The mechanism of the thermal decarbonylation of 2,2-dimethyl-3-butenal

Abstract

. Can. J. Chem. 55,3951 (1977).The thermal decarbonylation of 2,2-dimethyl-3-butenal is shown to be an intramolecular extrusion of carbon monoxide concerted with the transfer of hydrogen (deuterium) to the y-position. The reaction displays a kinetic isotope effect of 2.8 (at 296.9"C) and follows first order kinetics (E, = 44.2 L-0.2 kcal mol-l, log A = 13.4 k 0.3).ROBERT J. CRAWFORD, STUART LUTENER et HIROKAZU TOKUNAGA. Can. J. Chem. 55,3951 (1977).On dkmontre que la dkcarbonylation thermique du dimkthyl-2,2 buttne-3 a1 est une extrusion intramoltculaire de monoxyde de carbone concertke avec un transfert d'hydrogkne (deutkrium) vers la position y. La rtaction prtsente un effet isotopique cinttique de 2.8 (a 296.9"C) et suit une cinktique du premier ordre (E, = 44.2 + 0.2 kcal mol-', log A = 13.4 + 0.3).[Traduit par le journal] IntroductionRecently we examined the thermolysis of 2-vinyloxirane (1) and concluded that one of the initial products was 3-butenal which, depending upon the surface of the vessel, was tautomerized to E-or 2-2-butenal or produced propylene and carbon monoxide. Traces of oxygen brought about a catalytic reaction and large amounts of CO and propylene were produced, but even after the most careful conditioning propylene and CO were present. We suggested that the decarbonylation of 3-butenal was both radical catalyzed and under oxygen free conditions proceeding via an intramolecular mechanism. To study this more thoroughly we have examined the thermolysis of the non-enolizable 2,2-dimethyl-3-butenal (1). There are few instances of decarbonylation of P,y-unsaturated aldehydes. The most thoroughly studied is the work of Schaffner (2) where the singlet photosensitized decarbonylation of R-(+)-laurolenal (2) to S-(-)-1,2,3-trimethylcyclopentene (3) is observed.

Product Class 7: Imines

“…[115] On the other hand, the N-tert-butylimine of crotonaldehyde can be synthesized in 74% yield from crotonaldehyde and tert-butylamine in benzene using a Dean-Stark trap. [116] The synthesis of the unstable N-cyclohexyl-N-ethylideneamine can be done by simply mixing acetaldehyde and cyclohexylamine, and by drying this mixture consecutively with anhydrous sodium sulfate and magnesium sulfate. [117] Aromatic diimines, e.g.…”

Kinetic Determination of the Gas-Phase Decarbonylation of Butyraldehyde in the Presence of HCl Catalyst

“…The homogeneous, unimolecular gas‐phase elimination kinetics of α,β‐unsaturated aldehydes have been described to undergo decarbonylation through a three‐membered cyclic transition state as depicted in reaction (1) , whereas a single reported β,γ‐unsaturated aldehydes, 2,2‐dimethyl‐3‐butenal , was found to produce 2‐methyl‐2‐butene and carbon monoxide through a three‐membered cyclic transition state type of mechanism.…”

Gas-phase elimination kinetics of selected aliphatic α,β-unsaturated aldehydes catalyzed by hydrogen chloride

“…Publications on the gas‐phase elimination of simple aliphatic and aromatic aldehydes revealed complex processes of free radical type of reactions . Yet, few unsaturated aldehydes are found to proceed via molecular in nature . Only one β,γ‐unsaturated aldehyde, i.e.…”

“…Only one β,γ‐unsaturated aldehyde, i.e. 2,2‐dimethyl‐3‐butenal, was examined in the gas phase producing 2‐methyl‐2‐butene and carbon monoxide . This elimination reaction was found to be unimolecular and obeying a first‐order rate law.…”