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https://hdl.handle.net/2440/62187
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Type: | Journal article |
Title: | The gas phase Smiles rearrangement of anions PhO(CH₂)nO⁻ (n = 2-4): A joint theoretical and experimental approach |
Other Titles: | The gas phase Smiles rearrangement of anions PhO(CH(2))nO(-) (n = 2-4): A joint theoretical and experimental approach |
Author: | Wang, T. Nibbering, N. Bowie, J. |
Citation: | Organic and Biomolecular Chemistry, 2010; 8(18):4080-4084 |
Publisher: | Royal Soc Chemistry |
Issue Date: | 2010 |
ISSN: | 1477-0520 1477-0539 |
Statement of Responsibility: | Tianfang Wang, Nico M. M. Nibbering and John H. Bowie |
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. |
Rights: | This journal is © The Royal Society of Chemistry |
DOI: | 10.1039/c0ob00064g |
Grant ID: | ARC |
Published version: | http://dx.doi.org/10.1039/c0ob00064g |
Appears in Collections: | Aurora harvest Chemistry publications |
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