NMR line-broadening and transverse relaxation time measurements support a di-radical intermediate for the reaction of chlorosulfonyl isocyanate with electron-rich alkenes

Shellhamer, Dale F.; Beavis, Zachary J.; Brady, Dakota L.; Bucardo, Marcela S.; Elwin, Sarah L.; Fiorella, Nicholas; Gómez, Leticia Ester; Horne, Sara Van; Perry, Marc C.

doi:10.1016/j.rechem.2019.100015

Cited by 2 publications

(2 citation statements)

References 15 publications

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“…In Figure 6, 1 H NMR data show resonances attributable to the aromatic ring. In comparison with the non‐degraded control (black curve), a clear broadening of the peaks is observed, which can be interpreted as an indication of the presence of radical by‐products in the solutions [41] . The presence of free radicals is also consistent with the emergence of a few resonances at higher shifts either in photo or in thermodegraded samples, suggesting that radical reactions should be an important route in the degradation pathway.…”

Section: Resultsmentioning

confidence: 67%

Molecular Structure and Antibacterial Activity of Degradation Products from Cephalexin Solutions Submitted to Thermal and Photolytic Stress

et al. 2022

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Cephalexin is a beta‐lactam antibiotic of the first generation of cephalosporins which is very effective against various bacterial infections. In this work, we investigate the structure and antibacterial activity of cephalexin solutions submitted to forced degradation under heat stress and photolytic irradiation. A combination of analytical techniques gathering LC/ESI‐MS and NMR spectroscopy allowed us to identify different chemical species amongst the byproducts, revealing that photolysis via UVA light leads to significant amounts of oxidized species that conserve the dihydrothiazine ring adjacent to the beta‐lactam ring. In contrast, thermodegradation induces the rupture of the bioactive moiety possibly with the production of cephalosporinic acid and deaminated species, which are inactive to bacteria. Microbiological analyses using E. coli as a model organism indicated that the antimicrobial capacity of samples submitted to thermolysis is suppressed while solutions submitted to irradiation with UVA light preserve their bactericidal power. Atomic force microscopy showed that cells incubated with photodegraded cephalexin are much longer than those incubated with the undegraded antibiotic, indicating that byproducts from photolysis inhibit septum formation and likely affect the action of penicillin‐binding protein 3 in the divisome of E. coli cells.

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Section: Resultsmentioning

confidence: 67%

Molecular Structure and Antibacterial Activity of Degradation Products from Cephalexin Solutions Submitted to Thermal and Photolytic Stress

et al. 2022

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“…One piece of evidence that suggests that 2 was formed is the comparison of the NMR spectrum of 1 and that of the crude mixture (seen below in Figure 18). Previously reported literature 46 has used the peak broadening phenomenon due to the presence of radicals in solution to show that a reaction would undergo a di-radical pathway. When comparing the NMR spectra, the peaks from the nitroxyl radical crude mixture can be seen as more broad when compared to the starting material, which could indeed suggest the presence of 2.…”

Section: Nitroxyl Radical Derivativementioning

confidence: 99%

Synthesis and Characterization of Oil Lubricant Antioxidant Degradation Products

Rivada

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Lubricating oils play a critical role in the reliable operations of machinery.Numerous additives are used to preserve/extend the lifespan of lubricating oils (among other benefits). Among these additives, antioxidants are added to lubricating oils as a sacrificial substance, that extends the lifespan by preferentially being oxidized over the lubricating oil. GasTops Ltd. is a world leader in condition monitoring of rotating machinery and is interested in developing in-line sensors to accurately predict the remaining useful life of a lubricating oil by monitoring the quantity of antioxidant degradation products. One of the antioxidants of interest is the commonly used N-phenyl-1-aminonaphthalene (PAN). Three major oxidation products of PAN have been identified and herein synthesized and isolated in pure form: C-C coupled PAN dimer, C-N coupled PAN dimer, and naphthyl oxidized PAN (Fremy's PAN). Other products include N-O radical PAN, as well as phenyl oxidized PAN (phenol PAN). Attempts to independently synthesize samples of these PAN derivatives resulted in the unexpected syntheses of other known PAN derivatives. Preparation of C-C coupled PAN dimer resulted in the additional synthesis of Fremy's PAN as a side product. Synthesis of C-N coupled PAN dimer also resulted in the synthesis of the other two major PAN oxidation products: C-C coupled PAN and Fremy's PAN. The synthesis of N-O radical PAN also resulted in the unexpected production of C-C coupled PAN dimer, as well as Fremy's PAN.Figure 1. PAN (1), nitroxyl radical PAN derivative (2), carbon-carbon coupled PAN dimer (3), naphthyl oxidized PAN (4), carbon-nitrogen coupled PAN dimer (5), phenyl oxidized PAN (6).

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NMR line-broadening and transverse relaxation time measurements support a di-radical intermediate for the reaction of chlorosulfonyl isocyanate with electron-rich alkenes

Cited by 2 publications

References 15 publications

Molecular Structure and Antibacterial Activity of Degradation Products from Cephalexin Solutions Submitted to Thermal and Photolytic Stress

Molecular Structure and Antibacterial Activity of Degradation Products from Cephalexin Solutions Submitted to Thermal and Photolytic Stress

Synthesis and Characterization of Oil Lubricant Antioxidant Degradation Products

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