The Kinetics of the decomposition of chloral and its catalysis by iodine

The introduction of chlorine atoms into organic compounds causes marked changes in properties which can often be explained in terms of a displacement of electrons under the influence of the substituent. It is an interesting question how far these influences will show themselves in the kinetic behaviour of the substituted molecules. Accordingly the thermal decomposition of chloral and its catalysis by iodine have been studied. The decomposition is a homogeneous gaseous reaction which can be compared with the decomposition of acetaldehyde and propionic aldehyde.Apparatus The apparatus was of the usual type, with a silica reaction vessel heated in an electric furnace. A tube led to a capillary mercury manometer outside the furnace, and the course of the reaction was followed by observing the rate of pressure increase. In view of the relatively high boiling point of chloral it was necessary to keep all the connecting tubes heated to 80°-90° C. Considerable difficulty was experienced with the lubricants for the stop-cocks operating at this temperature. A special high temperature vapourless grease was used, but even this showed a tendency to run and foul the connecting tubes. The reaction products also tended to foul the apparatus so that frequent cleaning of the whole, including the manometer and the mercury pump, was required.