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  • The NMR analysis of the reaction media of

    2018-10-23

    The NMR analysis of the reaction media of β-CHO and t-BuOOH oxidation, revealed the formation of cysteine protease 6. The results obtained from 1D 1H, COSY and 1D selective NOESY experiments of the aqueous media of reaction, allowed the 1H NMR characterization of the molecule. Fig. 1 shows the structure of molecule 6 and the 1H spectrum of the reaction media with the assignment of proton signals of 6. Fig. 1b and c shows, respectively, the 1D selective NOESY spectra obtained when signals in the t-butyl region (1.15ppm) and when signal corresponding to H1 (5.13ppm) was irradiated. NOESY correlation between H1 and H13 confirmed the presence of the t-butyl moiety in the molecule (see Table 1). The intermediate of the reaction β-CHO-H2O2 was identified as the hydroxy peroxy derivative of β-CHO, compound 7. The 1H NMR spectra of β-CHO dissolved in D2O and of an aliquot from the mentioned chemical reaction in H2O–D2O (67:33) were compared. In the case of β-CHO, two species were observed in the aqueous solution, which corresponded to the equilibria of the aldehydic and the acetal forms of the molecule (see Fig. 2a). Some important differences were observed between the β-CHO spectra and that of the reaction sample in aqueous media. In the case of the later, just one species was observed, meaning that the aldehydic and/or acetal forms were not present anymore. Besides, the signal corresponding to H1 was slightly down field shifted compared to the acetal form of β-CHO (from 5.00 to 5.09ppm), which was consistent with the presence of a hydroxy peroxy moiety (see Table 1). Also, no other unidentified signals were observed in the 1H spectrum cysteine protease (see Fig. 2b). NMR spectroscopy allowed the identification of compound 8 yielded by the oxidation of β-CHO with hydrogen peroxide (see Fig. 3). Initially, β-CHO was 1H and 13C fully characterized by the concerted analysis of the 2D NMR correlations COSY, HSQC and HMBC (see Fig. 3 and Table 1) [2,3]. Likewise, a second sample consisting in the product of the oxidation reaction, dissolved in CDCl3, was analyzed. The analysis showed a new molecule, 8, and the presence of reactive β-CHO in a smaller amount. Fig. 3 shows the structure of 8 and the 1H NMR spectra of the analyzed samples with the assignment of the signals. Briefly, comparing with the spectrum of β-CHO, compound 8 showed no aldehydic proton and a new signal appeared at δ(1H) 5.39ppm and δ(13C) 99.37ppm. Also, protons H2 and H3 resonated at lower frequencies regarding their analogues of β-CHO (see Fig. 3). The DOSY experiment performed in the second sample (see Fig. 3c and Table 1) showed a significant lower diffusion (i.e. a smaller diffusion coefficient, D) of molecule 8 respect to β-CHO. This result, together with the information yielded by the 2D correlations, confirmed the dimeric structure of compound 8. Products 6–8 masses were confirmed by mass spectrometry (protocol not detailed, Supplementary material): HPLC-MS-MS (1200RR LC – Agilent Technologies, Santa Clara, CA, USA – and micrOTOF-Q with Apollo II Electrospray ion source – Bruker Technologies, Billerica, MA, USA) or MS (micrOTOF-Q II with Apollo II Electrospray ion source – Bruker Technologies). Those analyses were executed by SAQ (Servei d’Anàlisi Química, UAB, Barcelona, Spain).
    Acknowledgments We thank Dr. Alba Eustaquio and Dr. Maria Jesús Ibarz at Servei d’Anàlisi Química of the Universitat Autònoma de Barcelona for their assistance on mass spectrometry analyses. This work has been supported by Spanish MINECO (project number CTQ2014-53114R), cofinanced by European Regional Development Fund (ERDF).
    Data In this article, the data generated on mixing of shear thinning non-Newtonian fluids by a Rushton turbine in a cylindrical tank is reported. The data is obtained using CFD simulation of whole tank. The validation of this study is found in [1]. The data presented herein showed some significant information about the mixing time and dispersive mixing efficiency of a Rushton turbine. We include figures and tables containing quantitative and qualitative information on the mixing time and its dispersive efficiency.