Solvation of aminopyridines by water and methanol

Spencer, J. N.; Barton, Scott W.; Smith, K. A.; Wolbach, Wendy S.; Powell, Joan F.; Kirshenbaum, M. R.; Firth, D. W.

doi:10.1139/v83-034

Cited by 5 publications

(7 citation statements)

References 3 publications

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“…creases directly with the N-H bond enthalpy in almost a one-to-one correspondence. Similar results are found for corresponding interactions with 2-and 3-aminopyridine (8). The N-H, enthalpies for these two compounds are -3.5 and -3.7 kcal mol-', respectively, and the amino nitrogenmethanol interactions are -1.7 and -1.9 kcal mol-', respectively.…”

Section: Calculation and Discussionsupporting

confidence: 79%

“…The cavity and interaction terms for the benzene moiety are insignificant. The transfer enthalpy, water to methanol, is +0.8 kcal mol-' for the methyl group (9) and -0.4 kcal mol-' for the nitrogen (8,9). Thus the transfer enthalpy for the carbonyl group is +2.5 kcal mol-'.…”

Section: Calculation and Discussionmentioning

confidence: 99%

“…For adenine, the interaction at the amino group was considered to be the formation of two hydrogen bonds by the solvent, either methanol or water, to the N6 protons. These interactions were taken to be the same as those found from pure base calorimetric analysis for the amino group interaction of 2-aminopyridine with methanol and water, -3.5 and -2.8 kcal mol-', respectively (8). Previous studies of pyrrole, imidazole, the diazines (9), and the aminopyridines showed that an interaction by methanol at the nitrogen of amino groups and at the nitrogen of N-H ring groups was responsible for the greater enthalpic stability of the aminopyridines, pyrrole, and imidazole in methanol relative to water ( Table 1).…”

Section: Calculation and Discussionmentioning

confidence: 99%

“…The interactions at N1 and N3 of purine and adenine were The calorimetric methods used have been previously described as have the purifications of water and methanol (8). Aldrich tech.…”

Section: Calculation and Discussionmentioning

confidence: 99%

“…The model compound 1-methyl-2-pyridone and previously determined interaction enthalpies were used to make these assignments (8,9).…”

Section: Calculation and Discussionmentioning

confidence: 99%

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Hydrogen bonded interactions of methanol and water with purines and pyrimidines

Spencer¹,

Barton²,

Smith³

et al. 1983

Can. J. Chem.

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The solvation of benzimidazole, 4-azabenzimidazole, purine, adenine, uracil, thymine, and cytosine in water and methanol was determined by a combination of calorimetric and spectral analysis. Specific enthalpies have been assigned to each interaction site in the first solvation shell. Calculations, based on the enthalpies of hydrogen bond formation with water, and estimates for intermolecular hydrogen bond enthalpies, show that the self-association of purine and adenine in water through hydrogen bonded interactions is enthalpically possible.

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Section: Calculation and Discussionsupporting

confidence: 79%

Section: Calculation and Discussionmentioning

confidence: 99%

Section: Calculation and Discussionmentioning

confidence: 99%

“…The interactions at N1 and N3 of purine and adenine were The calorimetric methods used have been previously described as have the purifications of water and methanol (8). Aldrich tech.…”

Section: Calculation and Discussionmentioning

confidence: 99%

“…The model compound 1-methyl-2-pyridone and previously determined interaction enthalpies were used to make these assignments (8,9).…”

Section: Calculation and Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Hydrogen bonded interactions of methanol and water with purines and pyrimidines

Spencer¹,

Barton²,

Smith³

et al. 1983

Can. J. Chem.

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Alkylating properties of phosphate esters. 4. Medium effects on methylation of pyridines by trimethyl phosphate

Modro

1989

J of Physical Organic Chem

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The rates of N-methylation of pyridine and its ring-substituted derivatives by trimethyl phosphate were measured in D20 and in CDC13. Relative rates, together with the solvent activity coefficients of substrates for the transfer from chloroform to water, were used for determining the solvent activity coefficients of the activated complexes for this SN2 reaction. The results indicate early activated complexes for all pyridines, with the most nucleophilic substrate showing the most reactant-like activated complex.Studies of solvent effects on the rates of quaternization of tertiary amines are almost a century old,' and the Menschutkin reaction, equation (l), proved to be a well tested and convenient model for studies of medium effects on the reactivity of organic systems.'The suitability of reaction (1) to mechanistic studies stems from the fact that it offers structural variations in both the nucleophilic and the electrophilic reagents, as well as that its rate can be measured in a great variety of solvents. It is generally accepted that the Menschutkin reaction can be described as a classical sN2 reaction3 with a rather early activated complex (AC), occurring not further than at cu. 0.2-0.3 of the way along the reaction ~o o r d i n a t e .~ Scrutiny of the available data revealed that studies of sN2 reactions between non-ionic reactants seldom involved aqueous media, and that for reactions involving ions only in one isolated case the dialkylphosphate group was chosen as a leaving group (demethylation of trimethyl phosphate by azide ions).5 Because of our interest6 in the alkylating properties of organic phosphates, and because of the importance of the nucleophilic O-demethylation step in the 'triester' method of oligonucleotides ~ynthesis,~ we decided to investigate the effect of solvents on the reaction of methylation of the nitrogen atom in pyridine by trimethyl phosphate (TMP), equation (2). 'Author for corespondence. A . M. MODRO AND T. A. MODRO X-(@3) and attributed this to the hydrogen bonding of pyridine substrates by the solvent. Since in the aqueous medium, i.e. under conditions of an even stronger involvement of the pyridine

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Hydrophobic hydration of thymine

Spencer

Judge

1983

J Solution Chem

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Solvation of aminopyridines by water and methanol

Cited by 5 publications

References 3 publications

Hydrogen bonded interactions of methanol and water with purines and pyrimidines

Hydrogen bonded interactions of methanol and water with purines and pyrimidines

Alkylating properties of phosphate esters. 4. Medium effects on methylation of pyridines by trimethyl phosphate

Hydrophobic hydration of thymine

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