474. The heats and entropies of ionisation of some aromatic and N-heteroaromatic amines

Elliott, J. J.; Mason, S. F.

doi:10.1039/jr9590002352

Cited by 34 publications

(7 citation statements)

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“…Recent studies [ 20 to 22 ] indicate clearly that it is the nuclear, or pyridine, nitrogen of 4-aminopyridine which has much the greater attraction for the proton. Indeed, Hirayama and Kubota [ 21 ] found that the proton does not add in significant amounts to the amino nitrogen even in 50-percent sulfuric acid.…”

Section: Discussionmentioning

confidence: 99%

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Dissociation constant of 4-aminopyridinium ion in water from 0 to 50 C and related thermodynamic quantities

Bates¹,

Hetzer²

1960

J. RES. NATL. BUR. STAN. SECT. A.

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The d issociat ion co nstant of 'l -a minopy ridinium ion in water a t 11 tempcratures from 0° to 50° C has bee n d eterm ined from elec tromotive forc e meas urem en ts of 19 approximat e ly eq ulmolal aqu eou s buffer solutions of 4-aminopyridin c a nd 4-a minopyridillium chlorid e. Cells wi thout liq uid jun ction were used ; the cell is represe nted as foll ows:where In is molali ty .Between 0° and 50° C, t he di ssociation constant (K bh) is given as a function of temperature ( T ) Thermody namic co nstants for the basic di ssocia t ion of 4-amin opyridin e a t 25° C were also compu ted.

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Section: Discussionmentioning

confidence: 99%

“…Elliott and Mason [ 20 ] have calculated the heat and entropy of ionization of 4-aminopyridinium ion from values of −log K bh at three temperatures, namely 5.4°, 20°, and 35° C. Their results are as follows:

…”

Section: Thermodynamic Quantitiesmentioning

confidence: 99%

Dissociation constant of 4-aminopyridinium ion in water from 0 to 50 C and related thermodynamic quantities

Bates¹,

Hetzer²

1960

J. RES. NATL. BUR. STAN. SECT. A.

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“…As Cl1-.rk and Perrin (25) have noted, many dificalties beset quantitative correlations of the base strcngtlis of ;~i!rogen hetcrocycIes with M O quantities; although there are correlations between pK~, and eiectrcn density at nitrogen with aza-derivliti\,es of alternant hydrocarbons and with polycyciic aro~n:~tic alniiies (26,27). Thus9 althougi?…”

Section: Jfo Qltantirics R I M / Joiii~ntio~i Belza~'iormentioning

confidence: 99%

Purine analogues. I. The status of Hückel molecular orbital calculations as predictors of proton shifts, basic strengths, and reactivity

Lynch¹,

Robertson²,

Webb³

1969

Can. J. Chem.

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A detailed series of n~olecular orbital calculations based on the HMO method lias been made for the various possible ionic species of purine, pyrazolo(3,4-d)pyrirnidine, v-triazolo(4,5-d)pyrimidine, and pyrazolo(3,4-b)pyridine. rt-Electron densities and localization and delocalization energies for nucleophilic substitution have been derived.The results are compared with the observed proton chemical shifts in the conjugate acids of these n~olecules, with the relative rates of nucleophilic piperidinodehalogenations in the neutral molecules, and with the ionization constants.It is concluded that it is possible to reconcile the calculations with experimental results for the various positions within a six-membered ring, but that positions in six-and five-membered rings cannot be directly compared. The electron densities seem to be of little value in correlating the observed ionization patterns of purines and their analogues.Canadian Journal of Chemistry, 47, 1129Chemistry, 47, (1969 Introduction As a consequence of their involvement as determinants of biological processes, the purine components of nucleic acids and their analogues have received much attention from synthetic organic chemists (1, 2) and from quantum chemists (3). However, there is little constructive interaction between the two groups: uncritical applications of molecular orbital (MO) calculations by synthetic chemists (4) often suggest that the calculations have little value, while defences of the value of simple MO treatments (5, 6) often quote irrelevant or incorrect supporting data. In this paper, we seek to show where simple MO calculations on appropriate ionic species of purines and their analogues are of correlative or predictive value, and also to indicate areas where the simple approach gives predictions at variance with experimental facts.We have chosen three areas where detailed comparisons between theory and experiment are possible: calculated n-electron densities and

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“…The ammonium ion would, therefore, have to have a pK, of about 7. This is less acidic than typical phenylammonium ions, e.g., the conjugate acid of 2-aminoanthracene has a pK, of 3.40 in 50% aqueous ethanol at 25°C (8).…”

Section: -Amino-9io-anthracenediolmentioning

confidence: 99%

The influence of pH in the tautomerism of 9,10-anthracenediols and 1,3-diketones

Anderson¹,

Broadbent²

1986

Can. J. Chem.

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Equations have been derived to describe how the ratio of the total concentration of all keto forms to that of all enolic forms (K′) varies with changing pH, for a tautomeric system in which the enol and ketone are polyprotic acids. The influence of pH on the tautomerism of 2-amino-9,10-anthracenediol, 2,9,10-anthracenetriol, 2,4-pentanedione, and 1-(3-pyridyl)-1,3-butanedione was examined. The equilibrium constants for all the acid–base equilibria involved were calculated from the dependence of K′ on pH.

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474. The heats and entropies of ionisation of some aromatic and N-heteroaromatic amines

Cited by 34 publications

References 0 publications

Dissociation constant of 4-aminopyridinium ion in water from 0 to 50 C and related thermodynamic quantities

Dissociation constant of 4-aminopyridinium ion in water from 0 to 50 C and related thermodynamic quantities

Purine analogues. I. The status of Hückel molecular orbital calculations as predictors of proton shifts, basic strengths, and reactivity

The influence of pH in the tautomerism of 9,10-anthracenediols and 1,3-diketones

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