Carbon Atom Of Carbonyl Group Research Articles

Hydration of p-trifluoroacetyl benzoic acid heptyl ester: how it affects analytical characteristics of sulfate selective electrodes based on higher quaternary ammonium salts

Potentiometric studies of p-trifluoroacetyl benzoic acid heptyl ester (TFABAHE) and its hydrate in sulfate-selective electrodes based on higher quaternary ammonium salts (QAS) have shown that analytical characteristics of the electrodes deteriorate after 2 weeks. This process corresponds in time with accumulations of TFABAHE hydrate form in the membranes, that is confirmed by IR spectroscopy, thermal analysis, electron microscopy and NMR 1H spectroscopy data. It indicates that the solvation of sulfate ions with TFABAHE is performed most likely by the trifluoroacetyl carbonyl group carbon atom. The procedures for determination of sulfate ions in mineral water have been proposed.

N‐Hydroxyphthalimide Anchored on Diamond Nanoparticles as a Selective Heterogeneous Metal‐free Oxidation Catalyst of Benzylic Hydrocarbons and Cyclic Alkenes by Molecular O2

AbstractN‐hydroxyphthalimide (NHPI) derived from trimellitic anhydride has been covalently anchored (4 wt %) through ester bonds to the surface of commercial diamond nanoparticles previously functionalized by chemical and thermal treatments (DH). IR spectroscopy of the NHPI/DH solid shows the presence of a characteristic peak at 1735 cm−1 attributable to the ester bond, while solid‐state MAS 13C NMR spectroscopy shows two broad bands corresponding to carbon atoms of carbonyl groups (167 ppm) and aromatic carbons (127 ppm). NHPI/DH promotes autoxidation of isobutylbenzene involving superoxide (O2.−) and hydroperoxide (HOO⋅) radicals; NHPI/DH can be reused at least three times and reach a minimum turnover number as high as 20 600, which is probably due to the inertness of the diamond surface, allowing free diffusion of reactive oxygen species. Analogous materials in which NHPI was anchored on activated carbon and multiwall carbon nanotubes were inefficient as autoxidation catalysts. NHPI/DH is able to promote also selective aerobic oxidation of other benzylic hydrocarbons and cycloalkenes.

SYNTHESIS OF 3,5-DIBROMO- AND 2,4,5-TRIBROMO-1,8-NAPHTHALIMIDES

3,5-Dibromo-1,8-naphthalic acid and 2,4,5-tribromo-1,8-naphthalic acid were synthesized by oxidation of 1,5,7-tribromoacenaphthylene and 3,5,6-tribromoacenaphthylene by sodium dichromate in anhydrous acetic acid. The obtained naphthalic acids were heated for 2 hours at 110 °C, at which the acids were completely converted to corresponding naphthalic anhydrides with the overall yields of 53% and 45% respectively. Anhydrides were crystallized from acetic anhydride to form white needle crystals with melting points 207.5-208 °C and 222-223 °C for 3,5-dibromo-1,8-naphthalic anhydride and 2,4,5-tribromo-1,8-naphthalic anhydride respectively. 3,5-Dibromo-1,8-naphthalimide and 2,4,5-tribromo-1,8-naphthalimide were obtained by ammonolysis of corresponding anhydrides with aqueous ammonia solution. Formation of naphthalimide cycle takes place in several stages. At the first step ammonia molecule attacks the electrophilic carbon atom of carbonyl group with opening of the anhydride cycle following with proton migration from nitrogen to oxygen atom to form the monoamide of 1,8-naphthalenedicarboxylic acid. Further, the nitrogen atom of the amide group attacks the carbon atom of the carboxylic group to form a six-membered imide ring with cleaving the water molecule. Thus, the first stage of ammonolysis was carried out at room temperature to avoid the ammonia evaporation, the further cyclization reaction was carried out at 80 оC. 3,5-Dibromo-1,8-naphthalimide has been obtained by this procedure with the yield of 90 % as light yellow crystals with melting point 292-293 °C. In case of 2,4,5-tribromo-1,8-naphthalimide the product contained some unreacted 2,4,5-tribromo-1,8-naphthalic anhydride as impurity. The reaction mixture was treated with a 2% aqueous solution of sodium hydroxide to remove anhydride impurity. Target 2,4,5-tribromo-1,8-naphthalimide was obtained with the yield of 67 % as light yellow crystals with melting point > 300 °C. The structure of the synthesized naphthalimide derivatives has been confirmed by IR and NMR 1Н spectroscopy.

