Browsing by Author "Mesias-Salazar, Angela"

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    Approach to Circular Chemistry Preparing New Polyesters from Olive Oil
    (2023) Werlinger, Francisca; Caprile, Renato; Cardenas-Toledo, Valentino; Tarraff, Bastian; Mesias-Salazar, Angela; Rojas, Rene S.; Martinez, Javier; Trofymchuk, Oleksandra S.; Flores, Mario E.
    The transformation of cooking oils and their waste intopolyestersis a challenge for circular chemistry. Herein, we have used epoxidizedolive oil (EOO), obtained from cooking olive oil (COO), and variouscyclic anhydrides (such as phthalic anhydride PA, maleic anhydrideMA, and succinic anhydride SA) as raw materials for the preparationof new bio-based polyesters. For the synthesis of these materials,we have used the bis(guanidine) organocatalyst 1 andtetrabutylammonium iodide (Bu4NI) as cocatalyst. The optimalreaction conditions for the preparation of poly(EOO-co-PA) and poly(EOO-co-MA) were 80 degrees C for 5 husing toluene as solvent; however, the synthesis of poly(EOO-co-SA) required more extreme reaction conditions. Furthermore,we have exclusively succeeded in obtaining the trans isomer for MA-polyester.The obtained biopolyesters were characterized by NMR, Fourier transforminfrared, thermogravimetric analysis, and scanning electron microscopyanalyses. Since there are few examples of functionalized and definedcompounds based on olive oil, it is innovative and challenging totransform these natural-based compounds into products with high addedvalue.
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    Highly Active CO2 Fixation into Cyclic Carbonates Catalyzed by Tetranuclear Aluminum Benzodiimidazole-Diylidene Adducts
    (2021) Mesias-Salazar, Angela; Yepes, Yersica Rios; Martinez, Javier; Rojas, Rene S.
    A set of tetranuclear alkyl aluminum adducts 1 and 2 supported by benzodiimidazole-diylidene ligands L-1, N,N'-(1,5-diisopropylbenzodiimidazole-2,6-diylidene)bis(propan-2-amine), and L-2, N,N'-(1,5-dicyclohexyl-benzodiimidazole-2,6-diylidene)dicyclohexanamine were synthetized in exceptional yields and characterized by spectroscopic methods. These compounds were studied as catalysts for cyclic carbonate formation (3a-o) from their corresponding terminal epoxides (2a-o) and carbon dioxide utilizing tetrabutylammonium iodide as a nucleophile in the absence of a solvent. The experiments were carried out at 70 degrees C and 1 bar CO2 pressure for 24 h and adduct 1 was the most efficient catalyst for the synthesis of a large variety of monosubstituted cyclic carbonates with excellent conversions and yields.
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    hr Hydrophobic deep eutectic solvent as extractant phase for determining six carcinogenic polycyclic aromatic hydrocarbons in tea and coffee infusion samples
    (2023) Mesias-Salazar, Angela; Rebolledo-Robles, Kevin; Salazar-Gonzalez, Ricardo; Bravo, Manuel A.; Lucena, Rafael; Toledo-Neira, Carla
    In this work, an analytical methodology was developed for determining polycyclic aromatic hydrocarbons (PAHs) in tea and coffee samples. The new analytical methodology uses a hydrophobic deep eutectic solvent (DES), consisting of a thymol and lidocaine mixture, for the extraction of the analytes under dispersive liquid-liquid microextraction. The extraction procedure was optimized considering several variables (extraction phase composition, sample volume, vortexing and centrifugation time). Under optimum conditions, an using ultrahigh-performance liquid chromatography with fluorescence detection as instrumental technique, the limits of detection were 39 and 53 ng & BULL;L-1 in tea and coffee samples, respectively. The precision expressed as relative standard deviation was better than 6.3 %.The relative recoveries were in the 60.7-85.2 % interval. The proposed method was successfully applied to the analysis of tea and coffee samples. The levels found for the six carcinogenic PAHs are between 10-45 & mu;g & BULL;L-1 for tea infusions and 6-31 & mu;g & BULL;L-1 for coffee infusions. The methodology is defined as an excellent green method with a score of 80 using the analytical Eco-scale.
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    Mono- and Dinuclear Asymmetric Aluminum Guanidinates for the Catalytic CO2 Fixation into Cyclic Carbonates
    (2021) Rios Yepes, Yersica; Mesias-Salazar, Angela; Becerra, Alexandra; Daniliuc, Constantin G.; Ramos, Alberto; Fernandez-Galan, Rafael; Rodriguez-Dieguez, Antonio; Antinolo, Antonio; Carrillo-Hermosilla, Fernando; Rojas, Rene S.
    A set of trisubstituted guanidine ligands L1H2-L4H2 with general formula (PrHN)(2)CNR (R = Ph (L1H2), R = 2,4,6-Me3C6H2(L2H2), R = p-BrC6H4(L3H2), R = (C5H4)Fe(C5H5), Fc (L4H2)) was employed to synthesize a family of mono- and dinuclear asymmetric methyl aluminum guanidinato compounds ((L2H)AlMe2 (1), (L4H)AlMe2 (2), (L-1)Al2Me4 (3), (L-2)Al2Me4 (4), (L-3)Al2Me4 (5), (L-4)Al2Me4 (6), (L1H)(2)AlMe (7), (L2H)(2)AlMe (8), and (L4H)(2)AlMe (9)) that were characterized by NMR spectroscopy (1-9) and single-crystal X-ray diffraction (4 and 8). These compounds were tested as catalysts for the fixation of carbon dioxide with epoxides to give cyclic carbonates, using tetrabutylammonium iodide (TBAI) as cocatalyst. The reactions were performed under solvent-free conditions at 70 degrees C and 1 bar CO2 pressure. Complexes 1-9 were more active than their respective free guanidines under the same experimental conditions for the synthesis of styrene carbonate (11a). The dinuclear complex 6 was the most efficient and active catalyst for the synthesis of several monosubstituted carbonates (11a-1) with excellent conversions and selectivities. Furthermore, the formation of some disubstituted cyclic carbonates (13a-c) using this dinuclear aluminum catalyst was also studied.