The wide industrial use of poly vinyl chloride (PVC) is based primarily on its versatility, including a balance between low cost and good engineering properties. PVC can be modified with plasticizers to give flexible formulations, and it is used extensively in the medical field. Phthalate does not covalently bonded to PVC matrix, and therefore can migrate out from PVC matrix into food and other products. Studies have shown that high doses of certain phthalates can cause changes in hormone levels, cause birth defects and other metabolic disorders. Researchers at the Institute of Polymer Science & Technology of Spain have recently synthesized a modified phthalate product that can arrest its migration from PVC matrix. A molecule di (2-ethylhexyl) 4-mercaptophthalate (DOP-SH) and the di (2-ethylhexyl) 5-mercaptoisophthalate (isoDOP-SH) was synthesized and evaluated as plasticizer instead of phthalate. These molecules have physicochemical properties similar to DOP but contain an additional functional group that enables it to establish a covalent bond to the polymeric backbone. 4-sulfophthalic acid and 5-sulfophthalic acid sodium salt were used as the starting materials, to which PCl5 was added as halogenating agent that brought about the activation of the functional acid groups. This was followed by the selective esterification of acyl groups (COCl) using 2-ethylhexanol along with triethylamine as an acid scavenger. Finally, the selective reduction of the chlorosulfonyl group to a thiol moiety was performed by SnCl2 as the reducing agent. The reaction of PVC with these additives was carried out in cyclohexanone solution at 60°C. This resulted in the nucleophilic substitution of PVC's chlorine atoms and formation of CH-S bond. The plasticizing efficiency of this molecule is reduced significantly compared to DOP.