Abstract: An apparatus for multiple, simultaneous synthesis of compounds. The apparatus includes a reaction block having a heating layer, a cooling layer, each of which may perform both functions, and a collection sump. A plurality of reaction tubes are supported in the reaction block in a matrix. Each reaction tube has a top outlet, a bottom outlet and a filter above the bottom outlet. Spool valves are located to control the bottom outlets of the reaction tubes. Obturators are provided to close the top outlets of the reaction tubes and to provide venting for the reaction tubes. The collection sump alternately may be equipped with individual collection tubes for each reaction tube. Each reaction tube is formed with a restrictive waist and protrusions arranged in a pattern between the waist and its bottom outlet to improve the mixing of the resinous solid supports by creating turbulence. The restrictive waist limits the height of the vortex of solution during mixing and reaction to facilitate heating and refluxing.