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OPTIMIZACIJA REAKCIJSKIH PARAMETROV SUZUKI-MIYAURA REAKCIJE
Marinič Podbršček, Rok (Avtor), Gazvoda, Martin (Mentor) Več o mentorju... Povezava se odpre v novem oknu

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Izvleček
Cilj magistrskega dela je bil določiti optimalne reakcijske parametre Suzuki-Miyaura reakcije pod zelenimi pogoji z uporabo predkatalizatorja [Pd(Py-tzNHC)2](BF4)2. Pri optimizaciji smo poskušali čim bolj slediti principom zelene kemije, t.j. uporaba okolju prijaznih topil in baz ter reakcije izvesti pri čim nižji temperaturi ter z uporabo čim nižje količine paladija. Na izbrani modelni reakciji smo preverjali učinkovitost različnih topil in baz, pri čemer smo dobili najvišje stopnje pretvorb substrata v produkt pri uporabi vode kot topila, kar se je skladalo z željo po sledenju principom zelene kemije. Pri pregledu izbranih baz smo dobili visoke pretvorbe pri sledečih bazah: kalijev karbonat (K2CO3), kalijev fosfat (K3PO4) in dinatrijev hidrogenfosfat heptahidrat (Na2HPO4·7H2O), kjer je bila izbira baze za nadaljne reakcije (K2CO3) določena glede na njeno ceno in prijaznost okolju. Po dobljenih optimalnih reakcijskih parametrih za modelno reakcijo smo preverili učinkovitost metode na različnih substratih. Poleg vpliva temperature, baze in časa reakcije na stopnjo pretvorbe, imajo pri Suzuki-Miyaura reakciji vpliv tudi substituenti na substratih in morebitne sterične ovire, ki jih povzročajo, predvsem pa vrsta aril halida (Cl, Br, I). Izbor substratov je bil načrtovan tako, da smo lahko opazovali vpliv različnih substituentov pri aril borovih kislinah in aril halidih na stopnjo pretvorbe. Izbrali smo tudi različne (hetero)arilhalide in (hetero)borove kisline. Reakcije so učinkovito potekale na aril bromidih, medtem ko so aril kloridi do željenih produktov vodili z nižjimi stopnjami pretvorbe. Poleg preverjanja učinkovitosti paladijevega predkatalizatorja pri Suzuki-Miyaura reakciji smo izvedli še nekaj eksperimentov za določitev poteka katalize, torej ali gre za homogeno ali heterogeno katalizo, pri čemer smo ugotovili, da je kataliza homogena. Poskušali smo še določiti potek reakcije in izboljšati proces izolacije produkta. Predpostavili smo, da se karbonatni ion veže na borov atom v borovi kislini in tvori tetravalentni borov ion, ki nato reagira s produktom oksidativne adicije.

Jezik:Slovenski jezik
Ključne besede:Suzuki-Miyaura reakcija, kataliza, aril borova kislina, pripajanje, paladij, zelena kemija
Vrsta gradiva:Magistrsko delo/naloga (mb22)
Tipologija:2.09 - Magistrsko delo
Organizacija:FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Leto izida:2019
COBISS.SI-ID:1538323907 Povezava se odpre v novem oknu
Število ogledov:723
Število prenosov:213
Metapodatki:XML RDF-CHPDL DC-XML DC-RDF
 
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Sekundarni jezik

Jezik:Angleški jezik
Naslov:OPTIMIZATION OF REACTION PARAMETERS IN THE SUZUKI-MIYAURA REACTION
Izvleček:
The goal of this master thesis was to determine optimal reaction parameters of the Suzuki-Miyaura reaction under green conditions with the usage of the palladium precatalyst [Pd(Py-tzNHC)2](BF4)2. During the optimization we tried to follow the principles of green chemistry, which meant the usage of enviromentally friendly solvents and bases and low temperature of the reaction mixture. In process we also tried to use low loading of palladium catalyst. A model reaction was chosen to determine the most efficient base and solvent. Conviniently, water turned out to be the solvent of choice for studied reaction, which fits perfectly into the principles of green chemistry. The screening of bases showed that potassium carbonate (K2CO3), potassium phosphate (K3PO4) and disodium hydrogenphosphate heptahydrate (Na2HPO4·7H2O) were the most efficient bases. Since the above bases gave comparable results, the selection of base for further reactions (K2CO3) was made on the basis of its price and environmental friendliness. After the reaction parameters were determined, the efficiency of the method was tested on different substances. Besides the influence of the temperature, base and reaction time on the conversion rate, the electronic-influence and steric hindrance of substituents on substrates were found to play important role. Likewise, the type of halogen atom (Cl, Br, I) is crucial for (in)activity of this substrate. The selection of the substrates was based on the possibility of observing the effect of different groups on aryl boronic acids and aryl halides on the conversion rate.We have varieted different subsituents on both, aryl halides and boronic acids. We have also tested different (hetero)aryls and (hetero)boronic acids. High yields of products were obtained in the case of aryl bromides, whereas aryl chlorides returned low conversions of starting material. Besides the precatalyst efficiency on Suzuki-Miyaura reaction, we also wanted to determine the catalytic pathway, starting with determination whether the catalysis is either homogeneous or heterogenous. Mercury poisioning experiments confirmed that the system is operating via homogeneous catalysis. We tried to determine the course of reaction and improve the isolation process. We postulated that carbonate ion reacts with boron atom of boronic acid and creates tetravalent boron ion, which further reacts with the product of oxidative addition.

Ključne besede:Suzuki-Miyaura reaction, catalysis, aryl boronic acid, cross-coupling, palladium, green chemistry

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