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Title: | Density functional theory studies on the generation of trimethylenemethanes from the ring opening of dialkoxymethylenecyclopropanes and methylenecyclopropanethioacetals and follow-up reactions |
Authors: | Bekoe, Samuel Osei, Manasseh Kusi Tia, Richard Adei, Evans |
Keywords: | Trimethylenemethane Dialkoxymethylenecyclopropane Ring-opening reactions Mechanism Density functional theory Singlet–triplet energy gap |
Issue Date: | 21-Dec-2017 |
Publisher: | Springer-Verlag GmbH Germany |
Abstract: | This work reports a detailed DFT study on the generation of trimethylenemethanes (TMMs) from the ring opening of
dialkoxymethylenecyclopropane (DMCP), methylenecyclopropanethioacetal (MCPT), and substituted derivatives of DMCP
and MCPT, as well as follow-up reactions of the TMMs. The singlet DMCP and MCPT were found to be 51.32 and 53.77 kcal
mol−1 more stable than the triplet DMCP and MCPT respectively, corresponding to triplet:singlet population ratios of 1:1038 and
1:1040, respectively, at 25 °C using Boltzmann distribution, implying that the proportion of the triplet species is negligible at
25 °C. The ring-opening reactions occur through singlet transition states with barriers of 40.68 and 42.27 kcal mol−1 for DMCP
and MCPT, respectively, and yield TMMs that are very unstable compared to the precursors, with the triplet TMM being far more
stable than the singlet. Whereas the singlet TMMs readily undergo cycloaddition reactions with olefins to form five-membered
carbocyclic rings, the triplet species do not. The selectivity of the reactions of the DMCP TMMs is very sensitive to temperature;
at 25°C, cycloaddition with olefins and ring-closure to form ketenes have very comparable barriers while temperatures above
150 °C favor the exclusive formation of a ketene followed by dimerization. In MCPT, ring closure to form ketenes is the favored
reaction at all temperatures studied. |
Description: | An article published by Springer-Verlag GmbH Germany and also available at
https://doi.org/10.1007/s00894-017-3558-7 |
URI: | http://hdl.handle.net/123456789/12931 |
Appears in Collections: | College of Health Sciences
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