Nichtstationäre Kinetik bei SN1, SN2, E1, E2 und E1cb-Mechanismen

For the S_N1, S_N2, E₁, E₂, AND E₁cb mechanisms exact solutions of the kinetic equations are compared with solutions obtained under the hypothesis of stationarity. Exact integrals are calculated numerically for a set of the essential reaction rate constants. Comparison with the stationary state solution demonstrates that both types of solutions are approximately equal in many cases if the transient particle concentration remains low, whereas the conventional requirement | \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop x\limits^. $\end{document} | = 0 is unimportant. For approximation of exact kinetics by stationary kinetics, however, neither condition is sufficient nor necessary. Practical criterions for recognition of deviations from stationary kinetics are given.     

Notiz zur Synthese von (E)-12-Hydroxy-10-heptadecensäure, (5E, 10E)-12-Hydroxy-5, 10-heptadecadiensäure und (5Z, 10E)-12-Hydroxy-5,10-heptadecadiensäure

Note on the Synthesis of (E)-12-Hydroxy-10-heptadecenoic Acid, (5E, 10E)-12-Hydroxy-5, 10-heptadienoic Acid and (5Z, 10E)-12-Hydroxy-5,10-heptadienoic Acid The syntheses of two heptadecadienoic and one heptadecenoic acid, compounds which formally may be derived from prostaglandin-like molecules by removal of a C₃-fragment from the five-membered ring, are described.     

Short Syntheses of 4‐Deoxycarbazomycin B,Sorazolon E,and (+)‐Sorazolon E2

Short syntheses of 4‐deoxycarbazomycin B and sorazolon E were established through the condensation of cyclohexanone and commercially available 4‐methoxy‐2,3‐dimethylaniline, followed by Pd^II‐catalyzed dehydrogenative aromatization/intramolecular C−C bond coupling and deprotection. A chiral dinuclear vanadium complex (R _a,S,S )‐ 6 mediated the enantioselective oxidative coupling of sorazolon E, affording (+)‐sorazolon E2 in good enantioselectivity.     

Über die Umsetzung von P4E3I2 (E = S,Se) mit einigen Carbonsäuren und Dithiocarbonsäuren

On the Reaction of P₄E₃I₂ (E = S, Se) with some Carboxylic Acids and Dithiocarbamic Acids By the reaction of α-P₄E₃I₂ (E = S, Se) with carboxylic acids, dithiobenzoic acid or dithiocarbamic acids in the presence of triethylamin or with (C₆H₅)₃SnR, or of β-P₄E₃I₂ with tin-organic compounds α-P₄E₃(I)R, α(β)-P₄E₃R₂ [R = ? OC(O)C₆H₅, ? OC(O)CH₃, ? SC(S)NC₅H₁₀, ? SC(S)N(C₂H₅)₂], α-P₄S₃(I)SC(S)C₆H₅, α-P₄S₃(SC(S)C₆H₅)₂ and β-P₄E₃(I)R (R = ? OC(O)C₆H₅, ? OC(O)CH₃) were prepared in solution and identified by ³¹P NMR spectroscopy. In addition α-P₄S₃(NC₅H₁₀)(SC(S)NC₅H₁₀) was detected. The β-isomers could be obtained also with lesser yields by the reaction with the dithiocarbamic acids, too. The substitution of the second iodine ligand in β-P₄E₃I₂ resulted mainly in β-P₄S₃(R_exo)₂ and by inversion of the configuration at a phosphorus atom, in β-P₄E₃R_exoR_endo. α-P₄S₃I₂ reacted with methanol in CS₂ to α-P₄S₃(OCH₃)(SC(S)OCH₃) and α-P₄S₃(SC(S)OCH₃)₂. The ³¹P NMR data of the compounds are discussed. The ³¹P NMR spectra of the α(β)-P₄E₃ dithiocarbamates indicate dynamic processes in the solution, e. g. α-P₄S₃(I)(SC(S)NR₂) showed an intramolecular conversion, due to the anisobidentate dithiocarbamate ligand. This behaviour had not previously been noticed for compounds with a P₄S₃-skeleton.     

