X-Ray Diffraction,Thermal and Spectroscopic Studies on 2,4-Dinitrodiphenylamine (DNDPA)

2,4-Dinitrodiphenylamine (DNDPA) has been studied as regards its crystal structure and thermal decomposition characteristics using X-ray diffraction (XRD), simultaneous thermal analysis, ultraviolet and visible spectroscopy, infrared spectroscopy, hot-stage microscopy and high performance liquid chromatography (HPLC). The elementary cell parameters obtained from the XRD pattern are a=17.002 Å, b=17.002 Å, c=20.400 Å. The crystal structure belongs to the hexagonal system with c/a ratio 1.1999. IR spectra of 2,4-DNDPA have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal thermogravimetry (TG) and HPLC. The best linearity with a correlation coefficient of 0.994 was obtained for the two-dimensional diffusion controlled equation in TG. Activation energy was found to be 83.0 kJ/mol and log A (in s⁻¹)=6.0 from isothermal TG. The rupture of the C NH bond followed by the C NO₂ bond constitutes the primary step in the thermolysis and the decomposition is free-radical assisted.     

Thermal Decomposition of Energetic Materials XXIV. A comparison of the crystal structures,IR spectra,Thermolysis and impact sensitivities of nitroguanidine and trinitroethylnitroguanidine

The crystal structure of trinitroethylnitroguanidine (TNENG) was determined by X-ray diffraction for comparison with nitroguanidine (NGu). Pertinent crystal parameters are: orthorhombic, Pbca, a = 14.611 (7) Å, b = 11.973 (5) Å, c = 11.452 (5) Å, V = 2003 (2) ų, Z = 8, D(calcd) = 1.758 g/cm³, R(F) = 6.30%, R(wF) = 6.58%. A hydrogen bonded network like that present in NGu is largely responsible for the lattice cohesion of TNENG. The IR spectrum of the condensed phase using slow thermolysis, and the gas phase using slow and fast thermolysis, suggests that parallel C N and N N bond fission reactions take place in both TNENG and NGu. The calculated and experimental values of the impact sensitivity of TNENG and NGu are compared. We conclude that the impact sensitivity and the thermal decomposition of TNENG are dominated by the characteristics of the  C(NO₂)₃ group. The intermolecular hydrogen bonding that may desensitize nitroguanidine to impact has essentially no stabilizing effect on TNENG.     

X-ray diffraction spectroscopic and thermal studies on 1,3,5-trinitro-hexahydropyrimidine (TNP)

TNP, a heterocyclic nitramine containing a C NO₂ functionality, has been studied as regards the kinetics and mechanism of thermal decomposition, morphology and the gaseous products evolved therof, using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and hot stage microscopy. The elementary cell parameters obtained form the XRD pattern are: a = 18.818 ± 0.005 Å, b = 18.818 ± 0.005 Å and c = 4.867 ± 0.005 Å. The crystal belongs to the hexagonal system with c/a ratio = 0.259. IR spectra of TNP have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal TG and IR. The best linearity with a correlation coefficient of 0.986 was obtained for the three-dimensional diffusion controlled Jander-equation. Kinetic parameters were evaluated from the induction period as well as from isothermal TG. Activation energy was found to be 202.05 kJ/mol and log A(in s-¹) 22.78 from TG and 181.133 kJ/mol and log A (in s¹) 20.97 from IR, respectively. The corresponding values were 171.17 kJ/mol and log A (in s-¹) 21.20 from the induction period data. The effect of a series of additives incorporated to the extent of 5 %, on the initial thermolysis of TNP, has also been studied. Evolved gas analysis by IR showed that CO₂, NO₂, NO and N₂O are produced in larger amounts than CO and HCN. The cleavage of the N N bond appears to be the primary step in the thermolysis of TNP.     

d-NMR-Untersuchung der behinderten Rotation am N?C(X)-Bindungsfragment. XII. Substituenteneffekte auf die C?N-Rotationsbarriere in unterschiedlich N-substituierten Carbamidsäure-O-ethylestern

d-N.M.R.-Investigation of the Restricted Rotation at the N C(X)-Bonding Fragment. XII. C N-Rotational Barrier in Different N-Substituted Carbamic Acid O-ethyl Esters The ¹H-n.m.r. spectra of a series of different N-substituted urethanes R¹R²N-C(O)OC₂H₅ are studied at various temperatures. At low temperatures the syn/anti rotamers are assigned by using the LIS-values of the protons. The thermodynamic parameters ΔG_C± of the restricted rotation about the partial C-N double bond are determined and discussed with regard to inductive, conjugative and homoconjugative effects of the N-substituents.     

X-ray crystal structure of the dye 2-bromo-4-cyano-4′-N,N-diethylaminoazobenzene

The crystal structure of 2-bromo-4-cyano-4′-N,N-diethylaminoazobenzene has been determined from X-ray diffraction data: C₁₇H₁₇N₄Br, mol. wt = 357·1. Triclinic, Pī (No. 2), α = 13·162(5) Å, b = 7·516(3) Å, c = 8·496(4) Å, α = 101·63(4)°, β = 95·79(4)°, γ = 91·49(4)°, V = 818·10 ų, Z = 2, D_c = 1·45 g cm^?3, F(000) = 378, λ(Mo_Kz) = 0·7107 Å, μ(Mo_Kα) = 26·70 cm^?1. The structure was solved by direct methods and refined by full-matrix least-squares to R = 0·053 for 2081 independent reflexions. The molecule possesses an essentially planar azobenzene skeleton. The effects of substituents on the geometry of the azo group are discussed. Significant molecular parameters are: NN, 1·264(6) Å; ₁BrC, 1·904(5) Å; mean NC, 1·410(7) Å; NNC, 115·7(2)° and 113·0(2)°; NCC (cis relative to NN), 125·4(3)° and 123·1(2)°; CC(Br)C, 123·0(2)°.     

NMR-study of the stereochemistry and dynamic behaviour of thioacrylamides

Several model thioacrylamides, Me₂N CH = C(R) C(S) NMe₂ (R = H, Ph — 2a, b ) and (p)MeO C₆H₄ NH CHC(R) C(S) NMe₂ (R = H, Ph — 3a, b ) have been synthesized. The ¹H-n.m.r. spectra have been taken for discussing the E/Z-isomerism of the thioacrylamides and the assignment further strengthened by an added LIS-study. The 2-unsubstituted compounds have been found to exist exclusively in preferred configurations/conformations: 2a — E(s-cis); 3a — Z(s-cis); the 2-phenylsubstituted analogs are of divergent behaviour: in 2b the C(S) NMe₂ moiety is found to be twisted out of the common plane, and 3b prefers the flat s-trans conformations (E(s-trans) ⇌ Z(s-trans)). The compounds show restricted rotations about C¹, N- and C³, N-partial double bonds. The corresponding rotational barriers, determined as ΔG-values by dynamic n.m.r. spectroscopy, are discussed with respect to (i) the resonance branch at C¹, (ii) the influence of substituents, and (iii) the effect of steric hindrance in the thioacrylamide moiety generally.     

X-ray crystal structure of the dye 2-cyano-4-bromo-4′-N,N-diethylaminoazobenzene

The crystal structure and molecular conformation of 2-cyano-4-bromo-4′-N,N-diethylaminoazobenzene (C₁₇H₁₇N₄Br, mol. wt. = 357·2 a.m.u) has been determined from X-ray diffraction data; triclinic, P$\text{1}$ (No. 2), a = 10·132(11) Å, b = 12·216(16) Å, c = 6·966(11) Å, α = 104·21(9)°, β = 92·67(12)°, γ = 97·22(7)°, V = 826·5(9) ų, Z = 2, D_c = 1·436 g cm^?3, F(000) = 378, λ(MoKα) = 0·71069 Å, μ(MoKα) = 26·0 cm^?1. The structure was solved by the multiple solution direct method and refined by full-matrix least-squares to R = 0·059 for 1538 independent observed reflections. The azobenzene skeleton is planar to within 0·06 Å. Most significant bonding data are: NN, 1·290(8) Å; BrC, 1·866(6) Å; mean CN (azo) 1·380(8) Å; NNC, 113·6(4) and 115·3(4)°; NCC (cis relative to NN) 125·9(4)° and 126·7(4)°; NCC (trans) 116·8°(5)° and 116·1(4)°.     

Gibbs free energy of formation of Bi2O3 from EMF cells with δ-Bi2O3 solid electrolyte

Determination of thermodynamic data on the formation of Bi₂O₃ was established by emf measurements as a function of temperature in the range 660–820°C on the system Metal, Bi(1)|Bi₂O₃|Pt, O₂. From the results using a tungsten electrode the following relation was found: ΔG⁰ = ?(134.7 ± 1.2) + (64.0 ± 1.2) × 10^?3 T kcal mole^?1 (validity range: 940–1080 K). Standard thermodynamic data at 298 K were calculated as ΔG⁰ = ?119.2 ± 2.1 kcal mole^?, ΔH⁰ = ?139.0 ± 1.2 kcal mole^?1, and ΔS⁰ = ?66.3 ± 1.2 eu.     

X-Ray crystal structure of the Dye 2,4,6-Tricyano-4'-N,N-diethylaminoazobenzene

The crystal structure and molecular conformation of 2,4,6-tricyano-4'-N,N-diethylaminoazobenzene (C₁₉H₁₆N₆, mol. wt. 328.4a.m.u.) has been determined from X-ray diffraction data: monoclinic P2₁/c, a = 9.302(7)Å, b = 8.733(5)Å, c = 20.98(1) Å, β = 94.93(6)°, V = 1699(2)ų, Z = 4, D_c = 1.284gem^?3, F(000) = 688, λ(MoKα) = 0-71069Å, μ(MoKα) = 0.76cm^?1. The structure was solved by MULTAN andrefined by full-matrix least-squares toR = 0.050 for 1358 independent observed reflections. The azobenzene skeleton is planar to within 0.12Å. Most significant bonding data are: NN, 1.286(4) Å; mean C-N (azo) 1.383(4) Å; mean C-C (cyano) 1.439(5) Å; mean CN 1.146(5)Å; NN-C, 112.8(2)° and 115.9(2)°; N-C-C (cis relative to NN) 127.6(2)° and 124.3(2)° ; N- C- C(trans) 115.2(2)° and 117.7(2)°.     

The first example of half-sandwich cobalt(III) complex with hydrotris(pyrazolyl)borate ligand

This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp^*Co(Hpz^*)(NCS)₂]·H₂O·CH₃OH (Tp^*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz^*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group C_c, a=18.591(6) Å, b=10.536(3) Å, c=17.568(5) Å, β=11.284(5)°, Z=4, R₁=0.0501, wR₂=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp^*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study.     

Vinyl‐addition copolymerization of norbornene and polar norbornene derivatives using novel bis(β‐ketoamino)Ni(II)/B(C6F5)3/AlEt3 catalytic systems

Copolymerization of norbornene (NBE) and polar norbornene derivatives undergoes vinyl polymerization by using novel catalyst systems formed in situ by combining bis(β‐ketoamino)Ni(II) complexes {Ni[R₁C(O)CHC(NR₃)R₂]₂ (R_l = R₂ = CH₃, R₃ = naphthyl, 1 ; R₁ = R₂ = CH₃, R₃ = C₆H₅, 2 ; R₁ = C₆H₅, R₂ = CH₃, R₃ = naphthyl, 3 ; R_l = R₂ = CH₃, R₃ = 2, 6‐(CH₃)₂C₆H₃, 4 ; R₁ = R₂ = CH₃, R₃ = 2, 6‐′Pr₂C₆H₃ 5 ; R₁ = C₆H₅, R₂ = CH₃, R₃ = 2, 6‐′Pr₂C₆H₃, 6 )} and B(C₆F₅)₃/AlEt₃ in toluene. The 1 /B(C₆F₅)₃/AlEt₃ catalytic system is effective for copolymerization of NBE with NBE OCOCH₃ and NBE CH₂OH, respectively, and copolymerization activity is followed in the order of NBE CH₂OH > NBE OCOCH₃ > NBE CN. The molecular weights of the obtained poly(NBE/NBE CH₂OH) reached 5.97 × 10⁴ to 2.07 × 10⁵ g/mol and the NBE CH₂OH incorporation ratios reached 7.0–55.4 mol % by adjusting the comonomer feedstock composition. The copolymerization of NBE and NBE CH₂OH also depend on catalyst structures and activity of catalyst followed in the order of 2 > 1 > 3 > 5 > 4 > 6 . The molecular weights and NBE CH₂OH incorporation ratios of poly(NBE/NBE CH₂OH) were adjustable to be 1.91–5.37 × 10⁵ g/mol and 9.5–41.1 mol %  OH units by using catalysts 1 – 6 . The achieved copolymers were confirmed to be vinyl‐addition type, noncrystalline and have good thermal stability (T_d = 380–410°C). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

