Über die Gleichgewichts‐Isomerie zwischen Bornylchlorid, Isobornylchlorid und Camphen‐chlorhydrat

Meerwein, Hans; Emster, Konrad van

doi:10.1002/cber.19220550829

Cited by 160 publications

(83 citation statements)

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“…spectra of acidified 2-exo-norbornanol solutions is most satisfactorilj-accouilted for by fast hydrogen exchanges between inagnetically non-equivalent sites (7). * Such processes occur in the well-ltnown carbonium ion rearrangements which 2-exo derivatives of norbornane undergo, see steps [I], [2], and [3] below.…”

Section: R E S U L T S a N D Discussionmentioning

confidence: 99%

“…The operation of steps [2] and [3], a Namenliin rearrangement and a 6,2 hydride shift respectively would cause averaging of the chenlical shifts of the hydrogens on C2, C3, Cj, and Cc. The resultant averaged shift would not be expected to differ greatly from that for the hydrogens on C7, the peak a t 8.8 tau mould correspond to 9 hydrogens, that a t 7.8 tau to 2.…”

Section: R E S U L T S a N D Discussionmentioning

confidence: 99%

“…There is a vast literature which concerns carbonium ion rearrangements of bicyclic compounds (1)(2)(3). Of the inany systems studied none has been the subject of such intensive investigation as the reactions of 2-substituted norbornanes.…”

Section: Abstract Nuclear Magnetic Resonance Spectra Have Beenmentioning

confidence: 99%

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FAST REARRANGEMENT OF exo-NORBORNANOL IN STRONG ACID SOLUTIONS

Fraenkel¹,

Ralph²,

Kim³

1965

Can. J. Chem.

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A B S T R A C T Nuclear magnetic resonance spectra have been obtained a t several temperatures for solutions o f 2-exo-norbornanol in strong acids. T h e spectra change with temperature reversibly. I t isconcluded that the 2-era-norbornanol undergoes very rapid rearrangement, the fast steps being 2,6 and 3,2 hydride shifts, respectively. I N T R O D U C T I O NThere is a vast literature which concerns carbonium ion rearrangements of bicyclic compounds (1-3). Of the inany systems studied none has been the subject of such intensive investigation as the reactions of 2-substituted norbornanes. These detailed kinetic (4) and isotopic (5) studies of solvolysis and deamination reactions reveal the operation of 3,2 and 6,2 hydride shifts, respectively, and Wagner-iueerwein rearrangements and imply the intermediacy of several different carbonium ions. Hitherto these rearrangements have been observed in irreversible systems. In this work it will be shown by the methods of nuclear magnetic resonance (n.1n.r.) spectroscopy that 2-exo-norbornanol is stable in strong acid solutions and a t the same time undergoes fast skeletal rearrangements. R E S U L T S A N D DISCUSSIONThe n.m.r. spectruln of 2-exo-norbornanol in Inethylene chloride is shown in Fig. I. The absorptions a t 6.19 tau and 7.87 tau arise froin CHOH and the bridgehead hydrogens respectively. The remaining hydrogens on C3, C3, C6, and C7 give the multiplets in the region of 8.8 tau; the line for OH appears a t 8.21 tau. The same spectrum is obtained using dimethyl sulfate and methanol as solvents with the exception that the chemical shift of the OH proton changes with solvents due to differences in hydrogen bonding. The chemical shifts of the solvent protons are as listed in the literature (6). In all these solutions the n.m.r. absorption for the OH hydrogen consisted of a single line. Thus 0-H exchange was too fast to permit observation of CzH, OH coupling. However, using trifluoroacetic acid as solvent, the line for C2H appears a t 5.40 tau and the rest of the spectrum ( Fig. 2A) has a slightly different appearance froin those obtained with the other solvents. Furthermore, due to fast proton exchange, the OH resonances in the acid and alcohol are merged. Since 2-exo-norbornanol was quantitatively recovered from trifluoroacetic solution, these changes must be due to a specific solvent effect.When 2-exo-norbornanol is dissolved in 97% sulfuric acid or mixtures of trifluoroacetic acid and sulfuric acid the peak due to CHOH disappears and the remaining spectrum consists of two broad lines a t 7.8 tau and 8.8 tau (Fig. 2E). The starting material was quantitatively recovered from these solutions also. Hence the effects found here do not arise from unusual chemical reactions. On heating the solutions of 2-exo-norbornanol in H2SO4-CF3C02H between 0 and 60" the resonance due to CHOH broadens and disappears

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Section: R E S U L T S a N D Discussionmentioning

confidence: 99%

Section: R E S U L T S a N D Discussionmentioning

confidence: 99%

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FAST REARRANGEMENT OF exo-NORBORNANOL IN STRONG ACID SOLUTIONS

Fraenkel¹,

Ralph²,

Kim³

1965

Can. J. Chem.

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“…Glucklicherweise sind Molekulgraphen von maI3iger Komplexizitat, so daB es gelingt, Algorithmen zur Korrelation von Molekiilen uber ihre Substrukturen zu konzipieren, deren Rechenzeit-und Speicherplatzbedarf mit der GroBe und Zahl der Molekiile allenfalls polynomisch (Grad s 5 ) ansteigt. Es sind Algorithmen, die auf der stufenweisen Fragmentierung der Molekule und einer Einbettung der Stufenfragmente in ein Netzwerk von Vater-Sohn-Relationen beruhen, welches alle aufgelisteten Molekule urnfaat.…”

Section: Evkennung Und Kovvelation Von Substvukturenunclassified

Die computerunterstützte Lösung chemischer Probleme eine neue Disziplin der Chemie

et al. 1993

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“…Titelseite der er\ten Puhlikation iiher Ionen-Reaktionen in der Organischen Chemie von Meerwein et al [2].…”

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August Kekulé – dem Baumeister der Chemie zum 150. Geburtstag

Häfner

1979

Angewandte Chemie

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Phantasie, Kühnheit und kritischem Verstand sind die bis heute fortwirkenden Impulse zu danken, die die Chemie durch Kekulés theoretische Arbeiten empfing. „Lernen wir träumen, meine Herren, dann finden wir vielleicht die Wahrheit, aber hüten wir uns, unsere Träume zu veröffentlichen, ehe sie durch den wachenden Verstand geprüft worden sind. … Lassen wir immer die Früchte hängen, bis sie reif sind. Unreifes Obst bringt selbst dem Züchter wenig Gewinn; es schädigt die Gesundheit derer, die es geniessen; es gefährdet namentlich die Jugend, die Reif und Unreif noch nicht zu unterscheiden vermag.”︁ (Kekulé 1890).

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Über die Gleichgewichts‐Isomerie zwischen Bornylchlorid, Isobornylchlorid und Camphen‐chlorhydrat

Cited by 160 publications

References 5 publications

FAST REARRANGEMENT OF exo-NORBORNANOL IN STRONG ACID SOLUTIONS

FAST REARRANGEMENT OF exo-NORBORNANOL IN STRONG ACID SOLUTIONS

Die computerunterstützte Lösung chemischer Probleme eine neue Disziplin der Chemie

August Kekulé – dem Baumeister der Chemie zum 150. Geburtstag

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