The role of solvation and choice of anion in controlling the thermodynamic stability of the cyclooctatetraene and anthracene dianions

Abstract

The enthalpies of reaction for the alkali metal salts of the cyclooctatetraene dianion and sodium salt of the anthracene dianion with water were measured calorimetrically. These enthalpies were used in a thermochemical cycle with the heats of solution of the dianions In tetrahydrofuran (THF) and in hexamethylphosphoramide (HMPA) to evaluate the relative importance of solvation upon the thermodynamic stability of these dianions. It was found that the thermodynamic stability of the cyclooctatetraene dianion neutral ion aggregate (COT2-, 2M+) in THF and the solvated ions (COT2-+ 2M+) in HMPA relative to the gas-phase ions (COT2-g + 2M+g) follow the order Li > Na > K > Rb > Cs. This is attributed to the ion aggregate and cation enthalpies of solvation, which may vary as much as 110 kcal/mol with the choice of cation. In HMPA the single ion solvation enthalpies have been evaluated for the series of cations. The disodium salt of anthracene reacts more than twice as exothermically as does the COT salt.

Saturated and polymerizable amphiphiles with fluorocarbon chains. Investigation in monolayers and liposomes

“…Surface pressure-area diagrams of monolayers of different mixtures of 1 and 7 at 20 °C (subphase: H2OJ: Jt|, mole fraction of I. 4 for the muconic acid derivative 6 where the monolayer exhibits closer packing and a higher collapse pressure after polymerization.…”

“…Calcd for C28H15N04F34Br: C, 28.98; H, 1.74; N, 1.21. Found: C, 28.92; H, 1.74; N, 1.33. l//,lW,2//,2//-Perfluorododecyl Itaconate,4. 4 was prepared by refluxing a mixture of 0.5 g (4,5 mmol) of itaconic anhydride and 2.3 g (4 mmol) of 1H, 1 //,2//,2//-perfluorododecanol in toluene (30 mL) for 5 h in the presence of 100 mg of anhydrous ZnCl2 (added as a solution of 3 mL of acetone).…”

Condensation Products from the Anionic Radicals of C60 and the Common Solvent: Hexamethylphosphoramide

“…Clearly, these species do not yield metal hyperfine splittings. The weaker ion association is due to the better solvation of the smaller cations by the HMPA solvent system . The Li and Na systems yielding the hyperfine splitting from the single 31 P are analogous to those obtained in the C 60 3- (HMPA) • ,Cs + and C 60 3- (HMPA) • ,Rb + systems but without the tight ion association (structures I and II) and consequent metal hyperfine.…”

Untersuchungen an 1,4‐Naphthochinonen, 25. Mitt. Reaktion des Redox 5‐Lipoxygenase‐Inhibitors 2‐(3,5‐Di‐tert‐butyl‐4‐hydroxyphenyl)‐3‐hydroxy‐1,4‐naphthochinon mit O2•− und 3O2

“…Unsere Ergebnisse zeigen, d d sich die Reaktivittitsunterschiede im Oxygenierungssystem 02-DMSO-CO3" umkehren (Schema 5). 6 ist in DMSO bei RT sehr schlecht ldslich, eine unter diesen Bedingungen geriihrte Suspension zeigte keinerlei Reaktion. Bei 60-70 "C tritt LBsung ein und bei dieser Temperatur ist die Ausgangssubstanz nach 15 Stunden nicht mehr nachweisbar und 4 kann in 30proz.…”

“…Ausbeute isoliert werden. Im Gegensatz hierzu wird das in DMSO gut lbsliche Diphenohydrochinon 7 bereits bei RT in [6][7][8] Stunden uberwiegend zu 6 dehydriert und 4 wird nur noch als Nebenprodukt gebildet.…”