Discover the Secrets of Non-Conventional Energy Resources with B H Khan's PDF Book Free 47
im and co-workers have synthesized various poly-substituted biphenyl derivatives by using sodium methylate as base and aryl iodides as aryl source in the presence of solvent-free mechanomilling ( scheme45 ) . sodium methylate is a common reagent used in organic synthesis. it is also a convenient reagent for the synthesis of aromatic compounds and can also be prepared by the reaction of lithium methylate with dimethylformamide. aryl iodides are important intermediates for the preparation of various drugs and pesticide as well as building blocks for the synthesis of various aromatic heterocyclic compounds. the main advantages of this solvent-free mechanomilling technique over the traditional solution-phase procedures are its shorter reaction time, better yields and stability of the product. moreover, in this technique, the solvents play no role in the reaction, which is beneficial for the environment.
non conventional energy resources by b h khan pdf free 47
mechanochemical synthesis is the process in which the chemical reaction takes place in a high energy ball milling reactor with simultaneous mechanical mixing. the reaction might involve one or more steps of catalytic cycles. these reactions are difficult to be carried out by traditional chemical processes due to low mass transfer of reactants, solubility of reactants in traditional chemical reactor and the reaction is thermodynamically less favorable. sol-gel chemistry is a well-known technique, which has attracted much attention of chemical engineers and scientists due to its application in the fields of catalysis, sensing and coating technology . a thorough survey on sol-gel technology has been made by bassi and co-workers . as shown in scheme26, organic-inorganic hybrid sol-gels are prepared from organic solvents and precursors containing appropriate metal compounds. after hydrolysis of tetraethyl orthosilicate (teos) the silica gel is formed which further served as support for the catalysts immobilization. for the first time, from the early to mid-1970s, it was realized that mechanical-mixing could be effective as a powerful tool to prepare homogeneous catalysts .