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New reactions relating to Lewis acidic properties of borate esters

    Student thesis: Doctor of Philosophy

    Abstract

    The thesis reports the Lewis acidic properties and new reactions of borate esters
    and some related chemistry. In particular an investigation of the reaction between (CH3O)3B3O3 and Si(OCH2CH3)4. Products were identified as borosilicate glasses by IR, 1H, 11B, 13C and 29Si NMR, 11B and 29Si MAS NMR, elemental analysis and powder XRD, and a possible reaction mechanism is described. Under similar conditions crystalline metal dioxides of titanium and zirconium were obtained from the metal tetra alkoxides.
    The synthesis of 8 orthoborate, B(OR)3 {R = CH2CH2Cl, CH2CH2CH2Cl,
    CH2CH2CH2CH2Cl, CH2CHCl2, CH2CCl3, CH2CH2Br, CH2CH2I, CH2CF3} and 6
    metaborate, (RO)3B3O3 {R = ClCH2CH2, ClCH2CH2CH2, ClCH2CH2CH2CH2,
    Cl2CHCH2, Cl3CH2 and CF3CH2} esters are reported. The Lewis acidities were
    determined by Gutmann's Acceptor Number method and a correlation with Taft's
    substituent parameter was obtained. The orthoborate, B(OCH2CF3)3, and the metaborate, (ClCH2CH2CH2CH2O)B3O3, were shown to initiate for epoxide polymerisation of PGE and PY306. The Lewis acidity of tris(pentafluorophenyl)boroxine was also determined and its 1: 1 adducts with TEPO and 4-picoline were prepared. The effectiveness of
    tris(pentafluorophenyl)boroxine and metaboric acid as Oppenauer oxidation catalysts has also been discussed.
    A series of 9 previously unreported cyclo-boratetrasiloxanes, Me6Si3O4BR {R =
    2-CH3C6H4, 3-CH3C6H4, 4-CH3C6H4, 3-CH3OC6H4 , 4-CH3QC6H4, 2-BrC6H4, 3-BrC6H4 , 4-BrC6H4 and CH3CH2CH2CH2} were prepared and the Lewis acidities of selected examples has been determined by Gutmann's Acceptor Number method.
    The reaction between mono- and diisocyanates with metaborate esters leading to boroxine carbonate esters is described. The nature of the polymers and gels formed has been investigated. The products were hydrolytically unstable and hydrolysis products were characterised as the corresponding carbamates and B(OH)3.
    Date of AwardAug 2002
    Original languageEnglish
    Awarding Institution
    • University of Wales, Bangor
    SponsorsPILKINGTON GROUP LTD & EPSRC
    SupervisorMichael A Beckett (Supervisor)

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