1H-NMR-, 13C-NMR- und IR-Untersuchungen zur Tautomerie von 15N-markiertem 3-Methyl-1-phenyl-Δ2-pyrazolin-5-on

¹H-N. M. R., ¹³C N. M. R., and I. R.-Investigations Concerning Tautomerism of ¹⁵N-Labeled 3-Methyl-1-phenyl-Δ²-pyrazolin-5-one The behaviour of the ¹⁵N-mono and dilabeled compound in dependence on temperature and solvent polarity is described. Chemical shifts, ⁿJ(¹⁵N ¹H), and ⁿJ(¹⁵N ¹³C) coupling constants (n = 1 – 3) have been determined. In the cases of 2, 2, 2-trifluoroethanole and hexafluoroisopropanole the Δ⁴-pyrazolin-3-one is stabilized and detected by ³J(¹⁵N 2 H 4) = 3 Hz, ¹J(¹³C 3 ¹⁵N 2) = 11, 0 Hz and δ(¹³C 5). In HMPT the 5-hydroxypyrazole form predominates and is characterized by ³J(¹⁵N 1 H 4) = 5, 1 Hz and δ (¹³C 5). Coupling constants ³J(¹⁵N 2 H 4) and J(¹³C 3 ¹⁵N 2) could not be observed in this solvent. In accordance with ¹H- and ¹³C-n. m. r.-parameters i. r. measurements in dependence on temperature lead to the conclusion that in DMSO and THF for instance all three tautomers are present and variation of temperature does not change the equilibrium between the tautomers. A good relationship between the content of the CH₂, OH and NH forms and the Donor Numbers (DN) and Acceptor Numbers (AN) by Gutmann has been found.     

The synthesis and crystal structure of [M{H2B(tz*)2}2(H2O)] (M=Cu,Zn and tz*=3,5-dimethyl-1,2,4-triazole)

New ligand [KH₂B(tz^*)₂] (tz*=3,5-dimethyl-1,2,4-triazolyl) has been synthesized and the reactions of two different metal salts (copper and zinc) with the new ligand in agar gave two similar crystalline polymorphic forms: [Cu{H₂B(tz^*)₂}₂(H₂O)] (1) and [Zn{H₂B(tz^*)₂}₂(H₂O)] (2). A single crystal X-ray study revealed that the compound 1 was the monoclinic system with space group C2/c and a=8.462(3) Å, b=14.039(6) Å, c=19.991(8) Å, β=94.622(7)°, Z=4, R₁=0.0451, wR₂=0.1110. And the compound 2 was the monoclinic system with space group C2/c and a=8.4214(4) Å, b=13.8765(7) Å, c=20.2969(6) Å, β=95.615(2)°, Z=4, R₁=0.0667, wR₂=0.1375. The metal(II) ion in the complex is five-coordinated with four nitrogen atoms which come from triazolyl and one oxygen atom which come from water molecular. In both compounds, the hydrogen atoms of water molecule are connected by hydrogen bonding with N atoms of two adjacent complex molecules to form 2-D planes. The spectroscopic results are consistent with the crystallographic study.     

Azomethinimine. VI. Zum thermischen Verhalten des Photochromiesystems Azomethinimin/Diaziridin,untersucht an Pyrazolidon-(3)-azomethiniminen und deren Photoprodukten

Azomethineimine. VI. On the Thermic Behaviour of the Photochromic System Azomethineimine/Diaziridine, Investigated by Means of the Photoproducts of Pyrazolidone-(3)-Azomethineimines The photochemically obtained cycloproducts 2 of pyrazolidone-(3)-azomethineimines 1 react thermically to 1 in aprotic solvents. This backreaction was investigated by following up the growth of the intensive long wave absorptionband of 1 . The kinetic analysis was carried out according to SWINBOURNE [5, 6]. The thermic backreaction is accelerated by factors favouring a polarization of the C N(2)-bond (C^δ+  N^δ−) of diaziridine 2 . Such factors are polar solvents, donors in the substituent R and extensive, easily polarizable π-electronic systems in R. The influence of substituents on the backreaction can be correlated by means of the σ⁺-Hammett-constants. For most compounds the values of E_A ≈ ΔH^≠, Δ^≠ and ΔG^≠ were determined. The possible reaction mechanism is discussed. The influence of steric factors on the thermic backreaction is regarded as a first indication of an exo-form of the bicyclic diaziridines 2 .     

