China 
Africa 
Explore chapters and articles related to this topic
Quantum Chemical Analysis of Polyamic Acids and Polyimides
Published in Michael I. Bessonov, Vladimir A. Zubkov, Polyamic Acids and Polyimides, 2020
The potential function calculation results of Welsh et al.,106 leading to higher conformational freedom for Ph-S-Ph as compared to Ph-O-Ph, seem to be in favor of a positive answer to the question. Welsh et al.106 assumed barriers Uoc and Usc to be equal, respectively, to 13.6 and 3.4 kJ/mol found for phenol and thiophenol. However, in Ph-X-Ph the ratio between barriers Uoc and Usc observed in phenol and thiophenol may be changed if the sulfur atom in Ph-X-Ph promotes electron delocalization to a greater extent than the oxygen atom due to conjugation via swivel atom X. The existence of this effect is confirmed by CNDO/2 and EHT results.103–105,107 Moreover, the width of the highest occupied band may also be considered as a degree of electron delocalization in polymers (-Ph-X-)n. Recent electronic band structure calculations for polyphenylenesulfide (PPS) and polyphenylenoxide (PPO) have shown that the sulfur atom facilitates electronic conjugation along the chain skeleton to a greater extent than the oxygen atom does because the PPS and PPO valence bandwidths are equal to 1.2 and 0.1 eV, respectively.11 As will be shown below (Table 16), the Ph-S-Ph relaxation times are greater than those of Ph-O-Ph, indicating the higher rotation barrier for Ph-S-Ph. Hence, we are inclined to claim that in this particular case the CNDO/2 and EHT results are more reliable than the AMI ones.
Chemical Processing
Published in S. Komar Kawatra, Advanced Coal Preparation and Beyond, 2020
Some recent work has centered on the use of iron (III) or copper (II) chloride solutions, which was claimed to be capable of removing both organic and inorganic sulfur. Ferric chloride (FeCl3) has been shown to be more effective than copper chloride for removal of organic sulfur (Fan et al., 1987). Fan et al. (1987) treated six high organic sulfur coals sized to 74 × 38 µm for 1 h in a 10% (by weight) ferric chloride solution at 300°C, followed by washing in boiling 2M hydrochloric acid for 30 min. This treatment was reported to remove essentially all of the pyritic sulfur and 35%–50% of the organic sulfur in 1 h, with British Thermal Unit (BTU) recoveries of 74%–82%. Testing on model organic sulfur compounds showed this procedure to be ineffective for oxidation of the benzothiophene and dibenzothiophene forms of organic sulfur, although it was effective for breaking down thiophenol, phenyl disulfide, benzyl methyl sulfide, benzyl phenyl sulfide, benzyl disulfide, phenyl sulfide, and 2,5-dimethylthiophene. It should be noted that FeCl3 becomes unstable at approximately 300°C and forms an insoluble basic iron oxide that will precipitate on the coal. This insoluble material would dilute the sulfur, making it appear that more was removed than was actually the case. It would also increase the ash content of the coal.
Plasmon-Driven Surface Functionalization of Gold Nanoparticles
Published in Marc Lamy de la Chapelle, Nordin Felidj, Plasmonics in Chemistry and Biology, 2019
Mai Nguyen, Inga Tijunelyte, Marc Lamy de la Chapelle, Claire Mangeney, Nordin Felidj
Thiophenol SAM formation is not dependent on the plasmonic properties of the NCs since the thiol interaction with gold is not thermally or optically activated. Thus, to demonstrate the plasmon contribution to the thiol-ene reaction initiation we compared the absolute SERS intensities at the saturation points for both samples (Fig. 1.16). In the case of thiophenol SAM formation, the SERS signal on 110 nm diameter NCs is 2.5 higher than the one measured on the 200 nm NCs and can be attributed to plasmonic effects on the SERS signal enhancement. However, for the thiol-ene “click” reaction, the intensity ratio was close to 6. Such large ratio gives a clear evidence that the radical reaction is plasmon-induced on highly resonant NCs but less efficient for the NCs with the LSPR out of resonant.
Recent developments in the greener approaches for the dithioacetalization of carbonyl compounds
Published in Journal of Sulfur Chemistry, 2023
K. Bahrami and co-workers [115] have reported an eco-friendly method for dithioacetalization of carbonyl compounds in water in the presence of an effective Brønsted acid catalyst, trichloroacetic acid (TCA). They have employed sodium dodecyl sulfate (SDS) as a surfactant to make organic substrates soluble in water by forming micelles (Scheme 24). A wide variety of different aromatic aldehydes bearing both electron-rich and electron-deficient groups have been employed to react with various thiols such as benzyl thiol and thiophenol, 1,2-ethanedithiol and 1,3-propanedithiol. The reactions gave good to excellent yields of the desired products. Aliphatic, heteroaryl, norbornyl and α, β-unsaturated carbonyl compounds also afford their corresponding dithioacetals in high yields.
Desulfurization of thar lignite by oxidative alkali leaching under pressure
Published in International Journal of Coal Preparation and Utilization, 2022
Muhammad Azam Usto, Sikander Ali Abbasi, Ghulamullah Maitlo, Arshad Iqbal, Abdul Sattar Jatoi, Shoaib Ahmed, Muhammad Shahab Alam, Abdul Karim Shah, Zubair Hashmi, Aqeel Shah, Ghulam Abbas Kandhro, Shah Rukh Mamon
Sulfur in coal is present in different forms, like inorganic Sulfur (mostly in the form of pyrite), organic Sulfur (mostly present in trace amounts). Organic Sulfur in coal is present as thiol, sulfide, thiophenol, thiophenes and disulfide in different ranges (Kozłowski, Wachowska, and Yperman 2003). Coal desulfurization before combustion is important to avoid air pollution (Prasassarakich and Thaweesri 1996). Sulfur is covalently bonded with carbon (C-S bond) in these compounds, this bond is difficult to break down by any physical process. Hence it requires chemical processing for cleaving off the bond for Sulfur removal. Chemical leaching has the ability to remove the minerals that are strongly bound to the coal, and that cannot be removed easily with the physical method (Mukherjee and Borthakur 2003).
Aggregation dependent fluorescence switching in benzothiazole derivative based H-bonded mesogen
Published in Liquid Crystals, 2018
Bimal B. Chakraborty, Siddique Anwar, Saurav Das, Satya B. Paul, Golam Mohiuddin, Joydip De, Sudip Choudhury
The synthesis of the H-donors, the H-bond acceptor and the H-bonded complexes are presented in Schemes 1 and 2. The benzothiazole derivative, 2-(pyridin-4-yl) benzothiazole, to be used as the H-bond acceptor in this work was prepared by a modified scheme based on the method reported by Salehabadi and co-worker [31], by refluxing the aldehyde with o-amino thiophenol in the presence of catalytic amount of NH4Cl (Scheme 1). On the other hand, the alkoxy benzoic acids of different terminal chain length, employed as the H-donors, were prepared from the method described by Jones and coworkers [32] with necessary modifications.