Multiphasic reactions, especially those reactions using a phase transfer catalyst, are conducted in microchannel apparatus. Advantageously, these reactions can be conducted with two, planar microlayers of reactants in adjacent laminar flow streams. Microchannel apparatus and methods for conducting unit operations such as reactions and separations in microchannel apparatus is also described. Microchannel apparatus can provide advantages for controlling reactions and separating products, solvents or reactants in multiphase reactions.