Interaction of β-cyclodextrin as catalyst with acetophenone in asymmetric reaction: a theoretical survey.

The asymmetric reduction of acetophenone with sodium borohydride in the presence of β-cyclodextrin (β-CD) as catalyst can improve selectivity and yield. The interaction between acetophenone and β-CD plays an important role for the reduction of acetophenone. This work studies the reaction of acetophenone in the presence of β-CD using density functional theory (DFT) method. Energy is investigated to find out the lowest energy of two possible complexation models. The geometrical structure confirms that acetophenone inserts into the cavity mainly from the secondary hydroxyl side. Hydrogen bonds are researched on the basis of natural bonding orbital (NBO) analysis, the results confirm the donor-acceptor interactions of complex. Mülliken charge and frontier orbital are employed for revealing the electronic transfer. In addition, (13)C nuclear magnetic resonance ((13)CNMR) spectroscopy shows that the active site concentrates on the carbon atom of carbonyl group. The probable catalytic mechanism of β-CD is discussed in terms of the calculated parameters.

Crystal structure of (acetylacetonato) (dicarbonyl)iridium(I)

The structure of Ir(CO)2(acac) is determined by XRD at room temperature. Crystallographic data for C7H7IrO4 are: a = 6.4798(5) A, b = 7.7288(5) A, c = 9.1629(10) A, α = 105.738(2)°, β = 90.467(3)°, γ = 100.658(2)°, space group 1, P $$ \bar 1 $$ , V= 433.24(6) A3, Z = 2, d calc = 2.662 g/cm3, R = 0.0167. The structure is built of isolated mononuclear molecules. The central iridium atom has a square coordination environment formed by two oxygen atoms that belong to the acetylacetonate ligand and two carbon atoms of carbonyl groups. The average Ir-O and Ir-C bond lengths are 2.045(3) A and 1.832(6) A respectively. Molecules are stacked in such a way that the planes of coordination squares turn out to be parallel to the Ir...Ir distances between the nearest neighbors in the stack of 3.242 A and 3.260 A.

Comparative Bonding Behavior of Functional Cyclopentadienyl Ligands and Boron-Containing Analogues in Heterometallic Complexes and Clusters

