Thesis
K+ as a privileged facilitator of electron transfer reactions?
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2019
- Thesis identifier
- T15238
- Person Identifier (Local)
- 201569163
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The first part of these studies examines the role of KOtBu in electron transfer reactions when DMF is the solvent. Here, deprotonation of DMF leads to carbamoyl anion 1, which has been previously suggested to be an electron donor; in contrast, this thesis proposes the formation of the DMF dimer dianion 4 as the electron donor, based on experimental investigations.[1] Scheme 1. KOtBu-mediated DMF dimerisation and electron donor formation.[1] [Figure in thesis text] An extension of the capability for KOtBu to act as a powerful base is illustrated with deprotonation of aromatic and aliphatic aldehydes and formamides such as 5 and 7. This reaction type could be important for understanding the process which underpins formation of carbohydrates in the prebiotic era. Scheme 2. C-C bond formation promoted by strong bases. [Figure in thesis text] Long-standing controversial reports of electron transfer from KOtBu to benzophenone have been studied and resolved. These results now establish that a complex is formed between the two reagents, with the potassium ion providing the linkage. Photoactivation at room temperature by irradiation at defined wavelength (365 or 400 nm), or even by winter daylight, leads to the development of the blue colour of the potassium salt of benzophenone ketyl anion, whereas no reaction is observed when the reaction mixture is maintained in darkness or when NaOtBu is used.[2] Scheme 3. Photoreduction of benzophenone by KOtBu.[2] [Figure in thesis text] The second part of this study deploys KH in electron transfer reactions. Whilst in THF, KH promotes a concerted nucleophilic aromatic substitution, in benzene it promotes electron transfer reactions via organic electron donor formation. Here, again KH was found to have unique properties, different from NaH.[3] Scheme 4. Example of radical pathways triggered by KH in benzene as solvent. [3] [Figure in thesis text] The last part of this study reveals an unprecedented reactivity of K metal with benzene in presence of π-activators. Potassium cation is found to be more effective than sodium cation, promoting SET and reductive coupling of benzene leading to coupled product 11. The reaction in the absence of any cation source shows no reaction. Scheme 5. K metal determines homocoupling of benzene in presence of selected additives. [Figure in thesis text]
- Advisor / supervisor
- Murphy, John A., 1948-
- Resource Type
- Note
- This thesis was previously held under moratorium from 22 August 2019 until 22 August 2024.
- DOI
- Date Created
- 2018
- Former identifier
- 9912728484202996
Relations
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