Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-03-21T13:39:54Z No. of bitstreams: 1 2015 - Arthur Valbon Rodrigues.pdf: 2339821 bytes, checksum: 867f44f511f5a52dfdcf023619e589a9 (MD5) / Made available in DSpace on 2017-03-21T13:39:54Z (GMT). No. of bitstreams: 1 2015 - Arthur Valbon Rodrigues.pdf: 2339821 bytes, checksum: 867f44f511f5a52dfdcf023619e589a9 (MD5) Previous issue date: 2015-08-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / In this work six asymmetric thyourea, derived from benzylamine and phenethylamine, were synthesized by reaction of p-substituted phenyl isothiocyanates in the presence of benzylamine and phenethylamine in toluene as solvent by irradiation in ultrasonic bath, featuring the first report in the literature of the adoption of this method for such molecules. The compounds were obtained in high purity, requiring only one recrystallization from hexane/dichloromethane. Yields were very satisfactory, ranging from 89 to 98%. The compounds were characterized by spectroscopic techniques such as 1H, 13C Nuclear Magnetic Resonance and IR. The synthesized compounds were evaluated by electrochemical potentiodynamic polarization techniques, Electrochemical Impedance Spectroscopy and Linear Polarization Resistance as inhibitors to the corrosion AISI 1020 carbon steel in 1M HCl media. Molecular modeling was used for better visualization of the thiourea structures and to correlate theoretical parameters such as the energy of the symmetrical frontier orbital, Mulliken charge on the sulfur atom and dipole moment with the experimental results for corrosion efficiency. In general, all compounds showed corrosion inhibition efficiency with characteristics of mixed inhibitors with anodic trend, however compounds with nitro substituent showed less efficiency, a fact that may be related to their electrons withdrawing potential, which consequently decreases the electron density at the possible center of chemical adsorption, the sulfur atom. However, compounds which showed no substituent and those that contain electron donating group (OCH3) stood out as inhibitors, highlighting N- (p-methoxyphenyl) -N'-phenetylthiourea, which showed 95% efficiency corrosion inhibition, from Electrochemical Impedance spectroscopy. Thus, the asymmetric thiourea benzyl and phenethyl-substituted, especially methoxy-substituted phenyl, can be considered as promising corrosion inhibitors for carbon steel in acid. / Nesse trabalho de disserta??o foram sintetizadas seis tioureias assim?tricas, derivadas da benzilamina e fenetilamina. A obten??o ocorreu atrav?s da rea??o dos isotiocianatos de fenila p-substituidos na presen?a da benzilamina e fenetilamina em tolueno como solvente atrav?s de irradia??o em banho de ultrassom, sendo o primeiro relato na literatura dessa metodologia para tais mol?culas. Os compostos foram obtidos em alto grau de pureza, sendo necess?ria apenas uma recristaliza??o em hexano/diclorometano. Os rendimentos foram muitos satisfat?rios, variando de 89 ? 98%. Os compostos foram caracterizados por t?cnicas espectrosc?picas como Resson?ncia Magn?tica Nuclear 1H,13C e Infravermelho. Os compostos sintetizados foram avaliados atrav?s das t?cnicas eletroqu?micas de Polariza??o Potenciodin?mica, Espectroscopia de Imped?ncia Eletroqu?mica e Resist?ncia a Polariza??o Linear quanto ? a??o como inibidores de corros?o frente a a?o carbono AISI 1020 em HCl 1 mol.L-1. A Modelagem Molecular foi utilizada para melhor visualiza??o das estruturas das tioureias e correlacionar os par?metros te?ricos como a energia dos orbitais de fronteiras sim?tricos, carga de Mulliken no ?tomo de enxofre e momento dipolar com os resultados experimentais da efici?ncia anticorrosiva. De forma geral, todos apresentaram efici?ncia de inibi??o ? corros?o com caracter?sticas de inibidores mistos com tend?ncia an?dica, por?m os compostos com substituinte nitro apresentaram menor efici?ncia, fato esse que pode estar relacionado ao seu poder retirador de el?trons, que consequentemente, diminui a densidade eletr?nica no poss?vel centro de adsor??o qu?mica, o enxofre. Por?m, os compostos que n?o apresentaram substituintes e os que cont?m grupo doador de el?trons (OCH3) se destacaram como inibidores, dando destaque a N-(p-metoxi-fenil)-N?-fenetiltioureia, que apresentou efici?ncia de 95% de inibi??o da corros?o, pela t?cnica de Espectroscopia de Imped?ncia Eletroqu?mica. Assim, as tioureias assim?tricas benzil e fenetil-substitu?das, especialmente met?xi-fenil substitu?das, podem ser consideradas como promissores agentes inibidores da corros?o para o a?o-carbono em meio ?cido.