DIELS‐ALDER‐Reaktionen. II. Über die Anwendung linearer Freier‐Energie‐Beziehungen auf DIELS‐ALDER‐Reaktionen

Abstract

Die DIELS‐ALDER‐Reaktionen einiger C5‐Diene mit verschiedenen Philodienen wurden kinetisch untersucht. Auf Grund der Reaktionsgeschwindigkeiten mit Cyclopentadien in Dioxan bei 30°C kann man eine allgemeine Dienophilie‐Skala definieren, mit der sich die Geschwindigkeiten von Diels‐Alder‐Reaktionen anderer Diene nach dem Prinzip der linearen Freien‐Energie‐Beziehungen korrelieren lassen. Lineare Freie‐Energie‐Beziehungen mit Parametern der Lösungsmittelpolarität lassen sich nicht nur für das endo/exo‐Verhältnis der Reaktionsprodukte aus Cyclopentadien und Acrylmonomeren, sondern auch für die Geschwindigkeiten dieser Diels‐Alder‐Reaktionen aufstellen. Das spricht für relativ stark polare Übergangszustände bei Diels‐Alder‐Reaktionen von Dienkohlen‐wasserstoffen mit stark polaren Philodienen.

Integrated solvent and process design exemplified for a Diels–Alder reaction

“…Carboxyl acids and alcohols are found to be the most promising solvent types for accelerating the here investigated DA reaction. This is in good agreement with reported kinetic solvent effects where acetic acid was found to be the best solvent and the second to fifth solvents were all alcohols. The solvents in Table can be targeted for further experimentations.…”

“…One of the most interesting aspects of this reaction is its pronounced solvent dependency . Blankenburg et al systematically studied the effects of various solvents on the DA reaction between 1,3‐cyclopentadiene and various dienophiles. In this work, the reaction between 1,3‐cyclopentadiene and acrolein at 303 K is considered as example reaction where 15 solvents with a wide variation of physical and chemical properties were experimentally investigated.…”

“…. Molar volumes of the reactants and product ( i = cyc, acr, and nor) are presented in Supporting Information Table S1 of Appendix C. The reaction was reported to be an irreversible second‐order reaction with respect to the reactants . Therefore, the required reactor volume (m 3 ) can be expressed by …”

10.1007/s11176-008-1018-x

“…It should be emphasized that the term solvent polarity is used here by tradition; in fact, generalized solvating power depending on the ability for both specific and nonspecific solvation is concerned, and different solvent polarity parameters are not really related to the polarity in its physical sense (which is [13], cycloaddition of 1,4-naphthoquinone to 2,3-dimethylbuta-1,3-diene at 80oC (II) [14], and heterolysis of tert-butyl chloride at 25oC (V) [17], logarithms of the rate constants of quaternization of tripropylamine with methyl iodide at 20oC (III) [15] and quaternization of triethylamine with ethyl iodide at 25oC (IV) [16], and log (N/X) values for reaction I (VI) [13] ÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÂÄÄÄÄÂÄÄÄÄÄÂÄÄÄÄ No.³ Solvent ÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄ related to dipole moment of molecules). In particular, this was noted by Reichardt [5,12].…”

“…Table 1 contains values of W determined at 30oC for 17 solvents [5] and rate constants (or their logarithms) for the following reactions: I, cycloaddition of acrolein to cyclopentadiene at 30oC [13]; II, cycloaddition of 1,4-naphthoquinone to 2,3-dimethylbutadiene at 80oC [14]; III, quaternization of tripropylamine with methyl iodide at 20oC (so-called parameter j) [15]; IV, quaternization of triethylamine with ethyl iodide at 25oC [16]; V, heterolysis of tert-butyl chloride at 25oC [17]; and VI, N/X ratio in reaction I [13]. Table 1 contains values of W determined at 30oC for 17 solvents [5] and rate constants (or their logarithms) for the following reactions: I, cycloaddition of acrolein to cyclopentadiene at 30oC [13]; II, cycloaddition of 1,4-naphthoquinone to 2,3-dimethylbutadiene at 80oC [14]; III, quaternization of tripropylamine with methyl iodide at 20oC (so-called parameter j) [15]; IV, quaternization of triethylamine with ethyl iodide at 25oC [16]; V, heterolysis of tert-butyl chloride at 25oC [17]; and VI, N/X ratio in reaction I [13].…”