|M.Sc Student||Natalya Fridman|
|Subject||Chemical reactions in solid molecular compounds|
|Department||Department of Chemistry||Supervisor||Professor Emeritus Kaftory Menahem|
The Greek philosopher, Aristotle taught: "No coopora nisi fluida"("No reaction without solvent"). Recently, however, it was discovered that many organic reactions proceed in the solid state without solvent. In many cases organic solid-state reactions proceed more efficiently and selectively than do solution reactions. We have studied the solid-state intermolecular methyl transfer in cyanurates and thiocyanurates. All the studied compounds undergo solid-state methyl rearrangements. In some cases the rearrangement was topochemically controlled, in other cases the rearrangement was not topochemically controlled and in all other cases the rearrangement took place in the melt. The next step in this study is to find out to what extent these types of intermolecular methyl migration are general. Few compounds possessing the moieties that enable intermolecular methyl migration was analyzed by differential scanning calorimeter (DSC) and their crystal structures were determined. Compounds (1) and (2) undergo methyl rearrangement in the liquid-state. (2) crystallizes as three hydrate and hemihydrate, it is depend on solvent.
(1) (2) (3) (4) (5)
The crystal structures of the two compounds show that topochemically controlled solid-state methyl rearrangement is not possible. (3) on the other hand undergoes methyl rearrangement in the solid-state.
Two compounds were prepared as precursors to the methyl-esters that might undergo methyl rearrangement. (4) forms inclusion compounds when crystallized from various solvents (e.g. EtOAc, CH3COOH, EtOH) where the guest molecules play the role as space filling components. (5) forms inclusion compounds with the guest molecules containing hydrogen acceptor moiety (e.g. Acetone). The different behavior is mainly attributed to the adoption of different? conformation controlled by the absence (5) or the inclusion (4) of a methyl group.