Polymerization of α,β-unsaturated carbonyl monomers initiated by 9-borabicyclo [3.3.1] nonane

9-Borabicyclo[3.3.1]nonane (9-BBN) initiated the polymerization of α,β-unsaturated carbonyl monomers such as ethyl acrylate (EA) without an oxidant at low temperatures (to −90°C) under argon. Hydroquinone and 2,6-di-tert-butyl-p-cresol had little effect on the polymerization, indicating that the propagating chain end is not a free radical. The rate of polymerization was found to be proportional to [9-BBN]^1.0 and [EA]^1.5. Electron spin resonance measurements using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap showed the absence of any radical species under polymerization conditions. No copolymerization of EA with styrene occurred. On the basis of the results obtained, this polymerization was assumed to proceed via a non-radical mechanism.     

Radiation-induced copolymerization of α,β,β-trifluoroacrylonitrile with α-olefin

Homopolymerization and copolymerization of α,β,β-trifluoroacrylonitrile (FAN) with γ-olefins were carried out in bulk by γ-ray irradiation at 25°C. FAN gives very small quantities of brown and greasy low molecular weight polymer. Cyano groups in FAN polymer were found to be readily hydrolyzed to acid amide groups in the atmosphere. FAN was found to copolymerize with ethylene, propylene, and isobutylene via a radical mechanism to form equimolar copolymers in a wide range of monomer compositions. The polymerization rate increases linearly with FAN fraction in the monomer mixture. These copolymers are also hydrolyzed in the atmosphere, and the hydrolysis proceeds with more difficulty for the copolymer with higher α-olefin. The reactivity ratios r₁ (FAN) and r₂ (α-olefin) were determined to be 0.01 and 0.12 for the FAN/ethylene copolymerization and 0.01 and 0.07 for the FAN/propylene copolymerization. These results confirm that an alternating copolymerization takes place in the FAN/α-olefin system.     

Synthesis of α, α′, β-trideuterovinyl acetate

Reaction conditions for the synthesis of α, α′, β-trideuterovinyl acetate by the continuous vapour phase catalytic reaction of deuteroacetylene and acetic acid-d (CH₃COOD) are described.     

Poly(α,α,α′,α′-tetrafluoro-p-xylylene)

Poly(α,α,α′,α′-tetrafluoro-p-xylylene) was prepared by the pyrolysis of cyclo-di-(α,α,α′,α′-tetrafluoro-p-xylylene) and by the pyrolysis of α,α′-bis(alkylsulfonyl)-α,α,α′,α′-tetrafluoro-p-xylene. The pyrolysis of α,α′-dibromo-α,α,α′,α′-tetrafluoro-p-xylylene also gave the polymer, but the method is less satisfactory. Poly(α,α,α′,α′-tetrafluoro-p-xylylene) shows remarkable thermal and oxidative stability at elevated temperatures. Useful mechanical and electrical properties are retained after aging for 3000 hr at 250° in air. After initial change due to crystallization, tensile strength remains near 10,000 psi, elongation above 5%, and dielectric constants and dissipation factors at approximately 2.4 and .001, respectively.     

Synthesis and characterization of phenolic and amino resins based on α, β-unsaturated aldehydes

Phenolic and amino resins on the basis of α,β-unsaturated aldehydes were synthesized in bulk or solution. Catalysts were HCl, H₃PO₄, or formic acid, and in some cases NaOH. The course of the reactions was followed by GPC and NMR while the structure of the reaction products was determined by one- and two-dimensional NMR. The course of the reactions is influenced by experimental conditions: the type of monomers, their molar ratio, the type and quantity of the catalyst, the reaction time and temperature, and the reaction medium. At the beginning of the reaction the addition of a nucleophile to an aldehyde takes place through parallel 1,2-addition to and 1,4-addition to group. Oligomers with ? OH, , and ? CHO functional groups are able to add new monomer units or to react mutually to form higher molecular weight addition and condensation products. The overall rate constants for the beginning of the reactions were between 10^?3 L/mol s for the high reactive mixtures and 10^?7 L/mol s for the less reactive mixtures. The resins were cured by heating at temperatures above 135°C with the addition of hexamethylenetetramine.     

