Swedish
Albanian
Arabic
Armenian
Azerbaijani
Belarusian
Bengali
Bosnian
Catalan
Czech
Danish
Deutsch
Dutch
English
Estonian
Finnish
Français
Greek
Haitian Creole
Hebrew
Hindi
Hungarian
Icelandic
Indonesian
Irish
Italian
Japanese
Korean
Latvian
Lithuanian
Macedonian
Mongolian
Norwegian
Persian
Polish
Portuguese
Romanian
Russian
Serbian
Slovak
Slovenian
Spanish
Swahili
Swedish
Turkish
Ukrainian
Vietnamese
Български
中文(简体)
中文(繁體)
ACS Omega 2019-Jun

Equilibrium in the Catalytic Condensation of Carboxylic Acids with Methyl Ketones to 1,3-Diketones and the Origin of the Reketonization Effect.

Endast registrerade användare kan översätta artiklar
Logga in Bli medlem
Länken sparas på Urklipp
Alexey Ignatchenko
Thomas DiProspero
Heni Patel
Joseph LaPenna

Nyckelord

Abstrakt

Acetone is the expected ketone product of an acetic acid decarboxylative ketonization reaction with metal oxide catalysts used in the industrial production of ketones and for biofuel upgrade. Decarboxylative cross-ketonization of a mixture of acetic and isobutyric acids yields highly valued unsymmetrical methyl isopropyl ketone (MIPK) along with two less valuable symmetrical ketones, acetone and diisopropyl ketone (DIPK). We describe a side reaction of isobutyric acid with acetone yielding the cross-ketone MIPK with monoclinic zirconia and anatase titania catalysts in the absence of acetic acid. We call it a reketonization reaction because acetone is deconstructed and used for the construction of MIPK. Isotopic labeling of the isobutyric acid's carboxyl group shows that it is the exclusive supplier of the carbonyl group of MIPK, while acetone provides only methyl group for MIPK construction. More branched ketones, MIPK or DIPK, are less reactive in their reketonization with carboxylic acids. The proposed mechanism of reketonization supported by density functional theory (DFT) computations starts with acetone enolization and proceeds via its condensation with surface isobutyrate to a β-diketone similar to β-keto acid formation in the decarboxylative ketonization of acids. Decomposition of unsymmetrical β-diketones with water (or methanol) by the retrocondensation reaction under the same conditions over metal oxides yields two pairs of ketones and acids (or esters in the case of methanol) and proceeds much faster compared to their formation. The major direction yields thermodynamically more stable products-more substituted ketones. DFT calculations predict even a larger fraction of the thermodynamically preferred pair of products. The difference is explained by some degree of a kinetic control in the opposite direction. Reketonization has lower reaction rates compared to regular ketonization. Still, a high extent of reketonization occurs unnoticeably during the decarboxylative ketonization of acetic acid as the result of the acetone reaction with acetic acid. This degenerate reaction is the major cause of the inhibition by acetone of its own rate of formation from acetic acid at high conversions.

Gå med på vår
facebook-sida

Den mest kompletta databasen med medicinska örter som stöds av vetenskapen

  • Fungerar på 55 språk
  • Växtbaserade botemedel som stöds av vetenskap
  • Örter igenkänning av bild
  • Interaktiv GPS-karta - märka örter på plats (kommer snart)
  • Läs vetenskapliga publikationer relaterade till din sökning
  • Sök efter medicinska örter efter deras effekter
  • Organisera dina intressen och håll dig uppdaterad med nyheterna, kliniska prövningar och patent

Skriv ett symptom eller en sjukdom och läs om örter som kan hjälpa, skriv en ört och se sjukdomar och symtom den används mot.
* All information baseras på publicerad vetenskaplig forskning

Google Play badgeApp Store badge