摘要:

AbstractPoly(5,6‐anhydro‐1,2‐O‐isopropylidene‐α‐D‐glucofuranose) (1) the main chain structure of which is poly(oxyethylene) was obtained by anionic ring‐opening polymerization of 5,6‐anhydro‐1,2‐O‐isopropylidene‐α‐D‐glucofuranose (2) which contains a pendent oxirane ring. Polymerization by strong bases such as sodium hydroxide, potassium hydroxide, cesium hydroxide, and potassiumtert‐butoxide gave polymers with degrees of polymerization up to sixteen in high yield. The specific rotations of the polymers were almost constant, being mostly in the range from −44° to −40°. The factors affecting this polymerization were examined in order to elucidate the best conditions for polymerization. The polymer was hydrolyzed to 5,6‐glucan (3) with trifluoroacetic acid‐water at room temperature. The structures of the original polymer1and the hydrolyzed one were compared with those prepared

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800501

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe ring‐opening polymerization of (5S)‐1‐azabicyclo[3.1.0]hexane (1) derived fromL‐proline was attempted, by use of a catalytic amount of boron trifluoride etherate as an initiator, in order to obtain optically active polymers. Chiral polymers (2) were indeed easily formed when the above aziridine1was polymerized in bulk or in benzene. On the other hand, a stable BF3‐adduct was obtained in the form of colorless crystals when the dilute benzene solution (1%) of1was allowed to react with an excess of boron trifluoride etherate. The elemental analysis and the NMR (19F,11B, and13C) spectra of this adduct showed it to be a (5S)‐1‐azabicyclo[3.1.0]hexane‐boron trifluoride (1:1) complex (3). It was also found that the adduct initiated the polymerization of aziridine1more mildly than boron trifl

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800502

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractIn order to study the side reactions occuring during the synthesis of unsaturated polyesters, several 2‐hydroxypropyl esters were synthesized by reduction of the corresponding acetylmethyl esters1a–i. It was found that on heating they are partly isomerized to the 1‐methyl‐2‐hydroxyethyl esters. The extent of isomerization was determined at various temperatures by NMR spectroscopy, both in solution and in bulk. An analysis of the NMR spectra is given and a mechanism of the isomerization is

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800503

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe polymer prepared from 8‐hydroxyquinoline and 1,2‐dichloroethylene by Friedel‐Craft's condensation, showed to be a selective chelating ion‐exchange resin for certain metal ions. A batch equilibration method was employed in the study of the selectivity of metal ion uptake. This method involved the measurement of distribution of a given metal ion between the polymer sample and a solution containing the metal ions. The study was carried out over a wide pH range and in media of various ionic st

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800504

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractTo clarify the initiation process in radical polymerizations with diphenyl disulfide (DPDS) as initiator, spin trapping technique was applied to the reaction of vinyl monomers with the phenylthio radical (1), which was produced by photolysis of DPDS. 2‐Methyl‐2‐nitrosopropane (BNO) was used as a spin trapping agent. When DPDS was photo‐decomposed in benzene in the presence of BNO radical1was trapped as the corresponding aminyl oxide radical2, which is unstable at room temperature. The photolysis of DPDS in vinyl monomers of type H2CCXY, however, gave only aminyl oxide radicals resulting from their propagating radicals C6H5SCH2C˙XY. Contrary to the results obtained withtert‐butoxyl radicals, radical1was found to undergo exclusively addition reaction to the double bond of the α‐methyl‐substituted monomers, such as methyl methacrylate or methacrylonitrile, with no hydrogen‐abstraction reaction from their α‐methyl group. Relative rates of the initiation reactions of vinyl monomers with radical1were also determined by spin trapping technique. It was found that the reactivities of vinyl monomers toward radical1are controlled by both p

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800505

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractN‐hydroxysuccinimide (NHS) andN‐hydroxyphthalimide were found to initiate effectively vinyl polymerizations of acrylate monomers. The polymerization of methyl methacrylate (MMA) with NHS was investigated in detail. The polymerization rate (Rp) was found to depend highly on the solvents. The over‐all activation energy of the polymerization in ethyl acetate was calculated to be 76,2 kJ/mol (18,2 kcal/mol). In the low monomer concentration,Rpcan be expressed asRp=k[NHS]1/2[MMA]3/2. The copolymerization of MMA with styrene, initiated by NHS, could be shown to proceed via radical mechanism. In order to elucidate the initiation mechanism, spin trapping technique was applied to this polymerization system. In the reaction of MMA with NHS in acetone, the 2‐carbomethoxypropyl radical was trapped by 2‐methyl‐2‐nitrosopropane, a spin trapping reagent, to give the corresponding aminyl oxide radical2. From the results, the initiation mechanism of this polymerization is proposed

