University of Leicester
Browse

The reactivities of some carbon-metal bonds.

Download (318.06 MB)
thesis
posted on 2015-11-19, 08:48 authored by David Ralph Miles. Walton
The chemistry of acetylenic compounds containing Group IVB metals is reviewed. The rates of acid-catalysed cleavage of the aryl--silicon bond in the 4-halogeno-2-trimethylsilylanisoles have been measured and found to agree with values predicted on the assumption that the effects of meta--halogen and ortho-methoxy substituents are additive. The order of inductive electron-release to a saturated carbon atom by trimethyl-silyl, -germyl, and -stannyl groups has been determined by rate measurements of the acid-catalysed cleavage of the aryl-tin bond in the compounds p-Me3MCH2C6H4SnMe3 (M = Si, Ge, Sn). In the light of the order obtained: Me3Sn > Me3Ge > Me3Si, comments are offered on the electronegativity order of the Group IVB elements and on the mechanisms proposed for the cleavage of aryl-metal (Group IVB) bonds by electrophilic reagents. A study has been made of the cleavage of aryl-ethynyltriethylgermanes and of the hydration of aryl-acetylenes; both reactions being catalysed by acid. The effects of nuclear substituents are analysed in terms of the Yukawa-Tsuno extended free-energy relationship, and are in accord with rate-determining protonations at the acetylenic carbon, B to the aryl group. The cleavage by acids of the ethynyl-germanium bond is pictured as a true electrophilic substitution at an acetylenic carbon, and a simple mechanism is proposed for this reaction. In view of the low reactivity of ortho relative to para substituents, field effects are thought to make an important contribution to the overall effects of para substituents. The preparation and physical properties of thirty-two new organometallic compounds are described.

History

Date of award

1963-01-01

Author affiliation

Chemistry

Awarding institution

University of Leicester

Qualification level

  • Doctoral

Qualification name

  • PhD

Language

en

Usage metrics

    University of Leicester Theses

    Categories

    No categories selected

    Keywords

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC