The gas-phase reaction of acetic acid with hydrogen bromide. The effect of isobutene

1971 ◽  
Vol 24 (4) ◽  
pp. 765 ◽  
Author(s):  
NJ Daly ◽  
MF Gilligan
Keyword(s):  
Acetic Acid ◽  
Gas Phase ◽  
Initial Rate ◽  
Hydrogen Bromide ◽  
Pressure Change ◽  
Mesityl Oxide ◽  
Phase Reaction ◽  
Thermal Reactions ◽  
Pressure Time ◽  
Molecular Reaction

Addition of isobutene to reaction mixtures of acetic acid and hydrogen bromide brings about a lowering in the initial rate of pressure change. The lowering is proportional to the pressure of isobutene and is explained in terms of a molecular reaction producing mesityl oxide. Mesityl oxide is formed steadily throughout the course of the reaction in quantities proportional to the pressure of isobutene. The quantities of mesityl oxide detected are less than those required to account quantitatively for the lowering of dp/dt, but the presence of the products of the thermal reactions of mesityl oxide, and the minima observed in the pressure-time curves at 407� show that the discrepancies can be accounted for in terms of the polymerization undergone by mesityl oxide in the presence of hydrogen bromide. The reaction appears analogous to the formation of mesityl oxide by the acetylation of isobutene in solution.

The gas-phase reaction of methyl acetate and hydrogen bromide

1971 ◽  
Vol 24 (9) ◽  
pp. 1823
Author(s):  
NJ Daly ◽  
MF Gilligan
Keyword(s):  
Acetic Acid ◽  
Gas Phase ◽  
Kinetic Data ◽  
Methyl Acetate ◽  
Hydrogen Bromide ◽  
Mesityl Oxide ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
First Order ◽  
Order Form

In the gas phase methyl acetate reacts with hydrogen bromide over the range 419-497� to give methyl bromide, carbon monoxide, and methanol. Rate constants first order in both ester and hydrogen bromide are calculated from initial slopes, and are described by the equation �������������������� k2 = 1012.29exp(-32312/RT) ml mol-1 s-1 Kinetic data depart from this second-order form at early stages of the reaction. The addition of methanol can reduce the value of k2 to zero. A mechanism involving the reversible step : ������������������������ CH3COOCH3+HBr ↔ CH3OH+A* is proposed. The intermediate reacts with isobutene to form mesityl oxide, and is considered identical with that formed in the reaction of acetic acid with hydrogen bromide.

The gas-phase reaction of acetic acid with hydrogen bromide

1969 ◽  
Vol 22 (4) ◽  
pp. 713 ◽  
Author(s):  
NJ Daly ◽  
MF Gilligan
Keyword(s):  
Carbon Monoxide ◽  
Acetic Acid ◽  
Gas Phase ◽  
Rate Constant ◽  
Methyl Bromide ◽  
Hydrogen Bromide ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
First Order ◽  
The Family

In the gas phase, acetic acid reacts with hydrogen bromide in the temperature range 412-492� to give methyl bromide, carbon monoxide, and water. The reaction is first order in each reagent, and the variation of rate constant with temperature is described by the equation �� ����������������� k2 = 1011.67exp(-30400/RT) ml mole-1 sec-1 Possible transition states for the reaction are examined. A mechanism involving an intermediate of the type CH3CO+Br- is possible if the reaction is of the family represented by the hydrogen bromide catalysed decompositions of trimethylacetic, isobutyric, and propionic acids.

Gas-phase oxidation of butene-2

1958 ◽  
Vol 244 (1238) ◽  
pp. 331-344 ◽  
Keyword(s):  
Gas Phase ◽  
Pressure Change ◽  
Reaction Products ◽  
Peroxide Formation ◽  
Time Curve ◽  
Pressure Time ◽  
Initial Oxygen ◽  
Gas Phase Oxidation ◽  
Reactive Radicals ◽  
Reaction Processes

