A decision support method for designing vegetation layers with minimised irrigation need

Annals of Operations Research - Selecting a vegetation layer design goes along with determining its future irrigation need. Therefore, it is essential to take a design decision that is minimising...     

Janus Face All-cis 1,2,4,5-tetrakis(trifluoromethyl)- and All-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)- Cyclohexanes

We report the synthesis of all-cis 1,2,4,5-tetrakis (trifluoromethyl)- and all-cis 1,2,3,4,5,6-hexakis (trifluoromethyl)- cyclohexanes by direct hydrogenation of precursor tetrakis- or hexakis- (trifluoromethyl)benzenes. The resultant cyclohexanes have a stereochemistry such that all the CF₃ groups are on the same face of the cyclohexyl ring. All-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)cyclohexane is the most sterically demanding of the all-cis hexakis substituted cyclohexanes prepared to date, with a barrier (ΔG) to ring inversion calculated at 27 kcal mol⁻¹. The X-ray structure of all-cis 1,2,3,4,5,6-hexakis(trifluoromethyl)cyclohexane displays a flattened chair conformation and the electrostatic profile of this compound reveals a large diffuse negative density on the fluorine face and a focused positive density on the hydrogen face. The electropositive hydrogen face can co-ordinate chloride (K≈10³) and to a lesser extent fluoride and iodide ions. Dehydrofluorination promoted decomposition occurs with fluoride ion acting as a base.     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

Crystal structure of (4α,4aα,8aα)-(±)-octahydro-2-(phenylmethyl)-2H-1,2-benzoxazin-4-ol, 4-methylbenzenesulfonate(ester)

The title compound, a bicyclic tetrahydro-1,2-oxazine, crystallizes in a monoclinic lattice, space group P2₁/c, with a = 12.9809(18)Å, b = 12.920(2)Å, c = 13.631(2)Å, = 110.713(12)°, and Z = 4. The structure found in the solid state for this conformationally mobile molecule shows the tosyl group in an axial position and a benzyl group in an equatorial position of the bicyclic system.     

Molecular structures of [CpRu(PPh3)(dtoxa-H2O)]BF4 and {[CpRu(PPh3)2]2(μ-dtoxa)}(BF4)2, dtoxa=dithiooxamide

The reaction of [CpRu(PPh₃)₂(n-C₃H₇SH)]BF₄ with dithiooxamide (dtoxa) gave two products: {[CpRu(PPh₃)₂]₂(-dtoxa)} (BF₄)₂,1, and [CpRu(PPh₃)(dtoxa-H₂O)]BF₄,2. The structures of both complexes were determined by X-ray diffraction techniques. Compound1 crystallized in the triclinic space groupP _¯1,a=12.822(4),b=14.16(1),c=23.631(8) Å,=84.57(4),=83.64(3), =83.57(4)°,Z=2,R=0.069,R _w =0.084. The structure of1 shows two CpRu(PPh₃)₂ ⁺ units bridged through the S atoms of the dtoxa ligand. Ru-S distances are 2.377(6)Å for Ru1-S1 and 2.368(6) Å for Ru2-S2. Compound2 crystallized in the monoclinic space groupP2₁/c,a=13.446(3),b=13.461(7),c=31.214(7) Å,=100.78(3)°,Z=8,R=0.054,R _w =0.055. The structure of2 has two molecules in the asymmetric unit. The Ru is chelated to the dtoxa through the S atoms: Ru1-S1, 2.307(4); Ru1-S2, 2.300(4); Ru2-S3, 2.295(4); Ru2-S4, 2.287(4) Å. The coordination sphere of the Ru in2 is completed by a cyclopentadienyl ligand and a triphenylphosphine.     

Molecular structure of [CpRu(PPh3)2(C6H11SH)]BF4·CH2Cl2

The structure of the [CpRu(PPh₃)₂(C₆H₁₁SH)]BF₄·CH₂Cl₂ complex was determined by X-ray diffraction techniques; triclinic space group ,a=12.567(1),b=13.409(1),c=14.733(1) Å, =95.380(7), =111.041(7), =96.454(8)°,V=2278.5(4) ų,Z=2,R=0.056,R _w=0.088. The Ru is attached to two triphenylphosphine ligands, a cyclopentadienyl and the S atom of the cyclohexylthiol. The Ru–S distance is 2.389(2) Å and the S–H distance is 1.23 Å.     

Parahydrogen induced polarization of barbituric acid derivatives: 1H hyperpolarization studies

Homogeneous hydrogenation of barbituric acid derivatives with parahydrogen yields a substantial increase of the (1)H NMR signals of the reaction products. These physiologically relevant compounds were hydrogenated at both ambient and elevated temperatures and pressures using a standard cationic rhodium catalyst. The resulting nonthermal nuclear spin polarization (hyperpolarization) is limited by the spin-lattice relaxation time T(1) of the corresponding nuclei in the products, being shorter than the time constant of the hydrogenation. The signal-to-noise ratio of the NMR spectra could be further increased upon signal averaging the antiphase PHIP signals of 25 successive scans following 30 degrees pulse experiments and a delay of 10 s.     

Closo-alanes (Al4H4, AlnHn+2, 4 <or= n <or= 8): a new chapter in aluminum hydride chemistry

Anion photoelectron spectroscopy and density functional theory were employed to study aluminum hydride clusters, AlnHm- (4 相似文献   

Abläufe der Ammonolysen der Ammoniumhexafluorometallate des Aluminiums,Galliums und Indiums, (NH4)3MF6 (M = Al,Ga, In)

The Courses of the Ammonolyses of the Ammonium Hexafluorometalates of Aluminum, Gallium, and Indium, (NH₄)₃MF₆ (M = Al, Ga, In) The courses of the ammonolysis reactions of the ammonium hexafluorometalates (NH₄)₃MF₆ (M = Al, Ga, In) were investigated with the aid of in‐situ powder diffractometry and differential thermal analysis. Under these conditions, the reaction of (NH₄)₃AlF₆ with gaseous ammonia yields at about 360 °C AlF₃ via the intermediates NH₄AlF₄, Al(NH₃)₂F₃ and Al(NH₃)F₃. The ammonolysis of (NH₄)₃GaF₆ produces GaN at about 400 °C. Depending upon the actual reaction conditions, the intermediates NH₄GaF₄ and Ga(NH₃)F₃ as well as their ammonia adducts NH₄GaF₄ · NH₃ and Ga(NH₃)₂F₃ and the amide‐ammoniate Ga(NH₃)(NH₂)F₂ are observed. In the case of (NH₄)₃InF₆ the intermediates (NH₄)₃InF₆ · NH₃ and In(NH₃)F₃ may exist; there are also indications for the reduction of In(III) to In(I) and for the existence of In(NH₃)₂F and InF as products of the ammonolysis of (NH₄)₃InF₆.