The formation of grignard compounds—V: The reaction of iodomethane with magnesium in allyl phenyl ether. A second-order cidnp spectrum

Analysis of product formation reveals that in the reaction of iodomethane and magnesium in anyl phenyl ether ethane and 1-butane are the major side products. The latter product is formed mainly by addition of methyl radicals to the terminal CH₂ group of allyl phenyl ehter, followed by β-scission under extrusion of a phenoxy radical. This mechanism_f is confirmed by an analysis of the CIDNP spectra during the reaction; CH₃ radicals escaping from $\text{CH}{}_3\text{CH}{}_3$ pairs and adding to allyl phenyl ether give rise to a very clear example of a second order CIDNP spectrum in the product 1-butane, while polarization in $\text{CH}{}_3\text{C}{}_6\text{H}{}_5\text{O-CH-CHCH}{}_2$ pairs, formed after α-H abstraction from allyl phenyl ether, leads to net effects in the products ethane (E) and 1-methylallyl phenyl ether (A).     

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 $\text{k}{}_{\mathrm{t}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{/k}{}_{\mathrm{p}}$.     

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>}}$.     

Evaluation of the type of polymer property average

A method for evaluation of the type of average, which is experimentally obtained for a given property of polydisperse polymer, is described. A multivariable power function

where P is the polymer property, $\text{M}{}_{\mathrm{x}}$ is the x-average molecular weight, q is the polydispersity degree, A_p, a and a_px are constants, and the a_px = 0 criterion (a_px being the polydispersity exponent) is used for this purpose.     

Investigations on the influence of charge density on the mutual deactivation of polyion-macroradicals—II

Bimolecular rate constants (2 k_R) of the reaction R· + R· in aqueous solution were measured using the pulse radiolysis technique. R· designates radicals produced by H atom abstraction from polyvinyl alcohol partially acetalyzed with glyoxylic acid. Due to the expansion of the coils, 2 k_R increases with X_i the content of ionized base units in mole %. Above a critical value x_i (crit), 2 k_R decreases due to intermolecular repulsion. x_i(crit) decreases with increasing chain length $\text{n}{}_{\mathrm{<mtext>n</mtext>}}$ [x_i (crit) ≈ 0·5 mole % at $\text{n}{}_{\mathrm{<mtext>n</mtext>}}\text{= 3000}$ and x_i (crit) ≈ 1·5 mole % at $\text{n}{}_{\mathrm{n}}\text{= 270}$]. In the presence of NaClO₄, the following salt effects were observed: for x_i >x_i (crit), 2 k_R is increased because the intermolecular repulsion is partially depressed by screening. Below x_i (crit), 2 k_R is decreased since the coil expansion is diminished. At very low values of x_i where the coil expansion due to intramolecular repulsion is negligible, no salt effect was detectable.     

Synthesis and solution properties of poly(ditoluyl itaconates)

The three o-, m- and p- isomers of ditoluyl itaconate were obtained by esterification of cresols and itaconic acid in the presence of diphosphorous pentoxide, and then polymerized in bulk with AlBN as initiator. The polymers were investigated in dilute solution, including $\text{M}{}_{\mathrm{W}}$ determination and precipitation fractionations, and the results compared with those for poly(diphenyl itaconate). The presence and position of -CH, in the aromatic ring influence the initial rates of polymerization, polymer solubilities in organic solvents and $\text{[η]/}\text{M}{}_{\mathrm{W}}$ relations. Unperturbed dimensions, obtained by extrapolating to τ-conditions, vary slightly with the -CH, group position, due to steric and probably other effects.     

The kinetics and mechanism of photo-ageing of polyvinylbutyral

The mechanism of photo-ageing of polyvinylbutyral has been investigated. The quantum yields of photochemical reactions of the radicals are determined. It is shown that the cross-linking of the polymer is a result of thermal reactions of the radicals, whereas its decomposition is due to photodissociation of radicals

$\text{～ CH(O·CO·C}{}_3\text{H}{}_7\text{)·CH}{}_2\text{·C}\text{H}\text{?}\text{～}$

The relative contributions of decomposition and cross-linking depend on the spectral composition of the light and temperature of radiation.     

