Dell'Arciprete M.L.,National University of La Plata |
Santos-Juanes L.,Universidad Politécnica de Ingeniería |
Arques A.,Universidad Politécnica de Ingeniería |
Vercher R.F.,Universidad Politécnica de Ingeniería |
And 4 more authors.
Catalysis Today | Year: 2010
The reaction kinetics and mechanisms of three neonicotinoid insecticides, imidacloprid (IMD), thiacloprid (THIA) and acetamiprid (ACT), with singlet oxygen and Rose Bengal excited triplet state is reported. The rate constants (5.5 ± 0.5) × 106, (3.9 ± 1) × 107, and (1.3 ± 1) × 106 M-1 s-1 were determined for the chemical reaction of singlet oxygen, and the values (4.8 ± 1) × 107, (1.5 ± 1) × 108, and (3.6 ± 1) × 107 M-1 s-1 for the reactions with Rose Bengal triplet state for IMD, THIA, and ACT, respectively. The most important primary degradation product identified was 6-chloronicotinic acid. The results support a reaction mechanism involving a charge transfer reaction between the insecticides and singlet oxygen or Rose Bengal triplet state. The toxicity of the solutions towards Vibrio fischeri seems not to decrease during the early stages of the reactions. Depletion of the insecticides by singlet oxygen and naturally occurring excited states might be important abiotic pathways involved in natural waters. © 2010 Elsevier B.V. All rights reserved.
Lafuente L.,LADECOR |
Diaz G.,LADECOR |
Bravo R.,LADECOR |
Letters in Organic Chemistry | Year: 2016
Background: The ionic liquid triethylammonium acetate (TEAA) was found to be an efficient solvent in the acetylation of alcohols, amines, oximes and thiols to their corresponding acetyl compounds using only a 10% excess of acetic anhydride under mild conditions. Moreover TEAA is not only an inexpensive and recyclable solvent but also an anomeric selective catalyst in the per-O-acetylation of sugar moieties. Methods: Simple and effective organic synthesis protocols were provided for the selective acetylation of several substrates. The products were fully characterized by 1H and 13C NMR spectroscopy and the anomeric ratios were obtained from the 1H spectra. Results: Structurally diverse alcohols, phenols, thiols, amines, carbohydrates and oximes underwent acylation under mild conditions by this procedure to provide the corresponding acetates in excellent yields. TEAA ionic liquid is unique in its capability to act as both, solvent and high selective catalyst. As expected, the reaction proceeds with high b anomeric selectivity for sugars derivatives. Moreover, the ionic liquid was regenerated, recycled and reused for three times without apparent loss of reactivity and selectivity in all cases. Conclusions: The present procedure provides a powerful and versatile acylation method for alcohols, phenols, thiols, amines, oximes and carbohydrates. This protocol is endowed with several unique merits: selectivity, cost-efficiency, atom-economy and mild reaction conditions tolerable to acid sensitive functionalities. With these features, this method may be considered as a better alternative for the acetylation of a wide range of substrates. © 2016 Bentham Science Publishers.