Acidity of hydrocarbons.  XLVI.  Equilibrium ion-pair acidities of mono-, di-, and triarylmethanes toward cesium cyclohexylamide

Streitwieser, Andrew; Murdoch, Joseph R.; Haefelinger, G.; Chang, Chiu-Shan

doi:10.1021/ja00794a021

Cited by 40 publications

(16 citation statements)

References 3 publications

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“…Like 1 ⋅F, 2 ⋅F is extremely hygroscopic. In THF 2 ⋅F deprotonates 10 substantially and 4‐phenyltoluene (extrapolated DMSO p K a =37.650) to a visible extent; thus its basicity exceeds even that of the strongest phosphazene bases 41. An X‐ray crystal structure reveals the “nakedness” of 2 ⋅F 51…”

Section: Resultsmentioning

confidence: 99%

Anhydrous Phosphazenium Fluorides as Sources for Extremely Reactive Fluoride Ions in Solution

Schwesinger¹,

Link²,

Wenzl³

et al. 2005

Chemistry A European J

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Several peralkylated polyaminophosphazenium cations were evaluated for the generation of novel anhydrous F- salts. Two of them have been characterized by X-ray analysis and are particularly soluble, even in apolar aprotic solvents like benzene or THF, one of them even at -30 degrees C. Such solutions probably represent the most basic metal-free and stable media known to date. Comparison of these fluorides with known F- sources demonstrates that they are of unprecedented reactivity and selectivity in E2 elimination reactions.

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Section: Resultsmentioning

confidence: 99%

Anhydrous Phosphazenium Fluorides as Sources for Extremely Reactive Fluoride Ions in Solution

Schwesinger¹,

Link²,

Wenzl³

et al. 2005

Chemistry A European J

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“…The RCs C H A system has bee11 used extensively by Streitwieser and co-workers (13. 18) in their stirdies of the acidities of hydrocarbon acids and the pP(, scale pertaining to this system has been reliably established for a series of hjdrocarbon acids (13,19). The availability of a series of hydrocarbon acids of known and increasing pKa is central to the design of the present study.…”

Section: Resultsmentioning

confidence: 99%

Hydrogenolysis of organometallics and the acidity of hydrogen

Buncel¹,

Menon²

1976

Can. J. Chem.

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. Can. J. Chem. 54, 3949 (1976). The hydrogenolysis of a series of alkylcesiums in cyclohexylamine solvent has been studied spectrophoton~etrically. The cesium salt of p-phenyltoluene reacts with H2 (1 atm, room temperature), but the cesium salts of di-2,4-xylylmethane and of diphenylrnethane are unreactive. The results show that the acidity of Hz is intermediate between those ofp-phenyltoluene and of di-2,4-xylylniethane in this reaction system. Possible effects of ion association phenomena on the equilibrium processes are considered.ERWIN BUNCEL ei BALACHANDRAN C. MENON. Can. J. Chem. 54, 3949 (1976). On a etudie spectrophotometriquement I'hydrogCnolyse d'une serie d'alkylcesiuni dans la cyclohexylan~ine cornme solvant. Le sel de cesium du p-phenyltolukne reagit avec H2 (1 atm, B temperature de la piece) mais ies sels de cesium du dixylyl-2,4 methane et du diphenylmethane ne reagissent pas. Les resultats montrent que. dans ce systkme de reactions, l'acidite de Hz est intermediaire entre les acidites du p-phCnyltolukne et du dixylyl-2.4 methane. 0 1 1 considkre les effets possibles du phenomkne d'association des ions sur les processus d'equilibration.[Traduit par le journal]The pK, of molecular hydrogen, or deuterium: is of fundamental importance to the interpretation of the effect of structural changes on acidity (1-4). Literature estimates of this pKa vary between 29 and 38 ( 5 , 6), although no experimentally determined value has been given.In relation to our studies of isotopic exchange of molecular hydrogen (deuterium) in strongly basic systems (7-9), it was of interest to have direct knowledge of the acidity of H2 (El2), in order to be able to relate the kinetic and th, errnodynamic acidity parameters.Our approach to the determination of the acidity of hydrogen is based on quantitative measurements of the equilibrium between H2 and an organometallic indicator: It is clear from the reaction depicted in [I] that ifId2 is a stronger acid than RH the equilibrium will lie to the right hand side, and vice versa. Thus, by studying a series of hydrocarbons of increasing p&, a break in reactivity should be observed. When the pK, of the hydrocarbon R H is within 1-2 pK units of that of H2, the reaction [ l ] will proceed to equilibrium and the equilibri-'Carbanion mechanisms. Part V. The previous parts in the series are considered to be those in ref. 26. These publications concern the carbanions derived from i,3,5-trinitrobenzene (26a), 2,4,6-trinitrotoluene (26b), 1,3-dinitrobenzene (26c), and dimethyl sulfoxide (26d). urn constant (Krel) will be related to the Ka's of H Z and of R H via [2] and [3]:The method for pKa determination of H2 outlined above is analogous in principle to the method originally put forward (10) for pKa determination of carbon acids, via [4]:When the anions R1-and W2-have characteristic spectral absorptions in the ultraviolet or visible region, the position of the equilibrium in [4] is conveniently measured spectrophotometrically. In the present system, though one of the anionic species (H-...

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“…The anion of diphenylmethane reacts as Trdoes but the yields of Ph 2 CHCH 2 CH 2 NHCOZ are lower due to an incomplete deprotonation of Ph 2 CH 2 (pK a 33,4 vs. 31,4 for HTr [51]) by sodium naphthalenide [52]. Cyclic analogues X -, AHand Flof this carbanion (Scheme 14) are more easy to use and to generate from xanthene XH, dihydroanthracene AH 2 and fluorene FlH by means of BuLi or NaNH 2 .…”

Section: Nro By C-nucleophiles Of Low and Of High Basicitymentioning

confidence: 99%

Nucleophilic ring opening of aziridines

Stamm

1999

J. prakt. Chem.

102

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This account of research work on nucleophilic ring opening (NRO) of aziridines (Az's) demonstrates the broad synthetic scope of this reaction, inclusive secondary reactions, and it discusses the special mechanistic fundamentals and details as well as mechanistic variants. Formation of a C–C bond by NRO is the red thread in this report. A central mechanistic aspect is the quality of the leaving group in Az bases, aziridinium ions and activated Az's (acyl, sulfonyl; double activation). Factors controlling the regioselectivity of NRO are dealt with as well as the influence of the nitrogen pyramid. Competing reactions include carbonyl attack (acylated Az's) and electron transfer with cases of pseudo‐NRO (multistep radical paths).

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Acidity of hydrocarbons. XLVI. Equilibrium ion-pair acidities of mono-, di-, and triarylmethanes toward cesium cyclohexylamide

Cited by 40 publications

References 3 publications

Anhydrous Phosphazenium Fluorides as Sources for Extremely Reactive Fluoride Ions in Solution

Anhydrous Phosphazenium Fluorides as Sources for Extremely Reactive Fluoride Ions in Solution

Hydrogenolysis of organometallics and the acidity of hydrogen

Nucleophilic ring opening of aziridines

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