![]() ![]() As discussed in the previous chapter, this interaction leads to a rapid rise in temperature and faster reaction rates. The more polar a reaction mixture is, the greater its ability to couple with the microwave energy. With microwave heating, this becomes a more significant component, as microwaves directly couple with the molecules that are present in the reaction mixture. One of the most important characteristics of a solvent is its polarity. Most reactions take place in solution, and therefore, choice of solvent can be a crucial factor in the outcome of a reaction. Solvents play a very important role in organic synthesis. The more efficient a solvent is in coupling with the microwave energy, the faster the temperature of the reaction mixture increases. Safety Considerations for Microwave Synthesis.Setting Temperature, Time, and Power in Microwave Synthesis.Getting Started with Microwave Synthesis.Nucleophilic additions and substitutions.Organometallic cross-coupling reactions.Synthetic Applications for Microwave Synthesis.Solvent and Solvent Free (Neat) Reactions in Microwave Synthesis.Organic Solvents for microwave synthesis.What type of reactions are effected by microwave heating?.How do microwaves increase reaction rates?.Theory of Microwave Heating for Organic Synthesis.Because of the low acute toxicity and apparent lack of interaction, DMSO is a useful solvent for studying the effects of pesticides in animals. The depression was abolished by dilution. Undiluted DMSO produced a depression of spontaneous motor activity without an effect on hexobarbital sleeping time or the conditioned avoidance response. Some differences in the times of the onset of signs of toxicity were noted. The acute oral toxicities of thiram, dieldrin, carbaryl, MC-A-600, and parathion were generally similar whether administered in DMSO, in corn oil, or as an aqueous suspension. Some significant differences in the inhibition of cholinesterase by carbaryl in the various solvents were observed. None of these solvents influenced brain cholinesterase activity. A delayed toxicity was noted with DMSO, DMA, DMF, and PG by each route. The toxicities of DMSO and DMF were unchanged by dilution with water. The results indicate that DMSO is less toxic than DMA and DMF. The acute oral and intraperitoneal toxicities of dimethyl sulfoxide (DMSO), dimethyl acetamide (DMA), dimethyl formamide (DMF), and propylene glycol (PG), diluted and undiluted, were compared in rats after 24-hour and 5-day periods. ![]()
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