The reactivity of isolobal molybdenum carbonylmetalates containing a 2-boratanaphthalene, [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (5a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (5b), a 1-boratabenzene, [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (8), or a functionalized cyclopentadienyl ligand, the new metalate [Mo(eta5-C5H4Ph)(CO)3]- (7) and [Mo(eta5-C5H4NMe2)(CO)3]- (9), toward palladium (I and II) or platinum (I and II) complexes, such as trans-[PdCl2(NCPh)2], [Pd2(NCMe)6](BF4)2, trans-[PtCl2(PEt3)2], and [N(n-Bu)4]2 [Pt2Cl4(CO)2], has been investigated, and this has allowed an evaluation of the influence of the pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal-bonded heterometallic clusters. The new 58 CVE planar-triangulated centrosymmetric clusters, [Mo2Pd2(eta5-C5H4Ph)2(CO)6(PEt3)2] (11), [Mo2Pd2(eta5-2,4-MeC9H6BNi-Pr2)2(CO)6] (12), [Mo(2)Pd(2)(eta5-3,5-Me2C5H3BNi-Pr2)2(CO)6] (13), [Mo2Pd2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (15), [Mo2Pt2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (16), and [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (20), have been characterized by single-crystal X-ray diffraction. Their structural features were compared with those of the 54 CVE cluster [Re2Pd2(eta5-C4H4BPh)2(CO)6)] (4), previously obtained from the borole-containing metalate [Re(eta5-C4H4BPh)(CO)3]- (2), in which a 2e-3c B-C(ipso)-Pd interaction involving the pi-ring was observed. As an extension of what has been observed in 4, clusters 12 and 13 present a direct interaction of the boratanaphthalene (12) and the boratabenzene (13) ligands with palladium. In clusters 11, 15, 16, and 20, the pi-ring does not interact with the palladium (11 and 15) or platinum centers (16 and 20), which confers to these clusters a geometry very similar to that of [Mo2Pd2(eta5-C5H5)2(CO)6(PEt3)2] (3b). The carbonylmetalates [Mo(pi-ring)(CO)3]- are thus best viewed as formal four electron donors which bridge a dinuclear d9-d9 unit. The orientation of this building block in the clusters influences the shape of their metal cores and the bonding mode of the bridging carbonyl ligands. The crystal structure of new centrosymmetric complex [Mo(eta5-C5H4Ph)(CO)3]2 (10) was determined, and it revealed intramolecular contacts of 2.773(4) A between the carbon atoms of carbonyl groups across the metal-metal bond and intermolecular bifurcated interactions between the carbonyl oxygen atoms (2.938(4) and 3.029(4) A), as well as intermolecular C-H...pi(Ar)(C=C) interactions (2.334(3) and 2.786(4) A) involving the phenyl substituents.

Structures, thermochemistry, and infrared spectra of chloride ion–fluorinated acetone complexes and neutral fluorinated acetones in the gas phase: experiment and theory

The thermochemistry of chloride ion clustering onto acetone and four fluorinated acetones (CH 3C(O)CH 2F, CF 3C(O)CH 3, CF 3C(O)CF 2H, and CF 3C(O)CF 3) under thermal equilibrium conditions has been determined by pulsed-ionization high pressure mass spectrometry (PHPMS). The standard enthalpy (Δ H°) and entropy (Δ S°) changes obtained indicate a variety of different types of bonding in these complexes. Ab initio computational methods have been used to obtain more insight into the structures and energetics. Surprisingly, in the Cl −(CF 3C(O)CF 2H) complex the chloride ion is not linearly hydrogen bonded, despite the presence of a very acidic CF 2H bond. Instead, coordination with the carbonyl group carbon atom seems to be more pronounced, as found for the Cl −(CF 3C(O)CF 3) complex. For the Cl −(CF 3C(O)CF 3) clustering equilibrium a Δ S° value of −37.6 cal mol −1 K −1 has been measured, indicating that one or both CF 3 group rotations will be hindered upon complex formation. Excellent agreement between Δ H° 298 values calculated at the MP2/[6-311++G(3df,3pd)/6-311+G(2df,p)]//MP2/[6-31+G(d)/6-31G(d)] level of theory and experimental Δ H° values has been obtained. In addition, Δ acid H° 298 values for a set of small to medium sized organic and inorganic acids, and the fluorinated acetones have been determined at the G3 and G3(MP2) levels of theory. Good to excellent agreement was obtained compared to experimental data, indicating that these composite methods perform well for the determination of reliable Δ acid H° 298 results for medium sized molecules containing up to eight second row atoms. No linear correlation between clustering Δ H° 298 and Δ acid H° 298 values was found, indicating that most likely ion–dipole and ion-induced dipole interactions are determining the observed thermochemical trends. Finally, gas phase FT-IR spectra of CH 3C(O)CH 2F, CF 3C(O)CH 3, CF 3C(O)CF 2H, and CF 3C(O)CF 3 have been obtained, and the normal mode vibrational frequencies compared to results from calculations at the HF/6-31G(d) level of theory, scaled by 0.8953, and the B3LYP/6-311++G(3d,3p) level of theory. For the Cl −(CF 3C(O)CF 3) complex some large shifts in frequencies and IR absorption intensities are observed relative to CF 3C(O)CF 3, especially for the CO stretch.

