Synthesis and activity of four (N,N‐dimethylamino)benzamide nonsteroidal anti‐inflammatory drugs based on thiazole and thiazoline

Four compounds derived from 2‐aminothiazole and 2‐amino‐2‐thiazoline were prepared by coupling the respective bases with the acid chlorides of either 3‐ or 4‐(N,N‐dimethylamino)benzoic acid. Products were identified using infrared spectroscopy, ¹H NMR spectroscopy and electrospray mass spectroscopy and in two cases by single‐crystal X‐ray diffraction. Of the four, N‐(thiazol‐2‐yl)‐3‐(N,N‐dimethylamino)‐benzamide (1), N‐(thiazolin‐2‐yl)‐4‐(N,N‐dimethylamino)benzamide (2), N‐(thiazolin‐2‐yl)‐3‐(N,N‐dimethylamino) benzamide (3) and N‐(thiazolin‐2‐yl)‐4‐(N,N‐dimethylamino)benzamide (4), the hydrochloride salts of compounds 3 and 4 showed anti‐inflammatory activity across a concentration range of 10^?2?5 × 10^?4 M while 3 (at a concentration of 10^?5 M) was found to have no adverse effect on myocardial function. The X‐ray crystal structure of 2 and the 1:1 adduct structure of 3 with 3‐(N,N‐dimethylamino)benzoic acid are reported.     

Calculation of excited-state properties of some small molecules: Comparative study of the CNDO/S and CNDO/2-vn−1 potential methods

The transition energy and geometry of the lowest excited (nπ*) singlet and triplet states of CO, CS, HNO, H₂CO, HFCO, and F₂CO molecules are calculated by CNDO /S and CNDO /2-V_N?1 potential methods, and the results are compared with those of experimental and ab initio theoretical studies, wherever available. In the calculation of the vertical transition energy, the performance of the CNDO /S method is seen to be generally more satisfactory than that of the CNDO /2-V_N?1 potential method, while the reverse is true for the excited-state geometry. The CNDO /S method as such fails to describe the geometry of the excited state, but a combined version (CNDO /S-2) of CNDO /S and CNDO /2, as well as the CNDO /2-V_N?1 potential method is fairly successful in this regard.     

Studies on biaxial stretching of polypropylene film. IV. Overall orientation during one-step biaxial stretching and its application to the estimation of the principal refractive indices of isotactic polypropylene

Polypropylene film was biaxially stretched in one step in air at 140°C or 152°C, and the deformation was studied optically. A linear relation held between Δn_ss and v_A^?½ for v_A > 10, at both temperatures, where Δn_ss is the birefringence with respect to the normal to the film and v_A is the degree of stretching expressed as the factor by which the area of the film is increased. Extrapolation of data in this linear region yielded a value of 20 × 10^?3 for ?Δn_ss at infinite v_A. Since it is presumed that the polypropylene molecules lie completely parallel to the film surface when the film is stretched infinitely, ?Δn_ss at v_A^?½ = 0 must be just half Δn°, the intrinsic birefringence in the case of completely parallel orientation. Thus, Δn° must be 40 × 10^?3. This value was obtained experimentally in uniaxial stretching when the birefringence with respect to the direction of drawing was extrapolated to infinite extension. Similar relations held between n_p, the average of the refractive indices in the two stretching directions, and v_A, and between n_ss, the index normal to the film, and v_A. By similar extrapolations, (1/2)(n′_γ + n′_β) and n′_β = n*_α′ were estimated, and thence nα′ was obtained. Here, n′_α and n′_β are the refractive indices along the c axis (molecular chain axis) and b axis. All these optical parameters refer to a density of 0.900 g/cm³. Hence by applying a density correction to those values, the principal refractive indices and the intrinsic birefringence of polypropylene crystal were evaluated as follows: n_α = 1.5522, n_β = n*_α = 1.5106 and Δn_c° = 4.16 × 10^?3, where n*_α is the refractive index prependicular to the b and c axes of the crystal.     

