The polymerization of acrylates using a combination of a carbonyl compound and an amine as a photo-initiator system

Photo-initiator systems for the polymerization of acrylates, based on a mixture of an aryl ketone and an α,ω-diaminoalkane, have been investigated. Rate constants for the photoreduction of fluorenone by α,ω-diaminoalkanes have been evaluated: it was found that CH₃N groups are more relative than CH₃CH₂N groups. The relative rates of photo-oxidation of α,ω-diaminalkanes sensitised by benzophenone have been determined. Surprisingly, little correlation exists between the susceptibility of an amine towards oxidation and its ability to reduce excited carbonyl groups. Several mixtures composed of an aryl ketone and an α,ω-diaminoalkane were found to initiate the polymerization of methyl methacrylate. The efficiency of initiation appears to be related to the efficiency of reaction of the triplet carbonyl compound with the amine. The efficiency of a particular combination of an aryl ketone and an amine to cure films of acrylate oligomers is also governed to some extent by the efficiency of reaction of the triplet carbonyl compound with the amine. However, the structure of the amino alkyl radical produced in the initiation reaction appears to be of greater importance in determining the efficiency of polymerization. Radicals of the type R₂N?HCH₂OR were found to be highly efficient.     

Targeted synthesis of macrodiolides containing bis-methylene-separated Z-double bonds and their antitumor activity in vitro

An original strategy has been developed for the synthesis of valuable unsaturated macrocyclic lactones, macrodiolides, containing a 1Z,5Z-diene moiety in 57–79% yields and >98% stereoselectivity by hafnium triflate Hf(OTf)₄-catalyzed intermolecular esterification of aliphatic α,ω-dicarboxylic acids with α,ω-alka-nZ,(n+4)Z-dienediols (1,12-dodeca-4Z,8Z-dienediol, 1,14-tetradeca-5Z,9Z-dienediol, 1,18-octadeca-7Z,11Z-dienediol). The diols were obtained by homo-cyclomagnesiation of tetrahydropyran ethers of oxygenated 1,2-dienes with EtMgBr in the presence of Mg metal and Cp₂TiCl₂ catalyst (10?mol. %). The resulting macrodiolides exhibit high cytotoxic activity in vitro against Jurkat, K562, U937, Hek293 and HeLa tumor cell lines.     

Molar heat capacity of binary liquid mixtures: 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane

The molar heat capacity at constant pressure, C_P, of the two binary liquid mixtures 1,2-dichloroethane + cyclohexane and 1,2-dichloroethane + methylcyclohexane were determined at 298.15 K from measurements of the volumetric heat capacity, C_P/V, in a Picker flow microcalorimeter (V is the molar volume). For the molar excess heat capacity, C_P^E, the imprecision of the adopted stepwise procedure is characterized by a standard deviation of about ± 0.05 J K^?1 mole^?1, which amounts to ca. 3% of C_P^E. Literature data on ultrasonic velocities, on molar volumes, and on coefficients of thermal expansion were used to calculate the molar heat capacity at constant volume, C_v, and the isothermal compressibility, β_T, of the pure substances, as well as the corresponding excess quantities C_V^E and (Vβ_T)^E of the binary mixture 1,2-dichloroethane + cyclohexane. A preliminary discussion of our results in terms of external and internal rotational behavior (trans-gauche equilibrium of 1,2-dichloroethane) is presented.     

An efficient multigram-scale synthesis of 4-(ω-chloroalkoxy)phenols

Efficient multigram two-step syntheses of 4-(2-chloroethoxy)phenol and 4-(3-chloropropoxy)phenol in >70% yields starting from 4-hydroxybenzaldehyde and reagents with general formula Cl(CH₂) _n X (X = Cl, n = 2; X = OTs, n = 3) are proposed. 4-(2-Chloroethoxy)phenol can also be conveniently prepared from 4-methoxyphenol and 1,2-dichloroethane. The compounds thus obtained can be used in carbohydrate chemistry to synthesize glycosides bearing "universal" 4-(ω-chloroalkoxy)phenyl aglycons.     

