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A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy
A newly developed ultraviolet photoelectron spectrometer apparatus that utilizes a tunable 50 W CW CO 2 laser as a directed heat source is used to study the vacuum pyrolysis of 4-diazoisothiochroman-3-one ( 1 a). Analysis of the pyrolysate with ultraviolet photoelectron spectroscopy shows that 1 a u...
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Published in: | Canadian journal of chemistry 1996-12, Vol.74 (12), p.2536-2539 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | A newly developed ultraviolet photoelectron spectrometer apparatus that utilizes a tunable 50 W CW CO
2
laser as a directed heat source is used to study the vacuum pyrolysis of 4-diazoisothiochroman-3-one (
1
a). Analysis of the pyrolysate with ultraviolet photoelectron spectroscopy shows that
1
a undergoes a facile pyrolysis at a laser power level of less than 26 W, yielding two new compounds: thiaketene
3
a, the product of a Wolff rearrangement, and benzocyclobutenthione (
6
a), which can be derived from thiacarbene
4
a, the decarbonylation product of
3
a. Activation enthalpies/energies calculated at the AM1 and ab initio levels of theory indicate that, unlike the case of 4-diazoisochroman-3-one (
1
b), the Wolff rearrangement of the incipient carbene may be concerted with loss of nitrogen from
1
a. The activation enthalpy/energy calculated for the decarbonylation of
3
a is significantly higher (AM1, 20.5 kcal/mol; RHF/6-31G(d), 11.7 kcal/mol; MP2(full)//RHF/6-31G(d), 14.3 kcal/mol) than the activation enthalpy/energy for the decarbonylation of
3
b. This result is in keeping with the fact that we detect
3
a, but
3
b is not found in detectable amounts in the pyrolysate of
1
b. Key words: vacuum pyrolysis, 4-diazoisothiochroman-3-one, HeI ultraviolet photoelectron spectroscopy, AM1 and ab initio calculations. |
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ISSN: | 0008-4042 1480-3291 |
DOI: | 10.1139/v96-285 |