Model Compounds Of Poly Research Articles

The Crystal Structure of DL-Pentane-2,4-diol as a Model Compound for Poly(vinyl alcohol)

The crystal structure of DL-pentane-2,4-diol as a model compound of syndiotactic poly(vinyl alcohol) was determined. This crystal belongs to a monoclinic system with the dimensions of a=12.266(2), b=8.886(1), c=11.693(3)Å, and β=92.94(4)°. The space group was P21/n and Dm=1.08, Dc=1.086 and Z=8. The final R factor was 0.083 for 1891 observed reflections. There are two crystallographically independent molecules in the unit cell. The five carbon atoms of these molecules have TT sequences and the OH groups form intermolecular hydrogen bonds. A structure analysis suggests that the conformation of syndiotactic poly(vinyl alcohol) may take TT sequences, the carbon chain has a planar zigzag form and the hydroxyl groups form intermolecular hydrogen bonds.

Model compounds of poly(methyl methacrylate). Conformational structure of methyl 3-methoxy-2-methylpropionate

By analysis of 1H and 13C NMR spectra, and of infrared and Raman spectra of methyl 3-methoxy-2-methylpropionate, the formation of conformers generated by rotation about the bonds CH3O-CH2, CH2-CH and C-C=O was studied. The structure of the most highly populated conformer is proposed.

Photoreactions of trans-poly(vinyl cinnamate) and low molecular weight model compounds—Part I

Various cinnamates serving as model compounds for poly(vinyl cinnamate), trans-ethyl (trans-ECi), trans-methyl (trans-MCi), cisethyl (cis-ECi) and trans,trans-1,3-trimethylene dicinnamate (trans,-trans-TMCi) were irradiated at concentrations of 1–5 × 10 −5 mol litre −1 in chlorine-containing solvents (CH 2Cl 2, CCl 4, 1,1,2-trifluorotrichloroethane) and chlorine-free solvents (per-fluoro-2-(n-butyl)-tetrahydrofurane, 1-ethoxy-2-acetoxy-ethane, PMMA). For trans-ECi the quantum yield φ (trans → cis) is higher in chlorine-free solvents (0·40–0·45) than in chlorine-containing solvents (c. 0·26). Fluorescence spectra, recorded with trans-ECi and trans, trans-TMCi possess two peaks at 325 nm and at 375 nm in chlorine-containing solvents and only one peak at 325 nm in chlorine-free solvents. The fluorescence lifetime (slow mode) at 325 nm is 15±5 ns and at 375 nm 25±5 ns. Flash photolysis experiments revealed S 1 → S n absorption spectra (lifetime 15±5 ns) in all solvents and with all solutes. In chlorine-containing solvents an additional long-lived absorption (lifetime 5–10 μs) was observed. From the results it is concluded that singlet-excited cinnamates form exciplexes of C-T character with the chlorine-containing solvents used in this work. Moreover, the results revealed—in accord with earlier findings—that upon direct excitation, cinnamates undergo chemical changes exclusively via electronically excited singlet states.

Model compounds of poly(methyl methacrylate). Conformational structure of 2,2-dimethyl-1-methoxypropane and of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid

By analysis of infrared, Raman and 13C NMR spectra of 2,2-dimethyl-1-methoxypropane and of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid, the formation of conformers generated by rotation about the CH2-OCH3 and C-CH2 bonds was studied. It was found that in both molecules, only the form with trans orientation of the C-CH2-O-CH3 bonds is present. The conformational structure of the major form of the methyl ester of 3-methoxy-2,2-dimethylpropanoic acid was proposed.

Molecular dynamics of polystyrene model molecules: ultrasonic relaxation of 2,4-di(parabromophenyl)pentane

Ultrasonic attenuation of meso and racemic 2,4-di(parabromophenyl)pentanes, model compounds of poly(parabromostyrene), have been investigated as a function of temperature and frequency. The single relaxation observed for each isomer has been assigned to similar rotational isomerism as for the 2,4-diphenylpentanes, despite the large size of the bromine atoms. The substituent effect mainly appears in the lowering of the relaxation frequency.

