Kinetics and mechanism of the interaction of hexaaquochromium(III) with octacyanomolybdate(IV) ions

The kinetics of the interaction of hexaaquochromium(III) ion with potassium octacyanomolybdate(IV) have been studied using conductance and spectrophotometric data. The mechanism of the reaction is discussed and the effect of H⁺ ion and the ionic strength on the rate of the reaction determined. The reaction is found to be pseudo-first order with respect to potassium octacyanomolybdate(IV) and inverse first order with [H₃O⁺]. The rate of the reaction increases with increase in ionic strength and temperature. Activation parameters have been calculated using the Arrhenius equation and have the values ΔE^* = 1.3 × 10² kJ mol^?1, ΔH^* = 129 kJ mol^?1, ΔS^* = ?315 e.u., ΔF^* = 2.3 × 10² kJ and A = 1.5 × 10^?3. The mechanism proposed is based on ion-pair formation and the rate equation obtained is given by: k_obs=$\text{[}{}_{\mathrm{kK}}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k′K′k}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k}{}_{\mathrm{<mtext>h</mtext>}}\text{+[}\text{K}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{K′}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}$     

Extraction of cobalt(II) and nickel(II) with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HPMBP) and tri-n-octylamine (TOA)

The extraction of Co(II) with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one ((H)PMBP) and tri-n-octylamine (TOA) is investigated in order to explore the influence of diluents and inorganic anions with synergistic acidic extractant + liquid anion exchanger systems. Although it is proved that the same species [HTOA]⁺ [Co(PMBP)₃]^? is extracted from various inorganic media, with toluene as the diluent, the presence of ClO₄^? SO₄^2? or Cl^? anion modifies the distribution of the anions which are associated to (HTOA)⁺ in the organic phase, leading to different synergistic equilibria; with Cl^? or SO₄^2?: $\text{CO(PMBP)}{}_2$ + $\text{(HTOA}{}^{\mathrm{+}}$,PMBP^?) ?$\text{(HTOA}{}^{\mathrm{+}}$,Co(PMBP)₃^? (log K = 6.10) and with ClO₄^? : $\text{Co(PMBP)}{}_2$ + $\text{HPMBP}$ + $\text{(HTOA}{}^{\mathrm{+}}$,ClO₄^? ? $\text{(HTOA}{}^{\mathrm{+}}$,Co(PMBP)₃^? + H⁺ + ClO₄^? (log K = 2.34) The same synergistic equilibrium is observed for the extraction of Ni(II) from ClO₄^? medium, with a comparable value of the constant (log K = 2.45). The synergistic effect is cancelled in n-octanol.     

Solution properties of polytrimethylhexamethylenterephthalamide (trogamid TR)

For the polyamide Trogamid T^R, good as well as θ-solvents are available. Determinations of molecular weights by ultracentrifugation, light scattering, osmometry, viscometry and gelchromatography (GPC) are reported. For DMF at 25° the relation

$\text{[η] = 0.02737}\text{M}{}^{0.706}{}_{\mathrm{w}}\text{cm}{}^3\text{g}{}^{\mathrm{?1}}$

was established, [η] = f(T) shows a maximum between ? 70° and + 120°. θ-temperatures are 142° for aniline and 62° for pyrroline, the latter having a negative temperature gradient. The unperturbed dimensions are calculated from the viscosity in θ-solvents and in DMF; for the latter, the Stockmayer-Fixman extrapolation was used. Molecular dimensions proved to be small in comparison with those of similar polymers. This effect is due to the three methyl side-groups for each chain unit sterically preventing a more stretched conformation.     

Extraction of indium(III) from chloride medium with 1-phenyl-3-methyl-4-acylpyrazol-5-ones. Synergic effect with high molecular weight ammonium salts.

The extraction of In(III) from 1M (Na,H)(Cl,ClO₄) media with 4-acylpyrazol-5-ones (HL) in toluene at 25°C is described by equilibria In ³⁺ + 3 $\text{HL}$ ? $\text{InL}{}_3$ + 3 H⁺ (log K = 1.48, 1.03, 0.87 with acyl = benzoyl, lauroyl, 2-thenoyl), InCl ²⁺ + 2 $\text{HL}$ ? $\text{InClL}{}_2$ + 2 H⁺ (log K = 0.26, ?0.45, ?0.35 respectively) and In³⁺ + m Cl^? ? InCl_m^(3-m)+ (log β_m available from literature). The extraction from 1M (Na,H)(Cl,NO₃) medium is enhanced by addition of aliquat (TOMA⁺,Cl^?) and the following synergic equilibrium takes place : $\text{InCl}{}_2$ + $\text{(TOMA}{}^{\mathrm{+}}$,Cl^?) ? $\text{(TOMA}{}^{\mathrm{+}}$, InCl₂L₂^? (log K = 5.49, 5.25, 5.21 respectively). Cl^? of (TOMA⁺,Cl^?) is exchanged by NO₃^? with the equilibrium constant log K = 1.50. If (TOMA⁺,Cl^?) is replaced by tri-n-octylammonium chloride, the synergic effect is largely reduced (log K = 4.17 with acyl = benzoyl). The extraction from chloride solutions containing ClO₄^? remains unchanged by addition of ammonium salts.     

Synthesis of homoleptic tris(organo-chelate)iridium(III) complexes by spontaneous ortho-metallation of electronrich olefin-derived N,N′-diarylcarbene ligands and the X-ray structures of fac-[Ir{CN(C6H4Me-p) (CH2)2NC6H3Me-p}3] and mer-Ir{CN(C6H4Me-p)(CH2)2NC6H3Me-p}2 {CN(C6H4Me-p)(CH2)2NC6H4Me-p}Cl (a product of HCl cleavage)

Treatment of [{Ir(COD)(μ-Cl)}₂] with excess of the electron-rich olefin [$\text{CN(Ar)(CH}{}_2\text{)}{}_2\text{N}$Ar]₂ (abbreviated as (L^Ar)₂, Ar = C₆H₄Me-p or C₆H₄OMe-p) affords the ortho-metallated tricycle [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₃], which for Ar = C₆H₄Me-p (Ia) with HCL yields [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₂(L^Ar)]Cl (IV); X-ray data show that in IV there is an unexpectedly close Ir?C(o-aryl) contact (2;52(1) Å) involving the “free” L^Ar which compares with an IrC(o-aryl) distance of 2.09(3) Å in Ia or 2.07(3) Å in the ortho-metallated L^Ar ligand of complex IV.     

Standard enthalpies of formation of uranium compounds I. β-UO3 and γ-UO3

The standard enthalpy of formation of γ-UO₃ has been critically assessed; the value ?(292.5 ± 0.2) kcal_th mol^?1 is suggested.The enthalpies of solution of β-UO₃ and γ-UO₃ in 3 M H₂SO₄ have been measured and used to derive:

$\text{ΔH}{}_{\mathrm{f}}{}^{\mathrm{°}}\text{(β?}\text{UO}{}_3\text{, 298.15}\text{K}\text{) = ?(291.6 ± 0.2)}\text{kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?}}$

     

Standard enthalpy of solution and formation of cesium chromate. Derived thermodynamic properties of the aqueous chromate,bichromate, and dichromate ions,alkali metal and alkaline earth chromates,and lead chromate

Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔH_soln = (7622 ± 24) cal_th mol^?1 for a dilution of Cs₂CrO₄·21128H₂O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔH_soln^o = (7512 ± 31) cal_th mol^?1, whence the standard enthalpy of formation, ΔH_f⁰(Cs₂CrO₄, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcal_th mol^?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S⁰(298 K), of BaCrO₄ and PbCrO₄ were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) cal_th K^?1 mol^?1, respectively. There is evidence that ΔH_f⁰(SrCrO₄, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO₄^2?), bichromate (HCrO₄^?), and dichromate (Cr₂O₇^2?) ions. The new values at 298.15 K are as follows:

     

9.

Transfer to monomer in the polymerization of N-(3-dimethylaminophenyl) maleimide and N-(3-dimethylamino-6-methylphenyl) maleimide     

J. Lokaj  F. Hrabák 《European Polymer Journal》1978,14(12):1039-1043

The kinetics of the homopolymerizations of styrene, N-(3-dimethylaminophenyl) maleimide (I) and N-(3-dimethylamino-6-methylphenyl) maleimide (II) in benzene and dimethylformamide, and the molecular weights of the polymers were studied. N-(3-Dimethylaminophenyl) succinimide, regarded as a model for polymer I, did not affect the polymerization of styrene. The data indicate degradative transfer of polymer radicals to dimethylformamide and pronounced transfer to monomers I and II (C_M ≈ 0.06–0.07). The value of $\text{k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for II is 0.09 $\text{dm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$$\text{mole}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$$\text{s}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$.     

10.

Crystal structure,Mössbauer,and magnetic behavior of mixed valence compounds in the BaFeS system: Ba₃(Ba_1−xAl_x)Fe₂S₆[S_1−y(S₂)_y]     

J.T. Hoggins  L.E. Rendon-Diazmiron  H. Steinfink 《Journal of solid state chemistry》1977,21(2):79-90

The compounds $\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{[S}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{(}\text{S}{}_2\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{]}$ and Ba_3.6Al_0.4Fe₂S₆[S_0.6(S₂)_0.4], designated I and II, were prepared by reacting BaS, Fe, and S powders and Al foils in graphite containers sealed in evacuated quartz ampoules at approximately 1100°C. The crystal structure of I was determined using 1682 independent, nonzero X-ray reflections, while 3589 were used for II. They are triclinic, $\text{A}\text{l}$:

$\text{a=9.002(2)}\text{A}\text{?}\text{,b=6.7086(8)}\text{A}\text{?}\text{,c=24.658(4)}\text{A}\text{?}\text{α91.49(2)°,}$

$\text{β=105.10(2)°y=90.74(2)°,ψ}{}_{\mathrm{calc}}\text{=4.15g/cm}{}^3\text{,for I:}$

$\text{a=8.993(6)}\text{A}\text{?}\text{,b=6.708(7)}\text{A}\text{?}\text{,c=24.70(1)}\text{A}\text{?}\text{α91.11(6)°,}$

$\text{β=105.04(6)°y=90.90(9)°,ψ}{}_{\mathrm{calc}}\text{=3.90g/cm}{}^3\text{,for II:}$

BaS₆ trigonal prisms share edges to form distorted hexagonal rings which form one-dimensional chains leaving two free lateral edges. The chains link in a stairstep manner with the rings offset along the [301] direction. These stairsteps join in a complicated manner to form a three-dimensional network. Fe ions are in two sites forming isolated FeS₄ tetrahedra and isolated Fe₂S₆ dimers by edge-sharing tetrahedra. The Al substitution occurs in the trigonal prisms which have free edges with Al replacing Ba. Room-temperature Mössbauer isomer shifts are 0.20 mm/sec. for I and 0.30 mm/sec for II. These data indicate that upon Al substitution charge compensation occurs by reducing Fe³⁺. Valence calculations indicate that Fe in edge-sharing tetrahedra are reduced while the Fe in the isolated tetrahedron remains unchanged. The effective charge distribution in the Al substituted compound is approximately Fe³⁺, Fe^2.5+ with electron delocalization across the shared edge. Room temperature electrical resistivity is 10⁵ ohm/cm. The compositions of the crystals are best represented by the formulas $\text{[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_7\text{]}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{·[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{(S}{}_2\text{)]}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ and [Ba₃AlFe₂S₇]_0.4·[Ba₄Fe₂S₇]_0.2·[Ba₄Fe₂S₆(S₂)]_0.4. The replacement of a sulfide by a disulfide ion is thought to be strongly dependent on the sulfur activity during the preparation.     

11.

Hydrodynamic properties and equilibrium rigidity of polyamidobenzimidazole molecules in dimethylacetamide and sulphuric acid     

M.G. Vitovskaya  P.N. Lavrenko  O.V. Okatova  E.P. Astapenko  V.B. Novakovsky  S.V. Bushin  V.N. Tsvetkov 《European Polymer Journal》1982,18(7):583-588

Translational diffusion, velocity sedimentation and viscometry of polyamidobenzimidazole (PABI) solutions in the range of M = (1–61) · 10³ have been investigated in N,N-dimethylacetamide (DMA) and 98% H₂SO₄. The dependences of D₀, S₀ and [η] on M were obtained. Tsvetkov-Klenin's hydrodynamic invariant was found to be $\text{A}{}_0\text{= 3.55 · 10}{}^{\mathrm{?10}}\text{erg deg}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. The equilibrium rigidity of PABI molecules was characterized by the length of the Kuhn segment $\text{A = 250 ± 100}\text{A}\text{?}$. The chain diameter was $\text{7 ± 4}\text{A}\text{?}$. The values of A in 98% H₂SO₄ and in an aprotic solvent, DMA, were virtually identical, implying that the rigid-chain conformation of PABI molecules in 98% H₂SO₄ is due to their geometrical structure rather than to the protonization of amide bonds. The significance of the latter evidently increases in PABI solutions in 100% H₂SO₄ in which A is 1.5 times as high. The decrease in rigidity of PABI as compared to that of poly-p-phenylene terephthalamide ($\text{A = 400 ± 100}\text{A}\text{?}$) is in reasonable agreement with the presence of imidazole rings in PABI molecules. The presence of these rings results in kinks in the PABI chain with angles of about 30° and hence, in the depature from parallelism of rotating bonds.     

12.

Thermophysical properties of the intermetallic Mn3MN perovskites III. Heat capacity of the solid solution Mn3.2Ga0.8N     

Joaquín García  Juan Bartolomé  Domingo González  Rafael Navarro  Daniel Fruchart 《The Journal of chemical thermodynamics》1983,15(12):1169-1180

The heat capacity of the solid solution Mn_3.2Ga_0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at T_A = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at T_c ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are $\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}\text{= 15.16}$, $\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}\text{= 18.57}$, $\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{= 2896}\text{K}$, $\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{RT}\text{= 8.85}$. At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K^?2·mol^?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established.     

13.

Vinyl polymerization initiated by the (dimethylaniline-n-oxide)/(phenacyl bromide) system     

T. Sato  M. Yoshioka  T. Otsu 《European Polymer Journal》1984,20(7):747-751

Binary systems consisting of dimethylaniline-N-oxide (DMOA) and some α-halo-carbonyl compounds, such as phenacyl halide and α-halo-acetic acid ester, were found to induce radical polymerization of vinyl monomers. Bromo-derivatives showed higher initiating activities than chloroderivatives. The polymerization of methyl methacrylate (MMA) with DMAO and phenacyl bromide (PBr) was investigated kinetically. The polymerization rate (R_p) was expressed as follows; $\text{R}{}_{\mathrm{<mtext>p</mtext>}}\text{=}\text{k[DMAO]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{PBr}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{MMA}\text{]}$.The overall activation energy of the polymerization was calculated to be 42.7 kJ mol^?1. No noticeable chain-transfer from the polymer radical to DMAO or PBr was observed. The benzoyl radical was trapped by 2-nitroso-2-methylpropane, a spin trapping reagent, in the reaction of DMAO and PBr. The u.v. spectrum of poly (MMA) obtained suggests that the polymer contains end-groups similar to acetophenone and DMA. From the results, an initiation mechanism for the polymerization has been proposed and discussed.     

14.

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)     

I. Katime  A. Roig 《European Polymer Journal》1975,11(8):603-607

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

15.

Effect of benzophenone on the H₂O₂-induced photopolymerization of methyl methacrylate     

P. Ghosh  G. Mukhopadhyay  R. Ghosh 《European Polymer Journal》1980,16(5):457-461

Benzophenone (BP) in low concentrations (<0.001 mol 1^?1) produces a rate enhancing effect in the H₂O₂-induced bulk photopolymerization of MMA. R_p is proportional to [H₂O₂]^0.4 and [BP]^0.4, and $\text{k}{}_{\mathrm{p}}{}^2\text{k}{}_1$ at 30° is 1.00 × 10^?2 1.mol^?1 sec^?1. In diluted systems, different solvents produce different kinetic effects, reaction order with respect to monomer being negative for IPA and THF as solvent, positive but <1.0 for benzene and chloroform, 1.2 for acetonitrile, CCl₄ and t-butanol and 1.8 for DMA. The variable solvent effect is attributed to modification of the initiation process by the various solvents to different extents. Kinetic analysis of data for bulk photopolymerization gives evidence for primary radical termination and degradative initiator transfer.     

16.

Gas phase oxidative-addition reactions of alkyl radicals at complexed cobalt(II) centres     

G.W. Dillow  I.K. Gregor  M. Guilhaus 《Journal of organometallic chemistry》1985,294(1):131-137

Negative chemical ionisation mass spectrometry is used as a probe to identify reactions between hydrocarbon radicals and cornplexed cobalt(II) centres in the gas phase. Methane NCI mass spectra of a series of cobalt(II) complexes containing O₄, O₂N₂ and N₄ donor atom sets are characterised by adduct ions of the form [M + C_nH_2n+1]^? at m/z values above the molecular ion, [M]^?. Formation of such ionic species has been rationalised in terms of a one-electron oxidative-addition mechanism involving attack by hydrocarbon plasma-derived alkyl radicals at the metal centre prior to electron capture: Co^IIL_n + R^? → RCo^IIIL_n$\text{e}{}^{\mathrm{?}}$ [Co^IL_n]^?. The competing resonance electron attachment reaction: Co^IIL_n$\text{e}{}^{\mathrm{?}}$ also occurs within the ion source.     

17.

Thermochemical studies of three bis(O-alkyl-N-benzoylthiocarbamato)nickel(II) complexes     

《The Journal of chemical thermodynamics》2004,36(8):627-631

     

18.

Polymerisation radiochimique de l'acetaldehyde en phase solide     

D.P. Kiryukhin  I.M. Barkalov  V.I. Gol&#x;danskii 《European Polymer Journal》1974,10(3):309-313

The radiation induced solid-state polymerization and post-polymerization of crystalline acetaldehyde were studied in a diathermic calorimeter by measuring the heat evolution during polymerization. The heat of melting of crystalline acetaldehyde was found to be 1,4 ± 0,07 kcal mol^?1 and the heat of polymerization 2,5 ± 0,5 kcal mol^?1 at 80–150°K. Under isothermal conditions the rate of the solid state polymerization of acetaldehyde increased with irradiation time up to a maximum and thereafter it decreased. This phenomenon is connected with an increase of the concentration of active centres during irradiation. The propagation rate constant is $\text{k}{}_{\mathrm{p}}\text{? 5 × 10}{}^{\mathrm{?4}}\text{exp(?11,000/RT) cm}{}^3\text{sec}{}^{\mathrm{?1}}$ at 130–140°K and the average time of addition of one monomer unit is 10^?1–10^?2 sec.     

19.

Nd³⁺, Eu³⁺, and Gd³⁺ ions as local probes in the Na_xSr_3−2xLn_x(PO₄)₂ and KCaLn(PO₄)₂ rare earth phosphates     

C. Parent  P. Bochu  A. Daoudi  G. Le Flem 《Journal of solid state chemistry》1982,43(2):190-195

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

20.

“Normal” and “cine” substitution in the thioalkoxy-dehalogenation of halogenobenzofurazans—III: Investigation on the solvent effect     

Leonardo Di Nunno  Saverio Florio 《Tetrahedron》1977,33(12):1523-1525

The reaction of 4-chloro- and 4-chloro-7-deuteriobenzofurazan with MeS^-, isopropyl-S^-, and t-Butyl-S^- in different alcohols as solvents has been investigated. In going from methanol through isopropanol to t-butanol, a progressive decrease of the contribution of the cine-substitution as compared with the normal substitution pathway has been found. By proceeding in the same order, a decrease of the ratio and $\text{k}\text{MeS}{}^{\mathrm{?}}\text{k}{}_{\mathrm{<mtext>t</mtext>}}$-ButylS^? has also been observed.     

	$\text{S}{}^0\text{/}\text{cal}{}_{\mathrm{th}}\text{K}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{?1}}$	$\text{ΔH}{}_{\mathrm{f}}{}^0\text{/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$	$\text{ΔG}{}_{\mathrm{f}}{}^0\text{/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$
CrO42?(aq)	(13.8 ± 0.5)	?(210.93 ± 0.45)	?(174.8 ± 0.5)
HCrO4?(aq)	(46.6 ± 1.8)	?(210.0 ± 0.7)	?(183.7 ± 0.5)
Cr2O72?(aq)	(67.4 ± 3.9)	?(356.5 ± 1.5)	?(312.8 ± 1.0)

Transfer to monomer in the polymerization of N-(3-dimethylaminophenyl) maleimide and N-(3-dimethylamino-6-methylphenyl) maleimide

The kinetics of the homopolymerizations of styrene, N-(3-dimethylaminophenyl) maleimide (I) and N-(3-dimethylamino-6-methylphenyl) maleimide (II) in benzene and dimethylformamide, and the molecular weights of the polymers were studied. N-(3-Dimethylaminophenyl) succinimide, regarded as a model for polymer I, did not affect the polymerization of styrene. The data indicate degradative transfer of polymer radicals to dimethylformamide and pronounced transfer to monomers I and II (C_M ≈ 0.06–0.07). The value of $\text{k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for II is 0.09 $\text{dm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$$\text{mole}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$$\text{s}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$.     

Crystal structure,Mössbauer,and magnetic behavior of mixed valence compounds in the BaFeS system: Ba3(Ba1−xAlx)Fe2S6[S1−y(S2)y]

The compounds $\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{[S}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{(}\text{S}{}_2\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{]}$ and Ba_3.6Al_0.4Fe₂S₆[S_0.6(S₂)_0.4], designated I and II, were prepared by reacting BaS, Fe, and S powders and Al foils in graphite containers sealed in evacuated quartz ampoules at approximately 1100°C. The crystal structure of I was determined using 1682 independent, nonzero X-ray reflections, while 3589 were used for II. They are triclinic, $\text{A}\text{l}$:

$\text{a=9.002(2)}\text{A}\text{?}\text{,b=6.7086(8)}\text{A}\text{?}\text{,c=24.658(4)}\text{A}\text{?}\text{α91.49(2)°,}$

$\text{β=105.10(2)°y=90.74(2)°,ψ}{}_{\mathrm{calc}}\text{=4.15g/cm}{}^3\text{,for I:}$

$\text{a=8.993(6)}\text{A}\text{?}\text{,b=6.708(7)}\text{A}\text{?}\text{,c=24.70(1)}\text{A}\text{?}\text{α91.11(6)°,}$

$\text{β=105.04(6)°y=90.90(9)°,ψ}{}_{\mathrm{calc}}\text{=3.90g/cm}{}^3\text{,for II:}$

BaS₆ trigonal prisms share edges to form distorted hexagonal rings which form one-dimensional chains leaving two free lateral edges. The chains link in a stairstep manner with the rings offset along the [301] direction. These stairsteps join in a complicated manner to form a three-dimensional network. Fe ions are in two sites forming isolated FeS₄ tetrahedra and isolated Fe₂S₆ dimers by edge-sharing tetrahedra. The Al substitution occurs in the trigonal prisms which have free edges with Al replacing Ba. Room-temperature Mössbauer isomer shifts are 0.20 mm/sec. for I and 0.30 mm/sec for II. These data indicate that upon Al substitution charge compensation occurs by reducing Fe³⁺. Valence calculations indicate that Fe in edge-sharing tetrahedra are reduced while the Fe in the isolated tetrahedron remains unchanged. The effective charge distribution in the Al substituted compound is approximately Fe³⁺, Fe^2.5+ with electron delocalization across the shared edge. Room temperature electrical resistivity is 10⁵ ohm/cm. The compositions of the crystals are best represented by the formulas $\text{[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_7\text{]}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{·[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{(S}{}_2\text{)]}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ and [Ba₃AlFe₂S₇]_0.4·[Ba₄Fe₂S₇]_0.2·[Ba₄Fe₂S₆(S₂)]_0.4. The replacement of a sulfide by a disulfide ion is thought to be strongly dependent on the sulfur activity during the preparation.     

Hydrodynamic properties and equilibrium rigidity of polyamidobenzimidazole molecules in dimethylacetamide and sulphuric acid

Translational diffusion, velocity sedimentation and viscometry of polyamidobenzimidazole (PABI) solutions in the range of M = (1–61) · 10³ have been investigated in N,N-dimethylacetamide (DMA) and 98% H₂SO₄. The dependences of D₀, S₀ and [η] on M were obtained. Tsvetkov-Klenin's hydrodynamic invariant was found to be $\text{A}{}_0\text{= 3.55 · 10}{}^{\mathrm{?10}}\text{erg deg}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. The equilibrium rigidity of PABI molecules was characterized by the length of the Kuhn segment $\text{A = 250 ± 100}\text{A}\text{?}$. The chain diameter was $\text{7 ± 4}\text{A}\text{?}$. The values of A in 98% H₂SO₄ and in an aprotic solvent, DMA, were virtually identical, implying that the rigid-chain conformation of PABI molecules in 98% H₂SO₄ is due to their geometrical structure rather than to the protonization of amide bonds. The significance of the latter evidently increases in PABI solutions in 100% H₂SO₄ in which A is 1.5 times as high. The decrease in rigidity of PABI as compared to that of poly-p-phenylene terephthalamide ($\text{A = 400 ± 100}\text{A}\text{?}$) is in reasonable agreement with the presence of imidazole rings in PABI molecules. The presence of these rings results in kinks in the PABI chain with angles of about 30° and hence, in the depature from parallelism of rotating bonds.     

Thermophysical properties of the intermetallic Mn3MN perovskites III. Heat capacity of the solid solution Mn3.2Ga0.8N

The heat capacity of the solid solution Mn_3.2Ga_0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at T_A = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at T_c ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are $\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}\text{= 15.16}$, $\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}\text{= 18.57}$, $\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{= 2896}\text{K}$, $\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{RT}\text{= 8.85}$. At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K^?2·mol^?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established.     

Vinyl polymerization initiated by the (dimethylaniline-n-oxide)/(phenacyl bromide) system

Binary systems consisting of dimethylaniline-N-oxide (DMOA) and some α-halo-carbonyl compounds, such as phenacyl halide and α-halo-acetic acid ester, were found to induce radical polymerization of vinyl monomers. Bromo-derivatives showed higher initiating activities than chloroderivatives. The polymerization of methyl methacrylate (MMA) with DMAO and phenacyl bromide (PBr) was investigated kinetically. The polymerization rate (R_p) was expressed as follows; $\text{R}{}_{\mathrm{<mtext>p</mtext>}}\text{=}\text{k[DMAO]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{PBr}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{MMA}\text{]}$.The overall activation energy of the polymerization was calculated to be 42.7 kJ mol^?1. No noticeable chain-transfer from the polymer radical to DMAO or PBr was observed. The benzoyl radical was trapped by 2-nitroso-2-methylpropane, a spin trapping reagent, in the reaction of DMAO and PBr. The u.v. spectrum of poly (MMA) obtained suggests that the polymer contains end-groups similar to acetophenone and DMA. From the results, an initiation mechanism for the polymerization has been proposed and discussed.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

Effect of benzophenone on the H2O2-induced photopolymerization of methyl methacrylate

Benzophenone (BP) in low concentrations (<0.001 mol 1^?1) produces a rate enhancing effect in the H₂O₂-induced bulk photopolymerization of MMA. R_p is proportional to [H₂O₂]^0.4 and [BP]^0.4, and $\text{k}{}_{\mathrm{p}}{}^2\text{k}{}_1$ at 30° is 1.00 × 10^?2 1.mol^?1 sec^?1. In diluted systems, different solvents produce different kinetic effects, reaction order with respect to monomer being negative for IPA and THF as solvent, positive but <1.0 for benzene and chloroform, 1.2 for acetonitrile, CCl₄ and t-butanol and 1.8 for DMA. The variable solvent effect is attributed to modification of the initiation process by the various solvents to different extents. Kinetic analysis of data for bulk photopolymerization gives evidence for primary radical termination and degradative initiator transfer.     

Gas phase oxidative-addition reactions of alkyl radicals at complexed cobalt(II) centres

Negative chemical ionisation mass spectrometry is used as a probe to identify reactions between hydrocarbon radicals and cornplexed cobalt(II) centres in the gas phase. Methane NCI mass spectra of a series of cobalt(II) complexes containing O₄, O₂N₂ and N₄ donor atom sets are characterised by adduct ions of the form [M + C_nH_2n+1]^? at m/z values above the molecular ion, [M]^?. Formation of such ionic species has been rationalised in terms of a one-electron oxidative-addition mechanism involving attack by hydrocarbon plasma-derived alkyl radicals at the metal centre prior to electron capture: Co^IIL_n + R^? → RCo^IIIL_n$\text{e}{}^{\mathrm{?}}$ [Co^IL_n]^?. The competing resonance electron attachment reaction: Co^IIL_n$\text{e}{}^{\mathrm{?}}$ also occurs within the ion source.     

Polymerisation radiochimique de l'acetaldehyde en phase solide

The radiation induced solid-state polymerization and post-polymerization of crystalline acetaldehyde were studied in a diathermic calorimeter by measuring the heat evolution during polymerization. The heat of melting of crystalline acetaldehyde was found to be 1,4 ± 0,07 kcal mol^?1 and the heat of polymerization 2,5 ± 0,5 kcal mol^?1 at 80–150°K. Under isothermal conditions the rate of the solid state polymerization of acetaldehyde increased with irradiation time up to a maximum and thereafter it decreased. This phenomenon is connected with an increase of the concentration of active centres during irradiation. The propagation rate constant is $\text{k}{}_{\mathrm{p}}\text{? 5 × 10}{}^{\mathrm{?4}}\text{exp(?11,000/RT) cm}{}^3\text{sec}{}^{\mathrm{?1}}$ at 130–140°K and the average time of addition of one monomer unit is 10^?1–10^?2 sec.     

Nd3+, Eu3+, and Gd3+ ions as local probes in the NaxSr3−2xLnx(PO4)2 and KCaLn(PO4)2 rare earth phosphates

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

“Normal” and “cine” substitution in the thioalkoxy-dehalogenation of halogenobenzofurazans—III: Investigation on the solvent effect

The reaction of 4-chloro- and 4-chloro-7-deuteriobenzofurazan with MeS^-, isopropyl-S^-, and t-Butyl-S^- in different alcohols as solvents has been investigated. In going from methanol through isopropanol to t-butanol, a progressive decrease of the contribution of the cine-substitution as compared with the normal substitution pathway has been found. By proceeding in the same order, a decrease of the ratio and $\text{k}\text{MeS}{}^{\mathrm{?}}\text{k}{}_{\mathrm{<mtext>t</mtext>}}$-ButylS^? has also been observed.