β-Ketoester — a Rearranged Product of Epoxidation of α, β-Unsaturated Methyl Ester

Attempted epoxidation of long-chain α,β-unsaturated esters resulted in the formation of the rearranged products of the corresponding epoxyesters. It was observed that reaction of peracids with esters of C₁₆, C₁₈ and C₂₂ trans-2-enoic acids, instead of yielding the expected epoxides, gave the isomerized products characterized as β-ketoesters. The structure of β-ketoester as saturated 3-oxoester was unambiguously established by chemical methods as well as by IR, NMR and Mass spectrometry. The selectivity of this rearrangement provides a useful synthetic pathway for the preparation of β-ketoesters.     

Selectivity aspects in the multi-phase hydrogenation of α,β-unsaturated aldehydes over supported noble metal catalysts: Part I

The selective hydrogenation of cinnamaldehyde and other unsaturated aliphatic aldehydes under a two-phase liquid system using toluene and aqueous alkaline solution over supported palladium catalysts has been investigated with a view to obtaining the corresponding saturated aldehydes with sufficiently high selectivities. In the case of cinnamaldehyde, the effects of various process parameters on the reaction rate and selectivity with respect to the aldehyde have been investigated. The results obtained are likely to be useful for the rational design of the process for the production of industrially relevant products, such as hydrocinnamaldehyde and citronellal using cinnamaldehyde and citral as the starting materials.     

Selectivity aspects in the multi-phase hydrogenation of α,β-unsaturated aldehydes over supported noble metal catalysts: Part II

The hydrogenation of cinnamaldehyde to cinnamyl alcohol over a platinum on carbon catalyst could be intensified and made more selective in a two-phase system using toluene and aqueous alkaline solution. Enhancement in the selectivity with respect to citronellol was noticed in the two-phase hydrogenation of citronellal, while the reaction rate was marginally affected. Potassium hydroxide and sodium hydroxide were found to be efficient promoters.     

Photochemistry of α,α′-Disubstituted Azoalkanes. I. Photosolvolytic Inversion and Substitution of α,α′-Dichloro- and α,α′-Dialkoyloxyazoalkanes

A series of α,α′-dichloro (α DClA), α,α′-dialkoyloxy- (αDAlA) and α,α′-dibenzoxy-azoalkanes (αDBeA) without α-aryl substituents was found to undergo meso ? dl photointerconversion upon direct irradiation through Pyrex in the presence of oxygen in a number of solvents. Furthermore, irradiation of α,α′-dipropionoxy-azoalkanes in benzene in the presence of excess acetic acid leads to substitution of the propionoxy groups by acetoxy groups in addition to meso ? dl photointerconversion. Similar irradiation in the presence of CH₃CO₂D does not lead to deuterium substitution of the β-hydrogens. The presence of benzenethiol radical scavenger does not affect the course of these photoreactions. Photosolvolysis schemes involving heterolysis (in the case of αDAlA and αDBeA) or an unstable intermediate (in the case of αDClA) are proposed.     

Lewis acid induced additions to unsaturated fatty compounds IV: Synthesis of cyclopentenones from Friedel- Crafts acylation products of unsaturated fatty compounds with α,β-unsaturated acyl chlorides

The ethylaluminium dichloride induced Friedel- Crafts acylation of unsaturated fatty compounds such as oleic acid ( 1a ), methyl oleate ( 1b ) and 10-undecenoic acid ( 9b ) and furthermore of 1-octene ( 9a ) with α,β-unsaturated acyl chlorides e.g. crotonic acid chloride ( 2a ) and acrylic acid chloride ( 2b ) gave the corresponding allyl vinyl ketones. Nazarov cyclizations of the acylation products 3a/4a, 3b/4b, 10a and 10b afforded the alkyl substituted 2-cyclopentenones 5a/6a, 5b/6b, 11a/12a and 11b/12b . Catalytic hydrogenation of 5b/6b and 11b/12b gave the respective saturated cyclic products 7b/8b and 13b/14b as diastereomeric mixtures.     

