Elektrokemijska sinteza hipervalentnih jodovih(I) spojin

Maselj, Nik (author), Iskra, Jernej (mentor), Jovanovič, Primož (co-mentor)

Jodove(I) spojine so koristni reagenti za elektrofilno jodiranje. Raziskal sem novo pot priprave diklorojodatov(I) ([ICl2]-) s pomočjo elektrokemije. Gonilna reakcija za to pretvorbo je anodna oksidacija klorida v klor. Klor nato v naslednjem koraku oksidira jod, kar vodi v nastanek [ICl2]-. V ta namen sem raziskal elektrokatalitske lastnosti iridijevih nanodelcev in iridijevega oksida. Katalizatorja sem primerjal na osnovi njunih ciklovoltamogramov v prisotnosti enega ali obeh reagentov (37% vodne raztopine HCl in I2) v MeCN. Iridijevi nanodelci so se izkazali kot boljši, saj so pri nižjih napetostih dosegli višje tokove kot IrO2. V namen določanja potencialnega okna; v katerem lahko izvajamo anodno oksidacijo klorida v klor, sem posnel tudi ciklovoltamogram HICl2. Ta je pokazal nadaljnje oksidacije HICl2 pri potencialih, višjih kot 1,2 V. Generacija klora prične potekati pri 1 V. Naše potencialno okno je tako med 1 - 1,2 V. Tudi tu so se iridijevi nanodelci izkazali kot boljši, saj so omogočili večji razmik med reakcijo generacije klora in nadaljno oksidacijo produkta. Pregledal sem vpliv napetosti in hitrosti rotacije na generacijo HICl2. Napetost je imela majhen vpliv na izkoristek. Izkazalo pa se je, da ima hitrost rotacije velik vpliv na tvorbo HICl2 in pod določeno hitrostjo praktično ne poteka. Pogledal sem tudi vpliv pomožnega elektrolita na potek reakcije. Primerjal sem tetrabutilamonijev perklorat in LiClO4. Slednji se je izkazal kot slabši, saj je reakcija potekala počasneje, izkoristki pa so bili slabši. Nato sem poskusil uporabiti elektrokemijsko generirano raztopino HICl2 za jodiranje stirena. Reakcija zaradi vpliva pomožnega elektrolita ni potekla. Zato sem generacijo HICl2 izvedel še v brezvodni raztopini HCl/MeOH. Ta sistem se je izkazal kot boljši od MeCN/pomožni elektrolit in reakcija s stirenom je bila uspešna. Raziskal sem tudi, ali lahko reagent generiramo v prisotnosti organskih substratov in jih tako jodiramo. Pomeril sem ciklovoltamograme organskih spojin in izbral tiste, ki niso reagirale pod potencialnim oknom generacije klora (anisol, 1-deken in stiren). Nato sem s kronoamperometrijo izvedel elektrokemijsko sintezo HICl2 in analiziral nastale raztopine. Anisol je bil premalo aktriviran za jodiranje, na 1-decen in stiren pa je potekla elektrofilna adicija joda in klorida kot nukleofila.

• Language: Slovenian
• Keywords: jod, hipervalentne jodove spojine, elektrokemija, anodna oksidacija, klor, elektrokataliza
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-131489
• COBISS.SI-ID: 86481411
• Publication date in RUL: 28.09.2021

Secondary language

• Language: English
• Title: Electrochemical synthesis of hypervalent iodine(I) compounds

Abstract

Iodine(I) compounds are useful reagents for electrophilic iodination. I investigated a new pathway for the preparation of dichloroiodates(I) ([ICl2]-) using electrochemistry. The driving reaction for this conversion is the anodic oxidation of chloride to chlorine. Chlorine then oxidizes iodine in the next step, leading to the formation of [ICl2]-. To this end, I investigated the electrocatalytic properties of iridium nanoparticles and IrO2. The catalysts were compared based on their cyclovoltamograms in the presence of one or both reagents (37% aqueous solution of HCl and I2) in MeCN. Iridium nanoparticles have been proven to be a better electrocatalyst than IrO2, achieving higher currents at lower voltages. In order to determine the potential window in which the anodic oxidation of chloride to chlorine can be performed, I also recorded a HICl2 cyclovoltamogram. This showed further oxidations of HICl2 at potentials higher than 1.2 V while chlorine generation begins at 1 V. Our potential window is thus between 1 - 1.2 V. Iridium nanoparticles have proven to be better, as they have allowed for a greater interval between chlorine generation reaction and further oxidation of the product. I studied the influence of voltage and rotation speed on HICl2 generation. The voltage had little effect on efficiency. However, the rate of rotation has been shown to have a large influence on the formation of HICl2 and formation practically does not occur below a certain rotation rate. I also looked at the effect of the auxiliary electrolyte on the course of the reaction. I compared tetrabutylammonium perchlorate and LiClO4. The latter proved to be worse as the reaction proceeded more slowly and the faradaic efficiencies were poorer. I then tried to use an electrochemically generated HICl2 solution to perform a iodination reaction with styrene. The reaction did not proceed due to the influence of the auxiliary electrolyte. As a solution to this problem, I performed HICl2 generation in anhydrous HCl / MeOH solution. This system proved to be better than MeCN / auxiliary electrolyte and the reaction with styrene was successful. I also investigated whether the reagent can be generated in the presence of organic substrates, which would subsequently react to form iodinated products. I compared cyclovoltamograms of organic compounds and selected those that did not react under the chlorine generation potential window (anisole, 1-decane, and styrene). I then performed electrochemical synthesis of HICl2 by use of chronoamperometry and analysed the resulting solutions. Anisole was insufficiently activated for iodination, 1-decane and styrene however were successfully iodinated.

• Keywords: Iodine, hypervalent Iodine, electrochemistry, anodic oxidation, chlorine, electrocatalysis