Browsing by study line "Kemi"
Now showing items 41-43 of 43
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(2024)Positroniemissiotomografia (PET) on yksi suosituimmista kuvantamistekniikoista kehon metabolian ja kemiallisten muutosten kuvantamiseen nykypäivänä. PET-kuvantaminen edellyttää radiomerkkiainetta, ja fluori-18 on nykyään käytetyin radioisotooppi. Bio ortogonaaliset ja click-reaktiot ovat saaneet paljon huomiota uusien radiomerkkiaineiden valmistuksessa. Bio-ortogonaalisia reaktioita käytetään reaktioiden kohdentamiseen, jotta reaktiot tapahtuisivat nopeasti biologisissa olosuhteissa, esimerkiksi, tetrasiini-trans syklookteeni-reaktiot. Click-reaktiot ovat hyödyllisiä radioleimaamisessa, sillä lyhyet puoliintumisajat edellyttävät nopeita reaktiota. Esimerkiksi, rikki(VI)-fluoridi vaihto (SuFEx) reaktiot olisivat tehokkaita tähän tarkoitukseen. Tämän työn tavoitteena oli luoda uusi tetrasiini SuFEx-ryhmällä, jota voidaan radioleimata fluori-18:lla. Alifaattinen osuus halutusta molekyylistä tuotettiin korkealla saannolla. Tetrasiinin saanto oli alhainen, mutta odotettavissa kirjallisuuden perusteella. Suunniteltu bromi-linkkeri yhdistettiin tetrasiinin amiiniryhmään onnistuneesti. Kuitenkaan saatu yhdiste ei reagoinut hyvin alifaattisen osan kanssa. Tehtiin useita koereaktioita, kuten erilaisten linkkerien käyttö tetrasiinin ja alifaattisen osan välillä, pienemmän kaupallisesti saatavilla olleen alifaattisen osan käyttö ja SuFEx-ryhmän lisääminen suoraan tetrasiiniin. Jotkut näistä kokeista onnistuivat, mutta viimeistä synteesin tuotetta ei voitu analysoida, joten sitä ei voitu radioleimata.
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(2022)The demand for natural and man-made cellulosic-based materials is in an increase continually due to the world population growth. Cotton production does not meet this demand. Consequently, a rational strategy to close this “cellulosic products gap” is to increase the production of man-made cellulosic products, following the principles of green chemistry. Cellulose is an essential skeletal component in plants and is a nearly limitless polymeric raw material with intriguing structure and properties. Due to its inherent insolubility, this crystalline and stiff homopolymer has not yet reached its full application potential. The diversity of regenerated cellulose materials formed through physical dissolution and regeneration has been remarkable in recent decades, showing tremendous possibilities in the fields of textiles, packaging, biomedicine, water treatment, and optical/electrical devices. Since most of the agents used in the physical dissolution and regeneration process can be recycled and reused and the nature of cellulose is preserved, no chemical reactions take place. This method is therefore environmentally friendly and holds the promise of bringing about a new Green Revolution in the widespread use of cellulose-like natural resources. Given the fabrication of new materials using an ecologically benign technology and the replacement of petroleum-based materials, the effects and advantages of such physical processes on society are very fascinating. This thesis includes the dissolution of microcrystalline cellulose (MCC), which represents a highly crystalline and pure cellulose model substrate by 7-methyl-1,5,7- triazabicyclo [4.4.0] dec-5-enium acetate [mTBDH] [OAc] superbase ionic liquid (SIL), which has an extreme dissolution power for cellulose. Cellulose can be first dissolved in IL at 80 ◦C and then regenerated, upon cooling, with the addition of n-propanol as an antisolvent for cellulose, leading to a phase separation. The second part of the thesis is the regeneration of cellulose in the form of films from cellulose-IL solutions. [mTBDH] [OAc] IL was used for the first time as a plasticizer for the preparation of transparent cellulose films.
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(2023)Catechol is widely produced platform chemical, and many fine chemicals, including pharmaceuticals and pesticides, contain catechol moieties. Catechols are nucleophilic, but their polarity can be reversed by oxidizing them into electrophilic o-benzoquinones (OBQs). OBQs are highly reactive and react readily with nucleophiles but also with dienes, dienophiles and ylides. However, OBQs have many reactive sites, which often leads to lack of selectivity in reactions. In the literature review of this thesis, the methods to control selectivity in nucleophilic additions, cycloadditions and Wittig reactions of OBQs are reviewed. Selectivity is often increased by blocking undesired reactive sites by substituents. If substituents can’t be altered, it is possible to control selectivity by choice of catalysts and substrates as well as stoichiometric ratios of substrates. In addition, the literature review will also focus on how the use of o-benzoquinones have been utilized in organic synthesis. In the experimental part, nucleophilic additions of amino acids and silyl enol ethers to o-benzoquinones are studied in practice. Reactions of amino acids with OBQs resulted only in polymerization despite the efforts to control the selectivity. However, ZnCl2 catalysed addition of silyl enol ethers into OBQs yielded only 1,4-addition products. The method was then optimized with two model reactions after which 30 different 1,4-addition products were successfully synthesized. For most of these products this method is the only proven synthesis route.
Now showing items 41-43 of 43