M. John Perkins

A water-soluble, nitroso-aromatic spin-trap

The preparation and use in spin-trapping experiments of sodium 3,5-dibromo-4-nitrosobenzene-sulphonate and its dideuterio-analogue are described.

Concerning the mechanism of Gif oxidations of cycloalkanes

The oxygen atom of cyclodecanone, formed by oxidation of cyclodecane using FeCl3–H2O2 in pyridine–acetic acid, is largely derived from molecular oxygen: taken in conjunction with results of radical-trapping experiments, this supports a free-radical mechanism for the hydrocarbon activation.

Some nitrosoamino acids in bacon adipose tissue and their contribution to the total N-nitroso compound concentration

ZusammenfassungDer Gehalt an Nitrosoaminosäuren und ihr Anteil an den Gesamt-N-Nitrosoverbindungen im Fettgewebe von rohem Schinkenspeck wurde untersucht. In 80% der Proben wurde ein Gehalt an Nitrosoaminosäuren von bis zu 0,2 mg/kg festgestellt. Scheinbare Gesamt-N-Nitrosoverbindungen waren in allen Proben in einer Konzentration von 0,4 bis 3,7 mg (N-NO)/kg vorhanden. Die eigentlichen Nitrosoaminosäuren machen nur etwa 1% der scheinbaren Gesamt-N-Nitrosoverbindungen aus. Die Mehrzahl der scheinbaren Gesamt-N-Nitrosoverbindungen im Fettgewebe findet sich im nichtlöslichen Bindegewebe, wobei der verbleibende Rest chloroformlöslich ist.SummaryThe levels of nitrosoamino acids and apparent total N-nitroso compounds in the adipose tissue of raw bacon have been examined. Nitrosoamino acids were detected in 80% of the samples in levels of up to 0.2 mg/kg. Apparent total N-nitroso compounds were present in all samples in concentrations of between 0.4 and 3.7 mg (N-NO)/kg. Nitrosoamino acids accounted for approximately only 1 % of the apparent total N-nitroso compounds. The majority of the apparent total N-nitroso compounds in the adipose tissue were associated with the insoluble connective tissue fraction, with the remainder present as chloroform soluble species.

Electron spin resonance study of the fragmentation of some cyclic and acyclic dialkoxyalkyl radicals. The mechanism of 1,2-rearrangement of β-acyloxyalkyl radicals

The di-t-butoxymethyl radical and a series of 1,3-dioxolanyl and 1,3-dioxanyl radicals have been generated and studied by e.s.r. spectroscopy in soulution. All of these radicals undergo β-scission under appropriate conditions, β-acyloxyalkyl radicals resulting from the 1,3-dioxolanyl radicals. The kinetics of β-scission of these dialkoxyalkyl radicals have been measured, and it is found that the di-t-butoxymethyl radical decomposes much more readily than the analogous cyclic 4,4,5,5-tetramethyldioxolanyl radical undergoes ring opening. The relevance of these results to the mechanism of vicinai rearrangement of β-acyloxyalkyl radicals is discussed. The rate constant for addition of the di-t-butoxymethyl radical to nitrosobutane is found to be about 106 l mil–1S–1 at 40° in benzene.

Photochemical reduction of carbon–carbon and carbon–nitrogen double bonds by benzeneselenol

Irradiation of β-aryl-αβ-unsaturated carbonyl compounds and of some imino-derivatives of benzaldehyde in the presence of benzeneselenol leads to formation of the corresponding saturated compounds.

S H 2 reactions of diphenyl diselenide; preparation and reactions of bridgehead selenides

For the SH2 process R·+ PhSeSePh → PhSeR + PhSe·, k=ca. 5 × 107 mol–1 s–1 at 80 °C in benzene when R is primary alkyl; with 1-adamantyl radicals this SH2 displacement affords a route to 1-adamantyl phenyl selenide which, on oxidation and pyrolysis of the resultant selenoxide, gives adamantan-1-ol; in contrast the selenoxide from bicyclo[3.3.1]nonan-1-yl phenyl selenide decomposes via bicyclo[3.3.1]non-l-ene.

The preparation and rates of deprotonation of some cyclopropylcarbinyl ketones

A group of cyclopropylcarbinyl phenyl ketones has been prepared, and the rates of base-catalysed isotope exchange of the α-hydrogen atoms have been compared with those of suitable model compounds. The results support an earlier finding which suggests that a cyclopropyl group exerts little stabilisation on an adjacent carbanionic centre, whereas the effect of a vinyl group is considerable. Only small rate variations are found when the cyclopropane ring contains a phenyl or p-nitrophenyl substituent. Some novel reactions occurring during the synthesis of related polycyclic ketones are noted.

An unusual photochemical rearrangement of a ketone

Ultraviolet irradiation of a benzene solution of trans-1-phenyl-2-phenacylcyclopropane caused equilibration with the cis-isomer, and cyclization to 4-phenyl-3,4-methano-1-tetralone.

Electron spin resonance spectra of selenuranyl radicals R2Se–X

E.s.r. spectra assigned to the σ* selenuranyl radicals R2Se[graphic omitted]X (R = alkyl or aryl) are detected in solution during photochemical generation of X·[CF3S·, R′C(O)S·, Me3CO·, or Me3SiO·] in the presence of dialkyl or alkyl aryl selenides.

Determination of the thermodynamic parameters for transfer of alkoxyphenols from aqueous solution to SDS micelles by a Taylor–Aris diffusion technique

Using Taylor–Aris diffusion techniques, thermodynamic parameters have been measured for the transfer of a series of alkoxyphenols from water into SDS micelles. The results are compared with those for transfer to bulk organic solvents and to cells of Escherichia coli. The SDS micelles are found to be marginally more polar than n-octanol, but the results reveal significant differences between bulk solvents and the more ordered micellar pseudophase.