Journal article
The gas phase Smiles rearrangement of anions PhO(CH2)nO− (n = 2–4). A joint theoretical and experimental approach
Organic & Biomolecular Chemistry, Vol.8(18), pp.4080-4084
2010
Abstract
A combination of experimental data [using 18O labelling fragmentation data together with metastable ion studies in a reverse sector mass spectrometer (from a previous study)] and ab initio reaction coordinate studies at the CCSD(T)/6-31++G(d,p)//B3LYP/6-31++G(d,p) level of theory, have provided the following data concerning the formation of PhO- in the gas-phase from energized systems PhO(CH2)nO- (n = 2-4). All ΔG values were calculated at 298 K. (1) PhO(CH2)2O- effects an ipso Smiles rearrangement (ΔGr = +35 kJ mol-1; barrier to transition state ΔG# = +40 kJ mol-1) equilibrating the two oxygen atoms. The Smiles intermediate reverts to PhO(CH2)2O- which then undergoes an SNi reaction to form PhO- and ethylene oxide (ΔGr = -24 kJ mol-1; ΔG# = +54 kJ mol-1). (2) The formation of PhO- from energized PhO(CH2)3O- is more complex. Some 85% of the PhO- formed originates via a Smiles intermediate (ΔGr = +52 kJ mol-1; ΔG# = +61 kJ mol-1). This species reconverts to PhO(CH2)3O- which then fragments to PhO- by two competing processes, namely, (a) an SNi process yielding PhO- and trimethylene oxide (ΔGr = -27 kJ mol-1; ΔG# = +69 kJ mol-1), and (b) a dissociation process giving PhO-, ethylene and formaldehyde (ΔGr = -65 kJ mol-1; ΔG# = +69 kJ mol-1). The other fifteen percent of PhO- is formed prior to formation of the Smiles intermediate, occurring directly by the SNi and dissociation processes outlined above. The operation of two fragmentation pathways is supported by the presence of a composite metastable ion peak. (3) Energized PhO(CH2)4O- fragments exclusively by an SNi process to form PhO- and tetrahydrofuran (ΔGr = -101 kJ mol-1; ΔG# = +53 kJ mol-1). The Smiles ipso cyclization (ΔGr = +64 kJ mol-1; ΔG# = +74 kJ mol-1) is not detected in this system.
Details
- Title
- The gas phase Smiles rearrangement of anions PhO(CH2)nO− (n = 2–4). A joint theoretical and experimental approach
- Authors
- Tianfang Wang (Author) - University of AdelaideN M M Nibbering (Author) - Vrije Universiteit, NetherlandsJ H Bowie (Author) - University of Adelaide
- Publication details
- Organic & Biomolecular Chemistry, Vol.8(18), pp.4080-4084
- Publisher
- Royal Society of Chemistry (R S C) Publications
- Date published
- 2010
- DOI
- 10.1039/C0OB00064G
- ISSN
- 1477-0520
- Organisation Unit
- School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering; Centre for Bioinnovation
- Language
- English
- Record Identifier
- 99450143402621
- Output Type
- Journal article
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