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General Princlpes
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Organohalide compounds have halogen-substituted hydrocarbon molecules. This means that each compound has fluorine, chloride, bromine, or iodine atoms in its structure. Alkyl halides in this group include dichlo-romethane (found in paint strippers), carbon tetrachloride (refrigerants), and 1,2-dibromoethane (an insecticide). The alkenyl or olefinic organohalides include: vinyl chloride (used to produce polyvinyl chloride, PVC), a known carcinogen, trichlorethylene (used for degreasing and as a drycleaning solvent), tetrachloroethylene, and hexachlorobutadiene (used as a hydraulic fluid). Aryl halides are used in chemical synthesis and as pesticides and solvents. They are derivatives of benzene and toluene. Polychlorinated bi-phenyls (PCBs), highly toxic materials, are an example of a halogenated biphenyl. Chlorofluorocarbons (CFCs), halons, and hydrogen-containing chlorofluorocarbons are of significant importance to the environment. CFCs, once used primarily as refrigerants and aerosol propellents, are believed to have caused the breakdown of the ozone layer and have been banned from production. Halogens used in fire extinguishers as halon have also been implicated in the depletion of the ozone layer and are being phased out. Hydrogen containing chlorofluorocarbons (HFCs) are being touted as the substitute for CFCs as refrigerants and plastic foam blowing agents. Chlorinated phenyls such as pentachlorophenol, are used to treat wood against fungi and insect infestation. The byproduct of that process causes hazardous waste, which has been known to cause liver damage and dermatitis.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
An alkyl group (symbol R) is a group formed from an alkane by removal of a single atom of hydrogen (–CH3, methyl group; –CH3CH2, ethyl group, etc.). An aryl group is a group formed from an aromatic compound by removing a single hydrogen atom, such as the C6H5– group from benzene.
Benign synthesis of therapeutic agents: domino synthesis of unsymmetrical 1,4-diaryl-1,4-dihydropyridines in the ball-mill
Published in Green Chemistry Letters and Reviews, 2022
Cristina Blazquez-Barbadillo, Juan Francisco González, Andrea Porcheddu, David Virieux, José Carlos Menéndez, Evelina Colacino
The reaction scope towards the preparation of unsymmetrical N-aryl-5,6-unsubstituted-1,4-diaryl DHPs was investigated using the optimized ball-milling Method B1, with structural variations introduced simultaneously at the N-1 (Ar1 substituent), at C-4 (Ar2 substituent) and at the ester functional group (R2 substituent) (Scheme 4). Beyond the physical state of the final target (solid or liquid), key to choose the catalyst to be used, the reactivity of the system seemed to be driven by the nature of substitution: (i) on the enals (e.g. for compounds 3vs10, 8vs13, and 9vs14), with slightly better results obtained when o-nitrocinnamaldehyde was used, (ii) on the aniline component, with the better results obtained with electron-donating groups (EDG) (e.g. EDG = OMe, Me vs Ph, Cl, for compounds 11 and 16vs10, 11vs13 and 12vs14), enhancing the nucleophilicity of the amino group, while (iii) the reactivity was independent on the β-ketoester alkyl substitution (e.g. with alkyl = Et vs tBu for compounds 8vs9, 11vs12, 13vs14 and 16vs17).
Synthesis and characterization of mononuclear oxime-based palladacycles incorporating phosphorus ylides: application as a catalyst in Suzuki cross coupling reactions and their biological activities
Published in Journal of Coordination Chemistry, 2021
Ahmadreza Shiralinia, Sepideh Samiee, Elham Hoveizi
The Suzuki-Miyaura cross-coupling reaction of aryl halides with aryl boronic acids is one of the most reliable and powerful methods for synthesis of biaryl derivatives [12,17–19]. A variety of catalytic systems was reported for the Suzuki-Miyaura coupling reaction using mixed aqueous media [20–22]. Application of oxime-based palladacycles as efficient catalysts in Suzuki-Miyaura cross coupling reactions of aryl halides with phenylboronic acid under relatively mild experimental conditions is a goal of this work. Oxime-based palladacycles also have promising biological applications [13,14,23]. Currently, attention has turned to the development of new palladium complexes for anticancer applications as an alternative to cisplatin, the most widely used drug for cancer treatment [6,8,24]. Despite wide use, studies have shown that clinical success of cisplatin is limited due to side-effects including nephrotoxicity, neurotoxicity, ototoxicity and drug resistance. The search for new anticancer agents is far from over. In this regard, we have evaluated the cytotoxicity effects of oxime-based palladacycles against some cell lines as an antitumor agent.
Novel nematic and glassy liquid crystalline oligomers as electroluminescent organic semiconductors
Published in Liquid Crystals, 2021
Guang Hu, Stephen M. Kelly, Stuart P. Kitney, William Harrison, Brian Lambert
The final product 2,7-[bis(thien-2-yl)-9,9-dipropyl-fluorene-5,5-diyl]-bis-(2-methoxy-9-octylcarbazole) (21) was synthesised as shown in reaction scheme 3 according to modified literature methods [6,7]. The 2,7-bis-(5-bromothiophen-2-yl)-9,9-dipropyl-fluorene (20) was reacted with the (7-methoxy-9-octyl-carbzole-2-yl)boronic acid (19) in a Suzuki aryl-aryl cross-coupling reaction using Pd(OAc)2 as catalyst, an aqueous solution of K2CO3 and DMF as solvent to give the final product (21) in good yield (74%). The yield of the Suzuki aryl-aryl cross-coupling reaction using Pd(OAc)2-catalysed, ligand-free system was comparable yield to those obtained using Pd(PPh3)4 as a catalyst. Traditionally, the presence of the triphenyl-phosphine ligand is considered beneficial in palladium-catalysed Suzuki aryl-aryl cross-coupling reactions, helping stabilise the zero valence state of the palladium nanoparticles required for the catalytic reaction and produce higher yields. However, it was found that certain reaction mixtures were more difficult to purify, due to the formation of more by-products in the presence of added triphenyl phosphine ligand. In addition, commercial Pd(PPh3)4 tends to degrade more readily, is more expensive than the Pd(OAc)2 catalyst and can inhibit some Suzuki reactions [32–35].