Reversible Carbon-Carbon Bond Cleavage of a 3-Vinyl-1-Cyclopropene by Rh(I). Molecular Structures of Two Sterically Crowded 1,2,3,5-η-Pentadienediyl Complexes of Rh(III)

1,2,3-Tri-tert-butyl-3-vinyl-1-cyclopropene 6a reacts with [RhCl(C₂H₄)]₂ to give the dimeric 1,2,3,5-η-pentadienediyl complex 7a . The cyclopentadienyl derivative of this complex, 8a , is obtained by reaction of 7a with T1(C₅H₅). Crystal structures of both 7a and 8a were determined: 7a ; orthorhombic, Pbcn, a = 28.136 (4) Å, b = 10.637 (2) Å, c = 12.154 (2) Å, V = 3637.6 (1.2) ų, and Z = 4 : 8a ; triclinic, P 1 -bar, a = 9.906 (2) Å, b = 9.736 (2) Å, c = 12.126 (2) Å, α = 76.07 (2)°, β = 78.21 (2)°, γ = 65.34 (2)°, V = 1024.6 (3) ų, and Z = 2. Treatment of 7a with one equivalent of PMe₃ per Rh center results in regeneration of the vinylcyclopropene, demonstrating the reversibility of the ring opening reaction. Deuterium labelling studies show that both the ring opening and closing reactions proceed with retention of configuration at the vinyl olefin. Thus the trans-deuterated vinylcyclopropene 6b reacts with [RhCl(C₂H₄)₂]₂ to give 7b in which deuterium is located exclusively in the syn position. Treatment of 7b with T1(C₅H₅) yields 8b . Treatment of 7b with one equivalent of PMe₃ per Rh center results in formation of 6b as the sole organic product. Unlike their triphenyl relative 2 , the tri-Bu complexes 7a , 7b, 8a , and 8b are stereochemically rigid in solution at room temperature, and do not undergo an η³ → η¹ → η³ isomerization on the NMR time scale. However, after prolonged heating, syn-anti site exchange of H and D slowly takes place with 8b .     

d-NMR-Untersuchungen der behinderten Rotation am N?C(X)-Bindungsfragment. XV. Beeinflussung der Rotationsbarriere im NR2?C(X)?R1-Bindungsfragment durch elektronische und sterische Substituenteneffekte

d-N.M.R. Investigations of the Restricted Rotation at the N C(X)-Bonding Fragment. XV. Influence of the Rotational Barrier in the NR₂ C(X)–R¹-Bonding Fragment by Electronic and Steric Substituent Effects. The rotational barriers ΔG^≠ of the restricted rotation about partial C,N-double bonds are determined for 4 series of urea-derivatives, and analogous compounds by complete lineshape analysis and approximation equations. Some general conclusions are drawn about the validity range of the approximations independence on the low temperature splitting Δν, the possible corrections within the margin of error and the internal temperature measurement. The dependence of the determined free enthalpies of activation about the effect of heteroatoms X, the NR₂-substituents and the electronic and steric influence of the substituents R¹ are discussed.     

