Explore chapters and articles related to this topic
Atom Economy
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
Kunnambeth M. Thulasi, Sindhu Thalappan Manikkoth, Manjacheri Kuppadakkath Ranjusha, Padinjare Veetil Salija, Nisha Vattakkoval, Shajesh Palantavida, Baiju Kizhakkekilikoodayil Vijayan
Addition reactions are reactions in which there occur an addition of molecules or groups across a double or triple bond. These reactions are 100% atom economical (Trost, 2002), since the reactants combine to form the final product, without any elimination of side products. We can consider an example for addition reaction.
*
Published in Gabriel O. Shonaike, George P. Simon, Polymer Blends and Alloys, 2019
Rudolph D. Deanin, Margaret A. Manion
While modification during polymerization is more precise and therefore preferred in theory, the production of small batches of such specialized polymers is expensive and not often favored in commercial practice. Here it is generally easier and less expensive to take a major commercial polymer and run postpolymerization reactions on it in order to modify it into the form most suitable for physical compatibilization. These may be classified as addition reactions and substitution reactions.
Polyaromatic hydrocarbons with an imperfect aromatic system as catalysts of interstellar H2 formation
Published in Molecular Physics, 2023
Dávid P. Jelenfi, Anita Schneiker, Attila Tajti, Gábor Magyarfalvi, György Tarczay
In Table 1 the change of the HOMA indices upon the reaction, the reaction barriers and the reaction enthalpies at 0 K are also listed. It can be seen from the data that for each H-atom-addition reaction the HOMA index, and thus the aromaticity decreases. The largest reduction is obtained for benzene. For H-atom-abstraction reactions from the sp carbon, the HOMA index and thus the aromaticity increases. However, no strong correlation between ΔHOMA values and the log k values can be observed. This might be explained by the fact that besides electronic effects, steric effects also affect the rate constants to a notable extent. The correlation between the barrier heights and the log k values is much better, with a correlation coefficient of 0.88 (or 0.96, excluding H-atom-abstraction reactions), although this value is not very robust due to the limited sample size. This not perfect, but moderate correlation is due to the fact that we investigated similar H-atom-abstraction and H-atom-addition reactions, for which similar barrier widths can be expected. Nevertheless, from these data we can conclude that the change in the simple HOMA index is not sufficient to predict the relative rate constants, better predictions can be obtained by the computation of the barrier heights. For a more reliable estimation of the reaction rate, however, the more expensive instanton model computations are indispensable.
The demulsification of oily wastewater by a hyperbranched polymer grafted SiO2
Published in Journal of Dispersion Science and Technology, 2023
Yu Zhang, Jiazhe Kuang, Bin Li, Yuanzhu Mi, Ying Yang, Xuening Feng
The three-phase contact angle of synthetic samples was determined at ambient temperature using the tablet method. The results are shown in Figure 4. The contact angle of SiO2 is 24.95 ± 0.45°, because there are a lot of hydrophilic hydroxyl groups on its surface. Compared with SiO2, the contact angle of SiO2-KH570 increased to 126.4 ± 0.1°. The original hydroxyl groups in the surface of SiO2 are replaced by long alkyl hydrocarbon chains in KH570 molecules when KH570 is grafted onto SiO2, so SiO2-KH570 is highly hydrophobic. The terminal amino groups in PAMAM can react with the double bond in KH570 molecule by the Michael addition reaction. Therefore, the contact angle is changed to 84.45 ± 0.25° when PAMAM is used to cover SiO2-KH570, because there are a lot of terminal amino groups in PAMAM. In general, the hydrophilic end of the demulsifier molecule trends to enter the water phase while the hydrophobic end enters the oil phase when the demulsifiers transfer to the oil-water interface. In previous reports, a demulsifier has the best demulsification efficiency when the contact angle is about 90°.[26] In current experiments, the contact angle of PAMAM@SiO2 is 84.45 ± 0.25°, the appropriate amphiphilicity allows it to quickly migrate to the oil-water interface and achieve a good demulsification performance.
Quantitative Analysis of the Structure of Organic Acids and Their Degradation Rates during Ozonation Catalyzed with ZnAl Layered Double Hydroxide
Published in Ozone: Science & Engineering, 2023
Yunjing Jin, Liang Li, Liu Yu, Liuqiang Li, Siru Zhang, Yuanxing Huang
It could be concluded that Fukui(0)max, Fukui(+)max, EB3LYP, ELUMO, Bond orders(C-C)max and EHOMO had a significant correlation with the activation energy of catalytic ozonation. The Fukui index was an important indicator to analyze the reactive sites. And in the oxidation reaction, the hydrogen substitution of free radicals and the double bond addition reaction were the most critical steps (Shi, Hong, Chu, Lv 2010). In density functional theory, the Fukui function was a key regioselectivity index for electron transfer control reaction. Fukui(0) represented the possibility of atoms to be attacked by free radicals. The larger the absolute value, the more likely the atoms were attacked by free radicals, and the easier the reaction would proceed. That was, the larger the value of Fukui(0)max, the easier it was to attract hydroxyl radicals. On the other hand, the larger the Fukui(+)max, the easier it was for the reactive site to be attacked by ozone.