Abstract
Kinetic studies are a suitable tool to disclose the role of tiny reagent fractions. The title compound 2 reacted in a kinetic reaction order of 0.5 (square root of its concentration) with an excess of the electrophiles ClSiMe3, 1-bromobutane (n-BuBr), or 1-iodobutane (n-BuI) at 32 degrees C in Et2O or in hydrocarbon solvents. This revealed that the tiny (NMR-invisible) amount of a deaggregated equilibrium component (presumably monomeric 2) was the reactive species, whereas the disolvated dimer 2 was only indirectly involved as a supply depot. Selectivity data (relative rate constants ?obs) were collected from competition experiments with the faster reactions of 2 in THF and the addition reactions of 2 to carbonyl compounds. This provided the rate sequences of Et2C=O > dicyclopropyl ketone > t-Bu-C(=O)-Ph > diisopropyl ketone >> t-Bu2C=O > ClSiMe3 > n-BuI > n-BuBr approximate to (bromomethyl)cyclopropane (but t-Bu2C=O < ClSiMe3 in THF only) and also of cyclopropanecarbaldehyde > acetone >= t-BuCH=O. It is suggested that a deceivingly depressed selectivity (1 < kappa(obs) < k(A)/k(B)), caused by inefficient microscopic mixing of a reagent X with two competing substrates A and B, may become evident toward zero deviation from the correlation line of the usual inverse (1/T) linear temperature dependence of ln ?obs.
Dokumententyp: | Zeitschriftenartikel |
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Fakultät: | Chemie und Pharmazie > Department Chemie |
Themengebiete: | 500 Naturwissenschaften und Mathematik > 540 Chemie |
ISSN: | 0022-3263 |
Sprache: | Englisch |
Dokumenten ID: | 54360 |
Datum der Veröffentlichung auf Open Access LMU: | 14. Jun. 2018, 09:56 |
Letzte Änderungen: | 04. Nov. 2020, 13:34 |