The goal of this thesis is to probe the functionality of 2-mercaptobenzimidazole (MBI) as corrosion inhibitor of carbon-steel in both strong and weak aqueous acidic solutions (HCl and H2CO3). To achieve this target electrochemical techniques have been employed, in combination with substrate analysis. Concerning aqueous HCl media, results demonstrate that MBI is an effective corrosion inhibitor, functioning essentially equally well in 1 M, 0.1 M, and 0.01 M HCl concentrations. X-ray photoelectron spectra suggest that MBI is typically bound to the surface in two tautomeric forms (thione and thiol). Furthermore, these data indicate that substrate termination varies as a function of both HCl and MBI concentration, with the interface consisting of MBI bound to film-free carbon-steel on highly inhibited substrates. In further work, the impact of dissolved oxygen, solution temperature, and immersion time on MBI performance in HCl solutions has been assessed. The latter two parameters have considerable influence on MBI inhibition efficiency. More specifically, it was found that MBI decreases dramatically its inhibition efficiency between 60°C and 70°C in 1 M HCl, and also apparently work less well as substrate immersion time increases. As regards MBI performance in deaerated CO2-saturated NaCl (0.62 M) solution, results demonstrate that MBI effectively inhibits corrosion within the parameter space explored i.e. solution temperatures of 30°C and 55°C and total applied pressures (p(H2O) + p(CO2)) of 1 bar and 20 bar. The performance of MBI does not vary greatly for different combinations of these temperatures and pressures. Post immersion substrate characterisation with XRD and SEM indicate that no significant surface scaling occurs under these conditions.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-05T19:17:02Z No. of bitstreams: 1 joaovitordeassis.pdf: 9015544 bytes, checksum: 493b436d8f7e8eb4f99f7775b557aba2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T13:42:03Z (GMT) No. of bitstreams: 1 joaovitordeassis.pdf: 9015544 bytes, checksum: 493b436d8f7e8eb4f99f7775b557aba2 (MD5) / Made available in DSpace on 2017-05-17T13:42:03Z (GMT). No. of bitstreams: 1 joaovitordeassis.pdf: 9015544 bytes, checksum: 493b436d8f7e8eb4f99f7775b557aba2 (MD5) Previous issue date: 2009-07-17 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesse trabalho descreve-se, num primeiro momento, a síntese de derivados inositóis condensados com o 2-mercaptobenzotiazol ou com o 2mercaptobenzimidazol, potenciais agentes antibacterianos. A seguir é descrita a preparação de derivados clorados de inositol. No primeiro capítulo relata-se a obtenção e a avaliação das propriedades antituberculose de derivados do 2mercaptobenzotiazol e do 2-mercaptobenzimidazol condensados com um inositol. Tais compostos foram preparados via abertura de intermediário epóxido, o qual foi obtido a partir do L-quebrachitol, um produto natural isolável do látex da seringueira. Foram sintetizados 8 compostos inéditos, sendo quatro derivados do 2mercaptobenzotiazol e quatro derivados do 2-mercaptobenzimidazol. Na obtenção de alguns desses compostos foi empregada irradiação de microondas como fonte de aquecimento. Utilizou-se nestas reações um aparelho de microondas doméstico adaptado em nosso laboratório. Alguns desses compostos foram testados in vitro contra o Mycobacterium tuberculosis, no laboratório de Bacteriologia (IPEC) da FioCruz-RJ. Todavia, tais compostos não se mostraram ativos contra esse microorganismo. Alguns compostos também foram enviados para avaliação da atividade antibacteriana no National Institute of Allergy and Infectious Diseases (NIAID-EUA). O segundo capítulo desse trabalho relata-se a preparação de análogos clorados nas posições C2 ou C3 do quiro-inositol, usando-se também como material de partida o L-quebrachitol. Tais derivados halogenados são candidatos a possíveis compostos bioativos, assim como precursores interessantes para a preparação de outras moléculas. As estruturas dos produtos obtidos foram elucidadas por espectroscopia na região do infravermelho, RMN de 1H e RMN de 13C. Algumas dessas estruturas foram também evidenciadas por experimentos de COSY, HMQC, HMBC e espectrometria de massas. / In this work we describe, in a first moment, the synthesis of inositol derivatives condensed with 2-mercaptobenzothiazole or 2-mercaptobenzimidazole, potential antibacterial agents. In a second part, the preparation of chlorinated inositol derivatives is reported. In the first chapter, we describe the synthesis and antitubercular evaluation of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole derivatives condensed with inositol. These compounds were prepared by opening an epoxide intermediate, which was obtained from L-quebrachitol, a natural product isolated from Hevea brasiliensis. Eight new compounds were synthesized: four 2mercaptobenzothiazole and four 2-mercaptobenzimidazole derivatives. For the preparation of some compounds, microwave irradiation was used as the heating source. A domestic microwave apparatus was adapted for these reactions in our laboratory. Some compounds were evaluated in vitro against Mycobacterium tuberculosis at the laboratory of bacteriology (IPEC) of FioCruz-RJ. However, such compounds did not display biological activity against this microorganism. Some compounds were also submitted for antibacterial activity assay at National Institute of Allergy and Infectious Diseases (NIAID-USA). Chapter 2 of this work reports the preparation of inositols chlorinated at the C2 or C3 position, using as starting material L-quebrachitol. These halogenated derivatives are potential new bioactive compounds, as well as interesting precursors for the preparation of other molecules. The compounds were characterized by infrared spectroscopy, 1H and 13C NMR. Some structures were also characterized by COSY, HMQC, HMBC and mass spectrometry.