Quaternization of 2-aziridino-5-chlorobenzophenone,an efficient synthesis of medazepam

Quaternization of 2-aziridino-5-chlorobenzophenone (1) with methyl iodide resulted in formation of 2-(N-β-iodoethyl-N-methyl)aminobenzophenone ( 2 ), via an unstable quaternary compound. Rate constants for 1 → 2 conversion, as determined by an nmr method at 35 ± 0.1°, varied between 0.22 × 10^?3 sec^?1 in DMSO-d₆, and 0.95 × 10^?6 sec^?1 in methanol-d₄. Ammonolysis with hexamine, and subsequent cyclization afforded 7-chloro-l-methyl-5-phenyl-2,3-dihydro-lH-1,4-benzodiazepine (3, generic name medazepam) in 92% over-all yield.     

Studies on anionic polymerization of lactams. Part II. Effect of cocatalysts on the polymerization of pyrrolidone

The rates of addition of pyrrolidonate magnesium bromide (PyMgBr) to N-benzoyl-, N-acetyl-, and N-methylpyrrolidone were measured in solution in tetrahydrofuran (THF). The values found for the rate constants at 25°C. were 9.5 × 10^?2, 2.8 × 10^?2, and 5 × 10^?4 l./mole-sec., respectively. The rate constant for addition of PyMgBr to pyrrolidone was also measured and found to be 3 × 10^?9l./mole-sec. Possible causes for the large difference between the values of these constants are discussed.     

Thermal Studies of New Lead(II) Coated‐Wire Membrane Electrodes

Five plastic membrane Pb²⁺‐selective electrodes were prepared based on 1,4‐bis(N‐tosyl‐o‐aminophenoxy)butane I , 1,4‐bis(N‐allyl‐N‐tosyl‐o‐aminophenoxy)butane II , 1,4‐bis(N‐benzyl‐N‐tosyl‐o‐aminophenoxy)butane III , 1,4‐bis[N‐(o‐allyloxybenzyl)‐N‐tosyl‐o‐aminophenoxy]butane IV , and 1,4‐bis(N‐octyl‐N‐tosyl‐o‐aminophenoxy)butane V as neutral carriers. The electrodes exhibited nearly Nernstian responses over the concentration ranges, 2.5×10^?4–4.0×10^?2, 2.5×10^?5–4.0×10^?2, 7.9×10^?5–4.0×10^?2, 2.2×10^?5–4.0×10^?2, and 1.9×10^?4–4.0×10^?2 M for electrodes composed with the ionophores I–V , respectively. All electrodes showed pH range of about 4.0 to 11.5 and working temperature range of 22 to 70 °C with isothermal temperature coefficients of 1.19×10^?3, 1.16×10^?3, 1.16×10^?3, 1.00×10^?3 , and 1.32×10^?3 V/°C for electrodes I–V respectively.     

Relaxivity Study and X-ray Structure of Gd(III)-diethylenetriamine-N,N′,N′-triacetic-N,N″-bis(benzylamide). A Potential MRI Contrast Agent

The new bis(amide) derivatives of DTPA (diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid), diethylenetriamine-N,N′,N″-triacetic-N,N″-bis(benzylamide) (DTPA-BBA) have been synthesized. The crystal structure of gadolinium(III) complex of DTPA-BBA ([Gd(DTPA-BBA)]) has been determined by X-ray crystallography: C₂₈H₅₂GdN₅O₁₇, M_w = 889 g mol^?1, space group $ {\rm P}\bar 1 $ (#2) (triclinic), a = 12.645(4), b=14.125(8), c = 12.623(4) Å, α = 111.60(3), β = 114.79(3), γ = 88.39(4)°, V = 1881(1) ų, Z = 2, D_x = 1.569 g/cm³, λ(Mo Kα) =0.71069 Å, μ = 18.44 cm^?1, final R = 0.047, R_w = 0.046 for 3755 independent observed reflections at 23 °C. The coordination sphere of Gd(III) comprises three amine nitrogens, two amide oxygens, three carboxylic acid oxygens, and one water. The relaxivity of Gd(III) complex was determined to be R1 = 4.08(4) and R2 = 6.06(5) dm³ mmol^?1 s^?1 at pH = 7.0, 20 MHz, and 37(1) °C. Additionally, the R1 relaxivity for Gd(III) chelate was found to be invariant with respect to pH changes over the range of 2-10. This indicates that a constant inner-sphere hydration number is associated with the [Gd(DTPA-BBA)] complex. Hence the high stability of the complex is demonstrated.     