Vibrational Spectra of Cluster Anions. 2. Vibrational Spectra of Compounds with the Cluster Anions [E4]4−: M4E4 (M = K,Rb, Cs; E = Ge,Sn) and β‐Na4Sn4

Vibrational spectra of the compounds M₄E₄ (M = K, Rb, Cs; E = Ge, Sn) and of β‐Na₄Sn₄ with the cluster anions [E₄]^4? were analysed based on the point group of isolated tetrahedranide units. The lower individual symmetry of the anions in the real structure being more patterned and complex primarily affects the spectra of the tetrahedro‐tetragermanides. ν₃(F₂) clearly splits both in Raman and IR and in the case of K₄Sn₄ only in IR. Rb₄Sn₄ and Cs₄Sn₄ exhibit very simple spectra with three bands in Raman and one band in IR. The breathing mode ν₁(A₁) for the quasi isolated [E₄]^4? cluster appears only in the Raman spectrum and is hardly influenced by the structural environment and by the nature of the alkali metal cations: ν₁(A₁) = 274 cm^?1 ([Ge₄]^4?) and 183‐187 cm^?1 ([Sn₄]^4?), respectively. The calculated valence force constants f_d(E–E) are: [Ge₄]^4? : f_d = 0.89 Ncm^?1 ( K ), 0.87 Ncm^?1 ( Rb ), 0.86 Ncm^?1 ( Cs ) and [Sn₄]^4? : 0.67 Ncm^?1 ( Na ), 0.66 Ncm^?1 ( K ), 0.67 Ncm^?1 ( Rb ), 0.68 Ncm^?1 ( Cs ). Both, the frequencies and the force constants fit well into the range previously reported.     

(E,E,E)‐1,3,5‐Tris[4‐(acetyl­sulfan­yl)­styr­yl]­benzene toluene hemisolvate

The first crystal structure of a three‐terminal sulfur end‐capped oligo­phenyl­ene­vinyl­ene, C₃₆H₃₀O₃S₃·0.5C₇H₈, has been determined at 122 (1) K. The mol­ecular threefold symmetry is not utilized in the crystal structure. It is confirmed that the double bonds have been fully transformed into a trans configuration by iodine treatment.     

Vibrational Spectra of the Cluster Anions [E4]4– in the metallic Sodium and Barium Compounds Na4E4 and Ba2E4 (E = Si,Ge)

The vibrational spectra of the cluster anions [E₄]^4– (E = Si, Ge) in the metallic compounds Ba₂E₄ and Na₄E₄ have been measured and assigned based on the T_d symmetry of the discrete tetrahedranide anion. Due to the lower site‐symmetries in the respective crystals all degenerate modes are split, but to different extends. The characteristic breathing frequency ν(E–E) of the [E₄]^4– cluster appears exclusively in the Raman spectrum and is almost unaffected by the nature of counterions: ν(E–E) = 486 cm^–1 (E = Si) and 276 and 278 (Ge), respectively. The calculated valence force constants f_d (Si–Si) = 1.17 Ncm^–1 ( Na ); 1.15 Ncm^–1 ( Ba ) and f_d (Ge–Ge) = 0.98 Ncm^–1 ( Na ); 0.94 Ncm^–1 ( Ba ) are in good agreement with those previously reported.     

Efficient synthesis of 3E,13Z-octadecadienol,its acetate, 4E,6E,11Z-hexadecatrienal,and 4E,6E,11Z-hexadecatrienyl acetate,sex pheromones of some lepidopteran species

The title linear acetogenins have been synthesized by a strategy of joining acetylcyclopropane to 8Z-tridecenol or 5Z-decenol prepared after Julia, leading to the corresponding secondary cyclopropylcarbinols. The ZnBr₂/Me₃SiBrinitiated homoallylic rearrangement of the latter assures at a key step the stereospecific construction of transoid fragments of the target molecules.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2521–2529, November, 1991.     

