Giancarlo Angelini

Methane Activation by Metal-Free Radical Cations : Experimental Insight into the Reaction Intermediate

A precise jab to methane: The SO(2)(*+) radical cation (see figure) effectively activates CH(4) at room temperature through a [H(3)C(*)...HOSO(+)] methyl intermediate isolated in the gas phase by mass spectrometry. Methanol and ionized methyl hydrogen sulfoxylate, CH(3)OSOH(*+), are formed by selective, direct attack of the incipient methyl radical at the O atom of the intermediate. The reaction shows radical and charge effects in the activation of methane by metal-free radical cations.

Characterization of Graphene Nanoribbons from the Unzipping of MWCNTs

Graphene nanoribbons were obtained by oxidative unzipping reaction conducted on multi-walled carbon nanotubes (MWCNTs). The oxidized and reduced nanoribbons (after treatment with hydrazine) were characterized by FT-IR and Raman spectroscopy. Graphite oxide was used as reference material in FT-IR and highly oriented pyrolytic graphite was used as reference in the Raman study. The transmission electron microscopy (TEM) of the nanoribbons both in oxidized and reduced form show beautiful images confirming the single graphene structure of the nanoribbons. When heated in a thermobalance at 10°C/min under N2, the oxidized nanoribbons undergo an explosive decomposition at 152°C with formation of a fluffy carbon soot whose FT-IR spectrum is analogous to that of the hydrazine reduced nanoribbons.

Mechanistic Aspects of Gas‐Phase Hydrogen‐Atom Transfer from Methane to [CO].+ and [SiO].+: Why Do They Differ?

The reactivity of the two diatomic congeneric systems [CO](·+) and [SiO](·+) towards methane has been investigated by means of mass spectrometry and quantum-chemical calculations. While [CO](·+) gives rise to three different reaction channels, [SiO](·+) reacts only by hydrogen-atom transfer (HAT) from methane under thermal conditions. A theoretical analysis of the respective HAT processes reveals two distinctly different mechanistic pathways for [CO](·+) and [SiO](·+), and a comparison to the higher metal oxides of Group 14 emphasizes the particular role of carbon as a second-row p element.

Water activation by SO2˙+ ions: an effective source of OH˙ radicals

A novel O-H bond activation reaction is reported: thermal SO(2)(*+) radical cations activate water in the gas phase forming OH* radicals with 100% efficiency.

Stability toward High Energy Radiation of Non-Proteinogenic Amino Acids: Implications for the Origins of Life

A series of non-proteinogenic amino acids, most of them found quite commonly in the meteorites known as carbonaceous chondrites, were subjected to solid state radiolysis in vacuum to a total radiation dose of 3.2 MGy corresponding to 23% of the total dose expected to be taken by organic molecules buried in asteroids and meteorites since the beginning of the solar system 4.6 × 109 years ago. The radiolyzed amino acids were studied by FT-IR spectroscopy, Differential Scanning Calorimetry (DSC) and by polarimety and Optical Rotatory Dispersion (ORD). It is shown that an important fraction of each amino acid is able to “survive” the massive dose of radiation, while the enantiomeric excess is partially preserved. Based on the results obtained, it is concluded that it is unsurprising to find amino acids even in enantiomeric excess in carbonaceous chondrites.

Synthesis of Expanded Graphite Flakes by the Submerged Carbon Arc in Oleum

Graphite layers expansion and exfoliation can be achieved in a couple of minutes by arcing graphite electrodes submerged in oleum (fuming sulphuric acid with 30% SO3). Not only do the electrodes submerged in oleum expand dramatically, but also a fine dispersion of graphite particles in oleum can be obtained. The method proposed is extremely effective and overcomes the conventional methods of graphite hydrogensulphate preparation, which require very long swelling times (hours) of graphite in concentrated sulphuric acid. The dispersion of graphite particles derived from arcing graphite electrodes in oleum has been studied in great detail with electronic absorption spectroscopy in the UV-VIS and in the NIR. Unfortunately, the workup adopted to remove the excess of oleum from the exfoliated graphite particles and from the swelled electrodes causes a partial restacking and clumping of the particles and a partial collapse of the swelled graphite electrodes. After the workup, the swelled anode and cathode material as well as the graphite dispersion were studied by thermogravimetric analysis as well as by scanning electron microscopy (SEM) and energy dispersive x-ray measurements (EDX). The presence of residual amounts of HSO4 − ions in all matrices has been quantitatively determined and compared with previous results reported in literature.