Effects of substituents on the anionic copolymerization of ring-substituted cinnamonitriles

trans-Cinnamonitrile (M₁) was copolymerized with several of its ring-substituted derivatives (M₂) in toluene at 25°C, calcium zinc tetraethyl being used as catalyst. The ring substituents investigated include H, p-CH₃O, m-CH₃O, p-CH₃, m-CH₃, p-Cl, and m-Cl. It was found that the values of log (1/r₁) are linearly correlated with Hammett's σ constants with the reaction constant σ ρ 0.7. The effects of coordination between monomer and catalyst sites upon the Hammett relation are discussed.     

Study of substituted aryldiazonium salts and their crown ethers complexes by XPS

The complexes of fourteen substituted aryldiazonium salts RC₆H₄N₂+BF₄^? (R?H, p-CH₃, p-NO₂, p-I, p-Cl, p-F, m-Br, m-Cl. m-CH₃, o-CH₃, o-OCH₃, o-NO₂, o-Br, o-Cl) with crown ethers 18-C-6 (1) and dibenzo-24-c-8 (2) have been studied by XPS. The results show that the chemical shifts of α-N1s and β-N1s of substituted aryldiazonium salts are closely related to the induction and conjugation effects of R groups. It is interesting to note that charge transfer(β-N→O) take place upon complexation of substituted aryldiazonium salts with crown ethers. Therefore the decrease of binding energy of crown ether oxygen may be used as a measurement of the stabilities of these complexes.     

Silyl enol ethers as monomer. I. Radical copolymerizability of α-trimethylsilyloxystyrene

α-Trimethylsilyloxystyrene (TMSST), the silyl enol ether of acetophenone, was not homopolymerized either by a radical or a cationic initiator. Radical copolymerization of TMSST with styrene (ST) and acrylonitrile (AN) in bulk and the terpolymerization of TMSST, ST, and maleic anhydride (MA) in dioxane were studied at 60°C and the polymerization parameters of TMSST were estimated. The rate of copolymerization decreased with increased amounts of TMSST for both systems. Monomer reactivity ratios were found as follows: r₁ = 1.48 and r₂ = 0 for the ST (M₁)–TMSST (M₂) system and r₁ = 0.050 and r₂ = 0 for the AN (M₁)–TMSST (M₂) system. The terpolymerization of ST (M₁), TMSST (M₂), and MA (M₃) gave a terpolymer containing ca. 50 mol % of MA units with a varying ratio of TMSST to ST units and the ratio of rate constants of propagation, k₃₂/k₃₁, was found to be 0.39. Q and e values of TMSST were determined using the values shown above to be 0.88 and ?1.13, respectively. Attempted desilylation by an acid catalyst for the copolymer of TMSST with ST afforded polystyrene partially substituted with hydroxyl groups at the α-position.     

Chemistry of trifluorostyrenes and their dimers: 2. Synthesis of substituted α, β, β-trifluorostyrenes and α, β, β-trifluoroethenylnaphthalenes. Hammett correlations of their NMR parameters and the concept of “distorted π-electron clouds”

Six α, β, β-trifluorostyrenes with the following substituents, viz., p-MeO, p-Me, m-Me, p-Cl, m-Cl, and m-CF₃, were synthesized by the reaction of the corresponding Grignard reagents with tetrafluoroethylene in tetrahydrofuran. Similarly, α-and β-trifluoroethenylnaphthalenes were prepared. The substituent electronic effects on the ¹⁹F-NMR parameters were investigated for the trifluorostyrenes (I). Linear correlations between the Hammett σ constants and the following ¹⁹F-NMR parameters were established, namely, chemical shifts δ. (F¹) and δ (F²), coupling constants J₁₂, differences of chemical shifts Δδ_3-1 (δ (F³)—δ(f¹) or Δδ_3-2. The results are consistent with previous expectations based on the simple concept of “distorted π-electron clouds”. Facts are presented which indicate that the Δδ_3-1 (or Δδ_3-2) values may serve as empirical measures of the degree of polarization of the π bonds of these fluoroolefins.     

