Synthesis and evaluation of thiosemicarbazides and 1,3,4-thiadiazolium-2-phenylamine hydrochloride as corrosion inhibitors

Autor: Pereira, Danilo Sousa
Přispěvatelé: Lima, Aurea Echevarria Aznar Neves, Rezende, Michele Jakeline Cunha, Bauerfeldt, Glauco Favilla
Jazyk: portugalština
Rok vydání: 2014
Předmět:
Zdroj: Biblioteca Digital de Teses e Dissertações da UFRRJ
Universidade Federal Rural do Rio de Janeiro (UFRRJ)
instacron:UFRRJ
Popis: Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2019-12-27T17:03:29Z No. of bitstreams: 1 2014 - Danilo Sousa Pereira.pdf: 4194633 bytes, checksum: 42ac8e3592b6c39b6fceba67d42e2c5c (MD5) Made available in DSpace on 2019-12-27T17:03:29Z (GMT). No. of bitstreams: 1 2014 - Danilo Sousa Pereira.pdf: 4194633 bytes, checksum: 42ac8e3592b6c39b6fceba67d42e2c5c (MD5) Previous issue date: 2014-02-25 Six (6) thiosemicarbazides and five (5) 1,3,4-thiadiazolium-2-phenylamine hydrochloride were synthesized for this dissertation; two (2) of them are being reported for the first time. Thiosemicarbazides were synthesized via three (3) different methodologies: stirring with temperature variation (Method A), microwave irradiation (Method B), and solid-solid reaction (Method C). Mesoionic salts were also synthesized by different methods; firstly, under reflux in the presence of 1,4-dioxane as solvent, from cinnamic acid chlorides and N1,N4-substituted thiosemicarbazides (Method A). And secondly, using microwave irradiation in the presence of thionyl chloride, from cinnamic aldehyde and N1,N4-substituted thiosemicarbazides (Method B). The compounds were obtained in high purity and satisfactory yields: between 65% and 92% for thiosemicarbazides, and between 54% and 99% for mesoionic salts. All compounds were characterized by spectroscopic techniques. In order to obtain information on the structural and electronic properties that could contribute to the prediction of corrosion inhibition efficiency, the structures of the synthesized compounds were investigated using SPARTAN-PRO program in semi-empirical method. Mesoionic salts showed the lowest values forthe difference between energy levels of the frontier orbitals (HOMO and LUMO), which indicates that these compounds could be more effective in inhibiting corrosion than di-ortho-tolylthiourea. All synthesized compounds were experimentally evaluated against the corrosion of AISI 1020 carbon steel in HCl 1 M. The results generally showed significant percentages of corrosion inhibition; specially, for the mesoionic salt that contains the methoxy group in the cinnamic portion of the molecule, which reached levels of 77% and 94% in the technical Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization, respectively. In general, the methodologies used for experimental evaluation of corrosion activity and the technique of molecular modeling gave correlated results. Neste trabalho de pesquisa foram sintetizadas seis (6) tiossemicarbazidas e cinco (5) cloridratos mesoi?nicos pertencentes ? classe 1,3,4-tiadiazolio-2-fenilaminidas, dos quais dois (2) est?o sendo relatados pela primeira vez. As tiossemicarbazidas foram sintetizadas via tr?s (3) metodologias diferentes: agita??o com escala de temperatura (Metodologia A); irradia??o de micro-ondas (Metodologia B); e rea??o s?lido-l?quido (Metodologia C). Os sais mesoi?nicos tamb?m foram sintetizados via metodologias diferentes, sendo a primeira em refluxo na presen?a de 1,4-dioxano como solvente, a partir dos cloretos de ?cido cin?mico e tiossemicarbazidas N1,N4-substitu?das (Metodologia A) e, a segunda via irradia??o de micro-ondas na presen?a de cloreto de tionila, a partir de alde?dos cin?micos e tiossemicarbazidas N1,N4-substitu?das (Metodologia B). Os compostos foram obtidos em alto grau de pureza e em rendimentos satisfat?rios, variando entre 65 % e 92% para as tiossemicarbazidas e, entre 54 % e 99% para os sais mesoi?nicos. Todos os compostos foram caracterizados atrav?s de t?cnicas espectrosc?picas. As estruturas dos compostos sintetizados foram investigadas, utilizando o programa SPARTAN-PRO no m?todo semi-emp?rico, a fim de obter informa??es sobre as propriedades estruturais e eletr?nicas que pudessem contribuir para a previs?o sobre a efici?ncia de inibi??o da corros?o. Os sais mesoi?nicos apresentaram os menores valores da diferen?a entre os n?veis de energias dos orbitais de fronteira (HOMO e LUMO) indicando que esses compostos poderiam ser mais eficientes na inibi??o da corros?o quando comparados ? di-orto-toluiltiour?ia. Todos os compostos sintetizados foram avaliados experimentalmente frente ? corros?o de a?o carbono AISI 1020 em 1M de HCl. Os resultados mostraram, de forma geral, percentuais significativos de inibi??o da corros?o, com destaque para o sal mesoi?nico contendo o grupo metoxila na por??o cin?mica da mol?cula, que alcan?ou os ?ndices de 77 %e 94% nas t?cnicas Espectroscopia de Imped?ncia Eletroqu?mica e Polariza??o Potenciodin?mica, respectivamente. De forma geral, as metodologias utilizadas para avalia??o experimental da atividade anticorrosiva e a t?cnica de modelagem molecular apresentaram correla??o nos resultados.
Databáze: OpenAIRE
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