Structural Characterization and Thermal Behavior of 1-Amino-1-methylamino-2,2-dinitroethylene

A novel high energetic material, 1‐amino‐1‐methylamino‐2,2‐dinitroethylene (AMFOX‐7), was synthesized through 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) reacting with methylamine in N‐methyl pyrrolidone (NMP) at 80.0°C, and its structure was determined by single crystal X‐ray diffraction. The crystal is monoclinic, space group P2₁/m with crystal parameters of a=6.361(3) Å, b=7.462(4) Å, c=6.788(3) Å, β=107.367(9)°, V=307.5(3) ų, Z=2, µ=0.160 mm^?1, F(000)=168, D_c=1.751 g·cm^?3, R₁=0.0463 and wR₂=0.1102. Thermal decomposition of AMFOX‐7 was studied, and the enthalpy, apparent activation energy and pre‐exponential constant of the exothermic decomposition reaction are 303.0 kJ·mol^?1, 230.7 kJ·mol^?1 and 10^21.03 s^?1, respectively. The critical temperature of thermal explosion is 245.3°C. AMFOX‐7 has higher thermal stability than FOX‐7.     

Halide‐Anion Binding by Singly and Doubly N‐Confused Porphyrins

The halide‐binding properties of N‐confused porphyrin (NCP, 1 ) and doubly N‐confused porphyrins (trans‐N₂CP ( 2 ), cis‐N₂CP ( 3 )) were examined in CH₂Cl₂. In the free‐base forms, cis‐N₂CP ( 3 ) showed the highest affinity to each anion (Cl^?, Br^?, I^?) with association constants K_a=7.8×10³, 1.9×10³, and 5.8×10² M ^?1, respectively. As metal complexes, on the other hand, trans‐N₂CP 2–Cu exhibited the highest affinity to Cl^?, Br^?, and I^? with K_a=9.0×10⁴, 2.7×10⁴, and 1.9×10³ M ^?1, respectively. The corresponding K_a values for cis‐N₂CP 3–Cu and NCP 1–Cu were about 1/10 and 1/2, respectively, of those of 2–Cu . With the help of density functional theory (DFT) calculations and complementary affinity measurements of a series of trisubstituted N‐confused porphyrins, the efficient anion binding of NCPs was attributed to strong hydrogen bonding at the highly polarized NH moieties owing to the electron‐deficient C₆F₅ groups at meso positions as well as the ideally oriented dipole moments and large molecular polarizability. The orientation and magnitude of the dipole moments in NCPs were suggested to be important factors in the differentiation of the affinity for anions.     

Dimerisation and complexation of 6-(4′-t-butylphenylamino)naphthalene-2-sulphonate by β-cyclodextrin and linked β-cyclodextrin dimers

This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS^?  and its dimer, (BNS^? )₂, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and ¹H NMR studies, respectively, show that BNS^?  and (BNS^? )₂ form host–guest complexes with βCD of the stoichiometry βCD.BNS^?  (10^? 4 K ₁ = 4.67 dm³ mol^? 1) and βCD.BNS₂ ^2 ?  (10^? 2 K ₂′ = 2.31 dm³ mol^? 1), where the complexation constant K ₁ = [βCD.BNS^? ]/([βCD][BNS^? ]) and K ₂′ = [βCD. (BNS^? )₂]/([βCD.BNS^? ][BNS^? ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm³ at 298.2 K. (The dimerisation of BNS^?  is characterised by 10^? 2 K _d = 2.65 dm³ mol^? 1.) For N,N-bis((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)succinamide, 33βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)-N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂su, N,N-bis(6^A-deoxy-6^A-β-cyclodextrin)succinamide, 66βCD₂su, N-((2^AS,3^AS)-3^A-deoxy-3^A-β-cyclodextrin)-N′-(6^A-deoxy-6^A-β-cyclodextrin)urea, 36βCD₂ur, and N,N-bis(6^A-deoxy-6^A-β-cyclodextrin)urea, 66βCD₂ur, the analogous 10^? 4 K ₁ = 11.0, 101, 330, 29.6 and 435 dm³ mol^? 1 and 10^? 2 K ₂′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm³ mol^? 1, respectively. A similar variation occurs in K ₁ derived by UV–vis methods. The factors causing the variations in K ₁ and K ₂ are discussed in conjunction with ¹H ROESY NMR and molecular modelling studies.     

