Thermal degradation and stability of poly(4-vinylpyridine) homopolymer and copolymers of 4-vinylpyridine with methyl acrylate

The thermal stability and degradation behaviour of poly(4-vinylpyridine) (PVP) homopolymer and copolymers of 4-vinylpyridine and methyl acrylate (VP-MA) have been investigated. The reactivity ratios in the copolymerization were determined using an NMR method. The apparent activation energies of the degradation of the homopolymers and copolymers were calculated using the Arrhenius equation.     

Poly(4-vinylpyridine) catalyzed hydrolysis of methyl bromide to methanol and dimethyl ether

The hydrolysis of methyl bromide with neutral water is performed in the presence and absence of various amines in a batch reactor at different temperatures (50–125 °C). Screening of poly(4-vinylpyridine) as a potential reusable solid amine catalyst showed maximum efficiency. This significant enhancement in efficiency is due to the capture of HBr by solid PVP and remains phase-separated driving the reaction forward. The major advantage of this process is that the polymer can be easily regenerated and reused without loss of activity making it a very effective catalyst for the conversion of methyl halides to methanol and dimethyl ether.     

Poly(4-vinylpyridine) catalyzed selective methanolysis of methyl and methylene bromides

The effect of poly(4-vinylpyridine) (PVP) on the methanolysis of methyl bromide and methylene bromide was studied at temperatures between 75 °C and 125 °C. PVP acts as an efficient HBr scavenger promoting the formation of dimethyl ether (DME) and dimethoxymethane (DMM) from the corresponding bromomethanes and methanol in moderate yields with high selectivity. No reaction was observed in the absence of PVP under the conditions adopted. The activity of the catalyst remained unchanged even after five cycles showing the efficacy and application of the polymer as an environmentally green reagent as well as catalyst in this methanolysis reaction.     

Conjugate addition of chiral lithium methyl[o(cyclohexyldimethylaminomethyl)phenyl]cuprate to methyl 3-phenyl-2-propenoate and 4-phenyl-3-buten-2-o

Chiral lithium methyl[o-(cyclohexyldimethylaminomethyl)phenyl]cuprate reacts with methyl 3-phenyl-2-propenoate and 4-phenyl-3-buten-2-one to give the conjugate addition products, viz. methyl 3-phenylbutanoate and 4-phenylpentan-2-one respectively. The reaction rates and chemical yields (30–60%) are lower than in corresponding reactions with lithium dimethylcuprate and lithium methyl[2-(1-dimethylaminoethyl)phenyl]cuprate respectively. Lithium halides in the reaction favour the formation of one enantiomer. The highest asymmetric induction obtained is 4.4%.     

The addition of methyl radicals to hexafluoroacetone

The reaction of methyl radicals (Me) with hexafluoroacetone (HFA), generated from ditertiary butyl peroxide (dtBP), was studied over the temperature range of 402–433 K and the pressure range of 38–111 torr. The reaction resulted in the following displacement process taking place: where TFA refers to trifluoroacetone. The trifluoromethyl radicals that were generated abstract a hydrogen atom from the peroxide: such that k_6a is given by: where θ = 2.303RT kcal/mol. The interaction of methyl and trifluoromethyl radicals results in the following steps: Product analysis shows that k₁₇/kk = 2.0 ± 0.2 such that k₁₇ = 10^10.4±0.5M^?1 · s^?1. The rate constant k₅ is given by: It is concluded that the preexponential factor for the addition of methyl radicals to ketones is lower than that for the addition of methyl radicals to olefins.     

The addition of methyl radicals to tetrafluoroethylene

The addition of methyl radicals to tetrafluoroethylene in the gas phase has been studied over the temperature range 80–180°C, using a material balance method. Arrhenius parameters of 10^11.95±0.23 (mole^?1 cm³ sec^?1) and 5.7 ± 0.4 (kcal/mole) have been measured for the addition reaction. Electrophilic reagents such as O or CF₃ appear to react almost equally readily with ethylene and tetrafluoroethylene but methyl radicals add much more rapidly to tetrafluoroethylene than to ethylene, the difference in reactivity being principally due to an activation energy difference of ～2 kcal/mole.     