Photocatalytic degradation mechanism for heterocyclic derivatives of triazolidine and triazole

In an attempt to improve the understanding of the basic mechanisms on the degradation of pollutants in water by TiO 2 photocatalysis, we discussed the primary degradation mechanism of three triazolidine derivatives, such as 1,2,4-triazolidine-3,5-dione (TRIANE), 4-hydroxy-1,2,4-triazolidine-3,5-dione (OH-TRIANE) and 4-phenyl-1,2,4-triazolidine-3,5-dione (Ph-TRIANE) and one triazole derivative of the 4-phenyl-1,2,4-triazole-2,5-dione (Ph-TRIOLE), on the basis of the experimental results together with molecular orbital (MO) calculation of frontier electron density and partial charge. The above four heterocycles were selected as molecular probe, principally because the highest frontier electron density was situated at different places of the molecule, while their structures were very similar, two major pathways have been revealed by LC/MS analysis for each heterocyclic compound. The pathway (a) corresponded to the hydroxylation of the atom bearing the highest electron density, via oxidation on nitrogen atom of azo group with respect to the photodegradation of TRIANE, OH-TRIANE and Ph-TRIOLE and opening of aromatic ring when Ph-TRIANE was used. This initial attack occurred with the preferential electrophilic attack of OH radicals. The pathway (b) was caused by the attack of active species on to carbon atom of carbonyl group. Considering the calculation of the relative electrophilic density of this carbon atom for the four heterocyclics and the evolution of large amount of N 2 gas at the initial degradation step, it has been suggested that this step (b) was favored by adsorption of carbonyl group on TiO 2 surface as theoretically determined by partial charge and confirmed by IR analysis. The participation of hole (h +) to form R–CO + was envisaged in this step. The presence of 1,2,4,5-tetrazixane-3,6-dione also agrees with the participation of TiO 2 surface. The nitrogen inorganic analysis (N 2, NH 4 + and NO 3 −) determined by gas chromatography and ion liquid chromatography, show that the hydrazo group were photoconverted mainly into N 2 gas and partially to NH 4 + ions. No nitrate ions were observed at the beginning of the degradation even when a OH substituent was present on one nitrogen atom (case of OH-TRIANE). However, the presence of –OH group increased the NO 3 −/NH 4 + ratio observed after a few hours of irradiation. The presence of OH also improved the total mineralization of carbon atom into CO 2, which was attributed to mesomeric effect of –OH group.

Synthesis and spectroscopic characterisation of binuclear molybdenum-rhenium complexes

