Radical polymerization of allyl alcohol and allyl acetate

Monoallyl compounds are not readily homopolymerized by a conventional free‐radical mechanism. However, the polymerization of allylbiguanide hydrochloride was reported to proceed in a concentrated solution of hydrochloric or phosphoric acid in the presence of a radical initiator. Here we have studied the polymerization of allyl alcohol by a radical initiator in the presence of a Lewis acid (ZnCl₂, CuCl₂ or MgCl₂) in an organic solvent (toluene, hexane, methanol or isopropanol). Reactions were performed either at room temperature or 50°C under an atmosphere of nitrogen or in a sealed tube. The same polymerization was also carried out in water and in a concentrated acid solution. The polymer product was purified by dialysis in 0.2–3.7% yield and confirmed by elemental analysis, infrared spectroscopy and ¹H NMR. The molecular weight range of poly(allyl alcohol) was 10,000–35,000. The polymerization of allyl acetate by the radical initiator under the above conditions gave poly(allyl acetate) with the molecular weight range of 10,000–13,800 by multi‐angle laser light scattering. Copyright © 2007 John Wiley & Sons, Ltd.     

Linear polymers of allyl acrylate and allyl methacrylate

Allyl acrylate and allyl methacrylate were polymerized by anionic initiators to soluble linear polymers containing allyl groups in the pendant side chains. The pendant unpolymerized allyl groups of the resulting linear poly(allyl acrylates) were shown to be present by: (1) the disappearance of the acrylyl and methacrylyl double bond absorptions in the infrared spectra in the conversions of monomers to polymers; (2) postbromination of the allyl bonds in the linear polymer; (3) the disappearance of the allyl groups absorptions in the infrared spectra of the brominated linear polymers; and (4) the thermal- and radical-initiated crosslinking of the linear polymers through the allyl groups. Allyl acrylate and allyl methacrylate show great reluctance to copolymerize with styrene under anionic initiation, but copolymerize readily with methyl methacrylate and acrylonitrile. Block copolymers were prepared by reacting allyl methacrylate with preformed polystyrene and poly(methyl methacrylate) anions. The linear polymers and copolymers of allyl acrylate may be classified as “self-reactive” polymers which yield thermosetting polymers. Bromination of the linear polymers offers a convenient method of producing self-extinguishing polymers.     

Kinetics and mechanisms of the allyl + allyl and allyl + propargyl recombination reactions

The kinetics and mechanisms of the self-reaction of allyl radicals and the cross-reaction between allyl and propargyl radicals were studied both experimentally and theoretically. The experiments were carried out over the temperature range 295-800 K and the pressure range 20-200 Torr (maintained by He or N(2)). The allyl and propargyl radicals were generated by the pulsed laser photolysis of respective precursors, 1,5-hexadiene and propargyl chloride, and were probed by using a cavity ring-down spectroscopy technique. The temperature-dependent absorption cross sections of the radicals were measured relative to that of the HCO radical. The rate constants have been determined to be k(C(3)H(5) + C(3)H(5)) = 1.40 × 10(-8)T(-0.933) exp(-225/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.088) and k(C(3)H(5) + C(3)H(3)) = 1.71 × 10(-7)T(-1.182) exp(-255/T) cm(3) molecule(-1) s(-1) (Δ log(10)k = ± 0.069) with 2σ uncertainty limits. The potential energy surfaces for both reactions were calculated with the CBS-QB3 and CASPT2 quantum chemical methods, and the product channels have been investigated by the steady-state master equation analyses based on the Rice-Ramsperger-Kassel-Marcus theory. The results indicated that the reaction between allyl and propargyl radicals produces five-membered ring compounds in combustion conditions, while the formations of the cyclic species are unlikely in the self-reaction of allyl radicals. The temperature- and pressure-dependent rate constant expressions for the important reaction pathways are presented for kinetic modeling.     

Conformational study of allyl fluoride,allyl alcohol and allyl amine through the matrix-isolation technique

In a vibrational analysis of allyl compounds, which was made difficult because of autoassociation and conformational equilibrium, we have used the matr     

Catalyzed cross-coupling of allyl bromides with allyl tin reagents

The reaction of allyl bromides with allyl tin reagents, catalyzed by palladium or zinc chloride gives cross-coupled products without allylic transpostion in the allyl halide partner but with predominate allylic rearrangement from the tin partner.     

Gas-phase thermolysis of sulfur compounds. Part VIII. Chloromethyl allyl,cyanomethyl allyl, 1-cyanoethyl allyl and neopentyl allyl sulfides

The pyrolyses of four alkyl allyl sulfides with substituents on the α? C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: Cyanomethyl allyl sulfide: 1-cyanoethyl allyl sulfide: Neopentyl allyl sulfide: The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1–5 α? H atom shift is assisted by its acidic character.     

Gas-phase thermolysis of allyl propargyl amine,allyl cyanomethyl propargyl amine,allyl propargyl 2-thiapropyl amine,and allyl methanesulfonyl propargyl amine

The title amines have been pyrolyzed in a stirred-flow reactor, at temperatures of 360–500°C, pressures of 7–16 torr, and residence times of 0.5–2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7–1.6. The amines with CH₂CN and SO₂CH₃ substituents also formed HCN and SO₂. These appear to arise from complex free radical decomposition of the imine product. The first-order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine: Allyl cyanomethyl propargyl amine: Allyl propargyl 2-thiapropyl amine: Allyl methanesulfonyl propargyl amine: Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.     

