title: Cyanate as an Active Precursor of Ethyl Carbamate Formation in Sugar Cane Spirit.
abstract: The thermodynamic and kinetic aspects of ethyl carbamate (EC) formation through the reaction between cyanate and ethanol were investigated. The rate constant values for cyanate ion decay and EC formation are (8.0 ± 0.4) × 10(-5) and (8.9 ± 0.4) × 10(-5) s(-1), respectively, at 25 °C in 48% aqueous ethanolic solution at pH 4.5. Under the investigated experimental conditions, the rate constants are independent of the ethanol and cyanate concentrations but increase as the temperature increases (ΔH1(⧧) = 19.4 ± 1 kcal/mol, ΔS1(⧧) = −12.1 ± 1 cal/K, and ΔG1(⧧) = 23.0 ± 1 kcal/mol) and decrease as the solution pH increases. According to molecular modeling (DFT) that was performed to analyze the reaction mechanism, the isocyanic acid (HNCO) is the active EC precursor. The calculated ΔG1(⧧), ΔH1(⧧), and ΔS1(⧧) values are in very good agreement with the experimental ones.
authors.affiliation: Departamento de Quı́mica e Fı́sica Molecular, Instituto de Quı́mica de São Carlos, Universidade de São Paulo , Avenida do Trabalhador São Carlense 400, CP 780, CEP 13560-970 São Carlos, SP, Brazil.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Galinaro
authors.affiliation: Departamento de Quı́mica e Fı́sica Molecular, Instituto de Quı́mica de São Carlos, Universidade de São Paulo , Avenida do Trabalhador São Carlense 400, CP 780, CEP 13560-970 São Carlos, SP, Brazil.
authors.forename: Thiago H K
authors.initials: TH
authors.lastname: Ohe
authors.affiliation: Departamento de Quı́mica e Fı́sica Molecular, Instituto de Quı́mica de São Carlos, Universidade de São Paulo , Avenida do Trabalhador São Carlense 400, CP 780, CEP 13560-970 São Carlos, SP, Brazil.
authors.forename: Augusto C H
authors.initials: AC
authors.lastname: da Silva
authors.affiliation: Departamento de Quı́mica, Universidade Federal de Mato Grosso, Instituto de Ciências Exatas e da Terra , Avenida Fernando Correia da Costa S/N, Boa Esperança, CEP 78060-900 Cuiabá, MT, Brazil.
authors.forename: Sebastião C
authors.initials: SC
authors.lastname: da Silva
authors.affiliation: Departamento de Quı́mica e Fı́sica Molecular, Instituto de Quı́mica de São Carlos, Universidade de São Paulo , Avenida do Trabalhador São Carlense 400, CP 780, CEP 13560-970 São Carlos, SP, Brazil.
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Franco
mesh_terms: D000434:Alcoholic Beverages; D003485:Cyanates / Q000737:chemistry* / Q000378:metabolism; D000431:Ethanol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D031786:Saccharum / Q000737:chemistry*; D013816:Thermodynamics; D014520:Urethane / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003485:Cyanates; D014520:Urethane; D000431:Ethanol; C024835:potassium cyanate; C005057:isocyanic acid
keywords: cachaça; cyanate; distillate; ethyl carbamate; sugar cane spirit