Primary radical termination in polymerization: Evaluation of the characteristic constant

Polymerization experiments with styrene in benzene at 60°, initiated by benzoyl peroxide, covering a wide range of concentration of both monomer and initiator are reported; the results cannot be explained in terms of the classical rate relationship with $\text{R}{}_{\mathrm{p}}\text{∝ [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{M}\text{]}$. Deviations were reflected in unexpected orders of monomer up to [M]^1·4 and of initiator down to [I]^0·42 when the initiator concentration is increased and monomer concentration is decreased. Based on the concept of primary radical termination, an equation, viz.

$\text{ln}\text{R}\text{p}\text{2}\text{[I][M]}{}^2\text{=}\text{ln}\text{2f}{}_{\mathrm{k}}\text{k}{}_{\mathrm{d}}\text{k}\text{p}\text{2}\text{k}{}_{\mathrm{t}}\text{?2}\text{k}{}_{\mathrm{prt}}\text{k}{}_{\mathrm{i}}\text{k}{}_{\mathrm{p}}\text{×}\text{R}{}_{\mathrm{p}}\text{[M]}{}^2$

is proposed. Semi-log plots of R_p²/[I] [M]² vs R_p/[M]² show a wide range of linearity; the characteristic constant k_prt/k_ik_p and also f_k can be obtained from the slope and intercept, respectively, k_prt, k_i and k_p are, respectively, the rate constants of primary radical termination, initiation and propagation and f_k is the efficiency of initiation, defined as the fraction of radicals which come out of the solvent cage and take part in initiation, primary radical termination and primary radical recombination. The definition of f_k is thus differentiated from the conventional efficiency of initiation. Finally, we have derived an equation which allows determination of the classical efficiency of initiation as a function of [I]/[M]² and also allows a correction of R_p in handling the above equation by taking into account the small amount of monomer consumed in initiation.     

Kinetics of the dispersion polymerization of acrylamide

Aqueous solutions of acrylamide were dispersed with non-ionic surfactants within isoparafinic hydrocarbons to particles of approx. 1 μm and polymerized in a batch reactor by water-soluble and oil-soluble azo-initiators at 42 to 57°C. The resulting conversion-time curves are S-shaped showing a strong gel effect. For maximum rate of polymerization, the following kinetic expressions were determined for the conditions investigated:

$\text{r}{}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}{}^{0.5}\text{C}{}_{\mathrm{<mtext>M,o</mtext>}}$

for water-soluble initiators;

${}_{\mathrm{<mtext>max</mtext>}}\text{=kC}{}_{\mathrm{<mtext>I,o</mtext>}}\text{C}{}_{\mathrm{<mtext>E,o</mtext>}}{}^{\mathrm{?0.2}}$

For oil-soluble initiators, the overall rate constant k is a function of interface area and temperature. The interface area is dependent on the phase ratio, stirring speed and temperature. For constant interface areas, an activation energy of 26 kJ/mol was found. The overall activation energy of the polymerization is 88.2 kJ/mol, when temperature dependence of the interphase is not taken into account. Polymerization of acrylamide with oil-soluble initiators can be described at low conversions by a model which considers mass transfer of primary radicals, and to a lesser extent of initiator molecules, from the oil phase into the water phase as rate determining step and termination by primary radicals. The resulting molecular weights of the polymer are extremely high (10⁶g/mol) and depend on temperature, stirring speed and concentration of initiator, emulsifier and monomer.     

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.     

Inorganic Chemistry: Towards the 21st Century. : ACS Symposium Series 211 (Ed. M.H. Chisholm), American Chemical Society,Washington, D.C., 1983, ix + 566 pages, $67.95 ($55.95, USA and Canada)

The preparation of the first mixed metal cyclometallated compounds [ClP$\text{d(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHNNCH(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{))P}$tCl]_n (R = H, Cl) are reported; they were made from monocyclopalladated [(AcO)P$\text{d(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHNN}$CH(p-RC₆H₄)]₂ and PtCl₄^2?.     

