High-pressure reactivity of propene

In Situ Neutron Diffraction of Zn-MOF-74 Reveals Nanoconfinement-Induced Effects on Adsorbed Propene

Even though confinement was identified as a common element of selective catalysis and simulations predicted enhanced properties of adsorbates within microporous materials, experimental results on the characterization of the adsorbed phase are still rare. In this study, we provide experimental evidence of the increase of propene density in the channels of Zn-MOF-74 by 16(2)% compared to the liquid phase. The ordered propene molecules adsorbed within the pores of the MOF have been localized by in situ neutron powder diffraction, and the results are supported by adsorption studies. The formation of a second adsorbate layer, paired with nanoconfinement-induced short intermolecular distances, causes the efficient packing of the propene molecules and results in an increase of olefin density.

Raman Spectroscopy Study on Chemical Transformations of Propane at High Temperatures and High Pressures

This study is devoted to the detailed in situ Raman spectroscopy investigation of propane C₃H₈ in laser-heated diamond anvil cells in the range of pressures from 3 to 22 GPa and temperatures from 900 to 3000 K. We show that propane, while being exposed to particular thermobaric conditions, could react, leading to the formation of hydrocarbons, both saturated and unsaturated as well as soot. Our results suggest that propane could be a precursor of heavy hydrocarbons and will produce more than just sooty material when subjected to extreme conditions. These results could clarify the issue of the presence of heavy hydrocarbons in the Earth’s upper mantle.

Structure and Reactivity of the Ionic Liquid 1-Allyl-3-methylimidazolium Iodide under High Pressure

Poly(ionic liquid)s are an interesting class of compounds because of their unique chemical and physical properties gathering the characteristics of ionic liquids and polymers. Pressure and temperature have been demonstrated to be alternative parameters to obtain polymers from monomeric species using only physical tools. In this work, we investigate the reaction under high pressure and room temperature of the ionic liquid 1-allyl-3-methylimidazolium iodide by using the diamond anvil cell technique in combination with synchrotron X-ray diffraction and electronic and vibrational spectroscopies. The results indicate a chemical reaction happening through the terminal double bond of the allyl group both in crystalline and glassy phases with the onset of the reaction around ∼7 GPa. Vibrational spectra present evidence for an oligomerization reaction in both the phases. The reaction occurring both in glassy and crystal phases indicates a mechanism not driven by collective motions and likely related to local topological arrangements. The results presented herein extend our understanding of ionic liquid instability boundaries under high pressure and contribute to the development of alternative synthetic routes to achieve poly(ionic liquids).

Pressure-induced oligomerization of alanine at 25 °C

Pressure-induced oligomerization of alanine was found from high-pressure experiments.

Review of exchange processes on Ganymede in view of its planetary protection categorization

In this paper, we provide a detailed review of Ganymede's characteristics that are germane to any consideration of its planetary protection requirements. Ganymede is the largest moon in our solar system and is the subject of one of the main science objectives of the JUICE mission to the jovian system. We explore the probability of the occurrence of potentially habitable zones within Ganymede at present, including those both within the deep liquid ocean and those in shallow liquid reservoirs. We consider the possible exchange processes between the surface and any putative habitats to set some constraints on the planetary protection approach for this moon. As a conclusion, the "remote" versus "significant" chance of contamination will be discussed, according to our current understanding of this giant icy moon. Based on the different estimates we investigate here, it appears extremely unlikely that material would be exchanged downward through the upper icy layer of Ganymede and, thus, bring material into the ocean over timescales consistent with the survival of microorganisms.

Dimerization and polymerization of isoprene at high pressures

The high-pressure reactivity of isoprene has been studied at room temperature up to 2.6 GPa by using the diamond anvil cell technique in combination with Fourier transform infrared spectroscopy. Both dimerization and polymerization reactions take place above 1.1 GPa. At this pressure, the two processes are well separated in time, the dimerization being the only one occurring in the first 150 h. Both processes simultaneously occur as the pressure increases. The reaction product is composed of a volatile fraction, identified as sylvestrene, and a transparent rubberlike solid formed by cis-1,4- and 3,4-polyisoprene. The activation volume of the dimerization reaction has been obtained from the kinetic data. The photoinduced reaction, studied at room temperature for two different pressures, takes place through a two-photon absorption process, and the threshold pressure is lowered to 0.5 GPa. At this pressure, both the dimerization and polymerization processes occur, but the dimerization is not as selective as in the purely pressure-induced reaction. 4-Ethenyl-2,4-dimethylcyclohexene is obtained in addition to sylvestrene. By increasing the pressure, the photoinduced reaction becomes more selective, and the monomer is quantitatively transformed into the same polymer obtained in the purely pressure-induced reaction.

Constraining molecules at the closest approach: chemistry at high pressure

The purpose of this tutorial review is to illustrate the effects that the application of high pressures can have on chemical reactions involving highly compressible molecular materials. The essentials of the high-pressure technology (generation and in situ control of high pressures) are described with particular attention to the versatile diamond anvil cell (DAC) apparatus. The general effects of pressure on chemical equilibrium, reaction rate and reaction mechanism are discussed. The motivation for application of high-pressure methods (in the 1-300 MPa range) to chemical synthesis and in biochemistry are illustrated focusing the attention on environmental effects and with an excursus on developing biotechnological applications. The peculiarities and the unexpected outcomes of chemical reactions occurring at very high pressures (>or=300 MPa) are discussed considering the extraordinary results obtained in polymerization and amorphization of simple molecules and of unsaturated hydrocarbons. The possible connection of the high temperature-high pressure thresholds for chemical reactions with microscopic counterparts (intermolecular distances, molecular orientations) is also discussed.