Abspaltungsreaktionen und ihr sterischer Verlauf

Hückel, Walter; Tappe, Werner; Legutke, Günter

doi:10.1002/jlac.19405430117

Cited by 56 publications

(22 citation statements)

References 17 publications

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“…These results suggest that the elimination is occurring by means of an El mechanism. A comparison of our results with elimination reactions carried out by other workers on 2-methylcyclohexyl and menthyl neomenthyl derivations (3)(4)(5)(6)(7)(8) indicates that the mechanism is more complicated. In general, elimination reactions which are believed to occur by an El mechanism give almost identical product ratios from either the cis or trans starting material.…”

supporting

confidence: 51%

The Formation of Alkenes by the Thermal Elimination Reaction of N-Methyl-4-alkoxypyridinium Iodides. II. An Investigation of the Mechanism

Sçhmid¹,

Wolkoff²

1972

Can. J. Chem.

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A comparison of the products from elimination reactions of a number of compounds containing various leaving groups with those containing the N-methyl oxypyridinium leaving group suggests that the elimination is not occurring by means of a simple El mechanism. Changing the anion of the salt from iodide to methylsulphate and tetiafluoroborate affects the product composition indicating that the anion is taking part in the reaction. The mechanism of this reaction appears to be on the El-E2 borderline.Une comparaison des produits de reactions d'tlimination de certains composes contenant une variete de groupes labiles avec ceux contenant le groupe labile N-methyl oxypyridinium suggere que I'tlimination ne s'explique pas par un mecanisme simple de type E l . Lorsqu'on change I'anion du sel, soit le sulfate de methyl ou le tetrafluoroborate a la place de I'iodure, la composition du produit est affectee, ce qui indique que I'anion prend part a la reaction. Le mecanisme de cette reaction semble Ctre le resultat d'une contribution des deux mtcanismes El et E2.Canadian Journal of Chemistry, 50,1188Chemistry, 50, (1972 We have found that N-methyl-4-alkoxypyridinium iodides decompose upon heating to give olefins and the hydroiodide of N-methyly-pyridone (1). The olefins obtained from this reaction are not stereospecific and there is evidence that rearrangement occurs during the pyrolysis. These results suggest that the elimination is occurring by means of an El mechanism. A comparison of our results with elimination reactions carried out by other workers on 2-methylcyclohexyl and menthyl neomenthyl derivations (3)(4)(5)(6)(7)(8) indicates that the mechanism is more complicated. In general, elimination reactions which are believed to occur by an El mechanism give almost identical product ratios from either the cis or trans starting material. Results obtained in this work for the pyrolysis of the oxypyridinium iodides show that the menthyl, neomenthyl, and 2-methylcyclohexyl derivatives give products which resemble those formed under El conditions. Still there are significant differences in the products from cis and trans isomers. The question arises as to whether or not the iodide ion does actually play a part in the reaction. Hence, additional product studies were attempted wherein modifications were made in the leaving group. Specifically, the counter-ion was changed from iodide to methylsulfate and tetrafluoroborate. 'Holder of NRCC Scholarship, 1967-1971 The results for the pyrolysis of the N-methyl-4-(2'-octoxy)pyridinium salts are shown in Table 1. These results clearly show that the counter-ion affects the stereochemistry and regiospecificity of the products. The fact that the addition of 2,6-lutidine, a non-nucleophilic base, has little effect on the product ratios indicates that no isomerization of the initially formed olefins occurs.These results can be compared with the dehydration of 2-octanol with phosphoric acid at 120-130" which gives trnnslcis and 2-11-olefin ratios of 1.06 and 4.71 respectively. These ratios ...

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supporting

confidence: 51%

The Formation of Alkenes by the Thermal Elimination Reaction of N-Methyl-4-alkoxypyridinium Iodides. II. An Investigation of the Mechanism

Sçhmid¹,

Wolkoff²

1972

Can. J. Chem.

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“…The first pathway was supported by Huckel et al [2], while Barton and Cram [3,4] preferred the second mechanism. Experimental studies were also applied to investigate the Chugaev mechanisms.…”

Section: Introductionmentioning

confidence: 88%

“…In mechanism (A), the reaction occurs in one step, giving the products of reaction (1); in mechanism (B), the initial products are an alkene and unstable dithiocarbonate derivative that subsequently decompose to carbonyl sulphide and a thiol respectively. Huckel et al [2] postulated the first mechanism (A); Barton and Cram [3,4] proposed the second mechanism. Experimental evidence showing that a thione, rather than a thiol, sulphur atom attacks the ␤-hydrogen was obtained by Bader and Bourns, who performed a study of 34 C and 13 C isotope effects in the pyrolysis of trans-2-methyl-1-indanyl xanthate of natural isotopic abundance.…”

Section: Mechanism Of Decomposition Of Alkyl Dithiocarbonates (Xanthamentioning

confidence: 99%

Quantum mechanical studies of the kinetics, mechanisms and thermodynamics of gas-phase thermal decomposition of ethyl dithiocarbonate (xanthate)

Adejoro

Esan

Adeboye

et al. 2017

Journal of Taibah University for Science

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Theoretical studies were carried out to investigate the thermal decomposition of ethyl dithiocarbonates (xanthate) using Hartree-Fock at the HF/321-G* level and the density functional method with Becke 3 Lee Yang pair DFT/(B3LYP), 6-31G*, 6-31G**, 6-31+G*, MP2 and CCSD in the ab initio method of calculation using Spartan 10. Geometric parameters, such as the bond length, bond angles, dihedral angles, heat of formation, atomic charges and vibrational frequencies, were obtained. The data were used to calculate the thermodynamics parameters, change in entropy S, enthalpy change H, free energy G, pre-exponential factor A, rate k at 623 K, and variation of rate k with temperatures from 498-623 K at temperature intervals of 25 K. It was observed that the values obtained are in good agreement with the experimental values for the ab initio methods, and according to Arrhenius theory, the calculated rate k increases with increasing temperature.

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“…und (+)-A3-p-Mcnthcn in eincm Verhaltnis von 1 : 3 gebildet [7]. 4) Ein (+ )-truns-~"-P-Menthen-S)-ol, das in Bezug auf C(8) aus einem Uiastereomerengemisch im Vcrhaltnis von 1 : 1 bestcht, ist in der Zwischenzeit bekannt geworden [ 8 ] .…”

Section: Menthols Danach Werden ( + ) -F V U~s -A Z -unclassified

252. Zur Kenntnis der Chiralität von Verbindungen des 9‐Hydroxy‐p‐menthans

Schulte‐Elte

Ohloff

1966

Helvetica Chimica Acta

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Abspaltungsreaktionen und ihr sterischer Verlauf

Cited by 56 publications

References 17 publications

The Formation of Alkenes by the Thermal Elimination Reaction of N-Methyl-4-alkoxypyridinium Iodides. II. An Investigation of the Mechanism

The Formation of Alkenes by the Thermal Elimination Reaction of N-Methyl-4-alkoxypyridinium Iodides. II. An Investigation of the Mechanism

Quantum mechanical studies of the kinetics, mechanisms and thermodynamics of gas-phase thermal decomposition of ethyl dithiocarbonate (xanthate)

252. Zur Kenntnis der Chiralität von Verbindungen des 9‐Hydroxy‐p‐menthans

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