Understanding Interaction Capacity of CO2 with Organic Compounds at Molecular Level: A Theoretical Approach

In this chapter, interactions of CO2 with a number of organic compounds at molecular level are discussed in detail. The naked and substituted hydrocarbons along with compounds functionalized by hydroxyl, carbonyl, thiocarbonyl, carboxyl, sulfonyl, and amide groups have attracted much attention as CO2-philic agents. In general, interaction capacity between the functionalized organic compounds with CO2 is stronger than the hydrocarbon and its derivatives. An addition of more CO2 molecules into the interaction system formed by the functionalized organic compounds and CO2 leads to an increase in the stability of the complexes. The obtained results indicate that π…π linkages between CO2 and aromatic rings can significantly contribute to the interactions between CO2 and MOF/ZIF materials. Formic acid (HCOOH) is likely to be the most soluble compound as compared to the remaining host molecules (CH3OH, CH3NH2, HCHO, HCOOCH3, and CH3COCH3) when dissolved in CO2. The carbonyl (>C═O, >C═S) and sulfonyl (>S═O, >S═S) compounds have presented a higher stability, as compared to other functionalized groups, when they interact with CO2. Therefore, they can be valuable candidates in the design of CO2-philic materials and in the search of materials to adsorb CO2

A thorough theoretical investigation into complexes formed by interaction of dimethyl sulfoxide with two water molecules

A computational study of the stability and the cooperative effect of hydrogen bonds in the complexes of dimethyl sulfoxide and two water molecules was undertaken at the MP2/6-311++G(2d,2p) level of theory. The cooperative energies of obtained complexes are significantly negative, indicating that there is a large cooperativity between types of hydrogen bonds. The existence of the O−H∙∙∙O hydrogen bond present at dimer of water increases the stability of O−H∙∙∙O and C−H∙∙∙O hydrogen bonds in the ternary complexes compared to relevant binary complexes. By vibrational and NBO analyses, it is found that the magnitude of stretching frequency red shift of O−H bonds in the O−H···O hydrogen bonds is enhanced, whereas the extent of stretching frequency blue shift of C−H bonds in the C−H∙∙∙O hydrogen bonds is weakened when the cooperativity of hydrogen bonds happens in the ternary complexes. Obtained results of AIM analysis and stabilization energies indicate the larger contribution of the O−H∙∙∙O relative to the C−H∙∙∙O hydrogen bond to cooperativity. Keywords. Dimethyl sulfoxide, hydrogen bond, cooperativity

Remarkable shifts of C(sp2)-H and O-H stretching frequencies and stability of complexes of formic acid with formaldehydes and thioformaldehydes

Thirty‐six stable complexes of formic acid with formaldehydes and thioformaldehydes were determined on the potential energy surface, in which the XCHO···HCOOH complexes are found to be more stable than the XCHS···HCOOH counterparts, with X = H, F, Cl, Br, CH3, NH2. All complexes are stabilized by hydrogen bonds, and their contribution to the total stabilization energy of the complexes increases in going from C‐H···S to C‐H···O to O‐H···S and finally to O‐H···O. Remarkably, a significant blueshift of Csp2‐H bond by 81–96 cm−1 in the Csp2‐H···O hydrogen bond has hardly ever been reported, and a considerable redshift of O‐H stretching frequency by 206–544 cm−1 in the O‐H···O/S hydrogen bonds is also predicted. The obtained results in our present work and previous literatures support that a distance contraction and a stretching frequency blueshift of C‐H bond involving hydrogen bond depend mainly on its polarity and gas phase basicity of proton acceptor, besides the rearrangement of electron density due to complex formation. Markedly, we suggest the ratio of deprotonation enthalpy to proton affinity (R c) as an indicator to prospect for classification of hydrogen bonds. The symmetry adapted perturbation theory results show a larger role of attractive electrostatic term in XO‐n as compared to that in XS‐n and the electrostatic interaction is overwhelming dispersion or induction counterparts in stabilizing XO‐n and XS‐n, with n = 1, 2, 3

Investment in human capital and labor productivity in Vietnam : the case study on small and medium enterprises

This paper investigates the importance of training in Small and Medium Enterprises (SMEs) in Vietnam as a basis for improving productivity. Current training courses are ineffective, and need to be associated with practical work. Trainers need appropriate experience as well as knowledge of how to organize classes. SME Support Centres are evaluated in terms of trainers and training: findings show that training organization for SMEs should be classified by types of trainees; courses for employees should focus on particular skills; and policies should encourage management skills training as well. Development of new curriculum materials is urgent

Farming systems in the sandy area of the Thua Thien Hue Province, Central Vietnam, survey of socio-economic situation and constraints identified by farmers

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