Gas chromatography-mass spectrometry coupled with pseudo-Sadtler retention indices, for the identification of components in the essential oil of Curcuma longa L.

Gas chromatography-mass spectrometry was applied to the cyclohexane extract of Curcuma longa L. The chromatographic conditions generated retention indices very close i.e., greater than 99.9%, to those reported for structures in the Sadtler Standard Gas Chromatography Retention Index Library. In addition to the extensively reported sesquiterpene ketones, this essential oil extract contained a series of saturated and unsaturated fatty acids. Wiley mass spectra library matching for the free fatty acids, their trimethylsilyl esters and methyl esters narrowed their identity down to a few candidates. Combining this information with the retention indices of the fatty acid methyl esters in the Sadtler library allowed the identification of some of the double bond positions.     

Selective diphosphine ligand chelation and pi bond coordination in CoRu(CO)7(mu-PPh2): kinetics and X-ray structure of CoRu(CO)4(mu-bma)(mu-PPh2)

Thermolysis of CoRu(CO)7(mu-PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(mu-P-P)(mu-PPh2) [where P-P = bma (3a), bpcd (3b)] along with trace amounts of the known complex CoRu(CO)6(PPh3)(mu-PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(mu-P-P)(mu-PPh2) [where P-P = bma (2a), bpcd (2b)] have been prepared by separate routes (mild thermolysis and Me3NO activation) and studied for their conversion to CoRu(CO)4(mu-P-P)(mu-PPh2). The penta- and tetracarbonyl complexes have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2a-->3a and of 2b-->3b were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters (2a-->3a, delta H++ = 29.2 +/- 1.4 kcal mol-1 and delta S++ = 8.2 +/- 3.8 eu; 2b-->3b, delta H++ = 27.7 +/- 0.6 kcal mol-1 and delta S++ = 1.4 +/- 1.6 eu), a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(mu-bma)(mu-PPh2) (3a), as determined by X-ray crystallography, reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride pi bond is coordinated to the cobalt atom.     

A comparative investigation of the fatty acid compositions of the seeds of a number of lines of a genetic collection of Gossypium hirsutum

A comparative analysis has been made of the amounts of lipids and their fatty-acid compositions in the seeds of the lines of agenetic collection of cotton plants of the speciesGossypium hirsutum and their hybrids and the variety Tashkent-1. The results obtained on the fatty-acid compositions of some hybrids make it possible to recommend the use of individual lines of cotton plants as donors for improving the food-value indices of cottonseed oil.Institute of Chemsitry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 173–176, March–April, 1991.     

ETC and Thermal Ligand Substitution in PhCCo3(CO)9 with 2,3-Bis(diphenylphosphino)-N-phenylmaleimide(bppm). X-Ray Diffraction Structure of Co3(CO)6[μ2,η2, η1-C(Ph)(O)](μ2-PPh2)

The reactivity of the bidentate ligand 2,3-bis(diphenylphosphino)-N-phenylmaleimide (bppm) with the tetrahedrane cluster PhCCo₃(CO)₉ under thermolysis and ETC conditions has been studied and found to ultimately give Co₃(CO)₆[μ₂,η²,η¹-C(Ph) ${\text{C}}{\text{ = }}{\text{ = }}{\text{C(PPh}}_{\text{2}} {\text{)C(O)NPhC}}$ (O)](μ₂-PPh₂) as the final product. The intermediate cluster compound PhCCo₃(CO)₇(bppm), which was observed by IR and ³¹P NMR spectroscopies, readily and rapidly transforms into the product cluster under the reactions conditions. The solid-state structure of Co₃(CO)₆[μ₂,η²,η¹-C(Ph)fptt(O)](μ₂-PPh$_{2})$ was unequivocally determined by X-ray crystallography. Co₃(CO)₆[μ₂, η², η¹-C(Ph)Õ(O)](μ₂-PPh₂) crystallizes in the monoclinic space group P2(1)/n, a = 11.825(5) Å, b = 31.20(1) Å, c = 11.831(5) Å, β = 108.720(7)°, V = 4134(7) ų, Z = 4, d _calc = 1.567 Mg/m³; R = 0.0350, R _w = 0.0817 for 4747 observed reflections with I > 2σ(I). The X-ray structure confirms the coupling of the benzylidyne ligand with the bppm ligand in Co₃(CO)₆[μ₂,η²,η¹-C(Ph)Õ(O)](μ₂-PPh₂). The course of the thermolysis reaction is identical to those reactions carried out with the related diphosphine ligands bma and bpcd. The utility of electron-transfer catalysis (ETC) in the preparation of PhCCo₃(CO)₇(bppm) is discussed relative to the reduction potential of the bppm ligand and the tricobalt cluster PhCCo₃(CO)₉.     

Surfactant adsorption at the salt/water interface: comparing the conformation and interfacial water structure for selected surfactants

We report in situ spectroscopic measurements monitoring the adsorption of a series of carboxylate surfactants onto the surface of the semisoluble, ionic solid fluorite (CaF2). We employ the surface-specific technique, vibrational sum-frequency spectroscopy (VSFS), to examine the effect that surfactant adsorption has on the bonding interactions and orientation of interfacial water molecules through the alteration of the electric properties in the interfacial region. In addition, we report on the chain length and headgroup dependence of the formation of hydrophobic self-assembled monolayers on the surface of the solid phase. Differences in chain length and headgroup functionality lead to large changes in the adsorption behavior and structuring of the monolayers formed and the interactions of interfacial water molecules with these monolayers. Fundamental studies such as these are essential for understanding the mechanisms involved in the surfactant adsorption process, information that is important for industrially relevant processes such as mineral ore flotation, waste processing, and petroleum recovery.     

Enumeration of Almost-Convex Polygons on the Square Lattice

We classify self-avoiding polygons on the square lattice according to a concavity measure, m, where 2m is the difference between the number of steps in the polygon and the perimeter of the minimal rectangle bounding the polygon. We generate series expansions for the perimeter generating functions S_m(x) for polygons of concavity m. We analyze the series S_m(x) for m = 0 to 3. If N_m,n denotes the number of polygons of perimeter 2n and concavity m, with m = o(n^1/2), we prove that N_m,n ? 2^2n?m?7n^m+1/m!, and that the radius of convergence of the series counting all polygons with m = o(n) is equal to 1/4. Our numerical data leads us to conjecture that in fact for m = o(n^1/2), a result confirmed for m = 0 and 1.     

SO2:H2O surface complex found at the vapor/water interface

A weakly bonded SO2:H2O surface complex is found at the vapor/water interface prior to the reaction and dissolution of SO2 into the aqueous phase. The results have important implications for understanding the formation of atmospheric aerosols and understanding the atmospheric sulfur cycle.