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-08-29T19:26:49Z No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) / Made available in DSpace on 2018-08-29T19:26:49Z (GMT). No. of bitstreams: 1 2017 - Cristiane Frauches dos Santos.pdf: 7660831 bytes, checksum: d9f6418f111957d4be1789ee9411cc8f (MD5) Previous issue date: 2017-09-25 / CAPES / CNPq / FAPERJ / Petrobr?s / Corrosion is one of the serious problems faced in industrial processes, generating enormous financial losses. Several techniques are used to prevent or remedy corrosion in the different materials it affects. Among them, the use of organic or inorganic inhibitors has been widely used. Thus, in this thesis were synthesized 34 heterocyclic compounds, 18 chlorides of 1,3,4-thiadiazolium-2-phenylamines, (11 unpublished), and the other 16 compounds belonging to the class of mesoionic 1,3,4-triazolium -2-thiolate, (15 unpublished), with the objective of evaluating its efficiency as inhibitors of corrosion in acidic corrosion. Derivatives of the class 1,3,4-thiadiazolium-2-phenylamines were obtained with satisfactory purity and yields in the range of 42-96% and, in the class of 1,3,4-triazolium-2-thiolates in 20 -97%. All compounds were characterized by IR, 1H and 13C NMR spectroscopies. The theoretical study was conducted using the SPARTAN-PRO program in the semi-empirical method with the Hamiltonian AM1, to determine its structural and electronic properties of 1,3,4-thiadiazolium-2-phenylamines that could contribute to the efficiency of inhibition of corrosion. The compounds of 1,3,4-thiadiazolium-2-phenylamine class were tested against corrosion of AISI 1020 carbon steel in 0.5 mol L-1HCl and in 0.5 mol L-1 H2SO4. For this evaluation, the electrochemical techniques of Potenciodynamic Polarization (PP), Resistance to Linear Polarization (RPL) and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed significant percentages of corrosion inhibition in both acidic solutions, reaching the rate of up to 95% efficiency for the compound 4-phenyl-5-(3'-methoxy-phenyl)-1,3,4-thiadiazolium-2-phenylamine chloride in the concentration of 3.5x10-4 mol L-1 for the HCl solution, and 99% efficiency for the 2'-chloro and 2'-fluorosubstituted compounds in the concentration of3.5x10-4 mol L-1 for the H2SO4 solution. In addition to the electrochemical techniques, the gravimetric technique was used, which presented 99% of anticorrosive efficiency for the 2'-trifluoromethyl-substituted 1,3,4-thiadiazolium-2-phenylamine derivative, showed the best inhibitory effect in HCl solution. However, the 2'-trifluoromethyl-substituted 1,3,4-triazolium-2-thiol derivative showed less corrosion efficiency than its corresponding isomer. The methodologies used to evaluate the corrosion activity (PP, RPL and EIE), including the theoretical evaluation by molecular modeling, indicated the mesoionic chloridrates as efficient mixed corrosion inhibitors. / S?ntese e avalia??o da atividade anticorrosiva de cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas e 1,3,4-triaz?lio-2-tiolatos em meio ?cido. 2017. 251p Tese (Doutorado em Qu?mica, Ci?ncia exatas, s?ntese org?nica). Departamento de qu?mica, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, 2017. A corros?o ? um dos s?rios problemas enfrentados nos processos industriais, gerando enormes preju?zos financeiros. Diversas t?cnicas s?o utilizadas para evitar ou remediar a corros?o nos diferentes materiais que ela afeta. Dentre elas o uso de agentes inibidores org?nicos ou inorg?nicos tem sido muito utilizado. Assim, neste trabalho de tese foram sintetizados 34 compostos heteroc?clicos, sendo 18 cloretos de 1,3,4-tiadiaz?lio-2-fenilaminas (11 in?ditos) e os outros 16 compostos pertencentes ? classe dos mesoi?nicos 1,3,4-triaz?lio-2-tiolato (15 in?ditos), com o objetivo de avaliar sua efici?ncia como inibidores de corros?o em meio ?cido. Os derivados sintetizados da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram obtidos com grau de pureza e rendimentos satisfat?rios na faixa de 42-96% e, da classe dos 1,3,4-triaz?lio-2-tiolatos em 20-97%. Todos os compostos foram caracterizados por espectroscopia de IV, RMN de 1H e13C. Foi realizado o estudo de modelagem molecular, utilizando o programa SPARTAN-PRO com o m?todo semi-emp?rico, hamiltoniano AM1, para determina??o das propriedades estruturais e eletr?nicas dos 1,3,4-tiadiaz?lio-2-fenilaminas que pudessem contribuir para a efici?ncia de inibi??o da corros?o. Os cloridratos mesoi?nicos da classe 1,3,4-tiadiaz?lio-2-fenilaminas foram testados frente ? corros?o de a?o carbono AISI 1020 em solu??o de HCl 0,5 mol L-1 e em H2SO4 0,5 mol L-1. Para tal avalia??o foram utilizadas as t?cnicas eletroqu?micas de Polariza??o potenciodin?mica (PP), Resist?ncia ? polariza??o linear (RPL) e Espectroscopia de imped?ncia eletroqu?mica (EIE). Os resultados mostraram percentuais significativos de inibi??o da corros?o em ambas solu??es ?cidas, alcan?ando o ?ndice de at? 95% de efici?ncia para o composto cloreto de 4-fenil-5-(3?