The addition of methyl radicals to hexafluoropropylene

The addition of methyl radicals to hexafluoropropylene has been studied over the temperature range 81°–203°C using a mass-balance technique involving the photolysis of biacetyl in the presence of hexafluoropropylene–isobutane mixtures. For the reaction the rate constant is given by the equation The result suggests that methyl radicals are very unselective in their behavior reacting with tetrafluoroethylene and hexafluoropropylene at similar rates. This is in marked contrast to the behavior of oxygen atoms with these olefins.     

Homolytic addition of xylenes to methyl acrylate

Conclusions The homolytic addition of the isomeric xylenes to methyl acrylate, initiated by tertbutyl peroxide, was accomplished. The yields of the adduct decrease in the order: meta>ortho>para.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2360–2362, October, 1977.     

Facile retro diels-alder reaction of a vinyl lithium compound

Attempts to generate benzobarrelyne 8 by loss of lithium chloride from 4 resulted in a facile retro Diels-Alder reaction of the “dimeric” adduct formed by addition of 4 to 8.     

Diastereoselective addition of enantiopure lithium tert-butylsulfinylferrocene to imines

(S)-tert-Butylsulfinylferrocene was submitted to ortho-metalation, and the corresponding lithium derivative was trapped by alkyl or aryl imines bearing various electron-withdrawing groups on the nitrogen atom (Ts, Dpp, Boc). New aminosulfoxides were obtained with complete diastereocontrol when Dpp or Boc groups were used. The absolute configuration (SS,SFc,S) has been determined by single-crystal X-ray analysis and chemical correlation. An unusual pseudocyclic boatlike transition state has been proposed to explain the stereochemical course of this reaction.     

Ligand-mediated enantioselective addition of lithium carbazolates to aldehydes

The enantioselective synthesis of acyclic pyrrole, indole and other N-carbazole carbinols via ligand-mediated addition of lithium carbazolates to aldehydes, together with studies into their catalytic enantioselective synthesis using substoichiometric base and ligand, are reported. The subsequent exploitation of the resulting stereocentre as a controlling element in 1,3-syn- and anti-selective reduction of beta-ketones and elaboration to homoallylic alcohols is also described.     

Methyl radical addition to methyl ethyl ketone

From relative rates of acetone formation in the azomethane sensitized decomposition of methyl ethyl ketone at 290 °C, log₁₀(k/cm³mol^–1s^–1)=5.3±0.4 for the methyl radical addition to methyl ethyl ketone has been determined.

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290°C, , . lg₁₀(^{3 –1–1})=5,3±0,4.

     

Facile radical trifluoromethylation of lithium enolates

[reaction: see text] Highly basic lithium enolates are shown to be applicable to radical trifluoromethylation. The reaction is extremely fast, and the minimum reaction time is approximately 1 s.     

Facile synthesis of D,L-phosphinothricin from methyl 4-bromo-2-phthalimidobutyrate

Synthetic versatility of the title bromide is illustrated by simple preparations of D,L-phosphinothricin, D,L-2-amino-4-phosphonobutyric acid, and aminocyclopropanecarboxylic acid.     

Facile fabrication of porous pure and Ag nanoparticle-doped poly(4-vinylpyridine) films at the liquid-liquid interfaces

We reported an interfacial self-assembly of regularly layered porous poly(4-vinylpyridine)(P4VP) films at the interfaces of water-chloroform or -dichloroethane.The porous diameters were in the range from hundred nanometers to several micrometers.It was revealed that formation of such kind of porous materials was solvent dependent.Moreover,cyclic Ag nanoparticles could be grown in the porous P4VP films to form Ag-P4VP nanohybrids under radiation.     

A solid lithium electrolyte via addition of lithium isopropoxide to a metal-organic framework with open metal sites

The uptake of LiO(i)Pr in Mg(2)(dobdc) (dobdc(4-) = 1,4-dioxido-2,5-benzenedicarboxylate) followed by soaking in a typical electrolyte solution leads to the new solid lithium electrolyte Mg(2)(dobdc)·0.35LiO(i)Pr·0.25LiBF(4)·EC·DEC (EC = ethylene carbonate; DEC = diethyl carbonate). Two-point ac impedance data show a pressed pellet of this material to have a conductivity of 3.1 × 10(-4) S/cm at 300 K. In addition, the results from variable-temperature measurements reveal an activation energy of just 0.15 eV, while single-particle data suggest that intraparticle transport dominates conduction.