Conformations of molecules bearing two carbonyl groups on adjacent atoms

1988 ◽  
Vol 53 (6) ◽  
pp. 1260-1267 ◽  
Author(s):  
Otto Exner ◽  
Václav Jehlička ◽  
Bernard Tinant
Keyword(s):  
Crystal Packing ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Carbonyl Oxygen ◽  
Carbonyl Groups ◽  
Oxygen Atoms

Conformation of α-acyloxyketones IIIa-IIIc was determined from their dipole moments in benzene solution. Around the C-O bond the ap conformation prevails over sc, around the C-C bond several conformations are present and those with a larger distance between the two carbonyl oxygens are preferred. The conformation in thus quite different than in crystal. Similarities of the crystal conformations of III to I or II are due mainly to crystal packing forces, while the interaction of the two carbonyl oxygen atoms is of little importance.

Variability of shapes and properties of atoms in molecules: a case study of the carbonyl oxygen

1996 ◽  
Vol 74 (6) ◽  
pp. 1263-1270 ◽  
Author(s):  
Boris B. Stefanov ◽  
Jerzy Cioslowski
Keyword(s):  
Electronic Properties ◽  
Dipole Moments ◽  
Visual Assessment ◽  
Carbonyl Oxygen ◽  
Atoms In Molecules ◽  
Large Molecules ◽  
Neighbor Effects ◽  
Theoretical Considerations ◽  
Oxygen Atoms

A comparative study of carbonyl oxygen atoms in diverse molecular environments is presented. The variability of shapes of oxygen atoms is quantified with a newly developed similarity measure that confirms the qualitative conclusions of visual assessment. Electronic properties of these atoms, such as charges, energies, and dipole moments, are computed and their possible correlations with the atomic shapes are studied. Factors that affect atomic shapes are investigated and found to be distinct from those influencing electronic properties of atoms in molecules. The kinetic energies of the atoms under study correlate poorly with the atomic charges. The second-neighbor effects on the atomic energies and charges are approximately additive. Both the theoretical considerations and the numerical results definitively rule out the possibility of the shapes of atomic basins unambiguously determining the properties of atoms in molecules. The consequences of this observation for the recently contemplated approaches to the prediction of electronic properties of large molecules are discussed. Key words: atoms in molecules, properties of —; similarity of —; transferability of —.

Article

1998 ◽  
Vol 76 (4) ◽  
pp. 490-497
Author(s):  
Okba Saied ◽  
Benoit Bachand ◽  
James D Wuest
Keyword(s):  
Carbonyl Group ◽  
Carbonyl Compounds ◽  
Lewis Acids ◽  
Carbonyl Oxygen ◽  
The Other ◽  
Keto Group ◽  
Carbonyl Groups ◽  
Lone Pairs ◽  
Related Compounds ◽  
Oxygen Atoms

Carbonyl oxygen atoms have two formal lone pairs of electrons. In principle, both can be used simultaneously to form complexes with two or more Lewis acids. This multiple coordination promises to have a variety of interesting consequences; unfortunately, however, complexes of carbonyl compounds with multiple Lewis acids are extremely rare. To promote multiple coordination, we have made a series of symmetric ketodiesters and related compounds in which the carbonyl group of a ketone is flanked by two additional sites of Lewis basicity. In such compounds, the flanking bases and both lone pairs of the central ketone are available for binding two equivalents of suitable Lewis acids, thereby producing symmetric double chelates in which the central ketone interacts with two Lewis acids at the same time. As expected, treatment of 3-oxoglutarates and 4-oxopimelates with TiCl4 in a 1:1 ratio yielded unsymmetric single chelates in which the carbonyl groups of the ketone and one ester bind TiCl4, while the other ester remains free. Unfortunately, treatment of the same ketodiesters with TiCl4 in a 1:2 ratio did not produce the desired symmetric double chelates. Instead, 2:4 complexes were formed in which the free esters of the unsymmetric single chelates bind TiCl4 in the normal way, without assistance from the keto group. We attribute this observation to the inherent reluctance of ketones to bind multiple Lewis acids, as well as to unfavorable Cl · · ·Cl interactions created in the hypothetical double chelates by the simultaneous attachment of two octahedrally coordinated atoms of titanium to a single carbonyl oxygen atom.Key words: Lewis acids, chelation, ketodiesters, TiCl4.

