The aldol condensation of acetophenone with acetone

The kinetics and equilibria involved in the aldol condensation of acetophenone, acting as carbon acid, and acetone have been studied in aqueous alkaline solution. The reactions are all first order in hydroxide, with rate and equilibrium constants (defined for enone as initial compound) of: k12 = 3.3 × 10−4 M−1 s−1, k21 = 3.2 × 10−5 M−1 s−1K12 = 10.2, k23 = 8.0 × 10−2 M−1 s−1, k32 = 3.3 × 10−4 M−2 s−1, K32 = 4.1 × 10−3 M−1. The series methylbutenal, mesityl oxide, and 3-methyl-1-phenyl-2-buten-1-one can now be compared with regard to regularities and deviations from regularity. The related series cinnamaldehyde, benzalacetone, and chalcone also provides insights into the behaviour of this system. Key words: aldol, dehydration, equilibrium, acetophenone, acetone.

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The aldol condensation of acetone with acetophenone

Canadian Journal of Chemistry ◽

10.1139/v92-140 ◽

1992 ◽

Vol 70 (4) ◽

pp. 1055-1068 ◽

Cited By ~ 10

Author(s):

J. Peter Guthrie ◽

Xiao-Ping Wang

Keyword(s):

Kinetic Model ◽

Alkaline Solution ◽

Aldol Condensation ◽

Equilibrium Constants ◽

Analytical Data ◽

Initial Compound ◽

Aqueous Alkaline Solution ◽

First Order ◽

Carbon Acid ◽

Best Fit

The kinetics and equilibria involved in the aldol condensation of acetone, acting as carbon acid, and acetophenone have been studied in aqueous alkaline solution. The enone isolated is the E isomer. The reactions are all first order in hydroxide, with rate and equilibrium constants (defined for E-enone as initial compound) of: k12 = (5.55 ± 0.17) × 10−6 M−1 s−1, k21 = (8.00 ± 0.40) × 10−6 M−1 s−1, K21 = (1.44 ± 0.55) (ketol to E-enone), K24 = 0.160 ± 0.033 (ketol to Z-enone), K32 = (1.89 ± 0.26) × 10−3 M−1 (acetone plus acetophenone to ketol), k23 = 0.180 ± 0.005 M−1 s−1, k32 = (3.41 ± 0.49) × 10−4 M−2 s−1. There is an equilibration of the two enones in base that is faster than hydration to the ketol: k14 = (3.14 ± 0.84) × 10−5 M−1 s−1; k41 = (2.81 ± 0.61) × 10−4 M−1 s−1; K14 = 0.112 ± 0.019. To analyze the behavior of the enone:ketol equililbrium system in acid we simultaneously fitted analytical data for all three species (E-enone, Z-enone, and ketol) to a kinetic model, so that the rate constants were determined by the best fit to all of the data for an experiment.

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Reaction of Glutathione with Conjugated Carbonyls

Zeitschrift für Naturforschung C ◽

10.1515/znc-1975-7-808 ◽

1975 ◽

Vol 30 (7-8) ◽

pp. 466-473 ◽

Cited By ~ 177

Author(s):

Hermann Esterbauer ◽

Helmward Zöllner ◽

Norbert Scholz

Keyword(s):