Protonation of CpMo( η 3-C 3H 5)(CO) 2 followed by reactions with several diazole ligands produce the molybdenum half-sandwich complexes [CpMo(CO) 2L 2] + (L 2 = Bisimidazole (H 2Biim), pyrazole (Hpz) 2, Cpz 4, and [Bpz 4] −) in good yields. Deprotonation of [CpMo(CO) 2(H 2Biim)] + gives the anionic complex [CpMo(CO) 2(Biim)] −. The structure of [CpMo(CO) 2(H 2Biim)][ReO 4] was determined by X-ray single crystal analysis. The coordination geometry around the molybdenum atom in the complex cation [CpMo(CO) 2(H 2Biim)] + can be described as a distorted square pyramid. The basal plane is defined by two nitrogen atoms of H 2Biim bidentate ligand and two carbon atoms of carbonyl groups. The apical position is occupied by five carbon atoms of the η 5-C 5H 5 ligand. The Mo centre lies at 0.94(1) Å from the basal plane in the apical direction. [CpMo(CO) 2(Biim)] − reacts with ClReO 3 or MeReO 3 (MTO) to give binuclear complexes of the formula [{CpMo(CO) 2}(μ-Biim){Re(X)O 3}]Na (X = Cl, CH 3) in quantitative yields. [CpMo(CO) 2(μ-Cpz 4)][BF 4] reacts with ClReO 3 to yield [{CpMo(CO) 2}(μ-Cpz 4){Re(Cl)O 3}][BF 4]. The corresponding adduct [{CpMo(CO) 2}(μ-Cpz 4){Re(Cl)O 3}][BF 4] can not be obtained in a pure form. The reaction of [Bpz 4] − with ClReO 3 yields the known Bpz 4ReO 3, with MeReO 3 the sensitive [Bpz 4{Re(CH 3)O 3}]K is obtained. Deprotonation of the molybdenocene complex [Cp 2Mo(H 2Biim)] 2+ leads to the neutral compound Cp 2Mo(Biim). The latter compound can be reacted with CH 3ReO 3 or ClReO 3 to form [{Cp 2Mo}(μ-Biim){Re(X)O 3}] (X = CH 3, Cl). A 95Mo NMR investigation shows the influence of the overall charge of the complex and the electron donor capability on the Mo centre. It is shown by 95Mo, 17O, 1H NMR, and IR spectroscopy that the donor capability of the molybdenocene to the rhenium(VII) centre in the binuclear complexes is not very pronounced and can be compared to the strength of organic nitrogen donor complexes, e.g. 2,2′-bipyridyl. In donor solvents temperature dependent, rapid dynamic exchange processes can be observed.

X-ray structure of 6-(N,N-dimethylcarbamoyl)thioquinanthrene

The crystal and molecular structures of 6-(N,N-dimethylcarbamoyl)thioquinanthrene 1 have been determined as monoclinic, with space group C2/c, a = 22.484(4) A, b = 10.251(2) A, c = 16.972(3) A, β = 110.18(3)°. Due to the 6-dimethylcarbamoyl substituent causing overcrowding in the environment of position 6-, the carbonyl group carbon atom (C61) deviates from planarity with the parent pyridine ring by 0.249(8) A, and differences between respective bond lengths and bond angles in both pyridine rings by about of 4–5σ are also observed. X-ray data show spatial non-equivalency of N-methyl groups. The values of the S······S,S······O distances are well below the sum of the van der Waals radii of the heteroatoms.

Quantum-chemical study of the effect of hydration on the mechanism of the nucleophilic reactions of carbonyl compounds

Quantum-chemical calculations were carried out for the tetrahedral adducts formed as a result of nucleophilic attack of the carbonyl group carbon atom. Electically neutral, negatively charged, and positively charged adducts are metastable chemical compounds both in the gas phase and in aqueous solution, while the bipolar adducts may exist only in solution.

Crystal and molecular structure of tetracarbonyl(3,3,4,4-tetramethyl-3,4-dihydrodiazete)-tungsten dimer, [W(N 2C 2Me 4)(CO) 4] 2

Crystals of C 20H 24N 4O 8W 2 are orthorhombic, a 18.1355(24), b 18.6401(6), c 15.5086(11) Å; Z = 8; space group Pbca. The crystal structure has been determined by X-ray diffraction methods and refined to R = 0.028 for 2998 independent observed reflections. It consists of discrete dimeric complexes, in which each W atom is bonded to four carbon atoms of carbonyl groups and to two nitrogen atoms of two 3,3,4,4-tetramethyl-1,2-diazetine ligands, in a deformed octahedral coordination. The two metal atoms and the four bridging nitrogen atoms of the ligands form an irregular hexa-atomic ring.

