Molecular models of rubber and gutta-percha. These molecules are isomers. They have the same chemical fourmula but a different molecular structure. In this example, gutta-percha is the trans isomer (the side-chains alternate) and rubber is the cis isomer (the side-chains are on the same side). Gutta-percha is obtained from the Isonandra gutta tree, while rubber is obtained from the Hevea braziliensis tree. The difference in molecular structure means that gutta-percha has a higher melting point than rubber.