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Master's Dissertation
DOI
https://doi.org/10.11606/D.46.1999.tde-13062024-115844
Document
Author
Full name
Decio Arrais Campioti
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1999
Supervisor
Committee
Pardini, Vera Lucia (President)
Biaggio, Francisco Carlos
Janissek, Paulo Roberto
Title in Portuguese
Estudos Exploratórios da oxidação eletroquímica de sulfetos vinílicos Δ(5,6)- e Δ(6,7)-insaturados
Keywords in Portuguese
Compostos de enxofre
Físico-química orgânica
Abstract in Portuguese
Neste trabalho foi estudada a oxidação eletroquímica de l-feniltio-1,5-hexadieno (I), l-feniltio-1,6-heptadieno (II) e 1-metiltiol,5-hexadieno (III). Os potenciais de oxidação destes sulfetos vinílicos foram determinados através da voltametria cíclica em solução 0,1M NaClO4/MeCN usando anodo de Pt e como eletrodo de referência Ag/AgI. Estas experiências mostraram que o processo de oxidação dos substratos era irreversível. Não foi possível efetuar as eletrólises preparativas dos substratos em MeCN anidra ou contendo água quer utilizando anodo de Pt quer de carbono vítreo. Quando se empregou anodo de Pt e NaClO4/MeCN contendo água e um mediador, a tris-(4-bromofenil)amina, as eletrólises a potencial controlado de I e II conduziram a difenil dissulfeto e respectivamente, 2-feniltio-5-hexenal (Ia, 16%), 2-feniltio-6-heptenal (IIa, 13%), enquanto que a eletrólise de III conduziu a dimetil sulfeto e 2-metiltio-5-hexenal (IIIa, 39% clg). Com anodo de carbono vítreo e mantendo as outras condições experimentais, os substratos I e II foram recuperados. Nas eletrólises em CH2Cl2-MeOH contendo LiClQ4 e 2,6-lutidina e utilizando anodo de Pt, não houve formação de difenil dissulfeto e os seguintes produtos de dimetoxilação foram isolados como misturas diasteroméricas éritro e treo : 5,6-dimetoxi-6-feniltio-l-hexeno (Ib, 31%) a partir de I, 6,7-dimetoxi-7-feniltio-l-hepteno (IIb, 17%) a partir de II, 5,6-dimetoxi-6-metiltio-l-hexeno (IIIb, 42%) a partir de III. Com anodo de carbono vítreo a oxidação de I e II conduziu aos mesmos compostos porém com rendimentos menores. Uma tentativa de realizar a oxidação de I (anodo de Pt) na presença de tris-(4-bromofenil)amina, em CH2Cl2-MeOH resultou em uma mistura complexa de produtos. Com base nos tipos de · produtos formados nas eletrólises e em exemplos da literatura são propostos mecanismos de reação para explicar os resultados obtidos.
Title in English
Estudos Exploratórios da oxidação eletroquímica de sulfetos vinílicos Δ(5,6)- e Δ(6,7)-insaturados
Keywords in English
Compostos de enxofre
Físico-química orgânica
Abstract in English
In this work was investigated the electrochemical oxidation of l-phenylthio-1,5-hexadiene (I), l-phenylthio-1,6-heptadiene (II) and 1-methylthio-1,5-hexadiene (III). Their oxidation potentials were determined using cyclic voltammetry in 0.1M NaClO4/MeCN at Pt anode and Ag/AgI as reference electrode. The data showed that the oxidation process was irreversible. It was not possible to perform the electrolyses of compounds I-III in anhydrous or wet MeCN both at Pt or vitreous C anode. Using moist NaClO4MeCN at Pt anode in the presence of a mediator, tris-(4-bromophenyl)amine, the electrolyses of I-II afforded diphenyl disulfide and respectively, 2-phenylthio-5-hexenal (Ia, 16% ), 2-phenylthio-6-heptenal (IIa, 13%), and III afforded dimethyl disulfide and 2-methylthio-5-hexenal (IIIa, 39% glc). At vitreous C anode and under otherwise sarne conditions the starting materiais I and II were recovered. When CH2Cl2-MeOH solution containing LiClO4 and 2,6-lutidine was employed at Pt anode, the formation of diphenyl disulfide was not observed and the following dimethoxylated products were isolated as a mixture of threo and erythro diastereomers : 5, 6-dimethoxy-6-phenylthio-l-hexene (Ib, 31 % ), 6, 7-dimethoxy-7-phenylthio-1-heptene (IIb, 17%) and 5,6-dimethoxy-6-methylthio-1-hexene (IIIb, 42%), from. I, II and III respectively. With vitreous C anode the oxidation of I and II afforded the same compounds but in lower yields. An attempt to perform the oxidation of I (Pt anode) in the presence of tris-( 4-bromophenyl)amine in CH2Cl2-MeOH solution resulted in a complex mixture of products. Mechanistic proposals for the electrochemical oxidation of the investigated substrates were made based on the products found and literature data.
 
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Publishing Date
2024-06-13
 
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