Conformation and electronic structure of aromatic chloroformates

1987 ◽  
Vol 52 (4) ◽  
pp. 970-979 ◽  
Author(s):  
Otto Exner ◽  
Pavel Fiedler
Keyword(s):  
Electronic Structure ◽  
Oxygen Atom ◽  
Strong Interaction ◽  
Electron Distribution ◽  
Room Temperature ◽  
Functional Group ◽  
Dipole Moments ◽  
Carbonyl Oxygen ◽  
Nonpolar Solvents ◽  
Single Method

Aromatic chloroformates Ib-Ie were shown to exist in the ap conformation, in agreement with aliphatic chloroformates, i.e. the alkyl group is situated cis to the carbonyl oxygen atom as it is the case in all esters. While 4-nitrophenyl chloroformate (Ie) is in this conformation in crystal, in solution at most several tenths of percent of the sp conformation may be populated at room temperature and in nonpolar solvents only. A new analysis of dipole moments explained the previous puzzling results and demonstrated the impossibility to determine the conformation by this single method, in consequence of the strong interaction of adjoining bonds. If, however, the ap conformation is once proven, the dipole moments reveal some features of the electron distribution on the functional group, characterized by the enhanced polarity of the C-Cl bond and reduced polarity of the C=O bond. This is in agreement with the observed bond lengths and angles.

The chemistry of aliphatic unconjugated nitramines. II. Intramolecular properties and crystal packing

1969 ◽  
Vol 22 (12) ◽  
pp. 2505 ◽  
Author(s):  
J Stals
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Packing ◽  
Dipole Moments ◽  
Molecular Crystals ◽  
Bond Orders ◽  
Bond Energies ◽  
Electric Dipole Moments ◽  
Charge Distributions ◽  
Hydrogen Bonding Interactions ◽  
Vb Structures

The VESCF(BJ)-MO electric dipole moments, molecular ionization potentials, electronic bond energies, charge distributions, and bond orders for nitramide, N-methylnitramine, and s- and as-N,N- dimethylnitramines are reported. The packing of nitramide, RDX, and HNX in their molecular crystals is rationalized in terms of electrostatic and hydrogen-bonding interactions. Simple VB structures do not readily predict their calculated MO charge distributions and bond orders.

Undecacarbonyl(pyridine-κN)-tetrahedro-tetrairidium(4Ir—Ir)

2006 ◽  
Vol 62 (4) ◽  
pp. m838-m840 ◽  
Author(s):  
Alvaro J. Pardey ◽  
Manoa A. Moreno ◽  
Matthias Lutz ◽  
Matti Haukka ◽  
Reinaldo Atencio
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Triple Bond ◽  
Crystal Packing ◽  
Pyridine Molecule ◽  
Carbonyl Groups ◽  
Carbonyl Ligands

The title compound, [Ir4(C5H5N)(CO)11], shows a tetrahedral Ir4 core in which each Ir atom is linked to three other Ir atoms and three terminal carbonyl groups, except for one Ir atom, which carries two carbonyl ligands and one N-coordinated pyridine molecule. An intricate set of C—H...π hydrogen bonds stabilizes the crystal packing, where the π-systems are those of the C[triple-bond]O bonds of the carbonyl ligands.