Perfluorocycloalkyl(aryl) diazenes from heptafluoronitrosocyclobutane and nonafluoronitrosocyclopentane

The perfluoronitrosocycloalkanes, heptafluoronitrosocyclobutane and nonafluoronitrosocyclopentane, are convenient precursors to a family of new perfluorocycloalkyl(aryl) diazenes. With aniline and o-aminobenzamide, $\text{CF}{}_2\text{(CF}{}_2\text{)}{}_{\mathrm{x}}\text{C}$FNN$\text{C(CH)}{}_4\text{C}$H and $\text{CF}{}_2\text{(CF}{}_2\text{)}{}_{\mathrm{x}}\text{C}$FNN$\text{C(CH)}{}_4\text{C}$C(O)NH₂ (x = 2,3) are formed. Additionally, heptafluoronitrosocyclobutane gives $\text{CF}{}_2\text{(CF}{}_2\text{)}{}_2\text{C}$FNN$\text{CCFCFCHCFC}$F and $\text{CF}{}_2\text{(CF}{}_2\text{)}{}_2\text{C}$FNN$\text{C(CH)}{}_4\text{C}$NH₂ with 2,3,5,6-tetrafluoroaniline and o-phenylenediamine     

Etude des volumes specifiques partiels de polystyrenes-modeles—Influence de la masse moleculaire et de la nature des groupements terminaux

It is well known that the apparent specific volume η₂ of a polymer may be expressed by the following relationship: $\text{η}{}_2\text{= η}{}_{\mathrm{m}}\text{+ K/}\text{M}{}_{\mathrm{n}}$ where M?_n is the number-average molecular weight of the polymer, η_m the specific volume of the infinite polymer, and K a constant. We have shown that this relationship is valid for low molecular weight polystyrenes ($\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$) with different end-groups, independently of the nature of the solvent. The K values (and variations with the solvent and with the nature of the end-groups) may be predicted through simple calculations proposed here. We conclude that η_m does not represent the specific volume of the infinite polymer, since we observe a rapid decrease of η₂ for increasing M (when $\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$). The decrease is much greater than expected from the relationship $\text{η}{}_2\text{= ? (1/}\text{M}\text{)}$.     

Molecular structure of liquid alcohols

A new thermodynamic treatment of continuous association is presented, where the various equilibria between i-mers are replaced by a single equilibrium between an OH groups in the bonded and the non-bonded states, linked in both cases to an indefinite ensemble of molecules. The treatment leads to an association constant K which differs from those considered in the theories of Kretschmer and Wiebe and of Wiehe and Bagley. For pure alcohols the association constant can be estimated from the vapor pressure of the alcohol and that of the homomorphous hydrocarbon. The fraction γ of free OH groups determined in this way is markedly smaller than those calculated from the other theories. For the normal alcohols the product $\text{K}\text{V}{}_{\mathrm{<mtext>A</mtext>}}$ is approximately constant at a given temperature, $\text{V}{}_{\mathrm{<mtext>A</mtext>}}$ being the molar volume. This can be expected from the increasing of the standard entropy of the non-bonded molecules when the molecular volume increases. For secondary and tertiary alcohols the product K$\text{V}{}_{\mathrm{<mtext>A</mtext>}}$ is significantly lower due to steric hindrances. However for all the alcohols considered here the enthalpy of the hydrogen bond remains nearly constant — δH being equal to 24.8 ± 2 kJ mol^?1.     

The photodecomposition of platinacycloalkanes in solution: II. 1,4-butanediylplatinum(II) and (IV) compounds

The products of the photolysis of a number of platinacyclopentanes in solution at 25°C under a variety of conditions have been determined. With [I₂P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = PMe₂Ph, PPh₃) in CH₂Cl₂, CH₂Br₂ and (CH₃)₂SO the hydrocarbon products are exclusively ethylene and but-1-ene. Formation of the latter through a 1,3-hydrogen shift is preceded by phosphine ligand dissociation. The photolysis of [ICH₃P$\text{tCH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] gave methane, ethylene, but-1-ene and n-pentane together with a little n-butane, the methane being formed from internal hydrogen abstraction by the CH₃ group in the excited reactant molecule. Photodecomposition of the platinum(II) compounds [P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = (PMe₂Ph)₂, (PPh₃)₂, Ph₂PCH₂CH₂PPh₂) gave ethylene, but-1-ene, pent-1-ene (with the halogenated solvents) and with some systems appreciable yields of n-butane, the latter being the results of internal abstraction of two hydrogen atoms by the C₄H₈ moiety. The formation of pentene is probably preceeded by the addition of CH₂Cl₂ or CH₂Br₂ to the excited reactant molecule. Addition of diphenylphosphine promotes the production of n-butane.     

