Basicity, intrinsic

Cooks, R.G. Krager, T.L. Intrinsic Basicity Determination Using Metastable Ions. J. Am. Chem. Soc. 1977,99, 1279-1281. 

Heidler, R., janssens, G.O.A., Mortier, W.J., and Schoonheydt, R.A. (1995) Charge sensitivity analysis of intrinsic basicity of faujasite-type zeolites using the electronegativity equalization method... 

The intrinsic basicities of cyclopentenone and cyclohexenone (59), and their lactone analogues (60), have been accessed via measurement of their gas-phase proton affinities, and compared with the saturated carbonyl compounds in both cases. The results... 

Following Taft (83MI2), we define the intrinsic acidity of HAj (g) as the standard free energy change (AG ), corresponding to Eq. (1). The (AG ), value is also taken as a measure of the intrinsic basicity of Af" (g). 

Proton Affinities and Intrinsic Basicities of Azole Anions ... 

N-Methylation of azoles has no direct counterpart in the case of pyridines. As indicated in Section IV,A, experimental evidence shows that N-methylation increases the intrinsic basicity of azoles at least as much as C-methylation. This pattern is not reproduced in aqueous solution, where N-methylation either reduces or has no effect and the derived ions are solvated to a lesser extent than those of the parent compounds. 

Understanding the behavior of organic bases in solution requires some knowledge of their gas phase (intrinsic) basicities (proton affinities (PA)). These can be determined by ICR methods or by variable-temperature pulsed high-pressure mass spectrometry. Both methods afford basicities (termed thermodynamic vs. kinetic basicity), which have been compared in (91JOC179). 

In the gas phase, (3-lactams are weaker bases than acyclic amides. Ab initio calculations show that (3-lactams are oxygen bases, but the gap between the oxygen and nitrogen intrinsic basicities is much smaller than in normal amides, a result of redistribution due to hybridization changes (92JA4728). 

The intrinsic basicity (i.e. the standard Gibbs energy change for reaction 158 in the gas phase) for a variety of compounds XC(=S)Y have been determined by means of Fourier Transform Ion Cyclotron Resonance Spectroscopy (FT ICR) by the groups of Abboud39 and of Gal520. 

In the case of disubstitution, the ranking of substituent effects on the intrinsic basicities of C=S compounds, both measured or calculated39, is as follows ... 

M. Alcami, O. Mo and M. Yanez, Modeling Intrinsic Basicities The Use of Electrostatic Potentials and the Atoms-in-Molecules Theory, in Molecular Electrostatic Potentials Concepts and Applications (J. S. Murray and K. Sen, Eds.). Elsevier, Amsterdam 1996. Page 407. 

Table 1 lists known intrinsic basicities for some enamines, the experimental sources of the data and the most likely protonation sites according to the discussion below. 

Ever since Martin and Shirley17 and Davis and Rabalais18 demonstrated the analogy between the addition of a proton to a neutral molecule and the removal of a Is electron from its protonation site, a number of linear relations between intrinsic basicity (AG + or PA) values and measured or theoretically estimated Is binding energies have been reported19 for different families. 

Owing to their intrinsic basicity, marine invertebrate guanidine alkaloids have a rather polar behavior and their isolation from complex mixtures may be difficult. Isolation procedures frequently include chromatography on lipophilic Sephadex LH20, on reversed phase silica gel (such as Cig bonded, aminopropyl bonded, or cyanopropyl bonded), or even on ion-exchange resins. HPLC purification using acidic (TFA) or buffered eluents have frequently been employed. 

These quantitatively reversible enhancements and quenching of the photoluminescence of n-CdS semiconductors by the addition of gaseous bases and acids, respectively, clearly indicate not only that such phenomena are associated w ith the intrinsic basicity or acidity of these gases but also that... 

Computational studies concerning theoretical approaches to the intrinsic basicity of neutral nitrogen bases have been reported, including those of phos-phoranimines. The non-ionic phosphazene bases BEMP (112), BTPP (113) and (114, R = Ph) appear to be excellent catalysts for the Michael addition reactions. Thus the yield of the coupling reaction of ethyl isocyanoacetate with l,2-bis(4-bromomethylphenyl)ethane is increased by the addition of the phosphazene base BEMP. Polymer-supported BEMP (P-BEMP) has been applied for the allylation of 2H-benzo[d]l,3-dioxolan-5-ol by allyl bromide. " Cyclodehydration of 1,2 diacylhydrazines by tosyl chloride in the presence of P-BEMP leads to excellent yields of 1,3,4,-oxadiazoles. Addition of P-BEMP also improves the yield of the Hofmann elimination step in the synthesis of tertiary mines using REM resin (polymer-bound acrylate ester). ... 

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