No abstract

To understand the reaction network responsible for the observed oscillations in pH and heat of reaction in the PdI2-catalyzed carbonylation of phenylacetylene, the reaction was reduced to a number of subsystems to be studied separately. This study focuses on the subsystem that converts substrate to products. Experiments followed the pH, reactant consumption, and product formation. Results uncovered the influence of trace water on product distribution while the reactant addition sequence affected phenylacetylene conversion. Modeling the experimental observations enabled the proposal of a reaction network for this subsystem and the proposal of a prospective theory behind the oscillatory behavior. The results from this study are significant for the optimization of industrial carbonylation processes.

Reaction temperature plays a major role in product selectivity in the oscillatory mode of the palladium‐catalyzed phenylacetylene oxidative carbonylation reaction. At 40 °C, dimethyl (2Z)‐2‐phenyl‐2‐butenedioate is the major product whereas at 0 °C the major product is 5,5‐dimethoxy‐3‐phenyl‐2(5H)‐furanone. The occurrence of oscillations in pH coincides with an increase in the rate of phenylacetylene consumption and associated product formation. Experiments were performed isothermally in a reaction calorimeter to correlate reactant consumption and product formation with the occurrence of pH oscillations and the heat released by the reaction. An increase in the size of the pH drop in a single oscillation correlates with an increase in energy, indicating that this section of a single oscillation relates to reactant consumption. Based on these observations, a reaction pathway responsible for product formation is provided.

The direct synthesis of amides from the corresponding carboxylic acids and amines is shown to operate under varying degrees of mixed kinetic and mass transfer rate control when water is removed by azeotropic distillation. Unless the volumetric heat input rate is reported, it is not possible to make a valid comparison between different catalysts, as the difference in Q boil alone can be responsible for the apparent difference in observed rate. A systematic approach is developed to quantify the contribution of boil-up rate to conversion rate and so decouple the physical rates from the chemistry. Intensive boiling is used to improve the removal of water during azeotropic distillation and considerably enhance conversion. The results show that some acylations previously thought to be difficult or impossible can be achieved in the absence of coupling agents under green conditions. The use of a cascade of CSTR flow reactors operating under intensified conditions is assessed for scale up of direct amidation reactions and compared to a production scale batch reactor. The findings and conclusions of this work have general applicability to all condensation reactions.

SzcifimaryThe isomerisation of some diazo-acetamides into diazirinyl-aniides has been effected with visible light. DURING our investigations of the photochemistry of 01diazo-amides,l a study of the effect of wavelength revealed that irradiation of diazo-acetamides with visible light gave the isomeric diazirinyl-amides in about ZOO;, isolated yield.For example, N-diazoacetylpiperidine (1 ; R1 = C,H,,S, R2 = H), prepared from N-glycylpiperidine by treatment with nitrous acid, gave on irradiation with visible light for