Preparation,structural characterization,and acid-catalyzed isomerization of 3-, 7-, and 9-benzyl-6-benzylthiopurines

Benzylation of 6-benzylthiopurine was examined. Structural assignments of the products were determined by 1-D and 2-D nmr spectroscopy (HMQC, HMBC, and nOe). In the presence of base, the isomeric N3-, N7-, and N9-benzylated products 4, 3 , and 2 were isolated; however, only 9-benzyl-6-benzylthio-purine ( 2 ) was obtained in the absence of base. In the latter case, the initially formed N3- and N7-isomers were, in the presence of acid, converted to 9-benzyl-6-benzylthiopurine ( 2 ) via a 6-benzylthiopurine intermediate as evidenced by analysis of the reaction over time using reversed-phase hplc.     

Analysis of N-nitroso compounds encountered in metal-working coolant fluids

Summary The determination of an N-nitroso compound encountered in metal-working coolant fluids has been investigated using differential pulse polarography, gas chromatography and thin-layer chromatography. The only fluids found to contain an appreciable concentration (>0.5 g ml^–1) of an N-nitroso compound were those which were formulated to contain high concentrations of di- and tri-ethanolamines and sodium nitrite. The N-nitroso compound isolated from these fluids has been investigated using gas chromatography/mass spectrometry and the evidence obtained from this and other studies suggest that the N-nitroso compound present in metal-working fluids which have been allowed to stand for 6–12 months is the mono-nitrite ester of N-nitrosodiethanolamine.

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Analyse von N-Nitrosoverbindungen in Kühlflüssigkeiten, die bei der Metallbearbeitung verwendet werden

Zusammenfassung Die Analysen wurden mit Hilfe der Differential-Puls-Polarographie, Gas-Chromatographie und Dünnschicht-Chromatographie durchgeführt. Nennenswerte Konzentrationen an N-Nitrosoverbindungen (>0,5 g/ml) wurden nur in solchen Kühlflüssigkeiten gefunden, die hohe Konzentrationen an Di- und Triethanolamin sowie Natriumnitrit enthielten. Die aus diesen Proben isolierte N-Nitrosoverbindung wurde gas-chromatographisch/massenspektrometrisch analysiert und es ergab sich zusammen mit anderen Untersuchungen, daß es sich dabei um den Mononitritester von N-Nitrosodiethanolamin handelte (die Flüssigkeiten wurden in diesem Fall 6–12 Monate stehen gelassen).

     

The synthesis,characterization and reactions of a binuclear tetramethylplatinum(IV) complex

Reaction of excess MeLi and MeI with [PtCl₂SMe₂)₂] gives the first binuclear tetramethylplatinum(IV) complex [Pt₂Me₈(μ-SMe₂)₂]. The characterization of this complex, and its reactions with donor ligands to give cis-[PtMe₄L₂] (L₂ = Ph₂PCH₂PPh₂, Ph₂PCH₂CH₂PPh₂, 2,2′-bipyridyl, 1,10-phenanthroline or L = PMe₂Ph, PMePh₂) are described.     

Effect of alkoxides on chain termination and chain transfer of sodium-catalyzed polybutadiene

The reaction of butadiene with n-butylsodium or metal alkoxide-modified n-butylsodium was studied. A loss of “live ends” was observed when the polymerization of butadiene-1,3 with n-butylsodium was conducted in hexane solvent. This occurs, presumably, by elimination of NaH or Na metal in the allylic system. Similar results were obtained when the polymerization was carried out in the presence of sodium-tert-butoxide-modified n-butylsodium. However, the modification of n-butylsodium by lithium or potassium tert-butoxide in the butadiene-1,3 polymerization showed no loss of live ends for a period of two weeks. The results and an explanation are discussed.     

Matrices of bisimple regular semigroups

A semigroup S is a matrix of subsemigroups S_iμ, i ε I, μ ε M if the S_iμ form a partition of S and S_iμS_jν≤S_iν for all i, j in I, μ, ν in M. If all the S_iμ are bisimple regular semigroups, then S is a bisimple regular semigroup. Properties of S are considered when the S_iμ are bisimple and regular; for example, if S is orthodox then each element of S has an inverse in every component S_iμ.     

Translational hull of an inverse semigroup

The theory of ideal extensions of semigroups is dependent upon adequate knowledge of the translational hull. We characterize here certain basic structures in the translational hull, Ω(S), of an arbitrary inverse semigroup S: in particular, the semilattice of idempotents of Ω(S) and the group of units of Ω(S). An isomorphic copy of each of these structures is given in terms of the semilattice of idempotents of S.