Using torsional forces to explain the gradient temperature Raman spectra of endosulfan isomers and its irreversible isomerization

Abstract

benzodioxathiepine-3-oxide) Gradient Temperature-dependent Raman spectroscopy (GTRS) Raman ring-bending wavenumber temperature-dependent conformational change torsional force

Silver Nanoparticle Films Obtained by Convective Self-Assembly for Surface-Enhanced Raman Spectroscopy Analyses of the Pesticides Thiabendazole and Endosulfan

“…Additionally, symmetric, respectively asymmetric stretching vibrations of the dialkylsulfite group (C-SO 3 -C) were found at 1183 and 1219 cm −1 . The broad band observed at 1580–1600 cm −1 in both the calculated difference spectrum and the loadings of PC1 may be assigned to combined stretching vibrations of C5-C and C6-C, respectively deformations of C6H and C5H of ES ( Schmidt et al, 2017 ).…”

“…The ES pesticide is an asymmetrical molecule containing a rigid norbornene unit connected through a HC 5 -C 6 H bridge to a seven-membered flexible aliphatic ring unit ( Supplementary Figure S6 ), in which only the two methylene (CH 2 ) groups and the sulfite (SO 3 ) group can induce changes upon its conformation ( Schmidt et al, 1997 ). Therefore, the α- ES conformation is given by the twist chair forms ( Schmidt et al, 2001 ; Schmidt et al, 2014 ; Schmidt et al, 2017 ; Guerrini et al, 2008 ; Hapeman et al, 2013 ) adopted by the flexible seven-member ring ( Schmidt et al, 2017 ), in which the three protons on the left half are not equivalent with the three protons on the right half of the ring ( Schmidt et al, 1997 ).…”

“…The SERS spectral data for the coated ES film indicated weakening of some bands associated with Ag bounded monothiols, as well as the appearance of several bands that can be associated with ES. The assignment of the vibrations of ES in both the solid state and onto the AgNP thin films functionalized with HT/OT was performed on the basis of general published data ( Guerrini et al, 2008 ; Schmidt et al, 2014 ; Schmidt et al, 2017 ), as well as the theoretical calculations performed in this study. A good agreement between experimental and calculated spectrum of ES was obtained.…”

“…Additionally, the presence of the ES molecules leads to significant attenuation of the C-C skeletal vibrations observed at 1198 cm −1 and the CH 2 wagging vibrations at 1300 cm −1 , suggesting that the vibrations of thiol alkyl chains are hindered by the ES molecules. Weak ES characteristic bands are identified at 1434, 1456, and 1476 cm −1 that can be assigned to CH bending vibrations related to the C 7 -(HC 6 -C 5 H)-C 4 moiety, the ratio of the 1456 to the 1473 cm −1 bands being 3:1, specific to ES molecules ( Schmidt et al, 2017 ). In the OT functionalization case, the presence of ES did not induce significant attenuations of the thiol alkyl chain characteristic bands and ES specific bands are considerably diminished compared to the HT case.…”

DataSheet1.PDF

“…The ES pesticide is an asymmetrical molecule containing a rigid norbornene unit connected through a HC 5 -C 6 H bridge to a seven-membered flexible aliphatic ring unit (Supplementary Figure S6), in which only the two methylene (CH 2 ) groups and the sulfite (SO 3 ) group can induce changes upon its conformation (Schmidt et al, 1997). Therefore, the α-ES conformation is given by the twist chair forms (Schmidt et al, 2001;Schmidt et al, 2014;Schmidt et al, 2017;Guerrini et al, 2008;Hapeman et al, 2013) adopted by the flexible sevenmember ring (Schmidt et al, 2017), in which the three protons on the left half are not equivalent with the three protons on the right half of the ring (Schmidt et al, 1997).…”