Unsaturated Dimer Research Articles

Cationic oligomerization of anethole: Selective synthesis of dimers and trimers

AbstractA linear unsaturated dimer of anethole [II, (E)‐1,3‐bis(p‐methoxyphenyl)‐2‐methylpentene‐1], was prepared in 98% yield with an acetyl perchlorate (AcClO4) catalyst in a nonpolar solvent (C6H6) at a high temperature (70°C). At 0°C a linear unsaturated trimer was formed in high yield with dimer II. The geometric structure of the linear unsaturated dimers was determined by analysis of the nuclear Overhauser effect (NOE) on their 1H‐NMR spectra. NOE analysis showed that at 0°C with AcClO4, trans‐anethole gives the (E)‐form (II), whereas cis‐anethole yields the (Z)‐form. On the other hand, with a metal‐halide catalyst (BF3OEt2) a cyclic dimer and a cyclic trimer were produced in high yields in a polar solvent [(CH2Cl2)] at 70°C; higher oligomers (≥ tetramer) were scarcely formed. The effect of catalysts on the structure of oligomers was explained in terms of the interaction between a growing carbocation and a counterion.

Cationic Oligomerization of p-Hydroxystyrenes: Selective Preparation of Linear Styrene Dimers with Functional Groups

This paper describes the selective synthesis of multifunctional, linear unsaturated oligomers of p-hydroxy-, p-acetoxy-, and p-hydroxy-m-methoxy-styrenes (p-HOSt, p-AcOSt, and p-HO-m-MeOSt, respectively). A linear unsaturated dimer of p-AcOSt was selectively formed by oxo acids or their derivatives (CF3SO3H or AcClO4) in benzene at 70°C. p-AcOSt trimer and tetramer were also produced in high yields by the proper choice of catalysts and reaction conditions. Base-catalyzed hydrolysis of the p-AcOSt dimer and trimer quantitatively gave the corresponding p-HOSt oligomers not obtainable by direct reactions by p-HOSt itself. This finding provides a new method for preparing multifunctional phenols with linear unsaturated backbone, which are attractive as “reactive oligomers.” p-HO-m-MeOSt, whose oligomers are structurally related to lignin, was also converted to a linear unsaturated dimer in good yield by iodine or CH3SO3H catalyst.

Die thermische polymerisation von methylmethacrylat, 3. Verhalten des ungesättigten dimeren bei der polymerisation

AbstractThe thermal polymerization of methyl methacrylate is accompanied by the formation of appreciable amounts of an unsaturated dimer (H‐1). The behaviour of H‐1 during homopolymerization in presence of an initiator at 60, 80 and 100°C and during copolymerization with MMA in presence of an initiator at 60°C are investigated. The rate of (H‐1)‐homopolymerization is very low. The transfer constant to monomer H‐1 is about CH‐1 = 3·10−3 at 80°C as received from Pn‐determinations. The termination is essentially by disproportionation. The copolymerization parameters as resulting from polymerizations with labeled MMA at 60°C are rMMA = 1,8 and rH‐1 = 0,33, respectively.

Die thermische polymerisation von methylmethacrylat, 2. Bildung des ungesättigten dimeren

AbstractThe spontaneous thermal polymerization of methyl methacrylate (MMA) is accompanied by the production of serveral oligomers among which a linear unsaturated dimer H‐1 (dimethyl 1‐hexene‐2,5‐dicarboxylate) is predominant. The reaction kinetics of this dimer formation was investigated in bulk and in solution. The temperature dependence of the second order dimerization constant was determined as Reaction mechanisms for the thermal dimer formation of MMA are discussed.

Continuous-flow enrichment of a strain ofErwinia carotovora having specificity for highly methylated pectin

A pectinolytic bacterium was isolated from a mixed microbial population by means of a chemostat enrichment procedure. The bacterium, which was identified asErwinia carotovora, grew only on highly methylated pectin and produced a pectin lysase which released unsaturated monomer and dimer from 71% esterified citrus pectin. The pectin lyase was inducible only by pectins having a high methyl content and in pectin-limited chemostats its synthesis passed through a maximum at a dilution rate close to 0.04h-1.