Structure and reactivity of α,β-unsaturated ethers. VIII. Cationic copolymerizations and acetal additions of propenyl and isobutenyl ethyl ethers

Cationic copolymerizations of cis- and trans-propenyl ethyl ethers (PEE) with isobutenyl ethyl ether (IBEE) were carried out in methylene chloride at ?78°C with the use of boron trifluoride etherate as catalyst. Monomer reactivity ratios were r₁ = 24.0 ± 2.4 and r₂ = 0.02 ± 0.02 for the cis-PEE (M₁)–IBEE (M₂) system and r₁ = 19.1 ± 1.8 and r₂ = 0.04 ± 0.02 for the trans-PEE (M₁)–IBEE (M₂) system, indicative of the reactivity order: cis-PEE > trans-PEE ? IBEE. In separate experiments, these β-methyl-substituted vinyl ethers were allowed to react with various acetals in the presence of boron trifluoride etherate. The relative reactivities of these ethers were generally found to decrease in the order: cis-β-monomethylvinyl > vinyl > trans-β-monomethylvinyl > β,β-dimethylvinyl. Comparisons of these results with previously published copolymerization data have permitted the conclusion that, in both the copolymerizations and acetal additions, the single β-methyl substitution on vinyl ethers exerts little steric effect against their additions toward any alkoxycarbonium ion, whereas the β,β-dimethyl substitution results in a large adverse steric effect toward both β-monomethyl- and β,β-dimethyl-substituted alkoxycarbonium ions.     

Zum basenkatalysierten H/D-Austausch des acetylenischen Wasserstoffatoms in aromatischen Alkinylverbindungen

On the Base-Catalysed H/D-Exchange of the Acetylenic Hydrogen Atom in Aromatic Alkynyl Compounds H/D-exchange rates for a number of compounds of the general type 1 (X = p-CH₃O, m-CH₃O, p-CF₃, m-CF₃, p-CH₃, p-Cl, H; Z ? O, NH, CH₂) were determined in N-methyl-pyrrolidine (NMP)/D₂O mixtures at 25° (see Table 1). It is shown that the log k values of the H/D-exchange correlate nicely (r = 0.995) with the chemical shift of the acetylenic proton in 1 . Thus, the H/D-exchange rate is given by log k (min^?1) = 2.91 · δ (ppm) - 7.79 for the NMP/D₂O mixture at 25°.     

Novel Copolymers of Halogen Ring Substituted 2-Cyano-3-Phenyl-2-Propen- Amides and Styrene

ABSTRACT

Electrophilic trisubstituted ethylene monomers, halogen ring substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₄CH=C(CN) CONH₂ (where R is o-Cl, m-Cl, p-Cl, p-Br, and p-F) were prepared by Knoevenagel condensation. Novel copolymers of the propenamides and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator at 80°C. The order of reactivity (1/r ₁) for the monomers (M₁=styrene) was o-Cl (1.42) > p-F (1.19) > p-Cl (0.70) > m-Cl (0.60) > p-Br (0.44).     

Polymerization of β-cyanopropionaldehyde. X. Anionic copolymerization with methyl isocyanate

Anionic copolymerization of β-cyanopropionaldehyde (M₁) with methyl isocyanate (MeI, M₂) was studied with use of benzophenone–dilithium complex as initiator at ?78°C. The values of monomer reactivity ratio were determined to be r₁ = 8.3 ± 0.3 and r₂ = 0.01 ± 0.01. The structure of resulting copolymer was investigated by means of NMR analysis. The MeI unit is presumed to enter the copolymer chain through its C?N opening.     

Kinetics and mechanism of dimerization of arylmercurials

The kinetics of dimerization of arylmercurials XC₆H₄HgCl (X ? H, p-CH₃, m-CH₃, p-Cl, m-OCH₃, m-CO₂C₂H₅, and o-OCH₃) in the presence of [ClRh(CO)₂]₂ was studied in hexamethylphosphoramide (HMPA). The experimental rate law obtained is ?d[ArHgCl]/dt=k[ArHgCl]². The kinetic parameters of these reactions have been reported, and the variation, therein, has been explained on the basis of steric effect of substituents. The apparent activation energy E is linearly proportional to pre-exponential factor lnA. A most plausible mechanism has been proposed on the basis of experimental results. © 1993 John Wiley & Sons, Inc.     

