Katalizirana oksidativna cepitev dvojne vezi v stirenskih derivatih z vodikovim peroksidom

Šulc, Neža (author), Iskra, Jernej (mentor)

Zelena kemija je del kemije, ki se ukvarja z razvojem procesov, ki imajo čim manjši vpliv na okolje in zdravje ljudi. S tem predstavlja del razvoja trajnostne družbe, poglablja pa se predvsem v načine, kako bi določene reakcije zastavili bolj zeleno in okolju prijaznejše, saj se človeštvo v zadnjih desetletjih v vedno večji meri sooča z okoljsko problematiko, h kateri prispeva tudi kemija kot taka. Na področju zelene kemije je zastavljenih 12 principov, ki nam lahko predstavljajo vodilo za načrtovanje in razvoj kemijskih procesov. Posvetili smo se oksidativni cepitvi dvojne vezi med ogljikovima atomoma, predvsem pa smo se osredotočili na omenjeno pretvorbo na stirenu, pri čemer je bil glavni produkt benzojska kislina. V prvem delu eksperimentalnega dela smo si ogledali vpliv različnih topil na oksidativno cepitev dvojne vezi stirena s 30% vodno raztopino vodikovega peroksida in katalizirano z vanadijevim(V) oksidom, ciljni produkt pa je bila benzojska kislina. Ugotovili smo, da lahko najboljšo selektivnost in pretvorbo v benzojsko kislino dosežemo z uporabo acetonitrila kot topila. V drugem delu eksperimentalnega dela smo primerjali reaktivnost različno substituiranih stirenskih derivatov. Izmerili smo relativne konstante hitrosti substituiranih stirenov glede na stiren za oksidativno cepitev z vodikovim peroksidom in vanadijevim(V) oksidom. Na podlagi tega smo izrisali graf Hammettove korelacije, ki nam je podal vpogled v mehanizem reakcije. Ugotovili smo, da je reakcijska konstanta ρ pozitivne vrednosti, kar nakazuje, da elektron privlačne substituente povečajo hitrost reakcije oz. stabilizirajo njeno prehodno stanje. Vrednost reakcijske konstante je nizka, kar nakazuje, da se naboj v prehodnem stanju ne razvija, ta podatek pa nam nakazuje, da reakcija poteka po radikalskem mehanizmu. Ker pa je učinkovitost in »zelenost« reakcije potrebno kvantificirati, smo izračunali tudi metriko zelene kemije za naš proces in ga primerjali z nekaj klasičnimi in nekaj zelenimi pretvorbami stirena v benzojsko kislino. Rezultate smo ovrednotili in grafično prikazali na Adraosovih diagramih, ki so nam omogočili vpogled v ''zelenost'' posameznih reakcij.

• Language: Slovenian
• Keywords: zelena kemija, oksidacija, vodikov peroksid, oksidativna cepitev dvojne vezi, Hammettova korelacija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2024
• PID: 20.500.12556/RUL-155986
• COBISS.SI-ID: 194018563
• Publication date in RUL: 26.04.2024

Secondary language

• Language: English
• Title: Catalyzed oxidative cleavage of the double bond in styrene derivatives by hydrogen peroxide

Abstract

Green chemistry is a branch of chemistry that focuses on the development of processes with minimal impact on the environment and human health. It represents a part of sustainable development, delving into ways to make certain reactions more environmentally friendly. This is crucial as humanity increasingly grapples with environmental issues, with chemistry contributing to this challenge. In the field of green chemistry, 12 principles have been outlined, serving as guidelines for planning and developing chemical processes. Our focus was on the oxidative cleavage of double bonds between carbon atoms, particularly emphasizing this transformation in styrene, where the main product was benzoic acid. In the first part of the experimental work, we examined the influence of different solvents on the oxidative cleavage of the double bonds in styrene using a 30% aqueous solution of hydrogen peroxide catalyzed by vanadium(V) oxide. The target product was benzoic acid. We found that the best selectivity and conversion to benzoic acid could be achieved using acetonitrile as a solvent. In the second part of the experimental work, we compared the reactivity of differently substituted styrene derivatives. We measured the relative rate constants of substituted styrenes compared to styrene for the oxidative cleavage with hydrogen peroxide and vanadium(V) oxide. Based on that we constructed a Hammett correlation plot, providing information about the mechanism of the reaction. We observed a positive value for the reaction constant ρ, indicating that electron-attracting substituent groups increase the reaction rate or stabilize its transition state. The reaction constant value was low, suggesting that the charge in the transition state does not develop, hinting at a radical mechanism. To quantify the efficiency and "greenness" of the reaction, we calculated a green chemistry metric for our process and compared it with some conventional and green conversions of styrene to benzoic acid. We evaluated and graphically represented the results on Adraos diagrams, providing insight into the "greenness" of individual reactions.

• Keywords: green chemistry, oxidation, hydrogen peroxide, oxidative cleavage of double bonds, Hammett correlation