Photoreversible reactions of polymers containing cinnamylideneacetate derivatives and the model compounds

AbstractPhotoreversible reactions of 1,4‐butanediol dicinnamylideneacetate(BCA) and its photocyclized compound (BCD), the model compounds for poly(vinyl cinnamylideneacetate), were studied. They exhibited an excellent photoreversibility in a rigid medium at 77°K. The quantum yield of dimerization in the rigid medium is much larger than that in the solution and approximately equal to that in polymer film. Poly(vinyl esters) of substituted cinnamylideneacetic acids also showed photoreversibility to various extents, depending on the substituent. Poly(vinyl α‐cyanocinnamylideneacetate) showed the best photoreversibility among the series, reflecting the least amount of side reaction upon the photodimerization.

Crystal and molecular structure of 1,4‐bis(chloroacetyl)‐trans‐2,5‐dimethylpiperazine, a model compound of poly(trans‐2,5‐dimethyl‐1,4‐piperazinediylfumaroyl)

AbstractThe molecular and crystal structure of 1,4‐bis(chloroacetyl)‐trans‐2,5‐dimethylpiperazine synthesized by us, was determined from X‐ray diffractometer data. The structure was solved by Patterson and Fourier methods and refined by least‐squares techniques to R 0,065 for 1081 independent reflections. The crystals are monoclinic, space group P21/n, with Z = 2 in a unit cell of dimensions: a = 9,486 (6), b = 9,139 (6), c = 7,036 (5) Å, β = 95,73 (10)°, the numbers in parentheses being the estimated standard deviations refering to the last significant digit. The trans‐2,5‐dimethylpiperazine ring is in a flattened‐chair conformation with the side methyl groups in axial position. The atoms of the amide are nearly coplanar. It seems to be proved that the structure of the trans‐2,5‐dimethylpiperazine ring in poly(trans‐2,5‐dimethyl‐1,4‐piperazinediylfumaroyl) is similar to that found for 1,4‐bis(chloroacetyl)‐trans‐2,5‐dimethylpiperazine.

Solvent effect on the 13C NMR chemical shifts of meso and racemic 2,4‐dichloropentanes as the model compounds of poly(vinyl chloride)

AbstractThe 13C NMR chemical shifts of meso and racemic 2,4‐dichloropentanes as the model compounds of poly(vinyl chloride) in various solvents were observed, and were well interpreted theoretically by means of “solvaton”‐MO theory.The temperature dependence of the chemical shifts in pentachloroethane and dimethyl sulfoxide solutions were also well interpreted theoretically. Further, the similarity between these behaviours of the dimers and the polymer was discussed.

Studies on the formation of poly(ethylene terephthalate): 9. Thermal decomposition of ethylene dibenzoate as a model compound of poly(ethylene terephthalate)

As a model compound for poly(ethylene terephthalate), the thermal decomposition of ethylene dibenzoate (EDB) was carried out at 330°–350°C. The EDB was determined from the ethylene glycol obtained on hydrolysis of the reaction mixture. The rate of decomposition, on the basis of the above determination, was found to obey first order kinetics. A comparison of the quantity of decomposed EDB with the quantity of benzoic acid suggested that usual approaches to the thermal decomposition of EDB on the basis of the determination of the quantity of benzoic acid were liable to error.

Investigations on poly(vinyl chloride). II. Pyrolysis of chlorinated polybutadienes as model compounds for poly(vinyl chloride)

AbstractThe pyrolysis of chlorinated polybutadienes (CPB) was investigated by using a pyrolysis gas chromatograph. CPB corresponds to poly(vinyl chloride) (PVC) constructed with head–head and tail–tail linkages of the vinyl chloride unit. Benzene, toluene, ethyl‐benzene, o‐xylene, styrene, vinyltoluene, chlorobenzenes, naphthalene, and methylnaphthalenes were detected in the pyrolysis products from CPB above 300°C, and no hydrocarbons could be detected at 200°C. The pyrolysis products from CPB were similar to those from PVC and new products could not be detected. Lower aliphatics, toluene, ethylbenzene, o‐xylene, chlorobenzenes, and methylnaphthalenes were released more easily from pyrolysis of CPB than from PVC; amounts of benzene, styrene, and naphthalene formed were small. These results support the conclusion that recombination of chlorine atoms with the double bonds in the polyene chain takes place and that scission of the main chain may depend on the location of methylene groups isolated along the polyene chain during the thermal decomposition of PVC.

