The Synthesis and Properties of Cyclobutenyl Cations

Katz, Thomas J.; Gold, Elijah H.

doi:10.1021/ja01062a032

Cited by 39 publications

(10 citation statements)

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“…The frequency of the asymmetric CCC ϩ stretching of the allyl group in 12 at 1386 cm Ϫ1 (the scaled calculated value is 1336 cm Ϫ1 ) is close to values previously measured for other cyclobutenyl cation analogs. 7 The absorption of the amino group vibration at 3504 cm Ϫ1 is almost at the same position as in the spectrum obtained from the reaction of 2 with SbF 5 .…”

Section: Cyclobutanone Oxime (8)supporting

confidence: 56%

Oxime rearrangements: ab initio calculations and reactions in the solid state

Šimunić-Mežnarić

Mihalić

Vančik

2002

J. Chem. Soc., Perkin Trans. 2

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Section: Cyclobutanone Oxime (8)supporting

confidence: 56%

Oxime rearrangements: ab initio calculations and reactions in the solid state

Šimunić-Mežnarić

Mihalić

Vančik

2002

J. Chem. Soc., Perkin Trans. 2

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“…By −90 °C, this unsubstituted cyclohexenyl cation had already transformed, which was evident by the formation of a band at 1480 cm –1 . Katz and Gold measured the IR spectra of the 1,2,3,4-tetramethylcyclobutenyl cation in solution and found the allyl stretching vibration to appear at 1465 cm –1 …”

Section: Resultsmentioning

confidence: 99%

“…Katz and Gold measured the IR spectra of the 1,2,3,4-tetramethylcyclobutenyl cation in solution and found the allyl stretching vibration to appear at 1465 cm −1 . 85 The band positions associated with the allylic stretch of these cations are summarized in Table 1. The significant red shift of the allylic stretching vibration with decreasing ring size (Δν CCC+ ≅ 30−40 cm −1 ) may be associated with increasing ring strain.…”

Section: Differentiation Of Acyclic and Cyclic Monoenyl Cations And D...mentioning

confidence: 99%

Spectroscopic Signatures Reveal Cyclopentenyl Cation Contributions in Methanol-to-Olefins Catalysis

Hernandez

Jentoft

2020

ACS Catal.

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The conversion of methanol to olefins on zeolites and zeotypes is an industrially important process, yet the mechanistic details remain unresolved. Various cyclic alkenyl and alkadienyl carbenium ions have been proposed as active intermediates for light olefin production, but direct experimental evidence demonstrating the transformation of these hydrocarbon pool species with product formation is lacking. In this contribution, the interpretations of UV–vis and IR spectra are advanced to provide detail on the species present during catalysis; selected individual species are generated inside the catalyst pores, and their reactivity is tracked. The basis for the interpretation is a multitude of reference spectra of acyclic and cyclic dienes, trienes, and corresponding protonated species in the liquid phase (organic medium or sulfuric acid) or sorbed on dealuminated or acidic zeolites, augmented by trends extracted from these spectra. Accordingly, spectroscopic signatures indicate the presence of both polymethylbenzenium ions and alkyl-substituted cyclopentenyl cations during the conversion of methanol on H-ZSM-5 at 300 °C. To elucidate their role, alkyl-substituted cyclopentenyl cations are generated from acyclic polyenes adsorbed on H-ZSM-5 at room temperature. Cyclization and cleavage are monitored via changes in the electronic and vibrational absorption spectra with increasing temperature. The formation of ethene, propene, and butenes from alkyl-substituted cyclopentenyl cations, in the absence of methylbenzenium ions, is unambiguously demonstrated by temperature-programmed reaction (TPReact) spectroscopy coupled with online gas-phase product analysis. In the UV–vis range, the wavelength of maximum absorption, λmax, of the alkyl-substituted cyclopentenyl cation is linearly dependent on the total number of carbons in the cation. A blue shift in the position of λmax of these cyclopentenyl cations during the TPReact indicates a loss of three carbons, which matches the average size of the concomitantly produced olefins.

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“…Alternatively, placing increased positive charge on the carbon would stabilize the formation of the [Ph 3 C] ϩ cation, the presence of which is indicated by the distinctive yellow color of the solution. 19 The formation of a [Ph The temperature dependent partition between hydroxide exchange and alkane elimination is also observed for aluminium hydrides. The reaction of Ph 3 COH and ( i Bu) 2 AlH was carried out at both room temperature and Ϫ78 ЊC.…”

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confidence: 94%