The gas-phase thermal oxidation of butene-2 has been examined over the temperature range 289 to 395°C. No difference in behaviour of the cis and trans forms could be detected. At the higher temperatures the reaction resembled that of the oxidation of propylene in the shape of the pressure-time curve and in the identity of many of the reaction products. At the lower temperatures a decrease in pressure partly due to peroxide formation followed the induction period, and by the end of this time much of the initial oxygen had been consumed. At all temperatures excess olefin produced an apparent inhibiting effect manifested by a decreased yield of carbon monoxide and a fall-off in the maximum rate of pressure change and total pressure change. Reaction processes are discussed, and it is suggested that a peroxide precedes the formation of acetaldehyde. Branching occurs largely through reaction of acetyl radicals produced from the acetaldehyde. The inhibiting effects produced by excess olefin are attributed to the replacement of reactive radicals by the less reactive allylic-type radicals, and the addition reactions of olefin at higher olefin concentrations lead to polymerization and a low or negative overall pressure change.

Thermal reactions of mesityl oxide

1971 ◽  
Vol 24 (5) ◽  
pp. 955 ◽  
Author(s):  
NJ Daly ◽  
MF Gilligan
Keyword(s):  
Carbon Monoxide ◽  
Methyl Bromide ◽  
Hydrogen Bromide ◽  
The Other ◽  
Mesityl Oxide ◽  
Thermal Reactions ◽  
First Order ◽  
First Order Kinetics

Mesityl oxide (4-methylpent-3-en-2-one) thermally decomposes in the range 412-490� give methylbutenes, carbon monoxide, isobutene, and methane as major products. The initial 20% of reaction follows first- order kinetics and is described by the equation k1 = 1014.22exp(-63240/RT) s-1. A Rice-Herzfeld chain is proposed. Addition of hydrogen bromide leads to two reactions, one producing isobutene, carbon monoxide, and methyl bromide, and the other leading to polymerization. Likely steps in the polymerization are proposed.

The gas-phase decomposition of ethyl bromide

1971 ◽  
Vol 24 (10) ◽  
pp. 2031
Author(s):  
DA Kairaitis ◽  
VR Stimson
Keyword(s):  
Gas Phase ◽  
Initial Rate ◽  
Hydrogen Bromide ◽  
Bromine Atom ◽  
Ethyl Bromide ◽  
Phase Decomposition ◽  
Unimolecular Decomposition ◽  
Chain Reaction ◽  
Insight Into

The gas-phase decomposition of ethyl bromide at 423� in the presence of both ethylene and hydrogen bromide has been investigated. These additives, which are also the products, each influence the rate strongly but in opposite ways. The variation of initial rate with reactant pressure is given by (P in cm) ������������� k1 (min-1) = 15.2x10-3+19.5x10-3(PEtBrPHBr/PEne)1/2 This has been interpreted in terms of a unimolecular decomposition together with a bromine atom carried chain reaction with simple steps that involve the products. Some insight into the unaccompanied decomposition has been gained. Some remarks about the role of olefinic inhibitors in reactions producing hydrogen bromide have been made.

Catalysis by hydrogen halides in the gas phase. XX. Propionic acid and hydrogen bromide

1970 ◽  
Vol 23 (6) ◽  
pp. 1149
Author(s):  
DA Kairaitis ◽  
VR Stimson
Keyword(s):  
Gas Phase ◽  
Propionic Acid ◽  
Hydrogen Bromide ◽  
Initial Pressure ◽  
Pressure Change ◽  
Ethyl Bromide ◽  
Initial Reaction ◽  
Hydrogen Halides ◽  
First Order ◽  
Kinetic Form

Hydrogen bromide catalyses the decomposition of propionic acid at 405-468�. The initial products are ethyl bromide, carbon monoxide, and water; however, ethyl bromide decomposes into ethylene and hydrogen bromide at rates comparable with those of the initial reaction. The kinetic form of an individual run is therefore not simple, and initial pressure change has been used to measure the rate. The reaction,is first order in each reactant, and the variation of rate with temperature is given by K2 = 1.36 x 1012exp(-30850/RT) s-1 ml mol-1 Comparison with the hydrogen bromide catalysed decarbonylations of other acids and esters has been made. Isobutene added to the reaction affects the kinetic form of individual runs slightly and mainly through its effect on the decomposition of ethyl bromide.

Sign in / Sign up

Export Citation Format

Share Document