A Structural Study of Epoxidized Natural Rubber ENR-50 and Its Cyclic Dithiocarbonate Derivative Using NMR Spectroscopy TechniquesReportar como inadecuado




A Structural Study of Epoxidized Natural Rubber ENR-50 and Its Cyclic Dithiocarbonate Derivative Using NMR Spectroscopy Techniques - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1

Nanoscience Research Laboratory, School of Chemical Sciences, Universiti Sains Malaysia, Penang 11800, Malaysia

2

School of Industrial Technology, Universiti Sains Malaysia, Penang 11800, Malaysia





*

Author to whom correspondence should be addressed.



Abstract A structural study of epoxidized natural rubber ENR-50 and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping 1H-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 13C-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 CS2, 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 CS2 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 1H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The 13C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the C=S and quaternary carbon of cyclic dithiocarbonate. All other 1H- and 13C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.

Keywords: ENR-50; 2D NMR; triad sequence; cyclic dithiocarbonate ENR-50; 2D NMR; triad sequence; cyclic dithiocarbonate





Autor: Rosniza Hamzah 1, Mohamad Abu Bakar 1,* , Melati Khairuddean 1, Issam Ahmed Mohammed 2 and Rohana Adnan 1

Fuente: http://mdpi.com/



DESCARGAR PDF




Documentos relacionados