S1P n.m.r. spectroscopy was used to investigate the mechanism and kinetics of hydrolysis of zinc (II) O,O'-dialkyl dithiophosphates (ZDTP's) in aqueous 1,2-dimethyoxyethane solution at 85°C. All the major intermediates and products were identified and the relative reaction rates of the key steps in the hydrolysis determined. Diethyl ZDTP was found to be hydrolysed (k= 2.35 x 10~4 s"1) to phosphoric acid via O,O'-diethyl dithiophosphoric acid 9ktyj = 1.35 x 10~2 s"1) and thiophosphoric acid (kfcyj = 0.78 x 10~6 s"1); O-ethyl dithiophosphoric acid and dithiophosphoric acid were found to be intermediates; O-elhyl, O,O'-diethyl thiophosphoric and O-ethyl phosphoric acids were produced as by-products of the reaction. From a study of the order of appearance of the intermediates and products, a detailed mechanism for the hydrolysis of ZDTP's has been proposed. The relationship between the 'normal' salt of a ZDTP and its 'basic' form was also studied and the isopropyl derivative was found to dissociate in a variety of organic solvents (including xylene, toluene, diethyl ether, chloroform, 1,2-dimethoxy ethane, acetone, dimethyl formamide and dimethyl sulphoxide) via a facile equilibrium into its 'normal' salt and zinc (II) oxide. The dissociation was promoted by increasing temperature and solvent polarity and by increasing the water content in aqueous 1,2-dimethoxy-ethane. This equilibrium in favour of the 'normal' salt and zinc (II) oxide was also acid-catalysed. Zinc (II) oxide arising from the dissociation of the 'basic' form was found to inhibit the hydrolysis of 'normal' zinc (II) O,O'-diisopropyl dithiophosphate by reaction with its primary hydrolysis product, O,O'-diisopropyl dithiophosphoric acid. Eventual hydrolysis occurred after all the zinc (II) oxide was consumed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662718 |
| Date | January 1990 |
| Creators | Tan, Paul S. G. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14518 |
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