Polymerization of acrylonitrile initiated by the redox system peroxydisulphate-isoamyl alcohol catalyzed by silver ion

The polymerization of acrylonitrile in aqueous media initiated by peroxydisulphate-isoamyl alcohol(IAA) redox pair catalyzed by silver ion was studied at low conversion. The polymerization had kinetic orders 1.5 with respect to monomer, 0.6 (peroxydisulphate) and 0.5 (silver ion). The reactions were carried out at various temperatures and the overall activation energy was found to be 5.5 kcal/mol. The effect of certain water-miscible organic solvents was also investigated. A mechanism of initiation is tentatively proposed.     

Aqueous polymerization of acrylonitrile initiated by the Mn3+/citric acid redox system

Kinetics of polymerization of acrylonitrile initiated by the redox system Mn³⁺/citric acid were investigated in aqueous sulphuric acid in the range of 20–25°; initial rates of polymerization and Mn³⁺ disappearance etc. were measured. The effects of certain water miscible organic solvents and certain cationic and anionic detergents on the rate of polymerization have been examined. A mechanism has been suggested involving formation of a complex between Mn³⁺ and citric acid, decomposition of which yields the initiating free radical and with polymerization being terminated by mutual interaction of growing radicals.     

Polymerization of acrylonitrile. Kinetics of the reaction initiated by the vanadium(V)/thioglycollic acid redox system

The polymerization of acrylonitrile initiated by the vanadium(V)-thioglycollic acid redox system has been investigated in aqueous sulphuric acid under nitrogen over the range 30–45°. The polymerization is second order in monomer and first order in thioglycollic acid (TGA). The rate of vanadium(V) disappearance is proportional to (TGA) and [V(V)]. The effects of FeCl₃, CuSO₄ and acetic acid on the polymerization have been investigated. The proposed reaction scheme involves initiation by an organic free radical, produced by the interaction of V(V) with TGA and termination by V(V). Various rate parameters have been evaluated.     

Non-ideality in vinyl polymerization—VI: Polymerization of methyl methacrylate initiated by benzoyl peroxide

The polymerization of methyl methacrylate in benzene was initiated by benzoyl peroxide and examined by kinetic analysis particularly from the point of view of primary radical termination. It is concluded that the velocity constant for dissociation of the benzoyloxy radical to give the phenyl radical is affected by the nature of the medium.     

Electrical conductance,density, and viscosity of the molten system lead(II) dodecanoate/lead(II) oxide

Data are presented for densities, electrical conductances, and viscosities of the molten system lead(II) dodecanoate/lead(II) oxide concentrations up to 0.22 mole fraction of the oxide. Values of ?₀ obtained from extrapolation of graphs of density againts temperature are seen to decrease on adding small quantities of PbO, but to increase on adding further PbO. Results from thermal analysis suggest that this may be due to a change in structure of the liquid phase from small. spherical to long, cylindrical micelles. Over the concentration range studied, molar volumes are linear functions of concentration at any particular temperature. The molar volumes of the system lead(II) carboxylate/lead(II) oxide for the even chain acids C₁₀ to C₁₈ are linear functions of chain length. Arrhenius plots for the electrical conductance of the mixtures show curvature, as in other lead(II) dodecanoate systems. The activation energies for conductance in the low temperature region show a steady decrease with increasing PbO concentration and it is proposed that this arises from increased mobility of the charge carrier. The specific conductance at any temperature decreases with increasing mole fraction of oxide, indicating the oxide to be essentially undissociated in the melt. The activation energy for viscosity shows a dramatic increase on adding small amounts of PbO. This is suggested to arise from a change in the structure of the melt. Studies of the viscosities of the system lead(II) carboxylate/lead oxide as a function of chain length for the even chain acids C₁₀ to C₁₈ suggest a slight decrease in the size of the unit of viscous flow when oxide is present.     

Acidic peroxo salts: A new class of initiators for vinyl polymerization—II: Kinetics of polymerization of acrylonitrile initiated by potassium monopersulphate catalysed by Mn(II)

Kinetics of the polymerization of acrylonitrile initiated by an acidic peroxo salt (potassium monopersulphate) catalysed by Mn(II) have been investigated in aqueous systems over the range 30–50°. The rates of polymerization (R_p) have been studied for various concentrations of monomer and initiator. The efficiencies of various metal salts in catalysing the polymerization have been determined from the values of R_p. The effects of catalyst (MnSO₄), initiator, monomer and various aromatic and heterocyclic amines on R_p and conversion have been studied. The end-groups of the recovered polymers have been studied using standard methods. From the observed end-groups and kinetic results, a reaction scheme has been proposed, involving initiation by OH^. or S$\text{O}$₄^. radicals, generated by the interaction of the initiator with manganous sulphate, and termination by mutual combination.     

Non-ideality in vinyl polymerization—IV. Kinetics of polymerization of vinyl acetate in benzene initiated by azo-bis isobutyronitrile (AIBN)

Vinyl acetate was polymerized in bulk and in benzene at 50°C using a wide range of concentrations of azobisisobutyronitrile. Values of f_k (the efficiency of initiator) and k_prt/k_ik_p (the characteristic constant of primary radical termination) were found to be 0.53 and 2.00 × 10⁴ respectively from data for bulk polymerization. In solution polymerization, the initiator exponent is a function of initiator concentration ranging from 0.35 at high concentration to- about 0.65 at low concentration. This result has been explained on the basis of degradative chain transfer to solvent and primary radical termination. The results have been treated according to mathematical formulations already developed; the characteristic constant of degradative chain transfer and the transfer constant of the solvent have been determined. The results have been compared with literature values and discrepancies explained.     

Thermal decomposition kinetics of bisthiourea cadmuim(II) tetrathiocyanato diammine chromate(III)

Cadmium thiourea reinickate undergoes two-stage thermal decomposition on heating. The DTG peak temperatures are 291 and 469°C and the corresponding DTA temperatures are 255 and 490°C. The kinetic parameters for the first stage decomposition are E* ≈ 120kJ mole^?1; Z ≈ 1.2 × 10⁸ cm³ mole^?1 sec^?1 and ΔS* ≈ ?95 J mole^?1 K^?1. For the second stage, E* ≈ 133 kJ mole^?1; Z ≈ 6.1 × 10⁵ cm^?1 mole^?1 sec^?1 and ΔS* ≈ ?142 J mole^?1 K^?1.     

Polarographic analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III)

The analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III) and 1 M H₂SO₄ are investigated using the polarographic technique. The wave corresponding to the reduction of Fe(III) to Fe(II) was found to be completely suppressed by the addition of 1% pyrogallol. Thus, different mixtures of these elements, viz. Hg(II), Cu(II), Cd(II), As(III) and Fe(III)-mixture (A), Cu(II), Cd(II), Sb(III), As(III) and Fe(III)-mixture (B), and Cu(II), Cd(II), Ti(IV), U(VI) and Fe(III)-mixture (C), were quantitatively determined using 1% pyrogallol and 1 M H₂SO₄ as supporting electrolyte. The i₁/c results give excellent correlations in each case, as indicated from the results of leastsquares regression analysis.     

The unusual iron complex with a trimethylenemethane type ligand, (η5-cyclopentadienyldicarbonylmanganese)- (phenylmethylene)carbomethaneiron tricarbonyl [Cp(CO)2 MnC(CO)CHPh]Fe(CO)3

The binuclear complex with composition [Cp(CO)₂ MnC(CO)CHPh]Fe(CO)₃ is obtained by interaction of CpMn(CCHPh)(CO)₂ with Fe₂C0)₉. An X-ray study of this complex has shown that besides three carbonyl groups the iron atom is covalently bonded to four atoms, viz. the carbon of a phenylmethylene group, the carbon of a bridging CO group, the manganese atom and the central carbon of the organomanganese ligand lying just above iron. It seems to be the first example of a heteroatomic analogue of trimethylenemethane complexes.     

Phase transition in V5O9

Electrical resistivity, magnetic susceptibility, and heat capacity of V₅O₉ have been measured through its phase transition temperature (T_t) around 129 K. The associated changes in enthalpy and entropy were found to be 2095 J/mole and 19.24 J/mole · deg., respectively. A qualitative thermodynamic analysis has been attempted to correlate the crystal symmetry, electrical, magnetic, and heat capacity behavior at T_t. The metal-semiconductor transition appears as a consequence of the crystallographic order-disorder process, since the electrical and magnetic contributions to configurational entropy change are relatively small.     

Thermal decomposition of cesium hexanitratouranium(IV)

As cesium hexanitratouranium(IV), Cs₂U(NO₃)₆, has the same Cs:U stoichiometry as that of Cs₂UO₄, thermal decomposition of this nitrato complex in air and nitrogen was studied in detail as a possible alternate method of preparing pure Cs₂UO₄. The volatility of cesium nitrate, which is one of the intermediate products, changed this Cs:U ratio during thermal decomposition. Hence, only Cs₂U₂O₇ was obtained on heating the sample to 775 K or higher. A scheme for the thermal decomposition of Cs₂U(NO₃)₆ is given by combining the observed TG, XRD and IR data.     

Studies on the kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate—II. Mechanistic features in strongly acid solutions

The kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate in 1 M H₂SO₄ have been studied. Ceric ion and thiourea initially form an 1:1 complex which then reacts with uncomplexed ceric ion to form the initiating thiocarbamido radicals. The termination is predominantly biomolecular below an initial ceric concentration of 0.66 × 10^?2 M (depending upon the rate of initiation). At higher initial ceric concentrations, polymer radicals are terminated overwhelmingly by ceric ions. Substituted thioureas reduce the rate of polymerization according to the order of increasing electron density on the sulphur atom. The overall activation energy of polymerization is 12.1 kcal/mol in the region of bimolecular termination and 10.2 kcal/mol in the region of metal ion termination.     

Conformational analysis of some (E)-α-phenyl-β-(2-thienyl)- and -(2-furyl_acrylic acids

NMR spectral data of some (E)-α-phenyl-β-(2-thienyl) acrylic acids indicate that these compounds exist in the preferred s-trans conformation. In the case of (E)-α-phenyl-β-(2-furyl)acrylic acids and their methyl esters the presence of only s-cis rotamer has been established.     

Photoelectron spectroscopy of f-element organometallic compounds II. Tricyclopentadienyl derivatives of uranium(IV) and thorium(IV)

The photoelectron spectra of some cyclopentadienyI derivatives of uranium(IV) and thorium(IV), namely (C₅H₅)₃ ThCl, (C₅H₅)₃ UCl, (C₅ H₄ CH₃)₃ ThCl, (C₅ H₄ CH₃)₃ UCl, (C₅ H₄ CH₃)₃ UBr and (C₅ H₄ CH₃ )₃ UBH₄, are reported the metal 5f ionization has been detected in all the uranium derivative spectra and a simple molecular orbital scheme qualitatively accounts for the number and position of the observed low energy bands.     

Mixed ligand complexes in vinyl polymerization—II: [NN′-ethylenebis(salicylideneiminato)] (benzoylacetonato)cobalt(III) as an initiator

The polymerization of methyl methacrylate initiated by a mixed ligand complex. [NN′-ethylenebis(salicylideneiminato)](benzoylacetonato)cobalt(III) has been studied in bulk and in benzene at 70° and 80°. The rate of polymerization is proportional to (concentration of the chelate)${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and the monomer exponent is close to 1.5. The activation energy and the kinetic and transfer constants are evaluated. A free radical mechanism has been proposed.     

Ligand effects in the hydroformylation of acrylonitrile by cobalt carbonyl

The hydroformylation of acrylonitrile (VCN) using Co₂(CO)₈/L (L  HN(CH₂CN)₂, H₂C(CH₂)₃NMe, Me₂N(CH₂)₂NMeH, PPh₃, and PCy₃) has been examined in methanol solvent. Four reaction pathways are observed which are dependent on L. With no L or with L  HN(CH₂CN)₂, the reaction produces the desired acetal (MeO)₂CHCH₂CH₂CN. For the more basic amines the reaction produces ～ 50% yields of hydrodimerization products NCCHMe(CH₂)₂CN/NC(CH₂)₄CN in a 10/1 ratio and an ～ 30% yield of the hydrogenation product CH₃CH₂CN. These reactions are shown to be metal catalyzed. The main reaction for Co₂(CO)₈/PR₃ catalyzed systems appears to be a classical Michael addition reaction of the solvent, methanol, with acrylonitrile to give MeOCH₂CH₂CN. Evidence is given to show that this reaction is catalyzed by phosphine which has dissociated under reaction conditions and not by a ligated cobalt complex.     

Heat capacity of pure and doped V2O3 single crystals

Heat capacities have been measured for single crystals of V₂O₃, either pure or doped with 1 and 1.4 mole% Cr₂O₃ and Al₂O₃ over the temperature range 100–700°K. V₂O₃ undergoes a fairly sharp transition at low temperatures (～170°K) but fails to exhibit any thermal anomaly above 300°K. The thermal behavior of (M_xV_1?x)₂O₃, M = Cr, Al, is manifested by two transitions: one at low temperatures, 170–180°K for x = 0.01 and 180–190°K for x = 0.014, and the other at high temperatures. For x = 0.01, the high-temperature (HT) anomaly extended over the range 325–345°K (Cr-doped V₂O₃) and 345–365°K (Al-doped V₂O₃), respectively. The corresponding ranges for x = 0.014 were found to be 260–280°K and 270–290°K, respectively. Further, the HT anomaly was characterized by a large hysteresis (～50°K). The values of lattice heat capacity of pure and doped V₂O₃ were, however, found to be almost the same and could be empirically represented by the Debye (D)?Einstein (E) function $\text{D}\text{(}\text{580}\text{T}\text{) + 4}\text{E}\text{(}\text{θ}\text{T}\text{)}$ with θ values 430°K (T = 100–230°K) and 465°K (T > 230°K), respectively. Further, the enthalpy change ΔH associated with the HT anomaly in doped V₂O₃ (80 ≤ ΔH ≤ 510 J/mole) was 5–10 times smaller than the ΔH corresponding to the lower-temperature transition. The results cited here appear incompatible with the Mott transition model that has been invoked to explain the HT anomaly.     

Mechanistic studies on the photo-oxidation of commercial poly(butadiene)

Products from both the thermal and photo-oxidation of poly-butadiene have been studied using various analytical techniques such as infra-red and ultra-violet spectroscopy, gas-liquid chromatography and phosphorescence emission and phosphorescence excitation spectroscopy. Analyses have allowed a plausible mechanism to be formulated for the photo-oxidation of this polymer, consistent with all the observed physical and chemical changes. Both photo- and thermal oxidative polymer degradation initially result in the formation of α, β-unsaturated carbonyls which, under photo-degrading conditions, are subsequently photolysed to yield the observed final products.     

High-pressure magnetic susceptibility studies of spin-state transition in Fe(II) complexes

High-pressure magnetic susceptibility measurements have been carried out on Fe(dipy)₂(NCS)₂ and Fe(phen)₂(NCS)₂ in the pressure range 1–10 kbar and tempeature range 80–300 K in order to investigate the factors responsible for the spin-state transitions. The transitions change from first order to second or higher order upon application of pressure. The temperature variation of the susceptibility at different pressures has been analysed quantitatively within the framework of available models. It is shown that the relative magnitudes of the ΔG⁰ of high-spin and low-spin conversion and the ferromagnetic interaction between high-spin complexes determines the nature of the transition.