نتایج جستجو برای: chemical bond

تعداد نتایج: 440732  

Journal: :The Journal of Chemical Physics 2016

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2005
Yung Sam Kim Robin M Hochstrasser

The involvement of chemical exchange in 2D IR heterodyne echo spectroscopy is characterized through the hydrogen-bond exchange between CH3OH and the CN of CH3CN. The exchange dynamics on the hydrogen-bond potential surfaces associated with different quantum states of the high-frequency CN stretching mode contributes to strong cross peaks between CN groups in two different chemical configuration...

Journal: :international journal of bio-inorganic hybrid nanomaterials 0

in the present work, the structural and electronic properties, and conductivity of (5,5) and (6,6) single walled carbon nanotubes in the ground state have done by using the hartree-fock and density functional theory dft-b3lyp/6-31g* level. delocalization of charge density between the bonding or lone pair and antibonding orbitals calculated by nbo (natural bond orbital) analysis. these methods a...

ژورنال: مجله دندانپزشکی 2006
ایلخان, بانو , درریز, حسن ,

Background and Aim: The improvement of the physical and chemical properties of resins as well as great advances achieved in the field of chemical bonding of resin to metal has changed the trend of restorative treatments. Today the second generation of laboratory resins have an important role in the restoration of teeth. The clinical bond strength should be reliable in order to gain successful r...

Journal: :The journal of physical chemistry. A 2006
Norman C Craig Peter Groner Donald C McKean

Equilibrium structures have been determined for s-trans-1,3-butadiene and ethylene after adjusting the rotational constants obtained from rotational spectroscopy by vibration-rotation constants calculated from the results of quantum chemical calculations. For butadiene, the formal C=C bond length is 1.338 A, and the formal C-C bond length is 1.454 A. For ethylene, the C=C bond length is 1.3305 ...

2015
Wan Chin Ng Jacqueline S. R. Chin Kah Junn Tan Joanne Y. Yew

Insects use a spectacular variety of chemical signals to guide their social behaviours. How such chemical diversity arises is a long-standing problem in evolutionary biology. Here we describe the contribution of the fatty acid elongase Bond to both pheromone diversity and male fertility in Drosophila. Genetic manipulation and mass spectrometry analysis reveal that the loss of bond eliminates th...

Journal: :Chemical Society reviews 2015
Chao Shen Pengfei Zhang Qiang Sun Shiqiang Bai T S Andy Hor Xiaogang Liu

The development of mild and general methods for C-S bond formation has received significant attention because the C-S bond is indispensable in many important biological and pharmaceutical compounds. Early examples for the synthesis of C-S bonds are generally limited to the condensation reaction between a metal thiolate and an organic halide. Recent chemical approaches for C-S bond formation, ba...

Journal: :Ars Comb. 2008
A. Mahmiani A. Iranmanesh Y. Pakravesh

Abstract Topological indices of nanotubes are numerical descriptors that are derived from graph of chemical compounds. Such indices based on the distances in graph are widely used for establishing relationships between the structure of nanotubes and their physico-chemical properties. The Szeged index is obtained as a bond additive quantity where bond contributions are given as the product of th...

Journal: :Nano letters 2006
Borislav Naydenov Lucile C Teague Peter Ryan John J Boland

We present a study that maps out chemical bond formation between a Pt-inked probe and a single 1,3-cyclohexadiene (1,3-CHD) molecule on Si(100). By separating the mechanical and electronic contributions to the current during the approach to contact, we show that there are significant forces between the probe and the C=C of the molecule and we track the relaxation of the molecule, the emergence ...

Gholarn Hossein Shafiee Hadi Shafice Jamshid Najafpour Seyed Abdolreza Sadjadi

It seems that the general applicability of the quantum theory of atoms in molecules (QTAIM) oncharacterizing the bonded interactions is still questionable even afier 30 years since its formulation. Fordemonstrating the generality of bonding schemes in QTA IM, ea( isomers were chosen as the modelsystems and the results from molecular charge density analysis and vibrational normal modes werecompa...

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