Rearrangement ions—I: Mass spectrum of thionylaniline-1-13C

Recent publications^1,2 concerning the mechanism for the electron-impact induced loss of carbon monoxide from the molecular ion of thionylaniline have led to an examination of thionylaniline-1-¹³C. The results show that the C-1 carbon atom is not lost in this process, but only suggest the loss of the C-2 carbon atom.     

Tieftemperatur 13C-NMR.-Spektren von 13C-und 6Li-markierten Chlor-, Brom- und Jod-Lithium-Carbenoiden. Vorläufige Mitteilung

Low Temperature ¹³C-NMR. Spectra of ¹³C- and ⁶Li-Labelled Chloro-, Bromo-, and Iodo-lithiumcarbenoids The ¹³C-NMR. spectra of tetrahydrofuran solutions of 16 chloro-, bromo-, and iodo-⁶lithio- and -⁷lithio-carbenoids with ¹³C-labelled methane, ethane, ethylene, and cyclopropane C-skeletons have been measured at temperatures around ? 100° (for examples see Fig. 1 and 2). Invariably, the exchange of hydrogen or halogen by lithium causes deshielding (Δδ, see Table 1) of the ¹³C-signal by up to 289 and 434 ppm, respectively, and decrease of ¹J (¹H, ¹³C) and ¹J(¹³C,¹³C) couplings (see Table 2) with the C-atom of up to 104 and 30 Hz, respectively. The ¹J(⁶Li, ¹³C) and ¹J(⁷Li, ¹³C) coupling of ca. 17 and 45 Hz, respectively, obtained in ten cases (Table 1) is independant of the substitution pattern of the C-skeleton and of the particular halogen atom.     

The use of the modified simplex method for automatic phase correction in fourier-transform nuclear magnetic resonance spectroscopy

FT-n.m.r. spectra were automatically phase-corrected using the modified simplex method. Three optimization criteria for phase correction were investigated. Best results were obtained by maximization of the intensity minimum and maximization of the summed intensities below the baseline. The maximization of spectral area consistently failed to correct the spectral data satisfactorily.     

Computer-based system for correlating molecular structures with mass spectral data Methods for generating molecular substructures and for incorporating fragmentation rules

The masses of ions observed in the mass spectrum of a pure compound are correlated with the masses of the molecular substructures of the compound. Three methods are described for generating molecular substructures. Each method is evaluated to establish how effectively it generates the molecular substructures and correlates the masses of the molecular substructures with the masses of the observed fragment ions. Rules for mass-spectral fragmentation processes are incorporated into the mass spectral analysis software and illustrated for retro-aldol and lactone-ester reactions occurring in the thermospray mass spectra of oligomycin antibiotics.     

Synthesis and Diels-Alder Reactions of a New Kind of Chiral Dienophiles: Cyclic Vinyl-p-tolylsulfilimines

A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group.     

Nonnegativity and positiveness of solutions to mass action reaction–diffusion systems

We show that solutions of a mass action chemical kinetics reaction–diffusion system are nonnegative. Conditions for components of the solution to be strictly positive or identically zero are given, based on an indexing procedure due to A. I. Volpert [Mat. Sb. (Russian) 88, 578–588 (1972); Math. USSR Sb. (English) 17, 571–582]. The results are illustrated with some examples.