Neue Aspekte zur Fries‐Umlagerung

Effenberger, Franz; Klenk, Herbert; Reiter, Peter Ludwig

doi:10.1002/ange.19730851808

Cited by 16 publications

(4 citation statements)

References 4 publications

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“…On the other hand, CaCO 3 Á1/2H 2 O has the maximum density with the value of 2.23 g/cm 3 , while the CaCO 3 Á6H 2 O has the minimum values of 1.86 g/cm 3 , which is in agreement with the experimental values as 2.38 g/cm 3 for CaCO 3 Á1H 2 O and 1.8 g/cm 3 for CaCO 3 Á6H 2 O. [22,23] The calculated phonon dispersion curves of the calcium carbonate hydrates along the high symmetry direction in the BZ are shown in Figure 2. The calculated phonon spectra of CaCO 3 ÁxH 2 O (x = 1/2, 1 and 6) show no soft modes at any high-symmetry dispersion, suggesting that these calcium carbonate hydrates are dynamically stable, [24][25][26][27][28] Figure 2A, and the experimental data were obtained from the ref.…”

Section: Computational Methods and Detailssupporting

confidence: 84%

Investigation on the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates via first‐principles calculations

Zhou

Liu

et al. 2020

Int J of Quantum Chemistry

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Calcium carbonate (CaCO3) is an inorganic compound which is widely used in industry, chemistry, construction, ocean acidification, and biomineralization due to its rich constituent on earth and excellent performance, in which calcium carbonate hydrates are important systems. In Zou et al's work (Science, 2019, 363, 396‐400), they found a novel calcium carbonate hemihydrate phase, but the structural stability, optical, and mechanical properties have not been studied. In this work, the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates were investigated by using the first‐principles calculations using density functional theory. CaCO3·xH2O (x = 1/2, 1 and 6) are determined dynamically stable phases by phonon spectrum, but the Gibbs energy of reaction of CaCO3·1/2H2O is higher than other calcium carbonate hydrates. That is why CaCO3·1/2H2O is hard to synthesize in the experiments. In addition, the optical and mechanical properties of CaCO3·xH2O (x = 1/2, 1 and 6) are expounded in detail. It shows that the CaCO3·1/2H2O has the largest bulk modulus, shear modulus, and Young's modulus with the values 60.51 GPa, 36.56 GPa, and 91.28 GPa. This work will provide guidance for experiments and its applications, such as biomineralization, geology, and industrial processes.

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Section: Computational Methods and Detailssupporting

confidence: 84%

Investigation on the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates via first‐principles calculations

Zhou

Liu

et al. 2020

Int J of Quantum Chemistry

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“…In einer Kurzmitteilung haben wir uber die Fries-Umlagerung von Arylbenzoaten und die Retro-Fries-Umlagerung von ortho-Hydroxyaryl-ketonen in Gegenwart katalytischer Mengen Trifluormethansulfonsaure (TFMS) berichtet 7). Nachdem aus den damaligen experimentellen Befunden nur beschrankte Aussagen moglich waren, o b es sich dabei um echte Gleichgewichtsreaktionen handelt, haben wir weitere umfangreiche experimentelle Untersuchungen zu diesem Problem durchgefuhrt, deren Ergebnisse und Folgerungen bezuglich des Mechanismus der Fries-Urnlagerung Inhalt der vorliegenden Publikation sind.…”

Section: F Effenberyer Und R Gutmannunclassified

Die Fries‐Umlagerung als Gleichgewichtsreaktion

Effenberger

Gutmann

1982

Chem. Ber.

