Showing papers by "Maurício Boscolo published in 2001"

Copper(II) catalysis in cyanide conversion into ethyl carbamate in spirits and relevant reactions.

Abstract: The role of copper(II) species in the oxidation of inorganic cyanide to cyanate and in the conversion of cyanate or urea into ethyl carbamate was investigated. The oxidation process has been shown to be independent from the dissolved oxygen. Elemental analysis and infrared spectroscopy have shown the formation of a mixed copper carbonate/hydroxide in the process of oxidation of cyanide to cyanate in water/ethanol. The complexation to CuII of cyanate formed upon cyanide oxidation makes the former more susceptible to nucleophilic attack from ethanol, with conversion into ethyl carbamate. Comparatively, urea has a minor role with respect to cyanide in the formation of ethyl carbamate. Therefore, the urea present in some samples of Brazilian sugar cane spirit (cachaca) has been shown to have almost no influence on the ethyl carbamate content of cachacas, which comes essentially from cyanide. FeII,III affords results similar to those found with CuII. Some suggestions are presented to avoid ethyl carbamate form...

The kinetics and mechanism of the reaction between carbon dioxide and a series of amines: Observation and interpretation of an isokinetic effect

Abstract: Kinetics investigations have been made on the reaction of some organic amines with dimethylcarbonate (DMC) in the presence of carbon dioxide. N -alkyl-carbamates were formed and measurements were made for a series of substituents in the amine. Second-order kinetics was used in the analysis. The rate constants have been analyzed and the resulting Arrhenius parameters indicate an isokinetic effect. The stepwise increase of the activation energies and the value of the isokinetic temperature are such that the selective energy transfer (SET) model suggests a δ (COC) vibration mode of the dimethylcarbonate to be activated in the rate determining reaction step. The DMC molecule is hydrogen bonded to the quartenary ammonium cation. The energy source is suggested to be a closely related vibration mode of the dimethylcarbonate serving as solvent.