Anionic copolymerization of isocyanates with ketenes

Diphenyl-, phenylethyl, and phenylmethylketene have been copolymerized with phenyl isocyanate by use of sodium naphthalene in dimethylformamide (DMF) at ?45°C. Reactivity ratios of phenyl isocyanate (r₂) with diphenylketene (r₁) were r₁ = 0.10, r₂ = 0.29; with phenylethylketene (r₁) were r₁ = 1.6, r₂ = 0.10; and with phenyl methyl ketene (r₁) were r₁ = 4.8, r₂ = 0.02. The same initiator and solvent system were used for homopolymerization of phenylethylketene and copolymerization with m-chloro-, p-chloro-, p-methoxy-, and m-methoxyphenyl isocyanate as well as with phenyl isocyanate. Molecular weights ranged from 1740 to 4000. The effect of substituents on the order of isocyanate incorporation into the copolymer was m-Cl = p-Cl > m-MeO > H > p-MeO. Phenylethylketene was also copolymerized with m-methoxyphenyl, p-methoxyphenyl, and p-tolyl isocyanate in tetrahydrofuran (THF) at ?78°C. Molecular weights ranged from 2800 to 10,500. The least reactive isocyanate was incorporated into the copolymer to a greater extent in this solvent than in the more polar DMF. DTA showed the presence of crystallinity only in polymers of high isocyanate content. The ketenes copolymerized less readily with alkyl isocyanates, such as ethyl, n-butyl, n-hexyl, and cyclohexyl isocyanate, than with the aromatic isocyanates when sodium naphthalene was used in either DMF or THF.     

Base-catalyzed isomerization of phenylpropenes

The prototropic rearrangement of 3-phenyl-1-propenes to the corresponding 1-phenyl-1-propenes was investigated in basic media utilizing 0.1M sodium ethoxide in absolute ethanol at 81°C. It was found that the effect of substituents on the rate of such isomerizations follows the order: p-NO₂ > o-Cl > m-Cl ≥ m-F > p-Br > o-CH₃ > m-CH₃ > m-CH(CH₃)₂ > p-CH(CH₃)₂ ≥ p-C(CH₃)₃ > o-OCH₃. This is consistent with first-order kinetics and “BS” mechanism. Quantitative treatment in terms of Hammett's equation showed a straight line, with a slope (p value) of +2.25. An increase in the strength of the base was also found to cause an increase in the rate of isomerization.     

Cationic copolymerization of phenyl propenyl ethers

Ring-substituted phenyl propenyl ethers were found to form homopolymers without any rearrangement by metal halides. Phenyl propenyl ethers were less reactive than the corresponding phenyl vinyl ethers in cationic polymerization. In order to study the electronic effect of a substituent on the reactivity, cis-p-Cl,p-CH₃, and p-CH₃O-phenyl propenyl ethers were copolymerized with phenyl propenyl ether in methylene chloride at ?78°C with stannic chloride–trichloroacetic acid, and their ¹H- and ¹³C-NMR spectra were measured. The reaction constant ρ against Hammett σ_p was ?2.1. The cis-phenyl propenyl ethers were slightly more reactive than the corresponding trans isomers. On the other hand, an o-methyl group decreased the reactivity of phenyl propenyl ether. The low reactivity of o-methyl phenyl propenyl ether was attributed to the steric hindrance between the propagating carbocation and the monomer.     