Geminale Substituenteneffekte. VIII. Standardbildungsenthalpien von Acetalen

Geminal Substituent Effects. VIII. Enthalpies of Formation of Acetals The standard enthalpies of combustion ΔH_c° (1 or c) of the α-phenyl-substituted acetals ( 1 ) and diacetals ( 2 ) were measured calorimetrically. The enthalpies of vaporisation or sublimation ΔH_vap or ΔH_sub of 1–2 were obtained from the temperature function of the vapor pressure measured in a flow system, and the standard enthalpies of formation are obtained thereof: ΔH°_f (1 or c) and ΔH_f° (g) (in kJ mol⁻¹) for 1a = −308.40 ± 0.52(1), −248.94 ± 0.88; 1b = −343.48 ± 0.72 (1), −288.5 ± 1.5; 1c = −267.4 ± 1.3 (1), −205.3 ± 1.3; 1d = −343.8 ± 2.1 (c), −261.9 ± 2.2; 1e = −397.02 ± 0.86 (c), −311.3 ± 1.2; 1f = −414.52 ± 0.80 (1), −350.68 ± 0.86; 2a = −564.8 ± 2.4 (c), −467.1 ± 2.5; 2b = −547.6 ± 1.6 (c), −414.9 ± 2.7; 2c = −717.1 ± 7.5 (c), −587.0 ± 8.0. The results are combined into values of two strain free group increments CH[20, C_Ph] = −59.7 and C[20, C_Ph, C] = −71.3 kJ mol⁻¹; and compared to the aliphatic series of acetals.     

One Dimensional Structure of Zn(II) Metal Organic Framework (MOF) Assembled Rapidly at Room Temperature: Structural,Thermal Study,and Luminescent Properties

One-dimensional structure of Zinc(II) metal organic framework ([Zn₂(C₁₀H₈N₂)₃(NO₃)₄]_∞) has been synthesized at room temperature and structurally characterized by elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. The five-coordinated Zn(II) complex exhibits trigonal bipyramidal coordination geometry. The Zn(II) ion is stabilized by three-connected nodes to form 1D ladder structure. The 1D chain is further connected to each other via hydrogen bonding to form 2D structure. Disordered CH₂Cl₂ solvent molecules were trapped in the pores. The luminescent and thermal properties have been also investigated. In addition, the activation thermodynamic parameters, ΔE^*, ΔH^*, ΔS^* and ΔG^* are calculated from the DTA curves using Coats–Redfern method.     

Thermal Decomposition of Energetic Materials XVIII. Bis (cyanomethyl)nitramine and Bis(cyanoethyl)nitramine

The crystal structures of two potentially useful cyanonitramines are reported. Bis(cyanomethyl)nitramine (BCMN), (NCCH₂)₂NNO₂: monoclinic, C2, a = 10.247(1), b = 7.771(1), c = 12.230(2) [Å], β = 107.45 (2)^°, Z = 6, D_calc = 1.502 g.cm⁻³, R_F = 2.8%, R_wF = 3.1%. A syn (C₂) and anti (C_s) isomers of BCMN crystallize together in a 2:1 ratio in the unit cell. Bis(cyanoethyl)nitramine (BCEN), (NCCH₂CH₂)NNO₂: monoclinic, P2₁/c, a = 7.512(2), b = 10.840(3), c = 10.181(3) [Å], β = 97.39(2)^°, Z = 4, D_cale = 1.357 g.cm⁻³, R_F = 4.6%, R_wF = 4.7%. Only one conformation of the BCEN molecule having no symmetry is present in the unit cell. The IR spectrum shows that BCEN forms an amorphous phase when the melt is cooled or when an acetone or acetonitrile solution is rapidly evaporated. The amorphous phase slowly crystallizes at room temperature. High-rate thermolysis of BCMN liberates NO₂ as the predominant initial product. This difference is qualitatively predictable on the basis of the variation in the N-N bond distance in these two compounds.     

Zur Kupplung von 4-substituierten 2-Pyrazolin-5-onen mit p-Chinondiiminkationen; Nachweis isokinetischer Beziehungen

On the Coupling of 4-Substituted 2-Pyrazoline-5-ones with Quinone Diimine Cations; Detection of Isokinetic Relations The temperature dependence of the rate constant k_K of the coupling reaction between pyrazoline-5-ones 1a – i and quinone diimine cations 2a , b is determined in dependence of the substituents at the coupling position (R³:  H,  NN Ar, CHAr–pyrazoline-5-one). The activation enthalpies are between 7 and 60 kJ mol⁻¹ and the activation entropies between −132 and −19 J mol⁻¹ K⁻¹. An isokinetic relation with β = 106°C is found and a rate determining combination of the carbanions of 1a – i with 2a , b is proposed. Contrary to this, the 2-pyrazolin-5-ones 1j – l , n (R³:  S CNH₂NR) obey an isokinetic relation with β = −45°C. Taking into consideration the activation parameters, the low dependence of k_K on the ionic strength, and the decrease of k_K with the increase of the pK values of the couplers, a rate determining splitting off of R³ is assumed.