- Title
- The synthesis, empirical and theoretical studies of various (N→B) diarylborinate esters
- Creator
- Manana, Pholani Sakhile
- Subject
- Port Elizabeth (South Africa)
- Subject
- Eastern Cape (South Africa)
- Subject
- South Africa
- Date Issued
- 2021-12
- Date
- 2021-12
- Type
- Doctoral theses
- Type
- text
- Identifier
- http://hdl.handle.net/10948/53869
- Identifier
- vital:46027
- Description
- A series of core-functionalized borinic acids was synthesized from Grignard reagents and tributylborate and reacted with ethanolamine, amino acids, 2-pyridylmethanol as well as 2-(ethyl amino ethanol). Among the borinic acids synthesized were the ones bearing: para-(2, 15, 16, 22, 27)-methyl, (3, 20, 25)-chloro, (4, 23, 26)-fluoro, (5)-methoxy; meta-(7, 17)-methyl, (9)-fluoro; ortho-(6)-methyl, (8)-chloro, (10, 18, 19)-methoxy substituents on their respective aromatic systems. All compounds obtained by condensation of the borinic acids with the aforementioned nitrogen-containing substrates were characterized structurally by means of diffraction studies based on single crystals and found to constitute chelate esters/amides featuring covalent B-O and dative N→B bonds. The chelate compounds researched in this study could be classified into four families and represent the compounds: ethanol amine: (1) 2,2-diphenyl-1,3,2-oxazaborolidines, (2) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (3) 2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (4) 2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (5) 2,2-bis(p-methoxyphenyl)-1,3,2-oxazaborolidines, (6) 2,2-bis(o-tolyl)-1,3,2-oxazaborolidines, (7) 2,2-bis(m-tolyl)-1,3,2-oxazaborolidines, (8) 2,2-bis(o-chlorophenyl)-1,3,2-oxazaborolidines, (9) 2,2-bis(m-fluorophenyl)-1,3,2-oxazaborolidines, (10) 2,2-bis(o-methoxyphenyl)-1,3,2-oxazaborolidines. α-amino acids : (14) 4-methyl-2,2-diphenyl-1,3,2-oxazaborolidin-5-ones, (15) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (16) 4-methyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (17) 4-isopropyl-2,2-bis(m-tolyl)-1,3,2-oxazaborolidin-5-ones, (18) 4-methyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (19) 4-acetamidyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (20) 4-phenylethane-2,2-bis(p-chlorophenyl)-1,3,2 oxazaborolidin-5-ones. 2-pyridylmethanol: (21) 1,3-hydroxypyridyl-2,2-diphenyl 1,3,2-oxazaborolidines, (22) 1,3-hydroxypyridyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (23) 1,3-hydroxypyridyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines 2-(ethyl amino ethanol): (24) 3-ethyl-2,2-diphenyl-1,3,2-oxazaborolidines, (25) 3-ethyl-2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (26) 3-ethyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (27) 3-ethyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines. Apart from structural studies in the solid state, the compounds were also characterized by means of multinuclear NMR spectroscopy (1H, 11B, 13C) as well as UV/vis and FTIR. The typical 11B resonances were found in the range of (4-10 ppm). A series of characteristic metrical parameters for the compounds in the solid state as well as typical NMR shifts for the chelate target molecules was established that allowed for the determination of the coordination induced shift. The carbon atom bonded to the oxygen atom shifted upfield, while the carbon atom bonded to the nitrogen atom shifted downfield. Factors mentioned in the literature that has an influence on the hydrolytic stability on the heterocyclic borinate motif have been taken into consideration and verified for the systems researched in this study. The substitution at the nitrogen atom with one ethyl group caused the greatest increases in the N→B bond length (27) 1.714 Å, due to the increase in the nitrogen Lewis basicity, making it the least hydrolytically stable, these include compounds (24-26). Furthermore, DFT calculations were performed by employing Becke’s three parameter hybrid exchange functional with Lee–Yang–Parr functional (B3LYP) method using the Gaussian 16 program package (Rev. B01) employing the basis set 6-311++G(d,p), to corroborate and correlate the experimental findings, which gave a general R-squared value of 0.9978 for calculated vs experimental 13C chemical shifts. Thermal properties are recorded for select compounds, indicating the ΔH and the melting points.
- Description
- Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (289 pages)
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
- Rights
- All Rights Reserved
- Rights
- Open Access
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Manana, P.pdf | 12 MB | Adobe Acrobat PDF | View Details Download |