title: A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative using NMR spectroscopy techniques.
abstract: A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping (1)H-NMR signals of ENR-50 at δ 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the <(13)C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS(2)), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS(2) at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the (1)H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The (13)C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other (1)H- and (13)C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.
authors.affiliation: Nanoscience Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, Penang, Malaysia.
authors.forename: Rosniza
authors.initials: R
authors.lastname: Hamzah
authors.forename: Mohamad Abu
authors.initials: MA
authors.lastname: Bakar
authors.forename: Melati
authors.initials: M
authors.lastname: Khairuddean
authors.forename: Issam Ahmed
authors.initials: IA
authors.lastname: Mohammed
authors.forename: Rohana
authors.initials: R
authors.lastname: Adnan
mesh_terms: D002254:Carbonates / Q000737:chemistry*; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D012408:Rubber / Q000737:chemistry*
chemical_list: D002254:Carbonates; D004852:Epoxy Compounds; D012408:Rubber