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Production of alkyl lactate esters by the alkoxycarbonylation of vinyl acetate
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dc.contributor.advisor | Cole-Hamilton, D. J. (David John) | en |
dc.contributor.author | Rucklidge, Adam J | en |
dc.coverage.spatial | 231 p : ill., charts 30 cm. + 1 computer laser optical disc (4 3/4 in.) | en |
dc.date.accessioned | 2021-04-08T08:37:34Z | |
dc.date.available | 2021-04-08T08:37:34Z | |
dc.date.issued | 2005 | |
dc.identifier.uri | https://hdl.handle.net/10023/21797 | |
dc.description.abstract | The methoxycarbonylation of vinyl acetate to methyl 2 and 3- (acetoxy)methylpropanoate has been studied using a variety of bidentate phosphine ligands in the presence of a palladium precursor and acid. In some cases (Bu ᵗ₂P(CH₂)ₙPBuᵗ₂ and 1,2-bis(di-tert-butyIphosphinomethyl)benzene (DTBPMB) the ligands were already known, but new syntheses were established for a variety of other ligands, mostly with xylene backbones. The compounds of general formula 1,2- (RR'PCH₂)C₆H₄ were synthesised either from the reaction of o-xylene with a mixture of KOᵗBu and n-BuLi, followed by R₂PCl (R = ᵗBu, R = ⁱPr, R = Ph, R = Et) or by the reaction of LiPRR'(BH₃) with l,2-bis(dichloromethyl)benzene (R = ᵗBu R' = ⁱPr). LiPRR'(BH₃) was in turn prepared from the reaction of PRR'Cl with NaBH₄ to form PRR'H, and the subsequent reaction with n-BuLi. Similar reactions were used to prepare l,2-bis(di-tert-butylphosphinomethyl)naphthalene (borane protected route) and 2,3-bis(di-tert-butylphosphinomethyl)naphthalene (dianion route). The synthesis of unsymmetrical ligands such as ᵗBuₙPr₂₋ₙPCH₂C₆H₄PCH₂ᵗBu₂ (n = 0 or 1) proved much more problematic. Eventually, they were successfully prepared from the sequential reaction of the cyclic sulphates with Li PRⁱPr(BH₃) (R = ⁱPr or ᵗBu) and Li PᵗBu₂ (BH₃). During the methoxycarbonylation of vinyl acetate, the competing transesterification with methanol to give methyl acetate and dimethoxyethane via ethanal, usually drastically reduces the yield. The addition of tertiary phosphines such as PEt₃, but not DTBPMB, catalyses the degradation reaction, as does methanesulphonic acid. However, provided that the ligand is present in excess over the acid, so that all the acid is present as the phosphonium salt, the degradation reaction does not occur even at 80 °C. The phosphonium salt is sufficiently acidic to allow protonation of the palladium catalyst and DTBPMB promotes good activity for the methoxycarbonylation of vinyl acetate even under very mild conditions (1 bar CO, 25 °C). Optimisation studies have allowed the branched:dinear (b:l) to be improved from 1.2 at 30 bar and 80 °C to 3.6:1 at 1 bar and 25 °C. l,2-bis(di-tert-butylphosphinomethyl)naphthalene and 2,3-bis(di-tert-butylphosphinomethyl)naphthalene both give very similar results, but the other ligands are all inferior. The relative importance of steric and electronic effects on the reaction selectivity are discussed. | en |
dc.language.iso | en | en |
dc.publisher | University of St Andrews | en |
dc.subject.lcc | QD305.A2R8 | |
dc.subject.lcsh | Esters | en |
dc.subject.lcsh | Lactates | en |
dc.subject.lcsh | Lactic acid | en |
dc.subject.lcsh | Carbonyl compounds | en |
dc.subject.lcsh | Vinyl acetate | en |
dc.title | Production of alkyl lactate esters by the alkoxycarbonylation of vinyl acetate | en |
dc.type | Thesis | en |
dc.type.qualificationlevel | Doctoral | en |
dc.type.qualificationname | PhD Doctor of Philosopy | en |
dc.publisher.institution | The University of St Andrews | en |
dc.contributor.institution | Chemistry Theses | en |
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