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800506

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

Abstract6‐Trityl‐2,3‐dicarbanilyl and 2,3‐dicarbanilyl derivatives of amylose and cellulose have previously been used as a backbone to introduce oligosaccharide branches by (1 → 6) glycosidic bonds. Possible degradation prior and during the glycoside coupling was now followed by light scattering measurements on each step of derivatization. The results obtained with derivatives of technical and synthetic amyloses indicate that some degradation may occur in the tritylation reaction and possibly in the conversion to the 6‐trityl‐2,3‐dicarbanilate. In the following steps, e.g. detritylation and glycosidic condensation of glucose and maltose derivatives under the conditions applied, degradation appears to be almost absent. In corresponding studies with cellulose derivatives problems arise mainly in the tritylation step. The results of the light scattering and viscosity measurements are discussed with respect to the molecul

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800507

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractCarbanilated and tritylated derivatives of amylose and cellulose previously studied by light scattering were further characterized by measurement of optical rotatory dispersion (ORD) and circular dichroism (CD). No anomalous ORD and only a weak CD was found for 6‐tritylamylosein 1,4‐dioxane, indicating a widely unordered structure which is in accordance with the low viscosity of the compound. In comparison with the other carbanilated derivatives having substituents in C‐6 position, i.e. trityl‐, carbanilyl‐ or glucosyl groups, 2,3‐dicarbanilylamylose is distinguished by an especially high Cotton effect. This result suggests a helical chain,— clearly visible by excition splitting—, that may adopt a more regular orientation in case of free C‐6 hydroxyl groups, whereas trityl‐, carbanilyl‐, and glucosyl groups almost equally will contribute to a lower state of orientation. Conversely in thecellulosederivatives a clear steric dependence on the size of the C‐6 substituent was found. The increase of the Cotton effect observed for the bulky trityl group may arise from the β(1 → 4) linkage that causes an alternating or syndiotactic like structure in cellulose, which is more sensitive to restrictions of the free rotation due to steric effect. In addition, viscosity and optical rotation in NMP and 1,4‐dioxane were measured in the range of 20 to 70°C. An unusual behaviour is observed for 6‐trityl‐2,3‐dicarbanilylamylose in NMP indicating a conformation transition near 45°C, and is discussed in connection with the finding

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800508

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractIn order to study the polymerization of oxiranes and thiiranes containing an asymmetric carbon atom in the side chain a mixture (mole ratio 1:1) of the diastereoisomers 2R,3Sand 2S,3S1,2‐epoxy‐3‐methylpentane (1aet2a) and 2R,3Sand 2S,3S1,2‐epithio‐3‐methylpentane (1bet2b) as well as the almost pure diastereoisomers 2R, 3S(1b) and 2S, 3S(2a) were prepared. The diastereoisomeric composition of these compounds was established by1H NMR spectroscopy, at 250 MHz for the thiiranes and at 90 MHz for the oxiranes (in the presence of a chiral shift reagent). The optical activities of the different pure diastereoisomers were determined, and the chiroptical properties of these new monomers w

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800509

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY

摘要:

Abstract1,2‐Epoxy‐3‐methylpentanes (1) of different diastereoisomeric compositions were polymerized using anionic (tert‐BuOK, KOH), stereospecific (ZnEt2/H2O, ZnEt2/MeOH), or stereoelective (ZnEt2/R(−) 3,3‐dimethyl‐1,2‐butanediol (R( − ) DMBD)) catalysts. In all the cases a preferential incorporation of the (2R,3S) diastereoisomer in the polymer chain was observed. With anionic and coordinated anionic achiral catalysts the election was low but significant, whereas with the chiral ZnEt2/R( − ) DMBD system, in the case of the polymerization of the (2RS,3S) monomer, the election was high and corresponded to a stereoelectivity ratio ofr= 4, the highest one obtained up to now for oxiranes. The observed effects are due to the presence of a chiral centre in the side c

ISSN:0025-116X    

DOI:10.1002/macp.1979.021800510

出版商:Hüthig&Wepf Verlag    

年代:1979

数据来源: WILEY