Imidazolate bridged polynuclear rhodium(I) complexes. X-ray structure of [Rh(2-Meimidazolate)(CO) 2] 4

The synthesis and properties of polynuclear complexes of general formulae [M(RIm)(diolefin) x, [M(RIm)(CO) 2] x and [M(RIm)(CO)L] x (M  Rh, Ir; RIm  imidazolate, 2-methylimidazolate, 2-benzylbenzimidazolate; L  PPh 3 or P(OPh) 3) are reported. The crystal structure of the novel complex [Rh(2-MeIm)-(CO) 2] 4 (2-MeIm  2-methylimidazolate) has been determined by X-ray methods. The crystals are orthorhombic, space group P2 12 12 1, with Z  4 in a unit cell of dimensions a 19.427(12), b 13.419(8), c 12.346(9) Å. The structure has been solved by combined Patterson and direct methods and refined by full-matrix least-squares to R  0.043 for 937 independent observed reflections. It consists of discrete tetrameric complexes in which each Rh atom is in a nearly cis square planar arrangement, bonded to two carbon atoms of carbonyl groups and to two nitrogen atoms of two 2-methylimidazolate ligands, each of which, acting as an exo-bidentate ligand, bridging two metal atoms, so that the four bridging 2-MeIm ligands and the four Rh atoms form a multiatomic ring.

Solvent Effects on the Carbon – 13 NMR Chemical Shifts and Rotational Barriers of N,N-Dimethylbenzamide - Solvent Enhanced π Polarization

The 13C NMR chemical shifts of N,N-dimethylbenzamide in thirty solvents have been measured at high dilution. The solvent induced chemical shifts (s.i.c.s.) of the carbonyl group carbon atom in twenty three solvents and the thermodynamic barriers to rotation about the C-N bond in eleven solvents are linearly related to the solvent parameter, ET(30). Multi-parametric analysis of the carbonyl s.i.c.s. indicates hydrogen bond donor effects are more important than polar effects. Rotational barriers for N,N-dimethylbenzamide may be determined by measurement of the 13C chemical shift of the carbonyl group in a particular solvent. The s.i.c.s. of the aromatic ring carbon atoms may be explained by the polarization of the aromatic π electron system induced by the solvent enhanced polarization of the dimethylcarboxamido moiety. Hydrogen bonding solvents and polar solvents result in two effective dipoles on the dimethylcarboxamido moiety, which polarize the aromatic π electron system differently

Electron Spin Resonance of Semiquinones: Spin-Density Distribution and Carbonyl Sigma—Pi Parameters

The spin-density distributions in the 1,4-benzosemiquinone and 2,5-dioxy-1,4-benzosemiquinone ions have been estimated by measuring the proton and 13C splittings and using reasonable choices for the values of the sigma—pi parameters which relate the splittings to the spin densities for C–C and C–H bonds. The determination of the signs as well as the magnitudes of the 13C splittings was required to obtain the spin densities. With QCHH=−27.0 G in the relation aiH=QCHHρi π between proton splitting aiH and carbon-atom—pi-electron spin density ρiπ, the sigma—pi parameters for the 13C splitting at a carbonyl position were found to be QCOC=17.7 G and QOCC=−27.1 G. The values of QCOC and QOCC depend on the value assumed for QCHH. Contrary to earlier predictions made on the basis of molecular orbital calculations, the sign of the 13C splitting from the 2 position of the p-benzosemiquinone ion was found to be negative. This discrepancy results because the MO calculations were performed so as to reproduce proton splittings rather than the entire spin-density distribution, a procedure that is insensitive to the spin densities on the carbonyl carbon and oxygen atoms. New MO calculations were performed to fit the spin densities at all the positions in the radical. The results show that calculations fitted to proton splittings alone are inadequate for predicting spin densities at ``blind'' positions such as those at the carbon and oxygen atoms of a carbonyl group, or the nitrogen and oxygen atoms of a nitro group. Carbon-13 splittings were also observed in the anthrasemiquinone ion in both ethanol and 1,2-dimethoxyethane (DME) solutions. The sign of the 9-position 13C splitting changes from +0.70 G in ethanol to −0.47 G in DME solution. By using the sigma—pi parameters for the carbonyl group carbon atom, the spin densities were determined for this radical and MO calculations performed to reproduce the spin-density distributions. The variation of the splittings in the p-benzosemiquinone ion with solvent composition could be accounted for quantitatively by using the newly determined sigma—pi parameters.