Kinetic Energy and the Covalent Bond in H2 +

A modified version of Ruedenbergs innovative analysis of the chemical bond in the hydrogen molecule ion is presented that factors the bond energy into bonding and nonbonding contributions. This simplified approach clearly illustrates Ruedenbergs main thesis: chemical bond formation is driven by a decrease in electron kinetic energy.     

EPR Study of Covalent Bond in Transition Metal Complexes

The results of a study of a covalent bond in the anitibonding and bonding states of d¹ and d⁹ complexes obtained by analyzing the EPR and optical data are presented. The nature of the electron density delocalization in some of the complexes is discussed. The effect of the charge-transfer states on the covalent bond structure is considered. The vibronic effect on the ground state function is discussed. The electronic distributions determined from EPR spectra by different approximation methods are compared.     

两种新的二氢沉香呋喃倍半萜的结构

两种新的二氢沉香呋喃倍半萜的结构张王艳红陈耀祖＊（兰州大学应用有机化学开放实验室，兰州７３００００）关键词倍半萜分离圆锥红果藤卫矛科南蛇藤属植物在我国有广泛的分布，许多该类植物是人们传统使用的天然杀虫剂。［１］许多研究表明，卫矛科植物中的杀虫活性成...     

Covalent Bond or Noncovalent Bond: A Supramolecular Strategy for the Construction of Chemically Synthesized Vaccines

A novel noncovalent strategy to construct chemically synthesized vaccines has been designed to trigger a robust immune response and to dramatically improve the efficiency of vaccine preparation. Glycosylated MUC1 tripartite vaccines were constructed through host–guest interactions with cucurbit[8]uril. These vaccines elicited high levels of IgG antibodies that were recognized by transformed cells and induced the secretion of cytokines. The antisera also mediated complement‐dependent cytotoxicity. This noncovalent strategy with good suitability, scalability, and feasibility can be applied as a universal strategy for the construction of chemically synthesized vaccines.     

Shape‐Persistent Organic Cage Compounds by Dynamic Covalent Bond Formation

One area of supramolecular chemistry involves the synthesis of discrete three‐dimensional molecules or supramolecular aggregates through the coordination of metals. This field also concerns the chemistry of supramolecular cage compounds constructed through the use of such coordination bonds. To date, there exists a broad variety of supramolecular cage compounds; however, analogous organic cage compounds formed with only covalent bonds are relatively rare. Recent progress in this field can be attributed to important advances, not least the application of dynamic covalent chemistry. This concept makes it possible to start from readily available precursors, and in general allows the synthesis of cage compounds in fewer steps and usually higher yields.     

Natural Bond Orbital Study on the Nature of Binding in the H2 Molecule

We use the natural bond orbital (NBO) method to decompose a MO wavefunction into the intuitive valence bond (VB) structures. At least two natural orbital type MO are required to describe the essential binding of the H₂ molecule at all inter nuclear distances. At first the MO wavefunction is transformed into an unrestricted Hartree-Fock wave-function consisted of non-orthogonal localized orbitals u' and v', and then the NBO method is used to decompose u' and v' into the physical meaningful orthogonal localized orbitals. Our results show that the orbitals u' and v' are decomposed into an atomic and an overlap parts. The latter part gives rise to the conventional ionic structure in the VB picture.     

Molecular Single‐Bond Covalent Radii for Elements 1–118

A self‐consistent system of additive covalent radii, R(AB)=r(A) + r(B), is set up for the entire periodic table, Groups 1–18, Z=1–118. The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same fit. Both E–E, E–H, and E–CH₃ data are incorporated for most elements, E. Many E–E′ data inside the same group are included. For the late main groups, the system is close to that of Pauling. For other elements it is close to the methyl‐based one of Suresh and Koga [J. Phys. Chem. A 2001 , 105, 5940] and its predecessors. For the diatomic alkalis MM′ and halides XX′, separate fits give a very high accuracy. These primary data are then absorbed with the rest. The most notable exclusion are the transition‐metal halides and chalcogenides which are regarded as partial multiple bonds. Other anomalies include H₂ and F₂. The standard deviation for the 410 included data points is 2.8 pm.     

Molecular Double‐Bond Covalent Radii for Elements Li–E112

The previous systems of triple‐bond and single‐bond self‐consistent, additive covalent radii, R(AB)=r(A)+ r(B), are completed with a fit for σ²π² double‐bonds.The primary bond lengths, R, are taken from experimental or theoretical data corresponding to chosen group valencies. All r(E) values are obtained from the same, self‐consistent fit. Many of the calculated primary data came from E?CH₂ and H? E?CH₂ models. Homonuclear LE?EL, formaldehyde‐type Group 14–Group 16 and open‐shell, X ³ Σ Group‐16 dimer data are included. The standard deviation for the 316 included data points is 3 pm.     

