Mass spectrometric investigation of the side-arm lariat effect of ortho- and para-methoxyphenoxymethyl-15-crown-5 in the gas phase

Mixtures of unsubstituted 15-crown-5 and its analogues containing ortho- and para-methoxyphenoxymethyl substituents with sodium salts were investigated by matrix assisted laser desorption/ionization (MALDI) mass spectrometry. Peaks of cationized molecules [M+Na]⁺ and cluster ions [2M+2Na+An]⁺, where M is the crown ether molecule and An is monobasic acid anion, were observed in the mass spectra. It was shown that an increase of the shielding degree of the sodium cation in complexes with crown ethers, i.e., the lariat effect, led to a significant decrease in the intensity of peaks of the cluster ions.     

STRUCTURE OF SOME ADAMANTYL-CONTAINING UREAS AND HYDROGEN BONDS IN THEIR CRYSTALS

Journal of Structural Chemistry - Molecular and crystal structures of five substituted urea derivatives with bulky adamantyl fragments in their substituents are considered. It is shown that the...     

Synthesis and Properties of N,N′-Disubstituted Ureas and Their Isosteric Analogs Containing Polycyclic Fragments: XIV. N-[(Adamantan-1-yl)(phenyl)methyl]-N′-substituted Ureas and Symmetrical Bis-ureas

Russian Journal of Organic Chemistry - A procedure has been developed for the synthesis of rac-1-[isocyanato(phenyl)methyl]adamantane from rac-2-(adamantan-1-yl)-2-phenylacetic acid in 95% yield....     

Real-Space Interpretation of Interatomic Charge Transfer and Electron Exchange Effects by Combining Static and Kinetic Potentials and Associated Vector Fields**

Intricate behaviour of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Channels of locally enhanced kinetic potential and corresponding saddle Lagrange points were found between chemically bonded atoms. Superposition of electrostatic and kinetic potentials and electron density allowed partitioning any molecules and crystals into atomic - and potential-based -basins; -basins explicitly account for the electron exchange effect, which is missed for -ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between zero-flux surfaces of - and -basins. The gap between - and -basins represents the charge transfer, while the gap between - and -basins is a real-space manifestation of sharing the transferred electrons caused by the static exchange and kinetic effects as a response against the electron transfer. The regularity describing relative positions of -, -, and - basin boundaries between interacting atoms was proposed. The position of -boundary between - and -ones within an electron occupier atom determines the extent of transferred electron sharing. The stronger an H⋅⋅⋅O hydrogen bond is, the deeper hydrogen atom's -basin penetrates oxygen atom's -basin, while for covalent bonds a -boundary closely approaches a -one indicating almost complete sharing of the transferred electrons. In the case of ionic bonds, the same region corresponds to electron pairing within the -basin of an electron occupier atom.     

Synthesis of water-soluble bis-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">O</Emphasis>-chelate nickel(II) complexes based on new ligands – <Emphasis Type="Italic">P</Emphasis>-pyridyl-containing phospholane oxides

A series of new N,O-hybrid ligands was synthesized by oxidation of pyridyl-substituted phospholanes. These ligands were employed in the first synthesis of water-soluble mononuclear nickel(II) complexes [NiL₂(H₂O)₂](BF₄)₂ and [NiL₂(MeCN)₂](BF₄)₂. Physicochemical properties and crystalline structures of the synthesized compounds were thoroughly studied.     

H2, B−H,and Si−H Bond Activation and Facile Protonolysis Driven by Pt-Base Metal Cooperation

We report a series of heterobimetallic Pt/Zn and Pt/Ca complexes to study the effect of proximity of a dicationic base metal on the organometallic Pt species. Varying degrees of Pt⋅⋅⋅Zn and Zn interaction with the bridging Me group are achieved, showcasing snapshots of a hypothetical process of retrotransmetalation from Pt to Zn. In contrast, only weak interactions were observed for Ca with a Pt-bound Me group. Activation of H₂, B−H and Si−H bonds leads to the formation of hydride-bridged Pt−H−Zn complexes, which is not observed in the absence of Zn, pointing out the importance of metal-metal cooperation. Reactivity of PtMe₂/M²⁺ with terminal acetylene, water and methanol is also studied, leading to facile protonation of one of the Me groups at the Pt center only when Zn is present. This study sheds light on various ways in which the presence of a 2+ metal cation significantly affects the reactivity of a common organoplatinum complex.     

Chiral para-alkyl phenyl ethers of glycerol: synthesis and testing of chirality driven crystallization,liquid crystal,and gelating properties

A series of enantiopure and racemic p-alkylphenyl glycerol ethers 1a–k were synthesized. A new, sensitive, and pictorial method of comparison of the IR spectra of solid enantiopure and racemic samples was developed to obtain preliminary information on the crystallization types of these compounds. In order to detect the subtle differences in the organization of the chiral solid phase, a new easily implemented approach, based on a chromatographic measuring of the relative abundance of the enantiomers in a single solution in equilibrium with a solid sample of arbitrary (0 < ee < 1) composition, is reported. One new conglomerate compound (Alk = n-Pr) and one borderline case (Alk = n-Bu) are disclosed. Higher members of the series of 1 (starting with an n-Bu derivative) are turned into liquid crystals upon melting; no significant differences between racemic and non-racemic samples were found. Only enantiopure methyl-, n-butyl, n-pentyl, n-hexyl, and n-heptyl substituted 1 were able to form supramolecular gels in hydrocarbon solvents; all racemic ethers 1 did not show such ability.     

Measuring the Acoustic Characteristics of a Helicopter Rotormodel in a Wind Tunnel

Acoustical Physics - The article presents the results of comparative experimental and computational studies of the acoustic characteristics of the model of a helicopter rotor performed in the...     

The reaction of 4-(1,3,2-benzodioxaphosphol-2-yloxy)-3-tert-butylpent-4-en-2-one with hexafluoroacetone

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