Cell wall-degrading enzymes of vascular wilt fungi. II. Properties and modes of action of polysaccharidases of Verticillium albo-atrum and Fusarium oxysporum f. sp. lycopersici

Single polysaccharidases of Verticillium albo-atrum degraded cell walls from vascular and other tissues of tomato stems without previous or simultaneous action of other enzymes. Endoxylanase, exo-galactanase and exo-arabinase of the pathogen had pH optima c. 5, 3 and 5 respectively. Cellulase degraded soluble and insoluble cellulose at optimum pH c. 7. Polygalacturonase (PG) and pectin lyase (PTE) behaved as typical endo-enzymes causing a rapid decrease in viscosity of solutions of substrates at rates proportional to the degree of substrate polymerisation. Although PTE degraded pectin at random, only unsaturated dimer was released from polypectate and cell walls. PG released galacturonic acid and oligogalacturonides which were rapidly degraded to the monomer but an exo-enzyme was not detected; this activity compares with the dual endo-exo action of homogeneous polygalacturonases from other pathogens and “multiple attack” of certain α-amylases. Wide and narrow range isoelectric focusing resolved PG into four endo-components of pI 5·0 5·9 6·2 and 6·7 and PTE into two fractions with activity profiles almost identical with the acidic PG components. PTE of V. albo-atrum and Fusarium oxysporum f. sp. lycopersici had a partial Ca 2+ requirement and pH optimum c. 9 which altered with substrate methylation. Activity of endo-PG of V. albo-atrum but not exo-PG of F. oxysporum was restricted by Ca 2+; calcium pectate gels were resistant to degradation. Pectic enzymes of V. albo-atrum macerated tomato stem tissue after long lag periods; other cell wall-degrading enzymes were ineffective. PTE of F. oxysporum macerated tissue more rapidly and was used alone or with other enzymes to compare degradation of tissue and cell walls isolated from susceptible or isogenically wilt-resistant tomato cultivars. There was no relation between varietal resistance and the susceptibilities of cell walls to enzymic degradation.

Dimerization of methylstyrenes by acetyl perchlorate and trifluoromethanesulfonic acid

AbstractRing‐substituted methylstyrenes (p‐, m‐, and o‐methylstyrenes) in conjunction with acetyl perchlorate (AcClO4) or trifluoromethanesulfonic acid as catalysts gave their linear unsaturated dimer in high yield in benzene at temperatures from 50 to 70°C. In particular, the yield of o‐methylstyrene dimer was as high as 90% in the AcClO4 catalysis at 50°C. The dimer yield depended on solvent and catalyst. The terminal structures of the dimers and higher oligomers were analyzed by NMR spectroscopy. Oligomers with a cyclic terminal structure increased in the products at higher temperature. The dimer yield was improved by codimerizing p‐methylstyrene with less reactive m‐methylstyrene or styrene with AcClO4 catalyst. The dimers obtained partly consisted of linear unsaturated codimers.

Selective dimerization of styrene to 1,3‐diphenyl‐1‐butene by acetyl perchlorate

AbstractThe linear unsaturated dimer of styrene, 1,3‐diphenyl‐1‐butene, was obtained exclusively in the oligomerization of styrene by acetyl perchlorate in various solvents. In benzene, the linear dimer was produced in more than 90% yield at 50°C. In n‐hexane and cyclohexane, the yield of the linear dimer was lower. The yield of the linear dimer was strongly dependent on the nature of solvent. When an increasing amount of 1,2‐dichloroethane was added to benzene, the yield of the linear dimer gradually decreased. On the other hand, when a small amount of 1,2‐dichloroethane was added to n‐hexane or cyclohexane, the yield of the linear dimer increased. The yield of the linear dimer was almost independent of the reaction temperature and the initiator concentration. For comparison, the dimerization of α‐methylstyrene was carried out, and the effects of the initiator and the solvent on the structure of dimers were investigated. On the basis of these results, the mechanism of the dimerization of styrene initiated by acetyl perchlorate is discussed.

Degradation of synthetic oligomers by microorganisms. I. Microbial degradation of styrene oligomer.

Of 72 soil samples, 10 samples have shown to possess one or more organisms capable of degrading styrene oligomer to some extent. In the course of investigation, dimers are found to disappear rapidly from the culture medium. Trimers, however, are degraded a little and oligomers higher than tetramer not at all. One of the isolates, Alcaligenes sp. 559, grows well on styrene oligomer and is selected for further study. This bacterial strain utilizes unsaturated dimer (1, 3-diphenyl-l-butene) as sole source of carbon and degrades cyclic dimer (1-methyl-3-phenylindane) together. No degradation of trimers by the strain was detected. Furthermore, the assimilation of various aromatic hydrocarbons by this strain was examined and insusceptibility of the oligomers higher than trimer was discussed according to the results.

Investigation of gamma-ray induced polymer formation in the carboranes—V: Structures of the products and mechanism of the radiolysis of 1-allyl- o-carborane

Investigation of the gamma-ray radiolysis of 1-allyl-1,2-dicarba- closo-dodecaborane-11, 1-allyl- o-carborane, indicated that it could be oligomerized with a DP n of five. It can be strongly inferred from the results of this work that the reactions involved are hydrogen atom initiated processes involving abstraction to form an allylic type radical and addition to form a propyl type radical. A concurrent stage of the reaction involves coupling of the allylic type radicals to give rise to seven different unsaturated dimer products. The oligomerization reaction involving the propyl type radical as the propagating species results in the formation of a saturated oligomer in a free radical chain process which is characterized by chain transfer. Both the dimer reaction and the oligomer process are terminated by bimolecular processes.