The thermal polymerization of styrene at temperatures up to 250°

The kinetics of the thermal polymerization of styrene have been studied over the range 60–250°. The overall energy of activation was 86 ± 2 kJ/mole, a value identical to that obtained for the thermal polymerization of styrene in diethyl adipate. As expected, the molecular weight of the polymer decreases with increase in the temperature of the polymerization, and the ratio $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ becomes greater than 2 for polymer formed at above 140°. The plot of log ($\text{1}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$) against (absolute temperature)^?1 can be represented by two straight lines yielding 24.5 and 32,0 kJ/mole for the activation energies at temperatures below 120° and above 140°, respectively. The former value is in keeping with the molecular weight being controlled by chain transfer with monomer; the latter value would be that expected if the termination process controls the molecular weight of the polymer. Mark Houwink relationships between intrinsic viscosity and $\text{M}$_n and $\text{M}$_w have been found to apply to polymer samples when the molecular weight averages were determined by osmometry and by light scattering. However, deviations were found for low molecular weight material when measured using gel permeation chromatography. The K values were considerably lower, and the α values higher than reported in the literature.     

Oxidation of polystyrene in solution

Polystyrene (PS) has been oxidized in carbon tetrachloride, chloroform, methylene chloride and cyclohexane under O₂ at atmospheric pressure using γ-initiation. Benzaldehyde, acetophenone and reductions in molecular weight were observed in all solvents. Yields of benzaldehyde and acetophenone were used to show that attack in chlorinated solvents is essentially random along the polymer chains and is predominantly by Cl^? radicals. Intramolecular propagation is much faster for attack on tertiary carbons than on secondary carbons. There are more neighboring hydroperoxide groups in PS oxidized in carbon tetrachloride and methylene chloride than in PS oxidized in chloroform, because, in chloroform, the solvent hydrogen is abstracted by polymer-based peroxyl radicals. For one set of conditions, about six intramolecular propagation steps took place in carbon tetrachloride and one in chloroform. At lower rates of initiation, the kinetic oxidation chains are longer and more intramolecular propagation occurs. HCl added in excess of that formed in these experiments decomposes hydroperoxide groups to give an autoaccelerating effect.Rates of scission were proportional to $\text{G}{}_{\mathrm{Cl?}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, where G_Cl? is proportional to the rate of production of Cl? radicals. The alkoxyl radicals on polystyrene, produced in bimolecular interactions of peroxyl radicals, did not abstract hydrogen from the solvents, and thus appear to be very short-lived.The amount of oxidation of polystyrene in cyclohexane is much smaller than in chlorinated solvents. The analytical techniques used were too imprecise to allow meaningful comparison with the oxidations in chlorinated solvents.     

Isotope effects in electron-donor-acceptor complexes involving aromatic hydrocarbons and fluoranil from NMR shift measurements

Equilibrium constants and NMR shift parameters have been determined for complexes of benzene, toluene and p-xylene and their perdeutero-analogues with fluoranil in cyclohexane solution from NMR shift measurements. Isotope effects are observed in the 1:1 equilibrium constants for the complexes of p-xylene $\text{(}\text{K}{}_1\text{(D)}\text{K}{}_1\text{(H)}$= 1.1₀) and toluene $\text{(}\text{K}{}_1\text{(D)}\text{K}{}_1\text{(H)}$ = 1.0₉). A much smaller effect was observed for the benzene complex which could not be quantified. These results may be interpreted through either the larger electronegativity of H over D, or the greater steric requirements of H over D.