Field desorption mass spectrometry of quaternary ammonium salts: Cluster ion formation

The field desorption mass spectra of salts such as quaternary ammonium and carbenium salts with organic cations in addition to high cation intensities show signals for cluster ions composed of the salt cation + salt molecule, i.e. [C + nM]⁺, n = 1–5, thus allowing determination of the molecular weights of salts. In some cases cluster ions of the type [nM – 1]⁺ are detected. Conditions for the formation of cluster ions are discussed.     

Synthesis of substituted 3-amino[6,5-b]triazinoindoles

4-[(9-Methyl-as-triazino[6,5-b]indol-3-yl)amino]-2-methyl-2-butanol ( 13 ) and the corresponding 2-methyl-3-imino derivative 12 were synthesized and tested in vitro against Rhino 2 virus. The two compounds were more active than the known triazino[5,6-b]indole 4 . 2,9-Dimethyl-3-methoxy-9H-as-triazino[6,5-b]indolium tosylate ( 21 ) and the related 3-methylthio compound 9 were prepared. Quaternary 21 formed a pseudo base, 22a , whereas quaternary 9 did not form a pseudo base.     

INTERACTION OF VIOLOGEN DYES WITH CHROMATOPHORES AND REACTION-CENTER PREPARATIONS FROM RHODOSPIRILLUM RUBRUM

Abstract —Various low-potential viologen dyes enhance light-induced absorption changes in the near-infrared region (ΔA870) in chromatophore preparations from Rhodospirillum rubrum in the presence of dichlorophenol indophenol and a high concentration of ascorbate (DCPIP + asc). An increase in ΔA870 was also observed in large reaction-center preparations from R. rubrum with viologens in the presence of ascorbate. Our results indicate that E'₀, of the primary electron acceptor X may be as low as -0.37 V, as suggested recently by P. A. Loach (1973, personal communication).     

Osmotic and activity coefficients in dilute solutions of ethanol in cyclohexane from freezing-point measurements

The calorimeter developed in this laboratory for isothermal enthalpy-of-dilution measurements is adapted for use as an adiabatic calorimeter for freezing-point studies. Results are obtained for ethanol solutions in cyclohexane at mole fractions of ethanol from 0.001 up to 0.08. Activities calculated from the results are used to test association models.     

The observation of predissociations in the oxygen molecular ion by low-energy electron impact

The kinetic energy distribution of the O⁺ ions formed by dissociative ionization of O₂ has been carefully examined in the range of 0.0 to 1.3 eV. In the peak at 600 meV fine structure is observed and interpreted by predissociation. The high energy side of the peak has been ascribed to the predissociation of the ²Δ_g, B²Σ^?_g and the C⁴Σ^?_u states of O⁺₂. The low energy side of the peak is presumably due to the predissociation of the b⁴Σ^?_g state or the ²Φ_u state of O⁺₂ or to autoionizing predissociation.     

Organosilicon compounds : LI. Further studies of the base-catalysed solvolysis of N-(triorganosilyl)anilines

Relative rates of solvolysis of some N-triorganosilylanilines in mixtures of ethanol and aqueous potassium hydroxide have been determined, with results as follows. (i) For XC₆H₄NHSiEt₃ compounds in MeOH (5 vol) + aq. alkali (2 vol) at 50°: (X =) H, 1.0;p-Me, 0.80;p-OMe, 0.83;m-Me, 0.90; o-Me, 0.87; p-SMe, 1.90; p-F, 1.7; p-Cl, 2.8; o-Cl, 14; m-Cl, 4.2; m-NO₂, 18; p-CN, ca. 43; p-NO₂, ca. 120. (ii) For PhNHSi(C₆H₄Y)₃ compounds in MeOH (10 vol) + aq. alkali (1 vol) at 50°: (Y =) H, 1.0; p-OMe, 0.12; p-Cl, ca. 32; m-Cl, ca. 84. (iii) For PhNHSiR₃ compounds in MeOH (5 vol) + aq. alkali (2 vol) : (R₃ =) Et₃, 1.0; Et₂Me, 18 (at 30°); Me₂-i-Pr, 8 (at 30°);Me₂-t-Bu, 0.012 (at 50°);i-Pr₃, 0.006 (at 50°). In series (i) the relative rates correlate with σ, or where appropriate σ^?-constants, with a ? value of 1.6. It is suggested that in the transition state of the rate-determining step the OSi bond is fully formed, or almost so, the SiN bond approximately 20—50% broken, and the bond between the nitrogen atom and a proton from the solvent ca. 10—30% formed.     

Synthesis of a 2, 4, 8-trisubstituted pyrimidino[5, 4-d]pyrimidine library via sequential SNAr reactions on solid-phase

A solid-phase synthesis of 2, 4, 8-substituted pyrimidino[5, 4-d]pyrimidines involving three controlled S(N)Ar reactions has been developed. Exploration of different heterocyclic starting materials and resin-bound intermediates is highlighted. The preferred method starts with the treatment of resin-bound anilines with 2, 4, 8-trichloropyrimidino[5, 4-d]pyrimidine. This intermediate is subsequently treated with various amines in two steps to yield the final products. The scope of each diversity step was determined and a library of 16, 000 compounds was synthesized.     

In vivo total body chlorine measurements using prompt-gamma neutron activation analysis

Total body chlorine (TBC1) provides an estimate of extracellular water. We have examined the feasibility of measuring TBC1 using the 5.6, 6.1, and 8.6 MeV C1 peaks produced during in vivo prompt-gamma neutron activation (dose<0.3 mSv). In subjects, background interference permitted the use of only the 8.6 MeV peak in C1 analysis. Preliminary analyses of the prompt-gamma spectra for 33 healthy females (ages: 24–40 yr) provided a mean estimate of 0.85 g C1 per kg body weight. It is therefore feasible to measure TBC1 concurrently with body nitrogen using relatively low-dose prompt-gamma neutron activation analysis.     

Extraction techniques in speciation analysis of environmental samples

One of the main problems in speciation analysis is that the different species of metals are present in complex matrices at very low concentration levels. Thus it is almost always necessary to separate the analytes of concern from the matrix and to concentrate them up to detectable concentration levels. Special care should be paid during extraction in order to avoid any contamination of samples, losses and changes in speciation of analytes of concern. The most common extraction techniques for speciation analysis of Pb, Sn, Hg, Cr, As, Se and Sb in liquid and solid samples are presented and briefly discussed. Due to the large quantity of material to be covered, speciation of alkyl, aryl, and macromolecular compounds (porphyrines, thioneines, etc.) has not been taken into account.