Complexation with diol host compounds. 13. Crystal structures and thermal analyses of inclusion compounds of 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol with cyclohexane,O-xylene,m-xylene and p-xylene

Abstract

It has been shown that host compound 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol is able to include polar guests and now we report on its ability to form clathrate compounds with apolar guests. The structures of this host with cyclohexane (1) and the ortho (2), meta (3) and para (4) xylenes have been determined and are discussed. Crystal data: (1) 2C₃₀H₂₂O₂C₆H₁₂, M _r = 913.20 g mol^?1, mono-clinic, C2/c, a = 22.851(6), b = 14.010(2), c = 17.076(6) Å, β = 108.71(3)°, V = 5178(2) ų, Z = 4, D _c = 1.17g cm^?3, N = 3326, R = 0.092. (2) 2C₃₀H₂₂O₂1 ½C₈H₁₀, M _r = 1976.5 g mol^?1, triclinic, P 1, a = 13.185(3), b = 15.466(3), c = 16.573(2) Å, α = 96.39(13)°, β = 106.96(15)°, γ = 114.94(18)°, V = 2822(2) ų, Z = 2, D _c = 1.16 g cm^?3, N = 6152, R = 0.075. (3) 2C₃₀H₂₂O₂1 ½C₈H₁₀, M _r = 1976.5 g mol^?1, triclinic, P 1, a = 13.267(5), b = 15.453(3), c = 16.654(5) Å, α = 97.12(2)°, β = 107.09(3)°, γ = 114.68(3)°, V = 2843(2) ų, Z = 2, D _c = 1.15 g cm^?3, N = 6505, R = 0.083. (4) 2C₃₀H₂₂O₂1 ½C₈H₁₀, M _r = 1976.5 g mol^?1, triclinic, P 1, α = 13.070(2), b = 15.348(3), c = 16.776(3) Å, α = 67.88<2)°, β = 74.27(1)°, γ = 65.29(1)°, V = 2817(1) ų, Z = 2, D _c = 1.15 g cm^?3, N = 6711, R = 0.050. Thermal analysis studies were also performed in order to examine their stability and the strength with which the guest species are held in the crystal lattice.     

Ab initio calculations on phosphorus compounds. II. Effects of disubstitution on ligand apicophilicity in phosphoranes

Geometry optimizations at the HF/3-21G(*) and HF/6-31G* levels of ab initio theory have been carried out for various isomers of model disubstituted phosphoranes PH₃XY(X, Y?OH, CH₃, NH₂, and SH). Reasonable agreement was obtained between the optimized geometries and available crystal structure data for analogous compounds. The isomers were further characterized by frequency calculations. The MP2/6-31G*//6-31G* + ZPE energy data reveal that the interactions between the ligands are relatively small (0–4 kcal mol^?1) for the most stable conformations of the isomers. Hence, for these conformations the apicophilicities (based upon monosubstituted phosphoranes) are approximately additive. The less stable PH₃XY conformations are in general transition states or higher-order saddle points, and their interligand interactions are larger in magnitude (up to 10 kcal mol^?1); the results with these conformations suggest that apicophilicities may not be as additive for some highly substituted phosphoranes. © 1993 John Wiley & Sons, Inc.     

Studies on the nuclease activity and interactions of the mixed‐polypyridyl [Ni2(1,3‐tpbd)(diimine)2(H2O)2]4+ complexes with thioredoxin reductase

Three new nickel(II) complexes formulated as [Ni₂(1,3‐tpbd)(diimine)₂(H₂O)₂]⁴⁺ [1,3‐tpbd = N,N,N′,N′‐tetrakis(2‐pyridylmethyl)benzene‐1,3‐diamine, where diimine is an N,N‐donor heterocyclic base like 1,10‐phenanthroline (phen),2,2′‐bipyridine (bpy), 4,5‐diazafluoren‐9‐one (dafo)], have been synthesized and structurally characterized by X‐ray crystallography: [Ni₂(1,3‐tpbd)(phen)₂(H₂O)₂]⁴⁺ (1), [Ni₂(1,3‐tpbd)(bpy)₂(H₂O)₂]⁴⁺(2) and [Ni₂(1,3‐tpbd)(dafo)₂(H₂O)₂]⁴⁺ (3). Single‐crystal diffraction reveals that the metal atoms in the complexes are all in a distorted octahedral geometry and in a trans arrangement around 1,3‐tpbd ligand. The interactions of the three complexes with calf thymus DNA (CT‐DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism and viscosity. The apparent binding constant (K_app) values are calculated to be 1.91 × 10⁵ m ^?1 for 1, 1.18 × 10⁵ m ^?1 for 2, and 1.35 × 10⁵ m ^?1 for 3, following the order 1 > 3 > 2. The higher DNA binding affinity of 1 is due to the involvement in partial insertion of the phen ring between the DNA base pairs. A decrease in relative viscosities of DNA upon binding to 1–3 is consistent with the DNA binding affinities. These complexes efficiently display oxidative cleavage of supercoiled DNA in the presence of H₂O₂ (250 µ m ), with 3 exhibiting the highest nuclease activity. The rate constants for the conversion of supercoiled to nicked DNA are 5.28 × 10^?5 s^?1 (for 1), 6.67 × 10^?5 s^?1 (for 2) and 1.39 × 10^?4 s^?1 (for 3), also indicating that complex 3 shows higher catalytic activity than 1 and 2. Here the nuclease activity is not readily correlated to binding affinity. The inhibitory effect of complexes 1–3 on thioredoxin reductase has also been examined. The IC₅₀ values are calculated to be 26.54 ± 0.57, 31.03 ± 3.33 and 8.69 ± 2.54 µ m , respectively, showing a more marked inhibitory effect on thioredoxin reductase by complex 3 than the other two complexes. Copyright © 2012 John Wiley & Sons, Ltd.     

Intermolecular interaction and magnetic coupling mechanism on a mononuclear CoII complex

Anti-ferromagnetic interaction was observed in a new crystal that consists of mononuclear Co^II complexes, namely [Co(PMP)(N₃)] (PMP?=?2,9-bis(pyridin-2-methoxyl)-1,10-phenanthroline); in the mononuclear complex Co^II has a distorted trigonal-bipyramidal geometry. Analysis for the crystal structure indicates six magnetic coupling pathways among adjacent complexes, in which three involve π–π stacking and the other three deal with intermolecular interactions. The fitting for the variable-temperature magnetic susceptibilities with the Curie–Weiss formula shows an anti-ferromagnetic interaction between adjacent Co^II ions with θ?=??5.49 K?=??3.82?cm^?1. Theoretical calculations on the spin section reveal that the three π–π stacking systems result in magnetic coupling constants 2J?=??0.10?cm^?1, ?0.10?cm^?1, and 1.24?cm^?1, respectively, and the three intermolecular interactions lead to weak anti-ferromagnetic interactions with 2J?=??0.36?cm^?1, ?0.26?cm^?1, and ?0.32?cm^?1, respectively. The theoretical calculations and the experimental magnetic data imply that the anti-ferromagnetic interaction involves the orbital contribution of the relevant Co^II ions.     

Decomposition kinetics of the N-bromoaminoacids,N-bromoalanine,N-bromo-2-aminobutyric acid,and N-bromonorvaline

A kinetic study of the decomposition reactions of N-bromoalanine, N-bromo-2-aminobutyric acid, and N-bromonorvaline shows them to be first-order with respect to N-bromoaminoacid concentration and independent of both excess aminoacid and pH over the interval pH 9–11. In this pH range the mean rate constants at 298 K were 1.20 × 10^?3 s^?1, 1.37 × 10^?3 s^?1 and 1.28 × 10^?3 s^?1, respectively. © 1993 John Wiley & Sons, Inc.     

Action de nucléophiles simples sur un bromoénurononitrile,précurseur et équivalent synthétique partiel d'un ynurononitrile

Reactions of Mononucleophiles with a Bromoenurononitrile, Precursor and Partial Synthetic Equivalent of an Ynurononitrile Several mononucleophiles (bases) have been reacted with one or the other of the geometrical isomers of the bromoenurononitrile 1. Depending on the nucleophile and the conditions, many different mechanistic pathways were followed, f. ex.: with OH^?, stereospecific elimination from (Z)- 1 leading to 2 , with N^?₃ and F^?, stereospecific E-A_N reactions leading from (Z)- 1 to (Z)- 8 and (Z)- 12 respectively, with PhCH₂SH, conjugate nucleophilic addition to 7, with Me₂NH, conjugate nucleophilic addition followed by a S_N2 to 11 , as well as several cases of nonstereoselective, probably A_N-E, reactions leading to 3,6,9 and 10. In spite of their diversified reactivity, bromoenurononitriles like 1 , partial synthetic equivalent of 2 , constitute useful synthetic intermediates.     

Molecular Structure,Theoretical Calculation and Thermal Behavior of DAG(NTO)

A new compound, [DAG(NTO)], was prepared by mixing the NaNTO•H2O aqueous solution and diaminogaunidine hydrochloride aqueous solution. Single crystals suitable for X-ray measurement were obtained by recrystallization from water at room temperature. The crystal belongs to triclinic, space group P-1 with crystal parameters of a＝0.6732(3) nm, b＝0.6745(3) nm, c＝0.9840(4) nm, α＝88.309(7)°, β＝77.255(6)°, γ＝86.520(7)°, V＝4.349(3) nm3, Z＝2, μ＝0.144 mm－1, F(000)＝228, and Dc＝1.674 g/cm3. The theoretical investigation on DAG(NTO) as a structural unit was carried out by B3LYP, MP2 and HF methods with 6-31＋G(d) basis set. The apparent activation energy and pre-exponential constant of the exothermic decomposition reaction of DAG(NTO) are 112.15 kJ•mol－1 and 109.603 s－1, respectively. The critical temperature of thermal explosion is 208.6 ℃.     

Base Hydrolysis of Pentaaminecobalt(III) Complexes: The [CoX(dien) (dapo)]n+ system. Part 2. Structure and reactivity of the pentacoordinate intermediate

Base hydrolysis of optically pure mer-exo(H)- and mer-endo(H)-[CoCl(dien)(dapo)]²⁺ ( A and B (X = Cl)), resp.; dien = N-(2-aminoethyl)ethane-1,2-damine; dapo = 1,3-diaminopopan-2-ol, k_OH = (1.13 ±0.09)·10⁵ M^?1s^?1 ( A (X = Cl), k_OH = (1.18 ± 0.11)·10⁵M^?1s^?1 ( B (X = Cl)); I = 1.0M (NaClO₄ or NaN₃)1, T = 298 K) is accompanied by retention of the mer-geometry and full racemization (99 ± 1%). It is shown this is not due to racemization of either reactants or products. This result, together with the fact that both A and B yield the same mer-exo(H)-product distribution, indicates the intermediacy of a pentacoordinate species II which is symmetrical (at least in the time average), viz. trigonal bipyramidal with a deprotonated (‘flat’) secondaryamine moiety. The H-exchange rates of the coordinated amine groups are consistent with this interpretation and indicate that loss of Cl^? is the rate-determining step, in agreement with an S_N1CB mechanism. The reactivity of the unsym-fac-exo(OH)- and unsy,-fac-endo(OH)-isomers C and D , respectively, is in sharp contrast: base hydrolysis is 3 orders of magnitue slower, and the reaction is accompanied by some change of coordination geometry ( C , 23%; D , 10%, some inversion of configuration ( C , 15%; D , 19%)); much lower acceleration of hydrolysis in base (10⁶ vs. 10¹⁰). Azide competition during base hydrolysis of the mer-isomer A and B is quite large (R = [CoN₃]_∞/[CoOH]_∞[N] = 1.4 ±0.2M^?1, I= 1.0M, T = 298 K) and indicates that the coordinatively unsaturated intermediate II is highly selective. The ratios of exo(H)- and endo(H)-azide competition products A and B (X = N₃), respectively, immediately after the substitution reaction (kinetic control) are independent of the engaged epierm A or B : 31.7 ± 0.9% of B (X = N₃) and 68.3 ± 0.9% of A (X = N₃, determined after ca. 10.t_½ of the base hydrolysis). This is agreement with the effective site of deprotonation at the secondayr(central)-amine group of dien, cis to the leaving group X , and with a common set of intermediates. Epimerization of A and B (X = Cl, N₃) is shown to proceed solely via the pentacoordinate (base hydrolysis) intermediate II , viz. the direct route involving a six-coordinate deprotonated intermediate is immeasurably slow. For the hydroxo products A and B (X = OH), the direct rotue may compete with the H₂O-substitution(exchange) path which can occur by an internal conjugate-base process. The kinetically controlled distribution of complexes A/B (X = N₃) is different from the quasi-thermodynamic one (19.1 ± 0.8% of B (X = N₃) and 80.9 ± 0.8% of A (X = N₃)). This is consistent with the differences in the base-hydrolysis rates of the reactants (kOh ( A (X = N₃))= (1.59 ± 0.04)·10²M^?1s^?1; k_OH ( B (X = N₃)) = (2.89 ± 0.22).10²M^?1s^?1). Various aspects of the investigated reactions are discussed on the basis of the widely studied reaction of base hydrolysis of pentaaminecobalt(III) complexes. Also, the structure and reactivity of the pentacoordinate intermediate II are discussed in relation to various current models.     

Novel Barium Beryllates Ba[Be2N2] and Ba3[Be5O8]: Syntheses,Crystal Structures and Bonding Properties

Ba[Be₂N₂] was prepared as a yellow‐green microcrystalline powder by reaction of Ba₂N with Be₃N₂ under nitrogen atmosphere. The crystal structure Rietfeld refinements (space group I4/mcm, a = 566.46(5) pm, c = 839.42(9) pm, R_int = 4.73 %, R_prof = 9.16 %) reveal the compound to crystallize as an isotype of the nitridoberyllates A[Be₂N₂] (A = Ca, Sr) consisting of planar 4.8² nets of mutually trigonal planar coordinated Be and N species. Averaged magnetic susceptibility values for the anion [(Be₂N₂)^2?] determined from measurements on A[Be₂N₂] with A = Mg, Ca, Ba allow to derive a diamagnetic increment for N^3? χ_dia = (?13±1stat.) · 10^?6emu mol^?1. Colorless Ba₃[Be₅O₈] was first obtained as an oxidation product of Ba[Be₂N₂] in air. The crystal structure was solved and refined from single crystal X‐ray diffaction data (space group Pnma, a = 942.9(1) pm, b = 1163.47(7) pm, c = 742.1(1) pm, R1 = 2.99 %, wR2 = 7.15 %) and contains infinite rods of Be in trigonal planar, tetrahedral and 3 + 1 coordination by O. The crystal structure is discussed in context with other known oxoberyllates. Electronic structure calculations and electron localization function diagrams for both compounds support the classification as nitrido‐ and oxoberyllate, respectively.     

Data on the thermochemistry of azoalkanes

The rate constant of the primary decomposition step was determined for four symmetrical and four unsymmetrical azoalkanes. From the experimental activation energies and some literature enthalpy data, the following enthalpies of formation of radicals and group contributions were calculated: ΔH_? (CH₃N₂) = 51.5 ± 1.8 kcal mol^?1, ΔH_? (C₂H₅N₂) = 44.8 ± 2.5 kcal mol^?1, ΔH_? (2?C₃H₇N₂) = 37.9 ± 2.2 kcal mol^?1, [N_A-(C)] = 27.6 ± 3.7 kcal mol^?1, [N_A-(?_A) (C)] = 61.2 ± 3.1 kcal mol^?1.