Photochemical Reactions. Part 64 [1]. The photochemistry of 3‐alkyl‐cyclopent‐2‐en‐ones

AbstractOn ultraviolet irradiation in toluene, cyclopent‐2‐en‐one (1a) and 3‐methylcyclopent‐2‐en‐one (1b) undergo dimerisation (→ 3a, b, 4b), whereas 3‐t‐butyl‐cyclopent‐2‐en‐one (1e) and the bicyclo [3.2.1]octenone 2a only react with the solvent (→ 5e–7e, 8–10). The 3‐ethyl‐(1c) and 3‐isopropyl‐cyclopent‐2‐en‐ones (1d) afford by dimerisation products 3c, d, 4c and by reaction with the solvent 5c, d, 6c, d, 7d. The β‐methoxy‐enones 1f and 2b are unreactive under comparable irradiation conditions. The head‐to‐head cyclobutane dimer 3b (HH) by separate irradiation at < 3400 Å in toluene, is reconverted to 1b. By similar irradiation each of the head‐to‐tail dimers 3b (anti‐ and syn‐HT) and also the unsaturated dimer 4b give a new isomer of unknown structure besides small amounts of monomer 1b and relatively large amounts of insoluble material.The photoreactions of 1b‐e can be quenched by naphthalene. Stern‐Volmer plots for the quenching of the dimers of 1b, 1c, and 1d, and of 3‐t‐butylcyclopentanone (5e) and the dihydro dimer 7e are linear and within each experiment, the slopes satisfactorily coincide, whereas the slope for the α‐benzyl ketone 6c is distinctly greater than that for the dimers 3c. A similar differentiation, although less pronounced, is found between the benzyl ketones 6d and 6e and the respective accompanying products.

The Isolation and Characterization of an a,4 (4,5 Dehydrogalacturonosyl) Galacturonate Hydrolase

SUMMARY– An unsaturated oligogalacturonate hydrolase was isolated from the cell extracts of a Bacillus sp. This enzyme attacked only the a 1,4 glycosidic bond adjacent to the terminal 4,5dehydrogalacturonate of unsaturated oligogalacturonides and preferentially attacked short chain unsaturated uronides. The rate of activity was maximal with unsaturated dimer followed by trimer (65% that of dimer), tetramer (47%) and pentamer (35%). The pH optimum was 6.3 to 6.6 and the enzyme did not require calcium ions for its activity. The enzyme was relatively stable below 30°C but lost 90% of its activity after 10 min at 40°C.

Spectroscopic studies on carbonium ions derived from aromatic olefins. Part III. Ions derived from styrene and cognate compounds

We have elucidated the origin of the u.v. spectrum given by solutions of styrene, its unsaturated dimer, and its cyclised dimer in 98% sulphuric acid, by working with extremely dilute solutions at low temperatures, and studying the products recoverable from these. No evidence for the existence of the 1-phenethyl ion was obtained, but the 1,3-diphenyl-n-butyl cation has been characterised and an explanation for its being more stable than the 1-phenethyl ion is given. The principal cation formed from styrene and the two dimers is the 3-methyl-1-phenylindanyl cation which has been characterised and which is slightly less stable than the triphenylmethyl ion. The very variable spectrum reported by previous authors as resulting from solution of styrene in concentrated sulphuric acid has been shown to be attributable to the 3-methyl-1-phenylindanyl cation and at least four other aralkyl cations derived from the cyclised dimer, which were characterised by protonation of the corresponding methanol or olefin.The formation of ions from styrene and the two dimers by reaction with excess of perchloric acid in methylene dichloride solution was studied spectroscopically and conductimetrically. From styrene first the unsaturated, and then the cyclised, dimer are formed, and if the excess of acid is not greater than about tenfold, reaction stops at that stage. With a greater excess the 3-methyl-1-phenylindanyl cation and a saturated compound are formed in approximately equal amounts. The kinetics of this ionogenic reaction indicate that it probably involves a complex of the cyclised dimer with perchloric acid reacting with its own kind. (We now know that our earlier views on the formation of ions from styrene and perchloric acid are incorrect.) Among the many ions chatacterised here is the dimethylphenylcarbonium ion.

