Structure and decomposition pathways of D-(−)-tartaric acid on Pd(111)

The Journal of Physical Chemistry A, 2012

In an effort to understand the chemical factors that stabilize dianions, experimental and theoretical studies on the stability of the tartrate dianion were performed. Quantum chemical calculations at the coupled cluster level reveal only a metastable state with a possible decomposition pathway (O 2 C− CH(OH)−CH(OH)−CO 2 ) 2− → (O 2 C−CH(OH)−CH-(OH)) •− + CO 2 + e − explaining the observed gas-phase instability of this dianion. Further theoretical data were collected for the bare dianion, this molecule complexed to water, sodium, and a proton, in both the meso and L forms as well as for the uncomplexed radical anion and neutral diradical. The calculations suggest that the L-tartrate dianion is more thermodynamically stable than the dianion of the meso stereoisomer and that either dianion can be further stabilized by association with a separate species that can help to balance the charge of the molecular complex. Mass spectrometry was then used to measure the energy needed to initiate collisionally induced dissociation of the racemic tartrate dianion and for the proton and sodium adducts of both the racemic and meso form of this molecule. Infrared action spectra of the dianion stereoisomers complexed with sodium were also acquired to determine the influence of the metal ion on the vibrations of the dianions and validate the computationally predicted structures. These experimental data support the theoretical conclusions and highlight the instability of the bare tartrate dianion. From the experimental work, it could also be concluded that the pathway leading to dissociation is under kinetic control because the sodium adduct of the racemic stereoisomer dissociated at lower collisional energy, although it was calculated to be more stable, and that decomposition proceeded via C−C bond dissociation as computationally predicted. Taken together, these data provide insight into the gas-phase stability of the tartrate dianion and highlight the role of adducts in stabilizing this species. Figure 1. Stereoisomers of tartaric acid. Article pubs.acs.org/JPCA

The formation constants of the complexes of D-, L-, DL-, and meso-tartaric acid ( H2L) with the hydrogen ion and the oxovanadium(iv) cation, [V0l2+, have been measured potentiometrically a t 25.0 "C and / = 0.10 mol dm-3 (K[NO,]).

Molecules, 1997

The conformation of dimethyl (R,R)-tartrate has been analyzed on the basis of the single crystal X-ray diffraction method as well as by ab-initio quantum chemical studies. The results showed that the extended T conformation containing two planar hydroxyester moieties predominates in both ab-initio and X-ray studies. The lowest energy conformer in ab-initio calculations has C 2 symmetry and hydrogen bonds between a hydroxyl group and the nearest carbonyl oxygen. The second in energetical sequence, with an energy difference of only 1.2 kcal/mol, is the asymmetrical conformer, which differs from the lowest energy form by the rotation of one of the ester groups by 180°. Intramolecular OH ... O hydrogen bonds observed in this rotamer again involve only proximal functional groups. This conformer is present in the crystal structure of the studied compound, although its conformation in the solid state is no longer stabilized by intramolecular hydrogen bonds of the type mentioned above. In the crystal, hydroxyl groups are mostly involved in intermolecular hydrogen bonds and form only a weak intramolecular hydrogen bond with each other. The planar arrangement of the α− hydroxyester moieties combined with the extended conformation of the carbon chain seems to be stabilized by the intramolecular hydrogen bonds between neighboring functional groups and by the long range dipole-dipole interactions between two pairs of CO and (β)C-H bonds.

Journal of Vacuum Science & Technology B, 2019

R,R-tartaric acid (RR-TA) thermal stability and decomposition on the rutile TiO 2 (110) surface was investigated by temperature programmed desorption. The authors show that a majority of RR-TA molecules are desorbed intact from multilayers at around 340 K, while they decompose from the first chemisorbed layer between 460 and 480 K. Complementary information on the chemical nature of RR-TA in the multilayer regime was gained by x-ray photoelectron spectroscopy, which shows that biacid molecules form the multilayer while they are monotartrate at the interface.

Chirality, 2005

The four-carbon chain in (R,R)-tartaric acid derivatives is predominantly antiperiplanar (trans) in the acid, its salts, esters, and NH-amides, while (À)synclinal (gauche) conformer is the most abundant in N,NV-tetraalkyltartramides. Trialkylsilylation or tert-butylation of the hydroxy groups at C2 and C3 does not appear to affect the conformational preference of NH-tartramides, but it does change the conformational equilibrium in the case of tartrates (toward (À)-gauche) and N,NVtetraalkyltartramides (toward trans), as judged from the NMR data. X-ray diffraction data point to the stabilizing role of antiparallel dipole-dipole interactions due to the 1,3-CO/CH bonds. These interactions can be found in the trans and (À)-gauche conformers but are not possible for the (+)-gauche conformers of (R,R)-tartaric acid derivatives. This rationalizes small proportion of (+)-gauche conformers in tartaric acid derivatives and points to a significance of 1,3-dipole-dipole interactions. The conformation around the C1-C2 (and C3-C4) bond is different in tartrates (O-C-C=O, syn) and tartramides (O-C-C=O, anti); the CD data (np * band) show that O-silylation or O-tertbutylation brings about conformational changes around the C1-C2 bond in the case of

