Polijodiranje aromatov z oksidativnim pristopom

Gabrovec, Katja (author), Iskra, Jernej (mentor)

Jodirane organske molekule so izredno pomembni intermediati v sintezni organski kemiji, saj se jih uporablja pri uvajanju C-C, C-N in C-O vezi v sistem. Poleg bistvenega pomena v kemiji, pa se vedno bolj uveljavljajo v medicini in farmaciji. V nuklearni medicini sta jodova izotopa 123I in 124I uvedena v različne molekule, ki nastopajo kot diagnostični markerji. Za boljšo učinkovitost metod jodiranja je bilo na začetku potrebno raziskovanje bioloških poti uvajanja halogenov v molekule, iz tega pa so se razvili različni pristopi k reševanju problema, kako na okolju prijazen način čim bolj selektivno in učinkovito pridobiti željene jodirane aromate. Najbolj logična izbira iz vidika zelene kemije je oksidativno jodiranje, ki omogoča boljšo ekonomiko jodovih atomov, saj se ob uporabi molekularnega joda in sočasni prisotnosti oksidanta nastajajoči HI pri jodiranju pretvori nazaj v elektrofilen jod. Izbira oksidanta pa po zgledu iz narave vodi do vodikovega peroksida in kisika, ker pri uporabi le teh ne nastajajo škodljivi stranski produkti, ampak le voda. V diplomski nalogi sem opisala dostopne metode za uvajanje več jodovih atomov v aromatski obroč. Ugotovila sem, da je nabor možnosti velik, vendar sem ob natančnejši študiji prišla do tistih metod, ki ponujajo dobre izkoristke in selektivnost ter so manj obremenjujoče za okolje. Najosnovnejša metoda je oksidativno jodiranje ob prisotnosti kisline kot katalizatorja, ki se izkaže za uspešno metodo. Korak naprej proti zeleni kemiji pa nudita oksidativno jodiranje v vodi ali pa oksidativno jodiranje brez uporabe topila, saj so organska topila med bolj problematičnimi komponentami procesov zaradi velike količine in njihove toksičnosti. Sistem jodiranja z uporabo zračnega kisika kot oksidanta prav tako omogoča uvajanje jodovih atomov v molekule. Zaradi širokega spektra pristopov k izvajanju reakcij je možno uporabiti tudi drugačne pristope, kot je elektrokemijsko jodiranje, jodiranje s pomočjo ultrazvočne kavitacije in jodiranje z mletjem.

• Language: Slovenian
• Keywords: oksidativno jodiranje, vodikov peroksid, kisik, aromati, halogeniranje
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2020
• PID: 20.500.12556/RUL-119389
• COBISS.SI-ID: 27720451
• Publication date in RUL: 08.09.2020

Secondary language

• Language: English
• Title: Poliidonation of aromatics by oxidative approach

Abstract

Iodinated organic molecules are extremely important intermediates in organic synthesis, as they are used for the introduction of C-C, C-N and C-O bonds into the system. In addition to being essential in chemistry, they are gaining ground in medicine and pharmacy. In nuclear medicine, the iodine isotopes 123I and 124I are introduced into various molecules, which act as diagnostic markers. In order to improve the efficiency of iodination methods, it was necessary to study the biological pathways of halogen introduction into molecules, which enabled the development of various approaches to obtain the desired iodinated aromatics as selectively and efficiently as possible in an environmentally friendly way. The most logical choice from the point of green chemistry is oxidative iodination, which allows a better economy of iodine atoms, because when molecular iodine is used in the presence of an oxidant, the by-product HI is converted back to molecular iodine. The choice of oxidant, following examples from nature, leads to hydrogen peroxide and oxygen, because their use does not produce any harmful by-products, only water. In my undergraduate thesis, I described the available methods for introducing several iodine atoms into an aromatic ring. I found the list of possibilities to be big, but on closer study I came up with those methods that offer good yields, are selective and are less harmful to the environment. The most basic method is oxidative iodination in the presence of acid as a catalyst, which is proving to be a successful method. However, a step forward towards green chemistry is offered by oxidative iodination in water or under solvent-free conditions, as organic solvents are probably one of the most problematic components of processes due to their high usage and toxicity. The iodination system using air as an oxidant also allows the introduction of iodine atoms into the molecules. Because of the variety of approaches to carry out reactions, it is also possible to use alternative methods, such as electrochemical iodination, iodination by ultrasound cavitation and method by grinding.

• Keywords: oxidative iodination, hydrogen peroxide, oxygen, aromatics, halogenation