ChemInform Abstract: ON THERMAL DEHYDROCHLORINATION OF MODEL COMPOUNDS FOR POLY(VINYL CHLORIDE) PART 2, EXTENDED HUECKEL AND ITERATIVE EXTENDES HUECKEL CALCULATIONS ON THE BETA‐CIS‐DEHYDROCHLORINATION OF ETHYL CHLORIDE

Chemischer InformationsdienstVolume 5, Issue 51 Preparative Organic Chemistry ChemInform Abstract: ON THERMAL DEHYDROCHLORINATION OF MODEL COMPOUNDS FOR POLY(VINYL CHLORIDE) PART 2, EXTENDED HUECKEL AND ITERATIVE EXTENDES HUECKEL CALCULATIONS ON THE BETA-CIS-DEHYDROCHLORINATION OF ETHYL CHLORIDE I. TVAROSKA, I. TVAROSKASearch for more papers by this authorV. KLIMO, V. KLIMOSearch for more papers by this authorL. VALKO, L. VALKOSearch for more papers by this author I. TVAROSKA, I. TVAROSKASearch for more papers by this authorV. KLIMO, V. KLIMOSearch for more papers by this authorL. VALKO, L. VALKOSearch for more papers by this author First published: December 24, 1974 https://doi.org/10.1002/chin.197451145AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume5, Issue51December 24, 1974 RelatedInformation

Nuclear magnetic resonance study on the model compounds for poly(N-alkylglycine)s.

AbstractCis‐trans isomerism was investigated with N‐acetyl and N‐propionyl, N‐alkylglycine dimethylamides as model compounds for poly(N‐alkylglycine dimethlamides as model compounds for (N‐alkylglycine)s using n.m.r. spectroscopy. The population of the cis isomer measured in benzene and methylene chloride solutions did not show any marked dependence on the bulkiness of N‐alkyl substituents. This contrasts with polyN‐alkylglycine)s, whose cis isomer population increased with the introduction of bulky N‐alkyl groups. Kinetics of the Cis‐trans isomerization was also investigated with N‐acetyldimethylamides of sacrosine, N‐n‐propylglycine, and N‐isopropylglycine in tetrachloroethane solution. The δG‡ values for Cis‐trans isomerization in these amides were 18 ∼ 19 kcal/mole, which were virtually the same as that of polysacrosine.

13C nuclear magnetic resonance studies on the stereochemical configurations of 2,4‐dimethoxypentane and poly(alkyl vinyl ethers)

Abstract13C nuclear magnetic resonance (CMR) spectra were obtained for 2,4‐dimethoxypentane, which is a model compound of poly(methyl vinyl ether), and the effects of the solvent and temperature on the chemical shifts were investigated. CMR spectra of poly‐(alkyl vinyl ethers) were also determined and analyzed. The diad tacticities were obtained from β‐methylene carbon resonances of poly(methyl vinyl ether), poly(ethyl vinyl ether), and poly(isobutyl vinyl ether), but not from those of poly(isopropyl vinyl ether) and poly(tert‐butyl vinyl ether). The methoxyl carbon resonance of poly(methyl vinyl ether) and the ethoxyl methylene carbon resonance of poly(ethyl vinyl ether) showed splittings corresponding to pentad and triad sequences, respectively. The α‐methine and quaternary carbon resonances of poly(tert‐butyl vinyl ether) showed splittings corresponding to pentad and triad sequences, respectively.

Calculation of the carbon‐13 chemical shifts of the methylene carbons of meso and racemic 2,4‐dimethoxypentanes as model compounds of poly(vinyl methyl ether)

AbstractThe 13C chemical shifts of the methylene carbons of meso and racemic 2,4‐dimethoxypentanes were calculated by the CNDO/2 method. The results were in fairly well accordance with the experimental results of poly(vinyl methyl ether). The cis form of the side chain was more stable than the trans form.

Analysis of NMR and Vibrational Spectra and Conformational Structure of Stereoisomers of 2,4,6‐Trichloroheptane

AbstractThe infrared and NMR spectra of syndiotactic, isotactic, and heterotactic 2,4,6‐trichloroheptane, model compounds of poly(vinyl chloride), have been measured over a wide temperature range. Conformational structures of these stereoisomers have been determined from C—Cl stretching vibrations in infrared spectra and from the temperature dependence of vicinal coupling constants obtained by a four‐spin analysis of the methylene proton bands in NMR spectra.