Formation of cyclic organosilicon compounds via organopolysilyl anions starting from methoxymethyldisilanes. A mechanistic study

In the presence of a catalytic amount of sodium methoxide, sym-dimethoxytetramethyldisilane was converted into α,ω-dimethoxypermethylpolysilanes, MeO(SiMe₂)_nOMe where n ? 3, at room temperature. On the other hand, similar treatment of the disilane in THF solution gave cyclic polysilanes, (Me₂Si)_n where n = 5–7. Decomposition of the disilane in the presence of diphenylacetylene afforded a trisilacyclopentene derivative under similar conditions. This compound was obtained also by the reaction between α,ω-dimethoxypermethylpolysilanes and diphenylacetylene in the presence of sodium methoxide. These cyclic products most likely were formed via permethyl polysilyl anion intermediates derived from α,ω-dimethoxypermethylpolysilanes. Also, the formation of α,ω-dimethoxypermethylpolysilanes could be elucidated in terms of the mechanism involving the base-assisted, concerted nucleophilic substitution or stepwise substitution by silyl anions, rather than the successive dimethylsilylene (Me₂Si:) insertion reaction.     

Long-chain α,ω-bisisothiocyanates from a marine sponge

Eighteen long-chain aliphatic α,ω-bisisothiocyanates were isolated from a marine sponge, Pseudaxinyssa sp. from Fiji. Eight compounds are di-, ten are monolefinic. Three additional constituents are α-isothiocyano-ω-formyl compounds.     

Catalytic reduction of NOx and oxidation of dichloroethane over α-MnO2 catalysts: Properties-Reactivity relationship

The reduction ability of NO to N₂ and the oxidation performance of 1,2-dichloroethane (DCE) over α-MnO₂ catalysts were investigated. The results show that α-MnO₂-3 exhibited the highest catalytic activity in 63.5 % conversion of NO_x reduction by C₃H₈ at 250 °C, and 80 % conversion of DCE combustion by O₂ at 338 °C. It is revealed the active phase of α-MnO₂-3 is tetragonal α-MnO₂ with the selectively exposed plane of (2 1 1). It was proposed the high DCE decomposition of α-MnO₂-3 was ascribed to the redox properties. The overall characterization results revealed that α-MnO₂-3 catalyst preserves more active sites of low valence Mn and higher surface adsorbed oxygen (O_ads) /lattice oxygen (O_latt) at the outermost layers, and lower reduction temperature in H₂-TPR profiles than that of other catalysts. Meanwhile, NH₃-TPD profile of α-MnO₂-3 also shows a large number of acid sites promote NO_x reduction.     

A new facile synthesis of α-dicarbonyl compounds by oxidation of alkynes with Mo(VI) peroxocomplex promoted by mercuric acetate

Mercuric acetate promoted oxidation of diaryl-, dialkyl-, and aralkyl alkynes with (HMPA)MoO(O₂)₂ in 1,2-dichloroethane affords the corresponding α-diketones in good yields. Likewise, terminal alkynes can be converted into α-ketoaldehydes in excellent yields by using the same oxidizing system.     

Synthesis of α,ω-bis-1,5,3-dithiazepanes and their fungicidal properties

A procedure was developed for preparative synthesis of α,ω-bis-1,5,3-dithiazepanes by heterocyclization of aliphatic α,ω-diamines with N,N,N′,N′-tetramethylmethanediamine and 1,2-ethanedithiol. The fungicidal activity of 1,2-bis(1,5,3-dithiazepan-3-yl)ethane and 3,3′-(3,6-dioxaoctane-1,8-diyl)bis-1,5,3-dithiazepane toward microscopic fungi affecting agricultural plants was studied.     

Der Gegenionen-Effekt bei der durch Perchlorsäure initiierten Polymerisation von Styrol

The effect of various counter-ions has been investigated in the cationic polymerisation of styrene in 1,2-dichloroethane at different temperatures (238 K, 253 K). The soluble silver salts of the corresponding acids HBF₄, HClO₄, HPF₆, HAsF₆, and HSbF₆ were added to the reaction medium before initiation by perchlorid acid. Monomer consumption is seen to be incomplete under these circumstances. Initial polymerisation rates and the final degree of monomer conversion rise with decreasing nucleophilicity of the counter-ions.A kinetic scheme is proposed which is able to describe the course of polymerisation and gives the approximate values of the rate constants for propagation, termination and chain transfer reactions, respectively. The information obtained from GPC-measurements on the polymeric products supports the view that chain propagation takes place by at least two different forms of active species, the ratio of which is strongly determined by the nature of the added silver salt.

