Richard J. Ranson

Reexamination of magnetic isotope and field effects on adenosine triphosphate production by creatine kinase

The influence of isotopically enriched magnesium on the creatine kinase catalyzed phosphorylation of adenosine diphosphate is examined in two independent series of experiments where adenosine triphosphate (ATP) concentrations were determined by a luciferase-linked luminescence end-point assay or a real-time spectrophotometric assay. No increase was observed between the rates of ATP production with natural Mg, 24Mg, and 25Mg, nor was any significant magnetic field effect observed in magnetic fields from 3 to 1,000 mT. Our results are in conflict with those reported by Buchachenko et al. [J Am Chem Soc 130:12868–12869 (2008)], and they challenge these authors’ general claims that a large (two- to threefold) magnetic isotope effect is “universally observable” for ATP-producing enzymes [Her Russ Acad Sci 80:22–28 (2010)] and that “enzymatic phosphorylation is an ion-radical, electron-spin-selective process” [Proc Natl Acad Sci USA 101:10793–10796 (2005)].

Mössbauer studies on ferrocene complexes : II. Ironhydrogen-bonded complexes of ferrocene

Abstract Ironhydrogen-bonded complexes of ferrocene have been studied by Mossbauer spectroscopy. The high quadrupole splittings are interpreted in terms of ring-tilting and charge distribution and compared with results from ferrocene mercuric chloride adducts. Correlations are found between isomer shift and quadrupole splittings in the compounds studied.

13C chemical shifts and carbonyl stretching frequencies as structural probes for ferrocenyl ketones

Abstract 13 C chemical shifts (δ(CO)) have been measured for a series of aromatic ferrocenyl ketones (FcCOC 6 H 4 X) and some sterically hindered analogues (FcCOR, R = mesityl, anthracyl, t-Bu, adamantyl). The shifts correlated quite well with those of the corresponding benzophenones. From the carbonyl carbon shifts (δ(CO)), estimates were made of the interplanar angle between the carbonyl sp 2 and the phenyl ring planes. Substituent effects of the Cp ring carbons are discussed. The solution (CCl 4 ) infrared spectra of the derivatives were obtained and the carbonyl stretching frequency (ν(CO)) was found to correlate roughly with δ(CO). Estimates were also made of the interplanar angle between the cyclopentadienyl ring plane and the carbonyl plane, for sterically hindered ketones using δ(CO) values.

Intramolecular catalysis. Part 5. The intramolecular Cannizzaro reaction of o-phthalaldehyde and [α,α′-2H2]-o-phthalaldehyde

o-Phthalaldehyde, as well as the α,α′-dideuterio isomer, has been shown to undergo a Cannizzaro reaction in water containing base, while partially hydrated and ionised. The reaction of the monoanion of the hydrate is intramolecular and of the first order in the monoanion of the hydrate, and either first or zero order in the base. The rate coefficients have been measured at several temperatures and activation parameters evaluated. The kinetic isotope effect, kH/kD, for the first and second order processes were found to be ca. 1.9 and 1.8, respectively. The alkaline hydrolysis of the corresponding lactone, phthalide, has also been studied under the same conditions. The evidence for the intramolecular Cannizzaro reaction indicates a mechanistic pathway involving rate-determining hydride transfer from the chain tautomers of both monoanion and dianion of the hydrate.

Reactions of carbonyl compounds in basic solutions. Part 17. The alkaline hydrolysis of substituted (E)-5,5′-diphenylbifuranylidenediones and 3,7-diphenylpyrano[4,3-c]pyran-1,5-diones

The alkaline hydrolyses of aseriesof substituted (E)-5,5′-diphenylbifuranylidenediones and 3,7-diphenylpyranq[4,3-c]pyran-1,5-diones have been shown to proceed by biphasic pathways. In both cases, a very rapid primary reaction gives hydrolysis of one lactone ring. This is followed by a less rapid secondary reaction giving hydrolysis of the second ring and identical products from both systems. Rate coefficients for the secondary reactions have been measured in 70%(v/v) dioxane–water at 30.0 °C and, for the parent substrates, at 49.0 °C. The enthalpies and entropies of activation have been evaluated. The effects of substitution have been assessed by means of the Hammett equation. Reaction pathways are suggested and the reactivity is related to the ring size.

Synthesis and reactivity of some bridgehead organotin derivatives of triptycene

Abstract New organotin derivatives of triptycene are reported. The reactivity of these compounds has been studied semi-quantitatively. In 9-trimethylstannyltriptycene, the tin—triptycene bond is inert to electrophilic substitution and the tin—methyl bonds are much less reactive than the corresponding bonds in 1-trimethylstannyladamantane. An alternative route to organometallic derivatives of triptycene via a Diels—Alder addition reaction of benzyne to the appropriate anthracene is also described.

