Abstract: In the present work synthesis routes and the reactions involved in the polymerization of two organic compounds similar to natural rubber were studied. To these routes and reactions, modifications related with the previously reported in the literature were performed in order to study them through theoretical tools and determine their prediction capability for the design of those analogs. The semiempirical method Austin Model 1 (AM1) was used for the study of electronic configurations and it was shown that the synthesis of the polystyrene polymer (PS) and the poly copolymer (styrene-butadiene) (SBR) is possible through the use of free radicals from styrene and 1,3-butadiene monomers using benzoyl peroxide as the catalyst in both cases; going through the intermediates 1-phenyl-2-[(phenylcarbonyl)oxy]ethyl and (2E)-4(oxy (phenylcarbonyl))2-buten-1-yl. The results show that the higher electronic densities are found over the active atom in the radical compared to the electronic densities over the ions and the interest atoms in a possible condensation. Additionally, the study of the reaction mechanisms for the designed organic synthesis routes was performed by applying the frontier orbitals theory developed by R. B. Woodward, and R. Hoffmann and the respective correlation diagrams that showed thermal viability were built demonstrating the consistency between the characteristics of the orbital symmetry in the concerted reactions of the reactants and products; therefore it is seen that the free radical synthesis do not show symmetry restrictions, and it is possible to make it by a thermal route with low activation energy thresholds. The experimental yields of polymerizations were 90% and 75% for polystyrene (PS) and poly (styrene-butadiene) (SBR) respectively. Additionally mechanical tests were performed to the synthesized polymers and it was proved that the properties of the synthesized compounds are consistent with those reported in the literature. In the future it is expected to explore unknown organic synthetic routes with this research it was demonstrated that the methods are reliable.