S?ntese e avalia??o da atividade anticorrosiva de tiossemicarbazonas, chalconas-tiossemicarbazonas e 1-tiocarbamoil-4,5-diidro-1H-piraz?is

• Ano de defesa: 2015
• Autor(a) principal: Goulart, Carla Marins
• Orientador(a): Lima, Aurea Echevarria Aznar Neves
• Banca de defesa: Nascimento, Maria da Gra?a, D`Elia, Eliane, Neves, Amanda Porto, Santos, Cl?udio Eduardo Rodrigues
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal Rural do Rio de Janeiro
• Programa de Pós-Graduação: Programa de P?s-Gradua??o em Qu?mica
• Departamento: Instituto de Ci?ncias Exatas
• País: Brasil
• Palavras-chave em Português: Tiossemicarbazonas; chalconas-tiossemicarbazonas; 1-tiocarbamoil-4,5- diidro-1H-piraz?is; inibidores org?nicos de corros?o e atividade anticorrosiva
• Palavras-chave em Inglês: Thiosemicarbazones; chalcones-thiosemicarbazones; 1-thiocarbamoyl-4,5- dihydro-1H-pyrazoles; organic corrosion inhibitors and corrosion activity
• Área do conhecimento CNPq: Qu?mica
• Link de acesso: https://tede.ufrrj.br/jspui/handle/jspui/4198

The advance of various industries, especially the oil industry, has generated a great demand for metallic materials, which increases the need for new products or techniques to prevent corrosion of these materials. Thus, this work describes the synthesis of 26 chalcones-thiosemicarbazones and 10 1-thiocarbamoyl-4,5-dihydro-1H-pyrazoles, and the evaluation of corrosion activity of 23 of the synthesized compounds. Three thiosemicarbazones previously synthesized were also evaluated. The synthesis of chalcones-thiosemicarbazones and 1-thiocarbamoyl-4,5-dihydro- 1H-pyrazoles were made from the reaction of chalcones with various substituents and three thiosemicarbazides, using two different methodologies. In methodology 1, the reaction was carried out in acid medium, for a period of 2-6 hours. 26 chalcones-thiosemicarbazones were obtained, being 18 unpublished. The reaction of cyclization of chalcones thiosemicarbazones gave six 1-thiocarbamoyl-4,5-dihydro-1H-pyrazoles, three unpublished. This cyclization was selective, occurring only in compounds containing electron donor substituents. Already the methodology 2 has been used exclusively for obtaining 1-thiocarbamoyl-4,5-dihydro-1H-pyrazoles, and involved reaction in ultrasound and basic medium, for a period of 20 minutes, generating four compounds. Twenty-four compounds, belonging to the three different classes, were tested against corrosion of carbon steel AISI 1020 in 1 mol L-1 HCl solution, by the electrochemical techniques of Potentiodynamic Polarization, Linear Polarization Resistance and Electrochemical Impedance Spectroscopy. The results showed that the compounds act as mixed inhibitors, with anodic tendency. The thiosemicarbazones reached the percentage of 90% of corrosion inhibition efficiency at the higher concentration evaluated (1x10-2 mol L-1). The chalcones-thiosemicarbazones (CTs) and 1-thiocarbamoyl- 4,5-dihydro-1H-pyrazoles (TPs) were even more potent with efficiency exceeding 75% in concentration 1x10-4 mol L-1. CTs and TPs containing three aromatic rings acted as the most potent inhibitors in comparison with the derivatives of these classes that have only two rings. The excellent results obtained for all tested compounds demonstrate that these can be used in the control and prevention of corrosion.