Synthese von Fluoro-λ5-monophosphazenen und Fluoro-1, 3-diaza-2λ5, 4λ5-diphosphetidinen mittels der Staudinger-Reaktion

Synthesis of Fluoro-λ⁵-monophosphazenes and Fluoro-1,3-diaza-2λ⁵,4λ⁵-diphosphetidines by Means of the Staudinger Reaction 35 Tetrafluoro- and 2 difluorodiaza-diphosphetidines as well as 4 difluoro- and 30 monofluoro-λ⁵-monophosphazenes were prepared by the Staudinger reaction between tervalent phosphorus fluorides, R_nPF_3?n (n = 1, 2; R = R₂N, (CH₂)₅N, O(CH₂)₄N, RO, (CH₂O)₂, alkyl, aryl) and phenylazides, X? C₆H₄N₃ (X = H, 4-CH₃, 4-Cl, 4-Br, 4-NO₂, 3-NO₂). PF₃ does not react with phenylazide The influence of substituents on the structure of the reaction products is discussed. Kinetic measurements allowed to determine the constants λ^P_I of the substituents (CH₂)₅N, O(CH₂)₄N and R(C₆H₅)N (R = CH₃, C₂H₅, n-C₄H₉).     

Anionic copolymerization of optically active α-methylbenzyl methacrylate and trityl methacrylate. I. Reactivity of monomers

The monomer reactivity ratios were determined in the anionic copolymerization of (S)- or (RS)-α-methylbenzyl methacrylate (MBMA) and trityl methacrylate (TrMA) with butyllithium at ?78°C, and the stereoregularity of the yielded copolymer was investigated. In the copolymerization of (S)-MBMA (M₁) and TrMA (M₂) in toluene the monomer reactivity ratios were r₁ = 8.55 and r₂ = 0.005. On the other hand, those in the copolymerization of (RS)-MBMA with TrMA were r₁ = 4.30 and r₂ = 0.03. The copolymer of (S)-MBMA and TrMA prepared in toluene was a mixture of two types of copolymer: one consisted mainly of the (S)-MBMA unit and was highly isotactic and the other contained both monomers copiously. The same monomer reactivity ratios, r₁ = 0.39 and r₂ = 0.33, were obtained in the copolymerizations of the (S)-MBMA–TrMA and (RS)-MBMA–TrMA systems in tetrahydrofuran (THF). The microstructures of poly[(S)-MBMA-co-TrMA] and poly-[(RS)-MBMA-co-TrMA] produced in THF were similar where the isotacticity increased with an increase in the content of the TrMA unit.     

Hydroxy-terminated poly(ε-caprolactone-co-δ-valerolactone) oligomers: Synthesis,characterization, and polyurethane network formation

Difunctional hydroxy-terminated poly(ε-caprolactone-co-ε-valerolactone) (PCV) oligomers were synthesized by the diol-initiated bulk copolymerization of ε-caprolactone (C) and δ-valerolactone (V). The two homopolymers were semicrystalline, with almost identical melting temperatures; copolymerization significantly lowered the melting point (T_m) compared to either homopolymer. Copolymer melting points were found to decrease with decreasing molecular weight and to be dependent on composition, i.e., the incorporation of a comonomer into either homopolymer resulted in a decrease in T_m, with the maximum decrease occurring at a copolymer composition of about 60 mol % ε-caprolactone. The molar compositions of the copolyesters were determined from ¹³C-NMR spectra. The reactivity ratios of the two monomers (M₁ = C, M₂ = V) were determined to the r₁ = 0.25 and r₂ = 0.49. Number average molecular weight (M?_n) of the PCV diols was inversely proportional to the initial diol concentration within the studied molecular weight range of 900 to 11,100 g/mol. Crosslinked polyurethane networks were prepared by reacting PCV diols with triphenylmethane triisocyanate. Network characterization included determination of sol content by solvent extraction, glass transition (T_g) and T_m by DSC, and tensile properties by stress-strain measurements. Completely amorphous networks resulted from PCV diols of M?_n ≤ 2,400; semicrystalline networks resulted from PCV diols of M?_n ≥ 3,600.     