Catalytic Effect ◽

Biological Activities ◽

Equilibrium Constants ◽

Reverse Reaction ◽

Mesityl Oxide ◽

Forward Reaction ◽

First Order ◽

First Order Kinetics ◽

Proton Donors ◽

The Stability

Abstract 1. GSH reacts with conjugated carbonyls according to the equation: G SH+R-CH=CH-COR⇆R-CH(SG)-CH2-COR. The forward reaction follows second order, the reverse reaction first order kinetics. It is assumed that this reaction reflects best the ability of conjugated carbonyls to inactivate SH groups in biological systems. 2. The rate of forward reaction increases with pH approx. parallel with αSH. Besides OH- ions also proton donors (e. g. buffers) increase the rate. The catalytic effect of pH and buffer is inter preted in view of the reaction mechanism. 3. The equilibrium constants as well as the rate constants for forward (k1) and reverse reaction show an extreme variation depending on the carbonyl structure. Acrolein and methyl vinyl ketone (kt = 120 and 32 mol-1 sec-1 , resp.) react more rapidly than any other carbonyl to give very stable adducts (half-lives for reverse reaction 4.6 and 60.7 days, resp.). Somewhat less reactive are 4-hydroxy-2-alkenals and 4-ketopentenoic acid (k1 between 1 and 3 mol-1 sec-1), but they also form very stable adducts showing half-lives between 3.4 and 19 days. All other carbonyl studied react either very slowly (e. g. citral, ethly crotonate, mesityl oxide, acrylic acid) or form very labile adducts (crotonal, pentenal, hexenal, 3-methyl-butenone). Comparing biological activities of con jugated carbonyls their reactivity towards HS (k1) and the stability of the adducts must be considered.

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Kinetics and mechanism of base-catalysed aldolization of 1,3-dimethoxy-2-propanone

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19852252 ◽

1985 ◽

Vol 50 (10) ◽

pp. 2252-2259 ◽

Cited By ~ 1

Author(s):

Michal Fedoroňko ◽

Mária Petrušová ◽

Vladimír Kováčik

Keyword(s):

Thermodynamic Parameters ◽

Alkaline Solution ◽

Equilibrium Constants ◽

Kinetics And Mechanism ◽

Reversible Reaction ◽

Aqueous Alkaline Solution ◽

Rate Determining Step ◽

Catalysed Reaction ◽

Starting Compound ◽

Intermediate Anion

1,3-Dimethoxy-2-propanone (HA) in an aqueous alkaline solution undergoes specifically base-catalysed aldolization with the formation of a dimer, 4-hydroxy-1,3,5-trimethoxy-4-methoxymethyl-2-pentanone (H2A2). The reaction is reversible and involves the formation or decomposition of an intermediate anion, HA2-, as the rate-determining step. The formation of a carbanion ion, A-, of the starting compound and of the HA2- anion are rapid, preceding, and generally base-catalysed reaction steps. The activation and thermodynamic parameters of the reversible reaction were determined from the dependences of the rate and equilibrium constants on the temperature.

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Enhanced Thermal Stability of Esterified Lignin in Different Solvent Mediums

Polymers from Renewable Resources ◽

10.1177/204124791800900103 ◽

2018 ◽

Vol 9 (1) ◽

pp. 39-49 ◽

Cited By ~ 1

Author(s):

Sharifah Nurul Ain Syed Hashim ◽

Sarani Zakaria ◽

Chin Hua Chia ◽

Sharifah Nabihah Syed Jaafar

Keyword(s):

Thermal Stability ◽

Alkaline Solution ◽

Room Temperature ◽

Hydroxyl Groups ◽

Aqueous Alkaline Solution ◽

Alkali Lignin ◽

Weight Percentage ◽

H Nmr ◽

Ft Ir ◽

Thermal Stability Of

In this study, soda alkali lignin from oil palm empty fruit bunch (EFB-AL) and kenaf core (KC-AL) are esterified with maleic anhydride under two different conditions, namely i) pyridine at temperature of 120°C for 3h and ii) aqueous alkaline solution at room temperature for 4h. As a result, the weight percentage gain (WPG) of the esterified EFB-AL (EFB-EL) and esterified KC-AL (KC-EL) in pyridine demonstrated a higher compared to aqueous alkaline solution. The FT-IR results of EFB-EL and KC-EL in both solvents exhibited some changes at the carbonyl and hydroxyl groups. Furthermore, the esterification process induced the carboxylic peak to appear in both alkali lignin samples. The outcome is confirmed by conducting H-NMR analysis, which demonstrated ester and carboxylic acid peaks within the spectral analysis. Finally, the TGA results showed both EFB-EL and KC-EL that are exposed to aqueous alkaline actually possessed better thermal stability and higher activation energy (Ea) compared to the esterified samples in pyridine.

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