Spectral properties and kinetics of the alkaline hydrolysis of chromium, tricarbonyl[3-[(η6-aryl)methylene]-Z-1(3H)-isobenzofuranones]

Abstract The infrared and 13 C NMR spectra and the kinetics of alkaline hydrolysis of chromium, tricarbonyl[3-[( η 6 -aryl)methylene]- Z -1(3H)-isobenzofuranones] have been studied in comparison with those of 3-arylmethylene- Z -1(3H)-isobenzofuranones. The 13 C NMR spectroscopy has been found to be the most suitable tool for recognition of the site of complexation in the 3-arylmethylene- Z -1(3H)-isobenzofuranone system. A statistically significant correlation has been found between the arithmetic means of the wave numbers of symmetric and asymmetric stretching vibrations of Cr(CO) 3 group and σ p constants of the substituents. The large slope of this linear dependence suggests an important role of the mesomeric mechanism in the transmission of electronic effects to the Cr(CO) 3 moiety. The strong electron-withdrawing effect of the Cr(CO) 3 group causes a significant decrease of the polarity of the phthalide CO bond. The reaction rates of the alkaline hydrolytic ring-opening reaction dramatically increase due to the effect of Cr(CO) 3 group. The absorption bands of the carbonyl stretching vibrations are markedly split due to Fermi resonance effect. After mathematical correction for Fermi resonance the wave numbers of the unperturbed fundamental CO stretching vibration and the log k values of alkaline hydrolysis exhibit significant linear correlations mutually, as well as with Hammett σ substituent constants. Chartons transmissive factors γ (PhCr(CO) 3 ) have been determined for tricarbonylchromiumphenyl system using the parameters of the linear correlations. The efficiency of the substituent effect transmission is high in CCl 4 , because a back-donation effect of the carbonyl ligands and decreases in CHCl 3 due to the hydrogen bonding between carbonyl groups and solvent molecules. The preparation of some novel chromium, tricarbonyl[3-[( η 6 -aryl)methylene]- Z -1(3H)- isobenzofuranones] is described.

Base‐catalysed hydrolysis of γ‐lactones: reactivity–structure correlations for 3‐(aryl‐ and alkylmethylene)‐(Z)‐1(3H)‐isobenzofuranones

Rate coefficients were measured for the base-catalysed hydrolysis of a series of γ-lactones, i.e. 39 substituted 3-(aryl- and alkylmethylene)-(Z)-1(3H)-isobenzofuranones (3-aryl- and alkylmethylenephthalides) in 70% (v/v) aqueous dioxane at 30·0 °C. A Hammett reaction constant for the 3- or 4-substituted phenyl series is ca 1·5, whereas those for the 2-substituted phenyl and 4-substituted 1-naphthyl series, using para-σ values, are ca 1·0 and 1·9. These results are related to an electrostatic field effect model. A very successful correlation between the rates of alkaline hydrolysis of all 39 phthalides and the carbonyl stretching frequencies in chloroform was found. Substituent effects in widely different environments give linearly related effects on both reactivity and physical properties. Computational studies using the semi-empirical AM1 method correctly modelled both the details of the mechanistic pathway and the substituent effects.

Base-catalysed hydrolysis of γ-lactones: reactivity–structure correlations for 3-(substituted phenoxy- and thiophenoxymethylene)-(Z )-1(3H )-isobenzofuranones

Rate coefficients were measured for the base-catalysed hydrolysis of a series of substituted 3-(phenoxy- or thiophenoxymethylene)-(Z)-1(3H)-isobenzfuranones (3-phenoxy- or thiophenoxymethylenephthalides) in 70% (v/v) aqueous dioxane at 30.0 °C, in addition to the carbonyl stretching frequencies in chloroform and tetrachloromethane following deconvolution and band separation, when required. The Hammett reaction constants for the alkaline hydrolysis of the 3-/4-substituted phenoxy and thiophenoxy series are ca 0.75 and 1.10, respectively. These results are related to electrostatic field and resonance effects. Successful correlations between the carbonyl stretching frequencies and substituent constants and the rates of alkaline hydrolysis were found. Computational studies using the semi-empirical AM1 method correctly model both the details of the mechanistic pathway and the substituent effects.

Nucleophilic substitution at sulphur. Part 3. The alkaline hydrolysis of some cyclic and open-chain sulphonate esters

The rates of alkaline hydrolysis of a number of aryl cyclic and open-chain sulphonate esters have been studied at various temperatures. The enthalpies and entropies of activation have been determined. The difference in reactivity between the five-membered sultone and other cyclic and open-chain analogues is shown to arise from a combination of both enthalpy and entropy strain. The detailed mechanism of alkaline hydrolysis of sulphonate esters and the cause of ring strain in sultones are discussed in some detail.