     

Thermodynamic and spectroscopic evidence in binary mixtures of nonelectrolytes

Nigam, R.K. and Aggarwal, S., 1986. Thermodynamic and spectroscopic evidence in binary mixtures of nonelectrolytes. Fluid Phase Equilibria, 26: 181–200.Molar excess enthalpies H^E_m of 1,2-dichloroethane (1)+pyridine (2), + α-picoline (2),+n-hexane (2), +n-heptane (2), n-heptane (1)+pyridine (2), +α-picoline (2), +γ-picoline (2), aniline (1)+pyridine 92), +α-picoline (2) and +γ-picoline (2) mixtures have been measured calorimetrically at 298.15 and 308.15 K.The data have been examined in terms of the Lacombe and Sanchez theory and the graph theoretical approach. It was found that these were described better by the graph theoretical approach. The NMR studies on 1,2-dichloroethane (1)+α-picoline (2), aniline (1)+pyridine (2) and aniline (1)+γ-picoline (2) mixtures have also been used to lend credence to the nature and extent of interaction in these mixtures.     

[6π+2π]-Cycloaddition of α,ω-Diallenes and α,ω-Diacetylenes to 1,3,5-Cycloheptatriene in the Presence of TiCl4-Et2AlCl

[6π+2π]-Cycloaddition of α,ω-diallenes and α,ω-bis(trimethylsilyl)diacetylenes to 1,3,5-cycloheptatriene in the presence of a two-component catalytic system TiCl₄-Et₂AlCl was performed that led to the formation of bis(endo-bicyclo[4.2.1]nona-2,4-dienes) and bis(8-trimethylsilyl-endo-bicyclo[4.2.1]nona-2,4,7-trienes) linked by polymethylene spacer in 69–86% yields.     

Preparation of amphiphilic polyisobutylenes-b-polyethylenamines by mannich reaction. I. Synthesis and characterization of α-phenololigoisobutylenes

The cationic polymerization of isobutylene initiated by 4-(2-hydroxy-2-propyl)phenol/BCl₃ system results mainly in α-phenol-ω-chlorooligoisobutylene; however p-(2-chloro-2,4-dimethyl-4-pentyl)phenol is present in all cases. α-Methyl-ω-chlorooligoisobutylene is formed only when the temperature is below?50°C; it results from initiation by the phenol/BCl₃ system. Thermal dehydrochlorination of α-phenol-ω-chlorooligoisobutylene is quantitative and leads to a mixture of isomeric ω-unsaturated oligoisobutylenes. α-Methyl-ω-phenololigoisobutylene is prepared by the Friedel—Crafts reaction between industrial unsaturated oligoisobutylene and phenol in the presence of SnCl₄ at ?30°C; the reaction is quantitative between ?50 and ?30°C degradation takes place. © 1993 John Wiley & Sons, Inc.     

Solvent effects in copper(I)-mediated 5-endo cyclisation of secondary bromo-enamides

Secondary bromoenamides 5, 14-18, 32 and 33 undergo efficient 5-endo cyclisation reactions to give α,β-unsaturated monoene lactams 9, 19–23, 34 and 35 under atom transfer conditions mediated by CuBr and the tripyridylamine 6 in refluxing toluene (59–87%). Changing the solvent to refluxing 1,2-dichloroethane furnishes α,β-unsaturated diene lactams 26-31, 36, and 37 instead (42–86%).     

Synthesis of poly(silylenephosphonate)s incorporating 2-chloroethylphosphonic acid (ethephon), a stimulant for the latex production by the Hevea brasiliensis

2-Chloroethylphosphonic acid (ethephon) is a well-known stimulant commonly used to improve the latex production by the rubber tree (Hevea brasiliensis). In order to prolong its stimulating activity, the purpose was to insert ethephon inside polymer chains which, afterwards, will be able to degrade slowly through time, and thus to release ethephon molecules. For that, linear poly(silylenephosphonate)s incorporating ethephon groups were synthesized by using a polycondensation procedure between ethephon (or one of its dialkyl phosphonate derivatives) and an α,ω-dihalogeno-silylated monomer. To make sure that polycondensation can occur, the reactivity of halogenotrimethylsilanes (X=Cl or Br) toward ethephon and its various dialkyl phosphonate derivatives, was examined first. Then, poly(silylenephosphonate) synthesis was achieved by polycondensation between diisopropyl (2-chloroethyl)phosphonate and α,ω-dichloro-silylated monomers. According to this procedure, cyclic polymers of low average molecular weights (M_n<2000) were obtained, whatever the α,ω-dihalogeno-silylated monomer used.     

The emission of α,ω-diphenylpolyenes: A model involving several molecular structures

Available photophysical evidence for the emission of α,ω-diphenylpolyenes is shown to be consistent with a previously reported model [J. Catalán, J.L.G. de Paz, J. Chem. Phys. 124 (2006) 034306] involving two electronically excited molecular structures of 1B_u and C_s symmetry, respectively. The 1B_u structure is produced by direct light absorption from the all-trans form of the α,ω-diphenylpolyene in the ground state and its emission exhibits mirror symmetry with respect to the absorption of the compound. On the other hand, the C_s structure is generated from the 1B_u structure of the α,ω-diphenylpolyene by rotation about a C–C single bond in the polyene chain, its emission being red-shifted with respect to the previous one and exhibiting markedly decreased vibrational structure. At room temperature, both emissions give the excitation spectrum, which are ascribed to the first absorption band for the compound.     