Dipole moments induced in larger molecule. Long-chain aliphatic esters

1982 ◽  
Vol 47 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Otto Exner ◽  
Ayfer Bapçum
Keyword(s):  
Benzene Solution ◽  
Dipole Moments ◽  
Straight Chain ◽  
Basic Assumptions ◽  
Donor Acceptor ◽  
Eyring Theory ◽  
Aliphatic Esters ◽  
Long Chain

Dipole moments of straight-chain aliphatic esters Ia-Ic and IIa-IIf were measured in benzene solution. The observed trends are poorly reproduced by the classical Smith-Eyring theory; the reason may be partly the unknown conformation, partly even donor-acceptor complexes with the solvent. No deviations were observed with the highest members of the series, attributable to violation of some basic assumptions of the theory of dielectrics.

Chemistry of Aminochromes. Part XVIII. The Effects of pH and Substituents on some Aminochrome–Thiol Reactions

1974 ◽  
Vol 52 (6) ◽  
pp. 1019-1026 ◽  
Author(s):  
W. S. Powell ◽  
R. A. Heacock
Keyword(s):  
Addition Product ◽  
Carbonyl Oxygen ◽  
Carbonyl Groups ◽  
Effects Of Ph ◽  
Acidic Conditions ◽  
Ph Range

Aminochromes react with thiols in the pH range ca. 3–4 to give mainly 4-thiosubstituted-5,6-dihydroxyindoles (or the corresponding 5,6-dihydroxyindolines) along with reduction products (5,6-dihydroxyindoles or 5,6-dihydroxyindolines). There is also some evidence, in this pH range, for the formation of an addition product involving one of the aminochrome carbonyl groups directly. Under somewhat less acidic conditions (pH 5–6), however, the major products formed initially are, in general, 3a-thiosubstituted-3a, 4-dihydroaminochromes. These products, which are formed reversibly, are gradually replaced in the reaction mixture by the indolic products, which are formed irreversibly. The increased rate of formation of the 4-thiosubstituted-5,6-dihydroxyindoles at lower pH's is probably due to the increased protonation of the C-6 carbonyl oxygen. The 3a-thiosubstituted-3a, 4-dihydroaminochromes may be formed more readily at higher pH's due to the increased ionization of the thiol.

A New Binuclear Lutetium(III) Dimethyl-N-trichloroacetylamidophosphate Complex with a γ, γ'-Dipyridyl Bridge, {Lu[CCl3C(O)NP(O)(OCH3)2]3}2-μ(γ,γ'-dipy)

2001 ◽  
Vol 56 (3) ◽  
pp. 249-254 ◽  
Author(s):  
Victor A. Trush ◽  
Jolanta Swiatek-Kozlowska ◽  
Victor V. Skopenko ◽  
Vladimir M. Amyrkhanov
Keyword(s):  
Crystal And Molecular Structure ◽  
Carbonyl Oxygen ◽  
Carbonyl Groups ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Metal Centers ◽  
X Ray ◽  
Heterocyclic Ligand ◽  
New Type ◽  
Ir Spectroscopic

Abstract A new type of binuclear coordination compound of lutetium, {Lu2L6 · μ-(γ,γ '-dipy)} (where L = dimethyl-N-trichloroacetylamidophosphate anion and γ,γ '-dipy = 4,4'-dipyridyl), has been obtained. The IR spectroscopic data reveal that the ambidentate phosphoryl ligand is coordinated to the metal center in a bidentate manner via the phosphoryl and carbonyl oxygen atoms. The crystal and molecular structure of {Ln2L6-μ-(γ ,γ '-dipy)} has been determined by means of X-ray diffraction (triclinic, space group P i with parameters: a = 9.259(2), b = 12.530(3), c = 16.548(3) Å, α = 85.44(3)°, β = 75.64(3)°, γ = 70.56(3)°, Z = 1). The structure is made up of centrosymmetric binuclear molecules, in which the neutral heterocyclic ligand is coordinated to the metal centers in a bidentate bridging manner via its nitrogen atoms. The coordination number of each Lu(III) atom is 7 [60(L-) + N((γ ,γ '-dipy)]. Phosphoryl and carbonyl groups of the L- ligands are disposed in syn-position and are included in the six-membered chelate metallocycles. The coordination polyhedron of lutetium can be described as distorted mono-capped octahedron.

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