Complete thermodynamic analysis of the ''anomalous order '' of amine basicities in solution

, 675 (1984). A new method for production of chloride ion adducts, MC1-, via a sequence of bimolecular ion molecule reactions involving chloroformate esters is described. These reactions have been used in trapped-ion ion cyclotron resonance thermal equilibrium studies to determine the relative chloride ion affinities of twenty compounds with C1-binding energies in the range 10-25 kcal mol-I. The present results are found to be in good agreement with chloride affinities obtained by other methods. The resulting chloride affinity scale establishes a convenient framework for the systematic investigation of effects of molecular structure and chemical properties on the binding energy of Cl-to both Lewis and Bronsted acids.

“…[7] and [8]. [7] ClCOz-+ M + MC1-+ COz [8] C12C02R-+ M + M C l + CICOzR A typical result is that shown in Fig.…”

Section: Results and Discussion I Negative Ion Chemistry Of Chlorofmentioning

confidence: 79%

Gas phase negative ion chemistry of alkylchloroformates. A convenient method for bimolecular generation of chloride ion adducts and determination of chloride affinities from ion cyclotron resonance thermal equilibrium measurements

Larson¹,

McMahon²

1984

“…Amett and Taft have examined the gas and aqueous basicities of a majority of bases (14,15). By means of Born-type cycles involving the gas phase and the aqueous proton transfer reactions as well as associated thermochemical data, these authors were able to obtain the relative hydration energies of protonated bases BH+'s (14).…”

Section: Introductionmentioning

confidence: 99%

“…By means of Born-type cycles involving the gas phase and the aqueous proton transfer reactions as well as associated thermochemical data, these authors were able to obtain the relative hydration energies of protonated bases BH+'s (14). The substituent and solvent effects on proton transfer equilibria were fully discussed (15).…”

Section: Introductionmentioning

confidence: 99%

Relationship between gas-phase proton affinities of conjugate bases B's and free energies of hydration of conjugate acid ions BH⁺'s for B = alkyl-substituted H₂O and NH₃

Hiraoka¹

1987

KENZO HIRAOKA. Can. J. Chem. 65, 1258 (1987. An approximate linear relationship between the proton affinities of conjugate bases (B 's) and the free energies of hydration of conjugate acid ions (BH' 's) is found for B = alkyl-substituted H 2 0 and NH3. With increase in proton affinities, the free energies of hydration increase linearly with a slope of about 1 for analogous compounds. The charge delocalization in the protonated bases and the structure-making effect induced by the hydrophobic groups in the alkyl-substituted H 3 0 + and NH4' are crucial factors in the determination of the free energies of hydration.

“…The simple approach, based on a comparison of pKa values, led to the wellknown amine anomaly (9,10) where R2NH > R3N > RNH2, an order contrary to normal expectations based on inductive effects. It was subsequently found that the expected order was followed in the gas phase (1 [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and hence the anomaly could not be attributed to steric effects (15,16) or to other internal factors (17) but rather mas associated with solvation.…”

Section: Introductionmentioning

confidence: 97%

Thermodynamic parameters for the basic ionization of some cyclic amines in water

Lobo¹,

Murty²,

Robertson³

1976

SHEILA TERESA LOBO, TANIKELLA S. S. R. MURTY, and Ross ELMORE ROBERTSON. Can. J. Chem. 54, 3607 (1976).The thermodynamic parameters defining the basic dissociation in water of diethylamine, cyclohexylamine, piperidine, and quinuclidine have been determined by a dilution method based on conductance measurements. 54, 3607 (1976).Les paramktres thermodynan~iques dkfinissant la dissociation basique, dans l'eau. de la diethylamine, de la cyclohexylamine, de la pipCridine et de la quinuclidine ont Ct C determinis par une mkthode de dilution basCe sur des mesures de conductivitCs. A 25 ^C, les valeurs de ASaO et de ACPa0 pour l'ionisation acide des ions ammonium correspondants sont ASaO -8.08, -1.24, -8.51, -13.65 cal deg-I molkl et ACPa0 13.9, -2.7, 18.0, 4.2 cal deg-1 mol-1. On discute de la relation entre ces valeurs dCriv6es et les changements dans la solvation: on note les valeurs apparemment anormales du ACDaO de la cyclohexylan~ine et de la quinuclidine mais on ne peut les rationaliser.[Traduit par le journal] Introduction In this paper we report the thermodynamic quantities defining the ionization of certain cyclic amines in water and note the relationship between these quantities and structure.The search for structure-reactivity relationships for the ionization of amines in water has a long history (1-8). The simple approach, based on a comparison of pKa values, led to the well-