Molar excess volumes of ternary mixtures of nonelectrolytes

Molar excess volumes V^E_ijk of methylenebromide i + pyridine j + β-picoline (k, cyclohexane (i) + pyridine (j) + β-picoline(K), benzene(i)+toluene(j)+1,2-dichloroethane(k), benzene(i) + 0-xylene(j) + 1,2-dichloroethane(k) and benzene(i) + p-xylene(j) + 1,2-dichloroethane(k) mixtures have been determined dilatometrically at 298.15 K. The data have been examined in terms of Sanchez and Lacombe theory and the graph-theoretical approach, and it is found that they are described well by the latter. Self- and cross-volume interaction coefficients V_jk, V_jjk and V_jkk, etc., have also been evaluated and the values utilised to study molecular interactions between the jth and kth molecular species in the presence of the ith in these i + j + k mixtures.     

Multicomponent reactions of amino alcohols with CH2O and dithiols in the synthesis of 1,3,5-dithiazepanes and macroheterocycles

A series of new hydroxyl-substituted 1,3,5-dithiazepanes and N,N′-(2-hydroxyethyl)tetrathiadiazacycloalkanes were synthesized by the multicomponent reactions ₍MCRs) of amino alcohols with formaldehyde and α,ω-dithiols. The MCR with 1,2-dithiol proceeds via a (1+2+1)-cyclocondensation with selective formation of 1,3,5-dithiazepanes. Stereochemistry of the dithiazepane ring was determined by X-ray diffraction. The reaction with higher α,ω-dithiols (1,3-propane-, 1,4-butane-, 1,5-pentane-, 1,6-hexanedithiol and 2-[2-(2-sulfanyletoxy)ethoxy]-1-ethanethiol) yielded OH-substituted macroheterocycles as a result of (2+4+2)-cyclocondensation. The structure of the latter was determined by NMR spectroscopy, MALDI–TOF and electrospray ionization methods. The doubly charged ions like [M+2H]²⁺ are found in the ESI spectra of the macrocycles.     

Intramolecular C-glycosylation of 2-O-benzylated pentenyl mannopyranosides: remarkable 1,2-trans stereoselectivity

The IDCP-promoted intramolecular C-glycosylation of pentenyl α-mannopyranosides carrying, at O-2, an activated benzyl group gave, unexpectedly, the 1,2-trans-fused bicyclic product which corresponds to an α-C-aryl mannopyranose derivative. This remarkable, strained C-glycosyl compound was rapidly epimerized to the more stable 1,2-cis product on treatment with BF₃·Et₂O. The IDCP-reaction product could be elaborated into a 2-(α-C-mannopyranosyl)-3,4,5-trimethoxybenzyl alcohol derivative.     

Excess enthalpies of the liquid systems: 1,2-dichloroethane + n-alkanes or +2,2,4-trimethylpentane

Hahn, G. Svejda, P. and Kehiaian, H.V., 1986. Excess enthalpies of the liquid systems: 1,2-dichloroethane + n-alkanes or +2,2,4-trimethylpentane. Fluid Phase Equilibria, 28: 309-323.Molar excess enthalpies, h^E, at 293.15 K and atmospheric pressure are reported for the binary liquid mixtures of 1,2-dichloroethane + haptane, + decane, + dodecane, + tetradecane, + hexadecane or + 2,2,4-trimethylpentane, all determined by means of a flow microcalorimeter of the Picker-type. These measurements could be reproduced within the experimental limits by calculations according to a quasi-chemical group contribution theory, using constant values for two interchange energy coefficients, C_1,ad (Gibbs energy) and C_2,ad (enthalpy). Fair agreement between the calculated excess heat capacities, e^E_p, and the experimental literature values could be obtained by adjusting a third coefficient, C_3,ad (heat capacity). However, C_3,ad decreases with increasing chain length of the n-alkane. Even with three C_1,ad coefficients the model cannot reproduce the exact shape of the c^E_p versus composition curves. Apparently, not only the terms of an interchange of group surface contacts, but also conformational changes occurring in n-alkanes on mixing, contribute to the excess functions. The set of C_1,ad coefficients reported in this paper should prove useful in predicting phase equilibria in liquid 1,2-dichloroethane + n-alkane mixtures.