Statistical effects and the evaluation of entropy differences in equilibrium processes. Symmetry corrections and entropy of mixing

Bailey, William F.; Monahan, Audrey S.

doi:10.1021/ed055p489

Cited by 67 publications

(46 citation statements)

References 5 publications

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“…[15] As measured by 1 H integration, the deviation of the observed ratio of 1:2.3 (0.43) from the statistical ratio is small, indicating only a small preference for hetero-disulfide formation.…”

Section: Resultsmentioning

confidence: 87%

Disulfides, Imines, and Metal Coordination within a Single System: Interplay between Three Dynamic Equilibria

Sarma

Otto

Nitschke

2007

Chemistry A European J

116

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We report a system in which three distinct dynamic linkages, disulfide (S-S), imine (C=N), and coordinative (N-->metal) bonds were shown to be capable of simultaneous reversible exchange. The "disulfide layer" of the system under study consists of two homo-disulfides, bis(4-aminophenyl) disulfide 1 and bis(4-methoxyphenyl) disulfide 2 that equilibrate in the presence of catalytic amount of triethylamine to favor the formation of a hetero-disulfide product, 4-aminophenyl-4'-methoxyphenyl disulfide 3. The addition of 2-formylpyridine and a metal salt strongly perturbed this 1+2<-->3 equilibrium through the formation of metal complexes incorporating disulfide 1 as a subcomponent. CuI perturbed the equilibrium by a factor of 3.3, and FeII by a factor of 179, in both cases in favor of the homo-disulfides. The disulfide equilibrium could be further modified, following metal-complex formation, by coordinative (transmetallation: substitution of FeII for CuI) or covalent (imine exchange: the substitution of one amine residue for another) exchange. Thus, although the three kinds of dynamic linkages were demonstrated to be mutually compatible, changes at one kind of linkage could be used to predictably perturb an equilibrium involving another.

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Section: Resultsmentioning

confidence: 87%

Disulfides, Imines, and Metal Coordination within a Single System: Interplay between Three Dynamic Equilibria

Sarma

Otto

Nitschke

2007

Chemistry A European J

116

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“…Thus, M 1-3 constitute F (+ ,+) ,M 4-7 constitute F (0, +) ,M 8-11 constitute F (+ ,À) ,M 12-14 constitute F (0,0) ,M 15-18 constitute F (0,À) and M [19][20][21] constitute F (À,À) .The only 6dimers with very low concentrationsw eret hose of the two families combining BBs with chargesoft he same sign (F (+ ,+) and F (À,À) ).…”

Section: Resultsmentioning

confidence: 99%

“…The statistical composition of the library,t aking into account the 1:2h omo/heterodimer ratios, [19] can be calculated as 11.1 % for each of the families F (+ ,+) ,F (0,0) ,a nd F (À,À) ,w hereas it is 22.2 %f or the families F (0, +) ,F (+ ,À) ,a nd F (0,À) .F igure 1b clearly shows that in the absence of salt the composition of the library is markedlyd ifferent from the statistical distribution:T he library is initially far from the statistically likelys ituation. However,t he increase of the salt concentration appears to asymptoticallya pproacht he percentage of each familyt ot he corresponding values of 11.1 and 22.2 %.…”

Section: Resultsmentioning

confidence: 99%

Salt‐Induced Adaptation of a Dynamic Combinatorial Library of Pseudopeptidic Macrocycles: Unraveling the Electrostatic Effects in Mixed Aqueous Media

Atcher

Moure

Bujons

et al. 2015

Chemistry A European J

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Dynamic combinatorial libraries are powerful systems for studying adaptive behaviors and relationships, as models of more complex molecular networks. With this aim, we set up a chemically diverse dynamic library of pseudopeptidic macrocycles containing amino-acid side chains with differently charged residues (negative, positive, and neutral). The responsive ability of this complex library upon the increase of the ionic strength has been thoroughly studied. The families of the macrocyclic members concentrating charges of the same sign showed a large increase in its proportion as the ionic strength increases, whereas those with residues of opposite charges showed the reverse behavior. This observation suggested an electrostatic shielding effect of the salt within the library of macrocycles. The top-down deconvolution of the library allowed us to obtain the fundamental thermodynamic information connecting the library members (exchange equilibrium constants), as well as to parameterize the adaptation to the external stimulus. We also visualized the physicochemical driving forces for the process by structural analysis using NMR spectroscopy and molecular modeling. This knowledge permitted the full understanding of the whole dynamic library and also the de novo design of dynamic chemical systems with tailored co-adaptive relationships, containing competing or cooperating species. This study highlights the utility of dynamic combinatorial libraries in the emerging field of systems chemistry.

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“…This effectively corresponds to the removal of entropic contributions from purely statistical effects, which is required prior to any attempt to relate thermodynamic data to structural parameters such as steric effects, nonbonded interactions, etc. (8,9).…”

Section: Ch2ch3mentioning

confidence: 99%

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

St-Amour¹,

St‐Jacques²

1983

Can. J. Chem.

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The conformational properties of 2-alkyl (Me, Et, i-Pr, and t-Bu) and 2-phenyl derivatives of 1,3-dioxa-5,6-benzocycloheptene (1) were studied by 13C dnmr. Analysis of slow exchange spectra at 100.6 MHz indicates that all derivatives except tert-butyl exist in an equilibrium of chair (major) and twist-boat (minor) conformations. Substituent effects on the position of the equilibrium are rationalized in terms of steric effects.

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Statistical effects and the evaluation of entropy differences in equilibrium processes. Symmetry corrections and entropy of mixing

Abstract: Evaluation of entropy differences in terms of the symmetry properties of the species involved in the equilibrium is not only a pedagogically useful exercise, it is of fundamental importance in the evaluation of empirical thermodynamic data.

Cited by 67 publications

References 5 publications

Disulfides, Imines, and Metal Coordination within a Single System: Interplay between Three Dynamic Equilibria

Disulfides, Imines, and Metal Coordination within a Single System: Interplay between Three Dynamic Equilibria

Salt‐Induced Adaptation of a Dynamic Combinatorial Library of Pseudopeptidic Macrocycles: Unraveling the Electrostatic Effects in Mixed Aqueous Media

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

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