Pniktogenidostannate(IV) mit isolierten Tetraeder‐Anionen: Neue Vertreter (E1)4(E2)2[Sn(E15)4] (mit E1 = Na,K; E2 = Ca,Sr, Ba; E15 = P,As, Sb,Bi) vom Na6[ZnO4]‐Typ und die Überstrukturvariante von K4Sr2[SnAs4]

Pnictogenidostannates(IV) with Discrete Tetrahedral Anions: New Representatives (E1)₄(E2)₂[Sn(E15)₄] (with E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) of the Na₆[ZnO₄] Type and the Superstructure Variant of K₄Sr₂[SnAs₄] The silvery to dark metallic lustrous compounds (E1)₄(E2)₂[Sn(E15)₄] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na₆[ZnO₄]‐type structure (hexagonal, space group: P6₃mc, Z = 2; Na₄Ca₂[SnP₄]: a = 938.94(7), c = 710.09(8) pm; K₄Sr₂[SnAs₄]: a = 1045.0(2), c = 767.0(1) pm; K₄Ba₂[SnP₄]: a = 1029.1(6), c = 780.2(4) pm; K₄Ba₂[SnAs₄]: a = 1051.3(1), c = 795.79(7) pm; K₄Ba₂[SnSb₄]: a = 1116.9(2), c = 829.2(1) pm; K₄Ba₂[SnBi₄]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)₄]^8– orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K₄Sr₂[SnAs₄] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P6₃cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure.     

Syntheses of (−)-gabosine A, (+)-4-epi-gabosine A, (−)-gabosine E, and (+)-4-epi-gabosine E

(+)-4-epi-Gabosine A 1 and (−)-gabosine A 2 have been synthesized starting from methyl α,d-glucopyranoside and methyl α,d-mannopyranoside, respectively, by utilizing Pd(0) catalyzed Stille coupling as the key step. On the other hand, syntheses of (+)-4-epi-gabosine E 3 and (−)-gabosine E 4 have been accomplished from methyl α,d-glucopyranoside and from methyl α,d-mannopyranoside, respectively, by utilizing DMAP catalyzed Morita-Baylis-Hillman reaction as the key step. Presence of acetyl group at C-6 position of sugar derived cyclic enone prevented the aromatization of MBH adduct. A plausible mechanism is also described.     

(E)‐(4‐Hydroxyphenyl)(4‐nitrophenyl)diazene, (E)‐(4‐methoxyphenyl)(4‐nitrophenyl)diazene and (E)‐[4‐(6‐bromohexyloxy)phenyl](4‐cyanophenyl)diazene

Syntheses and X‐ray structural investigations have been carried out for (E)‐(4‐hydroxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₂H₉N₃O₃, (Ia), (E)‐(4‐methoxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₃H₁₁N₃O₃, (IIIa), and (E)‐[4‐(6‐bromo­hexyl­oxy)­phenyl](4‐cyano­phenyl)­diazene, C₁₉H₂₀BrN₃O, (IIIc). In all of these compounds, the mol­ecules are almost planar and the azo­benzene core has a trans geometry. Compound (Ia) contains four and compound (IIIc) contains two independent mol­ecules in the asymmetric unit, both in space group P (No. 2). In compound (Ia), the independent mol­ecules are almost identical, whereas in crystal (IIIc), the two independent mol­ecules differ significantly due to different conformations of the alkyl tails. In the crystals of (Ia) and (IIIa), the mol­ecules are arranged in almost planar sheets. In the crystal of (IIIc), the mol­ecules are packed with a marked separation of the azo­benzene cores and alkyl tails, which is common for the solid crystalline precursors of mesogens.     

Conformational polymorphism of (E,E)‐N,N′‐bis(4‐nitrobenzylidene)benzene‐1,4‐diamine

Two polymorphs of (E,E)‐N,N′‐bis(4‐nitrobenzylidene)benzene‐1,4‐diamine, C₂₀H₁₄N₄O₄, (I), have been identified. In each case, the molecule lies across a crystallographic inversion centre. The supramolecular structure of the first polymorph, (I‐1), features stacking based on π–π interactions assisted by weak hydrogen bonds involving the nitro groups. The second polymorph, (I‐2), displays a perpendicular arrangement of molecules linked via the nitro groups, combined with weak C—H...O hydrogen bonds. Both crystal structures are compared with that of the carbon analogue (E,E)‐1,4‐bis[2‐(4‐nitrophenyl)ethenyl]benzene, (II).     

Stationary properties of δE/δR

It is made clear that two different statements in the literature concerning energy derivatives are completely compatible by deriving them as two different interpretations of the same equation. Some other aspects of these results are also discussed.