Internuclear cyclisation. Part XXIII. Formation and rearrangement of 2-methylisoindoline-1-spirocyclohexa-2′,5′-diene-3,4′-dione. Synthesis of the octahydro-derivative of an unsaturated dimer

The decomposition of N-methyl-4′-(methylthio)benzanilide-2-diazonium salts (VIII) gives 2-methylisoindoline-1-spirocyclohexa-2′,5′-diene-3,4′-dione (IV) and methanethiol, rather than the corresponding thione and methanol. Similarly, 4′-methoxy-N-methylbenzanilide-2-diazonium sulphate (VIII; O for S) decomposes in 18O-enriched water to give the dione (IV) with incorporation of 18O. This spiro-dienone forming reaction does not intervene in Pschorr cyclisations since trans-2-amino-α-(2- and 4-methoxyphenyl)cinnamic acids give 1- and 3-methoxyphenanthrene-10-carboxylic acid in high yield.

Anionic oligomerization of acrylic esters

Oligomers of methyl acrylate and of ethyl acrylate were prepared by the use of methanolic and ethanolic solutions (respectively) of the corresponding sodium alkoxides as basic catalysts. Both terminally unsaturated oligomers and oligomers having alkoxyl end-groups were formed. The structure of the dimers was investigated; they were found to be α-methylene-dialkylglutarate and α-alkoxymethyldialkylglutarate. The i.r. and NMR spectra of the dimers are presented and discussed. The molar ratio of unsaturated dimer to saturated dimer was greater for the ethyl acrylate—ethanol system than for the methyl acrylate-methanol system. According to the proposed mechanism, the unsaturated dimers (and higher oligomers) were formed as a result of initiation by monomeric carbanions CH 2 C—COOR. These, in turn, were formed by transfer of the acidic α-hydrogen of the monomer to one of the propagating carbanionic species in the oligomerization mixture.

Polygalacturonic acid trans-eliminase of Xanthomonas campestris.

Polygalacturonic acid trans-eliminase from the culture fluid of Xanthomonas campestris was purified 66-fold by acetone precipitation, citrate extraction and chromatography on diethylaminoethyl- and carboxymethyl-cellulose. The optimum pH is 9.5 in glycine-sodium hydroxide buffer. Up to 1mm-calcium chloride brings about a remarkable stimulation of the enzyme activity and, at this concentration, no other cations promote or inhibit enzyme action except Ba(2+) ions, which cause complete inhibition. The enzyme degrades polygalacturonic acid in a random manner; it does not act upon polygalacturonate methyl glycoside, although it can cleave partially (68%) esterified pectin. The end products from polygalacturonic acid at 46% breakdown are unsaturated di- and tri-galacturonic acids, in addition to saturated mono-, di- and tri-galacturonic acids. Pentagalacturonic acid is split preferentially into saturated dimer plus unsaturated trimer, or into saturated trimer plus unsaturated dimer; at a lower rate, it is also split into monomer and unsaturated tetramer. Unsaturated pentamer is split into unsaturated dimer plus unsaturated trimer. Tetragalacturonic acid is split some-what preferentially at the central bond to form dimer and unsaturated dimer, but it is also split into monomer and unsaturated trimer. Unsaturated tetramer is split only at the central bond to yield only unsaturated dimer. Trigalacturonic acid is split into monomer and unsaturated dimer. Unsaturated trimer is cleaved into saturated dimer and probably 4-deoxy-l-5-threo-hexoseulose uronic acid, which has not yet been directly identified. Neither saturated nor unsaturated digalacturonic acid is attacked. The unsaturated digalacturonic acid was isolated and proved to be O-(4-deoxy-beta-l-5-threo-hexopyranos-4-enyluronic acid)-(1-->4)-d-galacturonic acid.

Internuclear cyclisation. Part XXII. Catalysed decomposition of diazonium fluoroborates from alkoxy-N-alkyl-2-aminobenzanilides

Copper-catalysed decomposition of dry diazonium fluoroborates from alkoxy-N-alkyl-2-aminobenzanilides affords several new reactions not found in the thermal, uncatalysed decompositions. The products include benzanilides, phenanthridones, spiro-cyclohexa-dienones and -dienols, an azoxy-compound, and unsaturated dimeric products.Formation of the dienones and dienol, where an extra oxygen atom has become incorporated, and the unsaturated dimers, can only be explained, simply, in terms of a free-radical mechanism. The initially formed aryl radical adds intramolecularly to the other benzene ring to give a stabilised cyclohexadienyl radical which can react with dissolved oxygen or dimerise. Clear evidence is thus provided for the participation of radicals in these catalysed diazonium decompositions.Base-catalysed aromatisations of the cyclohexadienol to a biphenyl, and the unsaturated dimer (XVII) to a p-quaterphenyl are also described.