Polymer precursor to diamondlike carbon prepared by the polymerization of α,α,α‐trichlorotoluene and acetonitrile

A novel liquid/solid two‐phase reaction of α,α,α‐trichlorotoluene (PhCCl₃) and acetonitrile (AN) has been discovered that produces a carbon‐based polymer with diamondlike structure at the atomic level. The solid phase is potassium hydroxide particles, and the liquid phase is a tetrahydrofuran solution of PhCCl₃ and AN containing a certain amount of tetrabutylammonium bromide as a phase‐transfer catalyst. The structure of the carbon‐based polymer has been characterized by elemental analysis, Fourier transform infrared spectroscopy, and ¹H‐ and ¹³C‐NMR spectroscopy. The pyrolysis of the carbon‐based polymer at 800°C under a nitrogen atmosphere leads to the formation of a diamondlike carbonaceous material according to the results of X‐ray photoelectron spectroscopy and Raman spectroscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 16–23, 2003     

Photosensitive polymers: Synthesis,characterization, and photocrosslinking properties of polymers with pendant α,β-unsaturated ketone moiety

Acrylate and methacrylate monomers with the photodimerizable α,β-unsaturated ketone moiety, such as 4-cinnamoylphenyl, 4-(4-methoxycinnamoyl)phenyl, 4-(4-nitrocinnamoyl)phenyl, or 4-(4-chlorocinnamoyl)phenyl, were prepared and homopolymerized using benzoyl peroxide as the initiator at 70°C in methyl ethyl ketone. The poly(meth)acrylates were characterized by ultraviolet, infrared, ¹H-nuclear magnetic resonance (NMR), and ¹³C-NMR spectra, and gel permeation chromatography. Their thermal properties were studied by thermogravimetric analyses in air and nitrogen, and differential scanning calorimetry. The photocrosslinking properties of the polymers were investigated as thin films and in solution in the presence and absence of sensitizer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2111–2120, 1998     

Heck Arylation of α,β‐Unsaturated Aldehydes

The Heck arylation of α,β‐unsaturated aldehydes is strongly dependent on the catalyst, the solvent and the base. Optimized conditions yielded either selectively cinnamyl derivatives (83%) or double arylation products (88% based on aryl conversion). A new α‐arylation of β,β‐disubstituted acrolein is also realized.     

Influence of isomer ratio and ring substituents in decomposition activation energies of α,α,α′,α′‐tetrasubstituted dibenzyls

Diethyl‐2,3‐dicyano‐2,3‐di‐(X‐substituted phenyl) succinates (X = p‐OCH₃, p‐CH₃, p‐Cl, H, p‐NO₂) can initiate the free‐radical polymerization of styrene. The decomposition rate constant and activation energy were measured by means of a dilatometer, and the results showed that they were strongly dependent on the ratio of meso‐ and dl‐isomers in the polysubstituted dibenzyl compounds and the properties of the ring substituents. On the other hand, it was found that the polystyrenes, which were obtained by initiation with hydrogen, had a much larger average molecular weight than that with p‐OCH₃ and p‐CH₃. The experimental phenomena were correlated with the structure of the radical resulting from hydrogen. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2964–2971, 2001     

Chemoselective Hydrogenation of α,β‐Unsaturated Nitriles

The chemoselective hydrogenation of cinnamonitrile to 3‐phenylallylamine proceeds with up to 80% selectivity at conversions of >90% with Raney cobalt and up to 60% selectivity with Raney nickel catalysts. Best results were obtained with a doped Raney cobalt catalyst (RaCo/Cr/Ni/Fe 2724) in ammonia saturated methanol at 100 °C and 80 bar. Major problems are the formation of hydrocinnamonitrile and of secondary amines, and overreduction to 3‐phenylpropylamine. Important parameters are the catalyst type and composition, the solvent type and the presence and concentration of ammonia. The catalytic system tolerates functional groups like OH, OMe, Cl, CO, but not aromatic nitro groups. Preliminary experiments indicate that other unsaturated nitriles with di‐ or trisubstituted CC bonds are also suitable substrates.     

Reactions with the arylhydrazones of some α,β-diketoesters

Treatment of the α, β-diketo-ester-α-arylhydrazones 1a–e and 2a–d with GRIGNARD reagents results in the formation of the ketocarbinols 3a–h and 4a–g , respectively. The arylhydrazones of ethyl mesoxalate 5a–e react with phenylmagnesium bromide to yield compounds 3a–e . A novel synthesis of α-arylazo-β-arylchalcones 6a–e and their reaction with hydrazines are reported. Whereas the arylhydrazones 10a, b, 2a, b, d, 13a–c and 14a–c react with piperidine and formaldehyde to yield the MANNICH bases 11a, b, 12a–c and 15a–c , compound 5a was recovered unchanged.