A new proton sponge 1,8-bis(tetramethylguanidino)naphthalene (TMGN) was utilized for the alkylation of benzoic acid by iodomethane in a continuous flow microsystem. Using this set-up, kinetics of the reaction was determined in different mixing strategies and the Hammett reaction constant was measured.Good performance and efficiency of this procedure were confirmed through several preparative studies.
Introduction:Chemical reactions are usually achieved by mixing of reagents or reagents/catalysts. 1 "Mixing" is a broad, generic term, which in a solution phase is defined as a phenomenon that creates homogeneity of all species in the solution. This is true if the mixing time is much shorter than the reaction time. In other words, if reaction is slower than mixing, the reaction proceeds in a homogeneous solution. 1 But there are some exceptions. Table 1 displays some mixing-sensitive reactions. Meanwhile, in general, decreasing the total mixing time to a level well below the time scale of the chemical reaction, is necessary to avoid the adverse effects of imperfect mixing on conversion and selectivity. 2 A facile technique for increasing the rate of mixing is to employ narrow, high aspect ratio reaction channels, hence increasing the interfacial surface area.During the current decade, the emergence and the development of microreactor technology offer to the synthetic chemists, innovative and alternative methods for mixing reagents with a better control on reactivity and selectivity. If extraordinary effects of such microreactor technology have been reported so far in synthetic chemistry, most of the fundamental physical and chemical phenomenons involved in such microdevices, responsible of such reactivity, have now to be quantified or/and elucidated.[a038]