTHOR]