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.     

Peroxo salts as initiators of vinyl polymerization—2. Kinetics of polymerization of acrylic acid and sodium-acrylate by peroxodisulphate in aqueous solution—effect of pH and Ag+ catalysis

Results on the rate of polymerization of acrylic acid by S₂O^2?₈ ion in alkaline and acid conditions are presented. R_p depended upon $\text{[S}{}_2\text{O}{}^{\mathrm{2?}}{}_8\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{[monomer]}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ both in acid and alkaline solutions. The influence of ionic strength, the effect of pH on R_p and the catalytic effect of Ag⁺ and Cu²⁺ on the system have been discussed. Suitable mechanisms are proposed.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen XX. Darstellung,eigenschaften und kristallstruktur von λ4-thia-λ5-phospha-h2-metallabicyclo[2.2.1]heptadienen und ihre verwendung zur synthese von metallorganischen und organischen verbindungen

The novel λ⁴-thia-λ⁵-phospha-h²-manganabicyclo[2.2.1]heptadienes (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{PR}{}^1{}_2\text{S}$] (R¹ = CH₃, C₆H₅; R² = CO₂CH₃, CO₂C₂H₅, CO₂C₆H₁₁) are formed by action of the activated alkynes R²C  CR² on the heterocycles [(OC)₄MnPR¹₂S]₂ via the isolable, five-membered heterometallacyclopentadienes (OC)₄$\text{MnSPR}{}^1{}_2\text{C(R}{}^2\text{)C}$(R²). The compound with R¹ = CH₃ and R² = CO₂CH₃ crystallizes in the triclinic space group P$\text{1}$ with Z = 2 and separates quantitatively the thiophene derivative $\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{S}$ under CO pressure or by reaction with (NH₄)₂Ce(NO₃)₆. The use of various acetylenes and of acetylenes with different alkyl groups yields the unsymmetric substituted manganabicycloheptadienes (OC)₃Mn[$\text{CR}{}^4\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P(CH}{}_3\text{)}{}_2\text{S}$] (R² = CO₂CH₃, R³ = R⁴ = CO₂C₂H₅; R² = R⁴ = CO₂CH₃, R³ = H). With propionic acid methylester the alkyne insertion proceeds regiospecifically. With Raney nickel selective S elimination under ring contraction and formation of the λ⁴-phospha-h²-manganabicyclo[2.1.1]hexenes (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P}$R¹₂] (R¹ = CH₃: R² = R³ = CO₂CH₃, CO₂C₂H₅; R² = CO₂CH₃, R³ = H; R¹ = C₆H₅: R² = R³ = CO₂C₂H₅) occurs. (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P}$(CH₃)₂] (R² = R³ = CO₂CH₃) crystallizes in the monoclinic space group P2₁/m with Z = 2. The IR and NMR spectra of the heterocycles are discussed in detail.     

A study on sorbitol-ceric ion initiated polymerization of acrylonitrile

The polymerization of acrylonitrile (M) initiated by the sorbitol (R)-Ce(IV) redox system has been studied in sulphuric acid in the range 30–40° under nitrogen. At moderately high concentrations of Ce(IV) (0.00015-0.02 M), the rate of polymerization (R_p) is proportional to $\text{[}\text{M}\text{]}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{[}\text{R}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and the rate of Ce(IV) disappearance is proportional to [R] and [Ce(IV)]. At lower concentration of Ce(IV) (0.00005–0.00015 M) R_p is proportional to [M], [R]^1/2 and [Ce(IV)]^1/2 and rate of Ce(IV) disappearance is proportional to [R] and [Ce(IV)]. The effects of certain salts, acid, solvent and temperature on both rates have been investigated. A kinetic scheme involving mutual termination has been proposed and various rate and energy parameters evaluated. At still higher concentration of Ce(IV) (0.02 M), a linear mode of termination seems to operate.     

Radiochemical studies of free radical vinyl polymerizations—IV. Polymerizations of esters of methacrylic acid

[¹⁴C]Azoisobutyronitrile has been used to initiate the polymerizations of methyl, ethyl, n-butyl, i-butyl, t-butyl, dodecyl, phenyl and cyclohexyl esters of methacrylic acid at 60°. Rates and efficiencies of initiation were measured and the mode of bimolecular termination of polymer radicals determined. Termination was predominantly by disproportionation in every case. No correlation could be found between n (the average number of initiator fragments per polymer molecule) and specific polar or steric effects for the ester groups but a possible correlation was detected between n and the ratio $\text{k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{/k}{}_{\mathrm{p}}$.     

Oligomerisation anionique de l'ethylene—VI. Amorcage par le nBuLi complexe par diverses polyamines bitertiaires

In the field of anionic initiators of ethylene oligomerization, we have studied the reactivity of nBuLi complexed by tertiary amines such as tetramethylethylenediamine (TMEDA), tetraethylethylenediamine (TEEDA) and pentamethyldiethylenetriamine (PMDT). RMN shows high field shift of the —CH₂— protons next to the lithium. This shift is less important for TEEDA compared to those for TMEDA and PMDT. Steric hindrance due to the ethyl groups of TEEDA seems to forbid easy access of the nitrogen atoms to the lithium counter-ion. These results agree well with the kinetic studies which indicate the absence of aggregated species. The following equations have been established: $\text{V}{}_{\mathrm{p}}\text{= k}{}_{\mathrm{p}}\text{·K}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{D}}\text{[(}\text{nBuLi:TMEDA}\text{)}{}_2\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{Et}\text{]}$. and V_p = k′_p[nBuLi:TEEDA][Et]     

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.     

Synthesis and solution properties of poly[2-methoxy-4,6-di(p,p′-isopropylidene diphenyloxy)-s-triazine] I

Poly[2-methoxy-4,6-di(p,p′-isopropylidene diphenyloxy)-s-triazine] has been synthesized by interfacial polycondensation of 2-methoxy-4,6-dichloro-s-triazine with bisphenol A. The conditions have been optimized to prepare a sample of both high solubility and molecular weight. The polymer has been fractionated by fractional precipitation and the fractions characterized by viscometry, osmometry and gel permeation chromatography. Mark-Houwink-Kuhn-Sakurada (MHKS) expressions have been developed for three solvents. The values of unperturbed dimensions $\text{(<R}{}^2\text{>}{}_0\text{/M)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, solvent-polymer interaction parameter (B and χ₁) and conformational parameter (σ) have been computed by applying the two-parameter theories of excluded volume developed by Fixman, Kurata, Stockmayer and Roig and by Flory, Fox and Schaefgen.     

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.     

Etude comparative des structures type K4NiF4 et pérovskite par la méthode des invariants

The study of K₂NiF₄ and perovskite structure type by the “method of invariants” leads to the relationship: $\text{(A-X)}{}_9\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? (A-X)}{}_{12}\text{=}\text{constant}$, where (A-X)₉ and (A-X)₁₂ are the invariant values associated with cation A in coordination number 9 and 12. In the case where A = K⁺ and X = F^?, we propose the relationship:

$\text{(K}{}^{\mathrm{+}}\text{?F)}{}_{\mathrm{R}}\text{= 2.832 R}{}^{\mathrm{<mtext>1</mtext><mtext>11.4</mtext>}}$

where R is the coordination number.     

Kinetics of the polymerization of potassium p-styrenesulphonate in various media

The free radical polymerization of potassium p-styrenesulphonate has been investigated at 70° for solutions in dimethyl sulphoxide (DMSO)-water mixtures (1:3 and 3:1) and in DMSO using 2,2′-azobisisobutyronitrile as initiator. The kinetic orders with respect to monomer and initiator increase but the rate of polymerization, the value of $\text{k}{}_{\mathrm{p}}\text{/k}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{t}}$ and the average molecular weight of the resulting polymer decrease with increasing DMSO concentration in the DMSO-water mixture. These effects have been attributed to changing of parameters of the electrostatic interactions in the system “macroradical-counterions-anions of monomer” with change of composition of the medium.     

Persulphate initiated polymerisation of methacrylamide—I: Kinetics and molecular weight dependences

A kinetic study of the aqueous persulphate initiated polymerisation of methacrylamide has shown that the rate of polymerisation is represented by the equation $\text{R}{}_{\mathrm{p}}\text{= k [}\text{M}\text{] [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ where the overall rate constant, $\text{k = 1.3 × 10}{}^9\text{exp}\text{(?18,400/}\text{RT}\text{) 1}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{?1}}$. Chain transfer with monomer, where C_M = 5.4 × 10^?3 at 60°, is shown to be the dominant transfer step. Comparison with kinetic studies of the analogous acrylamide polymerisation shed doubt on the ‘cage effect’ interpretation of complex orders with respect to monomer. An alternative explanation is proposed.     

Rate parameters for transfer reactions of some polymer radicals: in terms of Swain and Lupton's f and r and the unique positional weighting factors of Williams and Norrington

Rate parameters of the reaction of phenols, deuterated phenols and nitrobenzenes with polyvinylacetate radicals and of aromatic thiols with polymethylmethacrylate radicals have been correlated with Swain and Lupton's substituent constants (F_k and R_k) and Williams and Norrington's unique positional weighting factors (f_j and r_j) by the following equation: $\text{P}{}_{\mathrm{i}}\text{= α}{}_{\mathrm{i}}\text{?}{}_{\mathrm{j}}\text{F}{}_{\mathrm{k}}\text{+ β}{}_{\mathrm{i}}\text{r}{}_{\mathrm{j}}\text{R}{}_{\mathrm{k}}\text{+ e}{}_{\mathrm{i}}\text{+ P}{}^0{}_{\mathrm{i}}$where P_i's are the rate parameters, P⁰_i being that for a standard reference state. The correlations were found to be quite satisfactory. The sign and magnitude, and the ratio of the reaction dependent parameters α_i and β_i throw light on the nature of the transition state and the relative contributions of the mesomeric and inductive effects. The present studies also show that the mesomeric effect of meta-substituents is significantly greater than reported by earlier workers.     

“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.     

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=$\text{[}{}_{\mathrm{kK}}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k′K′k}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{k}{}_{\mathrm{<mtext>h</mtext>}}\text{+[}\text{K}{}_{\mathrm{<mtext>E</mtext>}}\text{[H}{}_3\text{O}{}^{\mathrm{+}}\text{]+}\text{K′}{}_{\mathrm{E}}\text{k}{}_{\mathrm{h}}\text{][Mo(CN)}{}_8{}^{\mathrm{4?}}\text{]}$     

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.     

Polymerization in liquid crystals—IV: The polymerization of cholesteryl-vinyl-succinate

The solid-, cholesteric- and liquid-state polymerizations of cholesteryl-vinyl-succinate (CVS) are studied. Only one of the three polymorphic modifications of CVS oligomerizes in the solid state into oligomers of degree $\text{P}\text{= 2}\text{to}\text{6}$ in a homogeneous topochemical reaction. The rate of polymerization in the cholesteric state is lower than that in the liquid state at the same temperature. Kinetic constants were measured at 85° using benzoyl peroxide as initiator and the Banfield radical, giving E_overall = 15.4, 36.4 kcal/mole^?1; $\text{f = 0.52, 0.19; k}{}_{\mathrm{p}}\text{/k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 0.0167, 0.0192}$, (1/mole sec)^{$\text{1}\text{2}$}, ($\text{E}{}_{\mathrm{p}}\text{?}\text{1}\text{2}\text{E}{}_{\mathrm{t}}\text{) = 0.40, 21.4}$ kcal mole^?1. The values refer to the liquid- and the cholesteric-state reactions, respectively. The average degree of polymerization is low in both cases ($\text{P}\text{= 20}\text{and}\text{22}$). It was concluded that the molecular weights are controlled by chain transfer and that the initiation reaction is mostly dependent on the phase where the reaction takes place.     

Nachbargruppeneffekte bei der aminolyse von estern—I: Kinetik der aminolyse von nitrophenylacetaten mit n-butylamin in dioxan

The kinetics of the aminolysis of different nitrophenylacetates were investigated with n-butylamine in dioxane at 20°C. The reaction rate can be described up to high concentrations of amine (~1 mole dm^?3) by the equation v=k₂[ester][amine]+k₃[ester][amine]². The ratio $\text{k}{}_3\text{k}{}_2$ is larger for p-nitrophenylacetates than for o-nitrophenylacetates, while for 2,4-dinitrophenylacetates a third order term is not observed.     

Transition metalcarbon bonds: LV. Cyclometallation and other reactions of PBut2Bui and PPh2Bui with platinum(II) and palladium(II)

The new phosphine, PBu^t₂Buⁱ (L), was prepared from Bu^t₂PCl and LiBuⁱ. PPh₂Buⁱ (L′) was prepared from Ph₂PCl and LiBuⁱ. Treatment of [PtCl₂(NCBu^t)₂] with L′ gives [PtCl₂L′₂] which does not cyclometallate even on prolonged boiling in 2-methoxyethanol. In contrast, [PtCl₂(NCBu^t)₂] reacts with PBu^t₂Buⁱ in boiling 2-methoxyethanol to give the cyclometallated complex [$\text{Pt}{}_2\text{Cl}{}_2\text{(PBu}{}^{\mathrm{t}}{}_2\text{CH}{}_2\text{-CHMeCH}$₂)₂] (II, X = Cl). The corresponding bromide, iodide and acetylacetonate were prepared. With PPh₃ II (X = Cl) gives [$\text{PtCl(PBu}{}^{\mathrm{t}}{}_2\text{CH}{}_2\text{CHMeCH}$₂)(PPh₃)] which with NaBH₄ gives [$\text{PtH(PBu}{}^{\mathrm{t}}{}_2\text{CH}{}_2\text{CHMeC}$H₂)(PPh₃)]. Na₂PdCl₄ with L (2 mol equivalents) gave trans-[PdCl₂L₂], which was converted into trans-[Pd(NCS)₂-L₂] by metathesis with KSCN. Treatment of Na₂PdCl₄ with L (1 mol equivalent) gave [Pd₂Cl₄L₂], which on heating in 2-methoxyethanol gave [$\text{Pd}{}_2\text{Cl}{}_2\text{(PBu}{}^{\mathrm{t}}{}_2\text{CH}{}_2\text{-CHMeCH}$₂)₂], as a mixture of syn- and anti-isomers. The complexes trans-[PdCl₂-L′₂] and [Pd₂Cl₄L′₂] were also prepared. ¹H- and ³¹P NMR data are given.