Radical-initiated homo- and copolymerization of α-methylene-γ-butyrolactone

The kinetics of α-methylene-γ-butyrolactone (α-MBL) homopolymerization was investigated in N,N-dimethylformamide (DMF) with azobis(isobutyronitrile) as initiator. The rate of polymerization (R_p) was expresed by R_p = k[AIBN]^0.54[α-MBL]^1.1 and the overall activation energy was calculated as 76.1 kJ/mol. Kinetic constants for α-MBL polymerization were obtained as follows: k_p/k_t^1/2 = 0.161 L^1/2 mol^?1/2·s^?1/2; 2fk_d = 2.18 × 10^?5 s^?1. The relative reactivity ratios of α-MBL(M₂) copolymerization with styrene (r₁ = 0.14, r₂ = 0.87) were obtained. Applying the Q–e scheme led to Q = 2.2 and e = 0.65. These Q and e values for α-MBL are higher than those for MMA     

Polymerization of α-methyleneindane: A cyclic analog of α-methylstyrene

α-Methyleniedane (MI), a cyclic analog of α-methylstyrene which does not undergo radical homopolymerization under standard conditions, was synthesized and subjected to radical, cationic, and anionic polymerizations. MI undergoes radical polymerization with α,α′-azobis(isobutyronitrile) in contrast to α-methylstyrene, owing to its reduced steric hindrance, though the polymerization is slow even in bulk. Cationic and anionic polymerization of MI with BF₃OEt₂ and n-butyllithium, respectively, proceed rapidly. The thermal degradation behavior of the polymer depends on the polymerization conditions. The anionic and radical polymers are heteortactic-rich. Reactivity ratios in bulk radical copolymerization on MI (M₂) with methacrylate (MMA, M₁) were determined at 60°C (r₁ = 0.129 and r₂ = 1.07). In order to clarify the copolymerization mechanism, radical copolymerization of MI with MMA was investigated in bulk at temperatures ranging from 50 to 80°C. The Mayo–Lewis equation has been found to be inadequate to describe the result due to depolymerization of MI sequences above 70°C.     

Radical reactivity of α-trifluoromethylstyrene

α-Trifluoromethylstyrene (TFMST) does not undergo radical homopolymerization with azobis(isobutyronitrile) (AIBN) in bulk at 60°C. Low-temperature initiation was not effective either. Radical copolymerization of TFMST (M₂) with styrene (ST, M₁) has yielded monomer reactivity ratios as follows: r₁ = 0.60 and r₂ = 0.00. It has been found that the cyclohexyl radical generated by reaction of cyclohexylmercuric chloride with sodium borohydride adds to the β-carbon of TFMST 7.5 times faster than that of ST. Combination of the copolymerization analysis and the “mercury method” has allowed us to estimate Alfrey–Price Q and e parameters for TFMST to be 0.43 and 0.90, respectively. Thus, due to the strongly electron-withdrawing effect of the trifluoromethyl group, this styrene is highly electron deficient. In spite of the favorable electronic effect, however, the ceiling temperature appears very low, presumably due to the steric hindrance.     

Spontaneous alternating copolymerization of N-phenylmaleimide with ethyl α-phenylacrylate

The spontaneous copolymerization of N-phenylmaleimide (NPMI) (M₁) with ethyl α-phenylacrylate (EPA)(M₂) were carried out in dioxane at 85°C. A high alternating tendency was observed. The monomer reactivity ratios were r₁ = 0.07 ±0.01 and r₂ = 0.09 ± 0.02. The maximum copolymerization rate and molecular weight occurs at 70–80 mol% (M₁) in feed ratio. The spontaneous alternating copolymerization is considered to be carried out via a contact-type charge transfer complex (CTC) formed between the monomers. Thermogravimetric analyses (TGA) indicate the resulting copolymers have high thermal stability. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2927–2931, 1998     

Orthomanganated arenes in synthesis VII. Transition-metal mediated formation of a P?P bond; the X-ray crystal structure of Mn2(μ-η1, η1-Ph2PPPh2)(μ-Cl)2(CO)6

The reaction of PPh₂Cl with orthomanganated acetophenone, 2′-CH₃C(O)C₆H₄Mn(CO)₄, gives Mn₂(μ-η₁,η¹-Ph₂PPPh₂)(μ-Cl)₂(CO)₆. An X-ray structure determination [triclinic, space group P1 , a = 10.908(4) Å, b = 11.756(3) Å, c = 12.186(3) Å, α = 96.20(2)°, β = 99.51(2)°, γ = 96.52(2)°] shows two Mn(CO)₃ groups held together by two bridging Cl ligands, and further bridged by a Ph₂P? PPh₂ group prepared in situ.