Polyhedron, 1997

Dibenzoyl-L-tartaric acid (db-L-tarH,) reacts with [Cu@-O,CCH,),(H,O)*] to form the tartrate complex [Cu(L-tar)] (1) (L-tarH, = L-tartaric acid). 1 reacts with 2,2'-bipyridine (bipy) and l,lO-phenanthroline (phen) yielding [Cu(L-tar)(bipy)]-6H20 (2) and [Cu(L-tar)(phen)] *4H,O (3), respectively. A crystal of composition {[Cu(L-tar)(phen)] * 6H,O), (4) was taken directly from the original mother liquor of 3. The X-ray crystal structure of the polymeric complex 4 shows each copper(H) ion to be six-coordinate, being chelated by a phenanthroline ligand and also chelated by a carboxylate oxygen atom and a hydroxyl oxygen atom from one end of a tartrate group. A carboxylate oxygen atom and a hydroxyl oxygen atom from one end of a symmetry-related tartrate ligand also chelates to the metal. Dibenzoyl-L-tartaric acid also reacts with [MO

ChemPhysChem, 2012

Tartaric acids and derivatives can (and in fact do) display numerous structures, due to configurational isomerism and con-Stereoisomers of one of the most important organic compounds, tartaric acid, optically active and meso as well as the ester or amide derivatives, can show diverse structures related to the rotation around the three carbon-carbon bonds. This study determines the controlling factors for conformational changes of these molecules in vacuo, in solution, and in the crystalline state using DFT calculations, spectroscopic measure-ments, and X-ray diffraction. All structural variations can be logically accounted for by the possibility of formation and breaking of hydrogen bonds between the hydroxy or amide donors and oxygen acceptors, among these the hydrogen bonds that close five-membered rings being the most stable. These findings are useful in designing molecular and crystal structures of highly polar, polyfunctional, chiral compounds.

Computational Methods in Science and Technology, 1996

(R,R)-tartaric acid (AC), its dimethyl diester (ME), diainide (AM) and N,N,N',N'tetramethyl diamide (TMA) as well as their model compounds, namely hydroxyacetic acid, its methyl ester and amide, have been studied in order to find general conformational preferences among (RR)-tartaric acid derivatives. A rotation around all rotable bonds have been scanned systematically using semiempirical methods for AC, ME, AM and TMA and ab-initio calculations for the model compounds have been carried out. In the case of AC and ME we found a tendency towards the extended conformation, which is in good agreement with available experimental data. For AM and TMA the results of semiempirical calculations are contradictory to each other. Conformations similar to those observed in the crystal structure were predicted by MNDO in the case of AM (the T conformer) and by PM3 in the case of TMA (the G" conformer). Energetically preferred conformational isomers are stabilized by intramolecular hydrogen bonds and the electrostatic CO/C*βH coplanar bond interactions. In T and G" rotamers, intramolecular hydrogen bonds leading to the formation of five-membered rings prevail, while in G + conformers, hydrogen bonded six-membered rings dominate.

Applied Catalysis, 1988

The catalq-tic vapour phase hydrodealkylation of LT tar acid fractions to low boiling phenols was studied in a flow system in the temperature range 480-65O'C, and over a wide range of space velocities on a chromia-alumina catalyst at atmospheric pressure. The feed, as well as the products, was analysed by gas chromatography. Optimum conditions for maximum yield of lower phenols were established. In the hydrodealkylation of tar acid fractions (i) b 170-21O'C, (ii) b 210-230°C and (iii) b 230-27O'C, the contents of lower phenols in the liquid products were found to be respectively. 98.6% (55.2% pheno1+43.4% cresols), 85.5% (2'7.4% phenol+Xl% cresols) and 79.9% (26.8% phenol+ 53.1% cresols) at 6OO'C. The catalyst was found to be highly specific in eliminating the dehydroxylation of phenolic substrates. The physico-chemical properties of the catalyst were determined. Based on an examination of the nature of the catalyst and the product pattern, a tentative mechanism for the reaction has been postulated. The results are interpreted as being due to the formation of chemisorbed phenoxy radicals and their subsequent reaction at the surface of the catalyst.

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2014

Single crystal of l-tartaric acid (LTA) has been grown by slow evaporation technique. The experimental and theoretical studies on molecular structure, vibrational spectra, electronic absorption spectra and non-linear optical property of the crystal are studied. The FT-IR, FT-Raman and UV-Vis-NIR experimental spectra of LTA crystal have been recorded in the range 400-4000cm(-1), 100-3700cm(-1) and 190-1100nm, respectively. Density functional theory calculations with B3LYP/6-311++G(d,p) basis sets was used to determine ground state molecular geometries, vibrational frequencies, ICT interactions, Mulliken population analysis on atomic charge, HOMO-LUMO analysis, non-linear optical response properties and thermodynamic properties for LTA and the results were discussed. Vibrational analysis confirms the formation of intramolecular OH⋯O hydrogen bonding. The stability of the molecule has been analyzed using NBO analysis. The results of electronic absorptions in gas phase and water phase L...