-met?xi-fenil)-1,3,4-tiadiaz?lio-2-fenilamina na concentra??o de 3,5x10-4 mol L-1 para a solu??o de HCl e, 99% de efici?ncia para os compostos 2?-cloro e 2?-fluor-substitu?dos na concentra??o de 3,5x10-4 mol L-1 para a solu??o de H2SO4. Al?m das t?cnicas eletroqu?micas, foi utilizada a t?cnica gravim?trica que apresentou 99% de efici?ncia anticorrosiva para o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-tiadiaz?lio-2-fenilamina que mostrou o melhor efeito inibidor em solu??o HCl. No entanto, o derivado 2?-trifluormetil-substitu?do da classe 1,3,4-triaz?lio-2-tiol apresentou menor efici?ncia anticorrosiva do que seu is?mero correspondente. As metodologias utilizadas para avalia??o da atividade anticorrosiva (PP, RPL e EIE), incluindo a avalia??o te?rica por modelagem molecular, indicaram os cloridratos mesoi?nicos como eficientes inibidores de corros?o mistos.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-11-09T17:58:22Z No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) / Made available in DSpace on 2017-11-09T17:58:22Z (GMT). No. of bitstreams: 1 2017 - Mariana de Albuquerque Almeida.pdf: 2619920 bytes, checksum: 48c00262629bac9a7779fc4ea9ec94a6 (MD5) Previous issue date: 2017-05-10 / CAPES / This dissertation presents the evaluation of four thiosemicarbazones, from extracts of species of vegetables Talinum triangulare, Physalis angulata e Theobroma cacao L. besides formulation obtained from the combination extract of thiosemicarbazones vegetables as corrosion inhibitor in the presence of carbon steel AISI 1020. Thiosemicarbazones were obtained with good level of purity, satisfactory throughput and identified by NMR of 1H and 13C. The watery extract of Talinum triangulare was obtained using ultrasound device. The extracts of Physalis angulata species were obtained by maceration in water and the other one in ethyl acetate. The watery extracts of Theobroma cacao L. species were obtained using ultrasound device and decoction and hydroalcoholic extract was obtained by maceration in ethanol:water (80:20). The thiosemicarbazones, the vegetable extracts and their formulation were tested in the presence of corrosion of carbon steel AISI 1020 in solution 1 mol. L-1 of HCl. For this evaluation it was used the gravimetric techinique of weight loss and electrochemical techiniques of potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that the presence of thiosemicarbazones, as well as, the formulation increased significantly the resistence of carbon steel AISI 1020 in acidic medium. The results obtained in different used essays (weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy) show that these techniques are complementary in relation to the evaluation of corrosion inhibition. The best anti-corrosion efficiency was observed for thiosemicarbazone chloro and hydroxy-substituted and its formulations with the extract of T. triangulare achieving 88% and 87% of efficiency, by electrochemical impedance spectroscopy, respectively. / Nesta Tese ? apresentada a avalia??o de quatro tiossemicarbazonas, dos extratos das esp?cies vegetais Talinum triangulare, Physalis angulata e Theobroma cacao L., al?m de formula??es obtidas pela combina??o extrato vegetal:tiossemicarbazonas, como inibidores de corros?o frente ao a?o carbono AISI 1020 em meio de ?cido cloridr?co. As tiossemicarbazonas foram obtidas com bom grau de pureza, em rendimentos satisfat?rios e, caracterizadas por IV, RMN de ^1H e ^13C. O extrato aquoso de Talinum triangulare foi obtido em aparelho de ultrassom, os extratos da esp?cie Physalis angulata, foram obtidos sob macera??o em ?gua e o outro em acetato de etila; j? os extratos aquosos da esp?cie Theobroma cacao L. foram obtidos em aparelho de ultrassom e decoc??o e, finalmente, o extrato hidroalco?lico foi obtido por macera??o em etanol:?gua (80:20). As tiossemicarbazonas, os extratos vegetais e suas formula??es foram testadas frente ? corros?o de a?o carbono AISI 1020 em solu??o 1mol.L-1 de HCl. Para tal avalia??o foi utilizada a t?cnica gravim?trica de Perda de Massa e as t?cnicas eletroqu?micas de Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica. Os resultados mostraram que a presen?a de tiossemicarbazonas, bem como, das formula??es aumentam significativamente a resist?ncia do a?o carbono AISI 1020 em ?cido. Os resultados obtidos nos diferentes ensaios utilizados (Perda de Massa, Polariza??o Potenciodin?mica e Espectroscopia de Imped?ncia Eletroqu?mica) mostraram que estas t?cnicas s?o complementares quanto a avalia??o da inibi??o da corros?o. A melhor efici?ncia anticorrosiva foi observada para as tiossemicarbazonas cloro e hidroxi-substitu?das e, para suas formula??es com o extrato da T. triangulare obtendo-se 88% e 87% de efici?ncia por espectroscopia de imped?ncia eletroqu?mica, respectivamente.