Conformations and vibrational spectra of allyl isocyanate and allyl isothiocyanate

The infrared spectra of allyl isocyanate and allyl isothiocyanate as vapours and liquids were recorded in the region 4000-50 cm^?1. Additional spectra of the amorphous and crystalline solids at ?180°C were recorded between 4000 and 400 cm^?1. p]Raman spectra, including semiquantitative polarization measurements were obtained of the liquids, and spectra of the unannealed as well as of the crystalline solids at ?180°C were recorded.A considerable simplification of the vibrational spectra of the crystals compared to the liquids was observed as a consequence of the conformational equilibria in these compounds. It can be concluded with confidence that a cis conformation of the allyl group was present in the crystals of both compounds with additional gauche conformers in the liquids. No definite conclusions can be reached regarding the conformational arrangement of the -NCX groups. A remarkable similarity was observed between the spectra of the two compounds, and all the fundamental frequencies except the lowest C-N torsion have been assigned for the cis conformers. More than ten fundamentals for the gauche conformers have also been assigned.     

Generation of allyl Grignard reagents via titanocene-catalyzed activation of allyl halides

A protocol for the generation of allyl Grignard reagents via the catalytic activation of allyl halides is described herein. Subsequent nucleophilic addition to carbonyl derivatives provided the desired homo allylic alcohols in excellent yields (84-99%). Evidence suggests that titanocene dichloride catalyzes the formation of an allyl Grignard species which reacts solely with the carbonyl electrophile as evidenced by the complete absence of Würtz coupling. This methodology will have wide-ranging applicability in the generation of highly reactive organometallic reagents.     

Transition metal-free tandem pyridinyl–allyl–allyl cross-coupling reaction

A transition metal-free, direct one-pot domino allylation reaction of 2-pyridinyl Grignard reagents with polysubstituted allyl chlorides for the regioselective synthesis of pyridinyl-substituted 1,5-diene derivatives has been disclosed. The reaction presumably proceeded through the coupling of polysubstituted allyl chloride to 2-PyMgX, which was in situ generated from 2-bromopyridine with i-PrMgCl·LiCl.     

含长叶烯结构硫氰酸烯丙酯和异硫氰酸烯丙酯的合成

研究ω-氯甲基长叶烯与不同硫氰酸盐的取代反应,选择性合成了含长叶烯结构的ω-硫氰甲基长叶烯和ω-异硫氰甲基长叶烯,采用FTIR、UPLC-QTOF/MS、1H NMR和13C NMR对产物进行结构表征.结果 表明,硫氰酸盐类型和反应体系对产物的选择性有较大影响.在60℃加热搅拌条件下,硬酸型阳离子K+、Na+和NH4+...     

Reaction of polyfluoroarenesulfonyl bromides with allyl bromide. Synthesis of allyl polyfluoroaryl sulfones

Reactions of polyfluoroarenesulfonyl bromides 4-XC₆F₄SO₂Br (X = F, H, Cl, Br, CF₃) with allyl bromide gave 84–94% of the corresponding allyl polyfluoroaryl sulfones.     

Experimental and theoretical studies on the isomerization of allyl thiocyanate to allyl isothiocyanate

The mechanism of isomerization of allyl thiocyanate to allyl isothiocyanate has been investigated both experimentally and theoretically. The kinetic study indicates that the reaction is unimolecular and is not ionic. The entropy of activation suggests strongly that the mechanism involves a cyclic transition state. The rate of reaction was retarded to a small extent in polar solvents relative to that in nonpolar solvents. Ab initio MO calculations indicate, in agreement with the experimental results, that the reaction proceeds through a cyclic transition state, one in which the SCN moiety is almost linear. Thus, this is a [3,3] sigmatropic rearrangement. The charge separation in the transition state was substantial. The retardation of the reaction in polar solvents was attributed to the difference in solvation in the original state and in the transition state. © 1997 John Wiley & Sons, Inc.     

The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm

The photodissociation of allyl iodide (C3H5I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C3H3+. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*(2P(1/2)) is more important than previously suspected.     

Polymerization of allyl phenyl ether

Allyl phenyl ether polymerized rapidly and quantitatively to a resin with a structure similar to a phenolic thermoset in the presence of boron trifluoride etherate at 50°C. The structure and properties of this polyphenol were studied. A reaction mechanism involving rearrangement was discussed.     

Catalyzed hydroboration of allyl sulfonamides

The hydroboration of allyl sulfonamides (4-H₃CC₆H₄SO₂NRCH₂CH=CH₂: R=H, 1; Ph, 2; Bz, 3) with catecholborane (HBcat) using different rhodium catalysts has been examined using multinuclear NMR spectroscopy. Reactions give complex product distributions, regardless of the choice of catalyst, arising from a competing isomerization reaction. This isomerization reaction can be used with N-substituted allyl sulfonamides 2 and 3 to give the corresponding enamines (4-H₃CC₆H₄SO₂CH=CH₂CH₃), which in turn react with HBcat to give regioselective formation of one isomer (4-H₃CC₆H₄SO₂NRCH₂CH₂(Bcat)CH₃).