2008
DOI: 10.1002/chem.200800337
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The Basicity of Unsaturated Hydrocarbons as Probed by Hydrogen‐Bond‐Acceptor Ability: Bifurcated NH+⋅⋅⋅π Hydrogen Bonding

Abstract: The competitive substitution of the anion in contact ion pairs of the type [Oct 3 NH + ]B(C 6 F 5 ) 4 − by unsaturated hydrocarbons L in accordance with the equilibrium Oct 3 NH + ⋯Anion − + nL ↔ [Oct 3 NH + ⋯L n ]Anion − has been studied in CCl 4 solution. On the basis of equilibrium constants K and shifts of νNH to low frequency, it is established that complexed Oct 3 NH + ⋯L n cations with n = 1 and 2 are formed, having unidentate and bifurcated N-H + ⋯π hydrogen bonds, respectively. Bifurcated H-bonds to u… Show more

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Cited by 26 publications
(23 citation statements)
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“…The hyperconjugation may not prevent the concerted libration of H atoms of CH 3 within the limits of a certain α-angle (Scheme 4), and then broadening of both stretch and bend C−H vibrations occurs. Earlier, we proposed a similar explanation for the strong broadening of N−H stretch vibration of the R 3 NH + cation, when it forms a π-hydrogen bond with a double or triple CC bond of alkenes and alkynes: 34 The π-H bond, directed toward the center of the CC or CC bond, is not fixed but fluctuates within a small range of some angle because the maximum of the π-electron density centered between the two carbon atoms is flat.…”
Section: The Journal Of Physical Chemistry Amentioning
confidence: 92%
“…The hyperconjugation may not prevent the concerted libration of H atoms of CH 3 within the limits of a certain α-angle (Scheme 4), and then broadening of both stretch and bend C−H vibrations occurs. Earlier, we proposed a similar explanation for the strong broadening of N−H stretch vibration of the R 3 NH + cation, when it forms a π-hydrogen bond with a double or triple CC bond of alkenes and alkynes: 34 The π-H bond, directed toward the center of the CC or CC bond, is not fixed but fluctuates within a small range of some angle because the maximum of the π-electron density centered between the two carbon atoms is flat.…”
Section: The Journal Of Physical Chemistry Amentioning
confidence: 92%
“…Because of their kinetic instability towards cationic alkene oligomerization, the thermodynamic acidities of carbocations are difficult to quantify, particularly in dilute solution. The νNH basicity scale applied to π systems 21 indicates that protonated alkenes (i.e. carbocations) are stronger acids than protonated alkynes (i.e.…”
Section: Resultsmentioning
confidence: 99%
“…The bands at 3350 and 3250 cm −1 are corresponding to associated H bridged OH/NH groups. The band at 3500 cm −1 appeared due to protonation of the system of the Pc molecules by the acidic OH group of methanol [33,34]. The absorption band belonging to ether groups of the substituent moiety is influenced in various ways; while the ether vibration mode in the metal free Pc is not influenced there is a clear shift of the ether absorbance band in the lower frequency range of the metal Pc spectrum.…”
Section: Characterisation Of Methanol Sorptionmentioning
confidence: 93%
“…In the difference spectra both bands adopt the shape of a differential function, which indicates very weak interaction processes between NH and acetonitrile. In the literature it is known that acidic groups, especially OH/NH, can interact with the -system of acetonitrile via -H hydrogen bonding [33,34] or non-bonding electronic doublet of N atom-H hydrogen bonding due to the basic character of this N atom.…”
Section: Characterisation Of Acetonitrile Sorptionmentioning
confidence: 99%