Related Experiment Video
Updated: Jun 1, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
Are uncatalyzed bromate oscillators truly gas-free?
Erik Szabo1, Lubica Adamčíková, Peter Ševčík
1Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, 842 15 Bratislava, Slovakia.
Abstract:
Gas evolution is a common byproduct of chemical oscillations but is seldom treated as anything but a complication. Its precise quantification is usually underestimated, and if not obvious enough, gaseous products are easily neglected completely. Reported herein is how evolution of gas from uncatalyzed bromate oscillators with pyrocatechol, pyrogallol, and 1,4-cyclohexanedione was measured by a high-precision batch-mode gasometric method, and the data obtained with unprecedented time resolution are presented. Even though within this completely closed arrangement of measurement no oscillations in rate of gas evolution were observed, it is verified that neither of the substrates can be considered totally free of gas production. Nevertheless, the amount of gas evolved from 1,4-cyclohexanedione was confirmed to be very small, and near negligible, if only oscillatory phase is of interest. Conversely, under identical conditions, the peak rates of gas evolution from the other substrates were reached much sooner, and even though the results in all three cases suggest some extent of suppression of gas production by oscillations, as much as 1 equiv of gas in total can be produced from the phenols, especially from pyrogallol, where the degradation was measured to be approximately twice as extensive. Greater caution is, therefore, recommended whenever the gas-free nature of these oscillators is considered.
Related Concept Videos
Regioselectivity of Electrophilic Additions-Peroxide Effect
Rate-Determining Steps
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...
Radical Halogenation: Thermodynamics
Halogenation of Alkenes
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Catalysis
Catalysis

