Low-temperature synthesis of tetraalkylureas from secondary amines and carbon dioxide

The reaction of dialkylamines with CO(2) giving tetraalkylureas can be performed at 60 degrees C. The reaction requires CCl(4), is weakly promoted by DMAN or PPh(3), and is not promoted by a Pd catalyst. A two-step procedure, in which dialkylammonium dialkylcarbamate is produced in situ and then reacted with CCl(4) and free dialkylamine, gave greater yields of urea than a simple single-stage procedure.     

A novel class of fused heterocycles,benzo­[b]­furo­[2,3‐c]­pyrroles

In the isomeric compounds 2‐benzyl‐3‐methyl‐1‐phenyl­benzo­[b]­furo­[2,3‐c]­pyrrole and 2‐benzyl‐1‐methyl‐3‐phenyl­benzo­[b]­furo­[2,3‐c]­pyrrole, both C₂₄H₁₉NO, the pyrrole ring, although presumably somewhat strained, does not differ appreciably from N‐methyl­pyrrole except for a relatively short C—C single bond in the pyrrole ring.     

On variations in size distributions of particles and aggregates upon dilution of magnetic fluids

Variations in size distributions of particles and aggregates upon dilution of kerosene-based magnetic fluids have been studied by dynamic light scattering. The data obtained on samples of magnetic fluids produced by three different manufacturers have shown that the dilution of an initial concentrated magnetic fluid leads to the formation of a system of unstable aggregates with sizes ranging from 70?100 nm to 1 μm. The aggregates peptize for 2?4 days to result in the establishment of stationary particle and aggregate size distributions.     

Fact or artifact: the representativeness of ESI‐MS for complex natural organic mixtures

Because mass spectrometers provide their own dispersion and resolution of analytes, electrospray ionization mass spectrometry (ESI‐MS) has become a workhorse for the characterization of complex mixtures from aerosols to crude oil. Unfortunately, ESI mass spectra commonly contain multimers, adducts and fragments. For the characterization of complex mixtures of unknown initial composition, this presents a significant concern. Mixed‐multimer formation could potentially lead to results that bare no resemblance to the original mixture. Conversely, ESI‐MS has continually reflected subtle differences between natural organic matter mixtures that are in agreement with prediction or theory. Knowing the real limitations of the technique is therefore critical to avoiding both over‐interpretation and unwarranted skepticism. Here, data were collected on four mass spectrometers under a battery of conditions. Results indicate that formation of unrepresentative ions cannot entirely be ruled out, but non‐covalent multimers do not appear to make a major contribution to typical natural organic matter spectra based on collision‐induced dissociation results. Multimers also appear notably reduced when a cooling gas is present in the accumulation region of the mass spectrometer. For less complex mixtures, the choice of spray solvent can make a difference, but generally spectrum cleanliness (i.e. representativeness) comes at the price of increased selectivity. Copyright © 2014 John Wiley & Sons, Ltd.