DNA中糖苷键碱基侧二共价键的喇曼特性分析

分析小牛胸腺ＤＮＡ的纤维和水溶液两种状态样品的激光喇曼光谱发现，嘌呤碱基糖苷键两侧共价键Ｎ９Ｃ４与Ｎ９Ｃ８的喇曼特性表现不同，分析与它们相联的Ｎ３与Ｎ７原子在原子电荷、一级水合层中水桥的形成，以及核苷酸单位内氢键形成等方面的差异，可认为在ＤＮＡ水溶液中Ｎ９Ｃ４明显的减色性是因Ｎ３原子的特殊性质所造成。     

The Nature of the Fourth Bond in the Ground State of C2: The Quadruple Bond Conundrum

Does, or doesn’t C₂ break the glass ceiling of triple bonding? This work provides an overview on the bonding conundrum in C₂ and on the recent discussions regarding our proposal that it possesses a quadruple bond. As such, we focus herein on the main point of contention, the 4th bond of C₂, and discuss the main views. We present new data and an overview of the nature of the 4th bond—its proposed antiferromagnetically coupled nature, its strength, and a derivation of its bond energy from experimentally based thermochemical data. We address the bond‐order conundrum of C₂ arising from generalized VB (GVB) calculations by comparing it to HC?CH, and showing that the two molecules behave very similarly, and C₂ is in no way an exception. We analyse the root cause of the deviation of C₂ from the Badger Rule, and demonstrate that the reason for the smaller force constant (FC) of C₂ relative to HC?CH has nothing to do with the bond energies, or with the number of bonds in the two molecules. The FC is determined primarily by the bond length, which is set by the balance between the bond length preferences of the σ‐ versus π‐bonds in the two molecules. This interplay in the case of C₂ clearly shows the fingerprints of the 4th bond. Our discussion resolves the points of contention and shows that the arguments used to dismiss the quadruple bond nature of C₂ are not well founded.     

Skin Bond Electron Relaxation Dynamics of Germanium Manipulated by Interactions with H2, O2, H2O,H2O2, HF,and Au

Although germanium performs amazingly well at sites surrounding hetero‐coordinated impurities and under‐coordinated defects or skins with unusual properties, having important impact on electronic and optical devices, understanding the behavior of the local bonds and electrons at such sites remains a great challenge. Here we show that a combination of density functional theory calculations, zone‐resolved X‐ray photoelectron spectroscopy, and bond order length strength correlation mechanism has enabled us to clarify the physical origin of the Ge 3d core‐level shift for the under‐coordinated (111) and (100) skin with and without hetero‐coordinated H₂, O₂, H₂O, H₂O₂, HF impurities. The Ge 3d level shifts from 27.579 (for an isolated atom) by 1.381 to 28.960 eV upon bulk formation. Atomic under‐coordination shifts the binding energy further to 29.823 eV for the (001) and to 29.713 eV for the (111) monolayer skin. Addition of O₂, HF, H₂O, H₂O₂ and Au impurities results in quantum entrapment by different amounts, but H adsorption leads to polarization.     

基于2(5H)-呋喃酮的碳-杂成键反应研究进展

2(5H)-呋喃酮结构单元广泛存在于天然产物中,同时许多2(5H)-呋喃酮类化合物也是重要的有机合成中间体.因此,基于常见2(5H)-呋喃酮(1)的有机合成研究近年来引起了人们的关注.根据在有机合成反应中成键方式的不同,综述了在2(5H)-呋喃酮(1)环上形成C-O,C-N,C-S,C-P,C-Se,C-Si等碳-杂键的反应研究进展.     

Factors determining bond angles from a classical valence bond perspective. Covalent structure of H2O

We identify the energy contributions that govern the interorbital and internuclear angles in the classical covalent structure of H₂O. The central atom valence state term plays a primary role in H₂O and other AH₂ molecules as well. Lone pair interactions of three different types are also of major significance.On leave 1977–78 at the University of California, Santa Barbara     

New Syntheses of Geiparvarin and 2,5-Dimethyl-3(2H)-furanone Via Co2 Mediated Bond Reorganization

A new synthesis of 3(2H)-furanones from 4-hydroxy-2-alkyn-1-one derivatives via CO₂ mediated bond reorganization has been developed to the preparation of an antitumor agent, geiparvarin and a constituent of flavors, 2,5-dimethyl-3(2H)-furanone.     

Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

Research on Chemical Intermediates - In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly...     

Theoretical Studies on the Stabilities and Hydrogen Bond Actions of （H2O）n Clusters

1 INTRODUCTION In the latest ten years, the structure and function of water clusters have captured the interest of chemists. One of the most important study objects in water cluster is to describe the behavior of water so- lution quantitatively at molecule level, which will pave the way for the solving of some environmental and other scientific problems, such as the formation of acid rain and nucleation mechanism of little water drop. Besides, weak interaction in water clusters could be al…