Matrix isolation infra-red and mass spectrometric studies of some arsenic and selenium oxides
Matrix isolation infra-red and mass spectrometric studies of some arsenic and selenium oxides
This thesis describes work carried out in an attempt to identify and characterise the vapour phase species generated on heating a number of arsenic and selenium oxo-compounds.
A brief survey of the physical techniques available for the study of vapour phase species is given. Particular emphasis is placed on the combination of mass spectrometry and infra-red spectroscopy. Details of the apparatus used in these studies are given and an account of the theory necessary to analyse infra-red spectra is provided.
The remaining chapters deal with individual areas of study, of which the principal results are as follows.
Spectra obtained from the vaporisation of alkali-metal selenates and selen-ites are consistent with the existence of discrete species M2Se04, M2SeO3 and MSeO2. The selenium isotope patterns observed in high resolution studies may be explained by assuming that these species adopt D2(j, C, and C2w structures respectively. The relative proportions of selenate and selenite appears to be determined by the alkali-metal involved and a possible explanation for this is discussed.
The vapour above heated selenium trioxide was studied in an attempt to identify monomeric selenium trioxide. Under normal conditions tetrameric selenium trioxide was the principal constituent, although monomeric SeO3 does appear to account for 2-3% of the vapour composition. However a dramatic increase in the relative proportion of monomeric selenium trioxide may be obtained in the vapour phase by heating mixtures of selenic acid and phosphorus pentoxide. Two of the three infra-red active fundamentals of monomeric SeC>3 are assigned and the molecule is shown to be planar.
A study of heated arsenic pentoxide yields results which agree with the previous findings, in that a mixture of oxides As4On (n = 6-10) exist in the vapour phase. For the first time, vibrational data for the As^Oe cage modes of the species As4Om (m = 7-9) are obtained and assigned. An attempt to identify similar species in the antimony-oxygen system proved unsuccessful.
Similar mass spectrometric and matrix isolation experiments in which the vapour above solid arsenic trioxide is super- heated yields a new species, which may be identified as, molecular AS4O5, whilst vaporisation of a
mixture of arsenic trioxide and tantalum powder produces a further new species, molecular AS2O3. Studies carried out on oxygen-18 enriched samples suggest that this latter species adopts a C2v 'V shaped structure when isolated in low temperature matrices.
University of Southampton
1988
Brisdon, Alan Keith
(1988)
Matrix isolation infra-red and mass spectrometric studies of some arsenic and selenium oxides.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis describes work carried out in an attempt to identify and characterise the vapour phase species generated on heating a number of arsenic and selenium oxo-compounds.
A brief survey of the physical techniques available for the study of vapour phase species is given. Particular emphasis is placed on the combination of mass spectrometry and infra-red spectroscopy. Details of the apparatus used in these studies are given and an account of the theory necessary to analyse infra-red spectra is provided.
The remaining chapters deal with individual areas of study, of which the principal results are as follows.
Spectra obtained from the vaporisation of alkali-metal selenates and selen-ites are consistent with the existence of discrete species M2Se04, M2SeO3 and MSeO2. The selenium isotope patterns observed in high resolution studies may be explained by assuming that these species adopt D2(j, C, and C2w structures respectively. The relative proportions of selenate and selenite appears to be determined by the alkali-metal involved and a possible explanation for this is discussed.
The vapour above heated selenium trioxide was studied in an attempt to identify monomeric selenium trioxide. Under normal conditions tetrameric selenium trioxide was the principal constituent, although monomeric SeO3 does appear to account for 2-3% of the vapour composition. However a dramatic increase in the relative proportion of monomeric selenium trioxide may be obtained in the vapour phase by heating mixtures of selenic acid and phosphorus pentoxide. Two of the three infra-red active fundamentals of monomeric SeC>3 are assigned and the molecule is shown to be planar.
A study of heated arsenic pentoxide yields results which agree with the previous findings, in that a mixture of oxides As4On (n = 6-10) exist in the vapour phase. For the first time, vibrational data for the As^Oe cage modes of the species As4Om (m = 7-9) are obtained and assigned. An attempt to identify similar species in the antimony-oxygen system proved unsuccessful.
Similar mass spectrometric and matrix isolation experiments in which the vapour above solid arsenic trioxide is super- heated yields a new species, which may be identified as, molecular AS4O5, whilst vaporisation of a
mixture of arsenic trioxide and tantalum powder produces a further new species, molecular AS2O3. Studies carried out on oxygen-18 enriched samples suggest that this latter species adopts a C2v 'V shaped structure when isolated in low temperature matrices.
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Published date: 1988
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Local EPrints ID: 460938
URI: http://eprints.soton.ac.uk/id/eprint/460938
PURE UUID: c82a0340-ead2-4af7-b6c8-5680aaeb813d
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Date deposited: 04 Jul 2022 18:32
Last modified: 04 Jul 2022 18:32
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Author:
Alan Keith Brisdon
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