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Die Fries-Umlagerung von Arylbenzoaten 1 -in 1,2-Dichlorethan mittels Trifluormethansulfonsaure als Katalysator -zu (ortho-und para-Hydroxyary1)phenylketonen 2 bzw. 3 ist bei 170°C reversibel und fuhrt zu Gleichgewichtsgemischen aus 1 , 2 und 3. Das Gleichgewicht wird, von den Arylestern 1 und den Hydroxyaryl-ketonen 2 bzw. 3 ausgehend, gleichermaflen eingestellt. Die groRere Stabilitat der ortho-gegenuber den para-Hydroxyaryl-ketonen kann aus den uber I3C-NMR-Spektren zuganglichen Verdrillungswinkeln 0 zwischen der Carbonylgruppe und dem aromatischen n-System zufriedenstellend erklart werden. Fur die Acylgruppenwanderung wird ein dissoziativer Mechanismus vorgeschlagen. The Fries Rearrangement as an Equilibrium ReactionThe Fries rearrangement of arylbenzoates 1, in 1,2-dichloroethane in the presence of trifluoromethanesulfonic acid (TFMS) as catalyst, to ortho-and para-hydroxyaryl ketones (2 and 3, resp.) is reversible at 170°C; an equilibrium of the compounds 1, 2, and 3 is established. The equilibrium is achieved starting from the aryl esters 1 as well as from the hydroxyaryl ketones 2 and 3, respectively. The higher stability of the ortho-compounds 2 compared to the para-compounds 3 can be explained by greater resonance interaction between the carbonyl group and the aromatic ring in 2. The torsion angles 0, which are good indicators of this interaction, can be determined from 13C NMR spectra. A dissociative mechanism is proposed for the acyl group migration.Die Umlagerung von Arylestern unter dem Einflufl von Lewis-bzw. Bronsted-Sauren (FriesUmlagerung) ist zweifellos die wichtigste Methode zur Herstellung von Hydroxyaryl-ketonen 3). Da bei der Umlagerung von Phenylestern je nach eingesetztem Substrat und angewandten Reaktionsbedingungen isomere ortho-und para-Hydroxyphenyl-ketone in sehr unterschiedlicher Verteilung entstehen, wurden eine Reihe von Untersuchungen zum Mechanismus der Fries-Umlagerung durchgefuhrt mit dem Ziel, Erklarungen fur die unterschiedliche Isomerenbildung zu finden.Dewar und Hart 4) kamen zu dem SchluR, daR bei den mit Aluminiumbromid durchgefuhrten Umsetzungen von Phenylbenzoat nebeneinander intramolekulare Umlagerung zum orthoHydroxyketon und intermolekulare Umlagerung zum ortho-und para-Hydroxyketon erfolgen. Die Autoren postulieren eine irreversible Bildung der Hydroxyaryl-ketone als notwendige Voraussetzung fur die Deutung des Reaktionsablaufs aus der Isomerenverteilung. Dafl die Fries-Umlagerung jedoch in bestimmten Fallen reversibel ist, konnten schon Rosenmund und Schnurr 5 ) bei der Umsetzung von 4-Acyl-3-alkylphenolen mit Bronsted-Sauren zeigen. Diese Befunde wurden zwar spater angezweifelt 6a), konnten jedoch von Miquel et al. 6b) bestatigt werden.

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“…TRIFLUOROMETHANESULPHONIC ACID (' triflic acid ') has been acclaimed as one of the strongest of all known monoprotic organic acids1 To date, however, most of the interest in the chemistry of this acid and its derivatives has centred around the remarkable efficiency of the triflate anion as a leaving particularly in s o l v o l y ~i s , ~~~ a l k y l a t i ~n , ~* ~~ acylation,l19l2 and nitration 1 3 9 1 4 reactions, and in the use of triflamides in organic synthesis.15 With the exception of reports on the use of triflic acid for the isomerisation and cracking of hydrocarbons,16-21 and as a catalyst for the Fries rearrangement , 22 there is little information about the effect of this acid in other reactions of synthetic importance. Triflic acid has several advantages over other strong acids in that it is non-oxidising, and has high thermal stability and resistance to oxidation and reduction.…”

Section: A Comparison Of the Effectiveness Of Sulphuric Acid And Trif...mentioning

confidence: 99%

A comparison of the effectiveness of sulphuric acid and trifluoromethanesulphonic acid in Koch carboxylation reactions

Booth¹,

EL-FEKKY²

1979

J. Chem. Soc., Perkin Trans. 1

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Neue Aspekte zur Fries‐Umlagerung

Cited by 16 publications

References 4 publications

Investigation on the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates via first‐principles calculations

Investigation on the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates via first‐principles calculations

Die Fries‐Umlagerung als Gleichgewichtsreaktion

A comparison of the effectiveness of sulphuric acid and trifluoromethanesulphonic acid in Koch carboxylation reactions

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