摘要:

Self-association of benzoic, octanoic, and octadecanoic acids was studied in solvents with a range of dielectric constants between 2.3 and 10. The number-average molecular weights were determined by means of vapor pressure measurements and were carried out at temperatures ranging from 25 to 90° C. It appears that, in these solvents of low dielectric constant, carboxylic acids are present mainly as molecular or ionic aggregates.

ISSN:0022-233X    

DOI:10.1080/00222337808063176

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Perdeuterioacrylonitrile can be prepared conveniently from succinonitrile in a two-step process. Succinonitrile is exchanged with D2O to obtain perdeuteriosuccinonitrile, which is then pyrolyzed at ∼550°C to obtain perdeuterioacrylonitrile and DCN. CDBCN and CzDsCN are by-products of this reaction. A chemical procedure for separating perdeuterioacrylonitrile from these materials was developed. This involved formation of the Diels-Alder adduct of cyclopentadiene with perdeuterioacrylonitrile, followed by pyrolysis of the purified adduct at -330°C. Cyclopentadiene was removed from the resulting pyrolyzate by reaction with maleic anhydride. Purified perdeuterioacrylonitrile exchanged with H2O to yield β,β-dideuterioacrylonitrile in good yield and good isotopic purity.

ISSN:0022-233X    

DOI:10.1080/00222337808063177

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Isocyanate-terminated polyethylene oxide (PEO) was prepared by reaction of hydroxyl-terminated PEO of different molecular weights and toluene diisocyanate (TDI), at a molar ratio of 1:2. Reaction was carried out with and without catalyst (dibutyltin dilaurate). When catalyst was used, some chain extension accompanied the endcapping reaction. When endcapping reaction was carried out without catalyst, chain extension was minimal as determined from endgroup analysis and viscosity measurements. It was also found that secondary reactions of the terminal isocyanate groups led to further increase in solution viscosity after completion of the endcapping reaction.

ISSN:0022-233X    

DOI:10.1080/00222337808063178

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Refluxing of a solution of poly(vinyl alcohol) and rhodium(III) chloride in methanol-water gives a colloidal dispersion of rhodium which is an effective catalyst for hydrogenation of cyclohexene in methanol at 30°C under atmospheric hydrogen pressure. Formaldehyde is produced quantitatively with the reduction of rhodium(III) chloride to metallic rhodium. The rhodium particles in the colloidal dispersion are found to consist of two kinds of particles, about 8 and 40 Å in diameter by electron microscopy. The sizes of the small (8 Å) and large (40 Å) particles are almost constant during the course of refluxing. The number of small particles, which is the great majority of particles at the early stage of refluxing, gradually decreases; concurrently the number of large particle increases on prolonged refluxing. An absorption peak appears at 260 nm at the early stage of refluxing. The presence of the 260 nm peak, which indicates the coordination of poly(vinyl alcohol) to rhodium(III) ion, is indispensable for the formation of a homogeneous colloidal dispersion of rhodium. The addition of ethylenediamine inhibits the formation of colloidal rhodium in refluxing. The catalytic activity of colloidal dispersion of rhodium is dependent upon the concentration of rhodium(III) chloride charged and is independent of that of poly(vinyl alcohol). The formation mechanism of colloidal rhodium is discussed.

ISSN:0022-233X    

DOI:10.1080/00222337808063179

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The acid-catalyzed condensation reaction of thioanisole (I) with formaldehyde was carried out in benzene in the presence of p-toluenesulfonic acid. Two compounds, a dimer (II) and a trimer (III) of thioanisole linked by a methylene group, were isolated from the reaction mixture as main products on the initial stage of this reaction.

ISSN:0022-233X    

DOI:10.1080/00222337808063180

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

This work deals with the determination of the various azeotropies in radical terpolymerization: unitary azeotropy (mi= Mi); binary azeotropy (mi/mj. = Mi/Mj), and ternary or true azeotropy (Mj= mjfor j = 1, 2, 3). General analytical solutions are given which are easily handled by a computer. In addition, these calculations show the existence of pseudo-azeotropy where the deviation between polymer and monomer feed compositions is very small, not only at the beginning of the reaction, but also with increasing conversion.

ISSN:0022-233X    

DOI:10.1080/00222337808063181

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A new method for deriving expressions for the mole fractions of alternating n-ads and the average lengths of the alternating sequences of n-component copolymers (n > 2) was developed based on the apparatus of finite Markov chains. These characteristics are considered as indexes of alternating tendency forn-component copolymerization. A specific property of n-component copolymerization (n > 3) compared with binary copolymerization is the fact that alternating n-ads might be constructed by two, three, or more types of monomeric units. In order to express this specific property of three and multi-component copolymers the term, alternating order, is introduced. The method developed in the paper permits the alternating indexes to be determined differentially in dependence of alternating order. Expressions for the average lengths and the compositions of all possible alternating sequences starting with a given monomer unit and ending with unit found only at that position, are derived as well. The alternating indexes for binary radical copolymerization of styrene and methyl methacrylate and for ternary radical copolymerization of styrene, methyl methacrylate, and acrylonitrile were determined.

ISSN:0022-233X    

DOI:10.1080/00222337808063182

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The radical copolymerization of indene (IN) with maleic anhydride (MA) was investigated. The charge-transfer complexes (CT complexes) between comonomers were studied by means of spectrophotometric measurements. It was found that the maximum copolymerization rate occurred at a comonomer feed ratio that did not correspond to the composition of the CT complex and the composition of copolymer. It was shown that rate maximum was displaced towards an excess of IN in the solvents with strong donicity. The Acceptor Number of solvent influences neither the initial rate nor the position of the rate maximum. Some kinetic calculations were made to assess values of the cross-propagation rate constants and to elucidate the mechanism of propagation of macromolecular chains.

ISSN:0022-233X    

DOI:10.1080/00222337808063183

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Penultimate effects detected on the vinylidene chloride-ended radical in the vinylidene chloride-vinyl chloride copolymers prepared in thtrahydrofuran had previously been interpreted in terms of head-to-head addition. But new1H-NMR analysis of the homopolymers and copolymers synthesized in proton-donor and inert solvents suggest these effects, giving abnormal structures, might be due to the proton-transfer reactions, particularly in strong proton-donor solvents. Chain transfer reactions have been found degradative, so the overall polymerization rate is drastically decreased.

ISSN:0022-233X    

DOI:10.1080/00222337808063184

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

(S)-4-Methyl-2-N,N-dimethylaminopentyl methacrylate (DMAPM) was synthesized from the reaction of N,N-dimethyl-L-leucinol with methacryl chloride, and its radical polymerization was investigated. It was found that DMAPM readily polymerized by α,α1-azobisisobutyronitrile (AIBN) as an initiator to give poly-DMAPM. The copolymerization of DMAPM(M1) with styrene(Mz) was also studied in various solvents with AIBN as an initiator at 60°C. From the result obtained in benzene, Q and e values of DMAPM were determined to be 0.64 and -0.04, respectively. Specific rotations of the copolymers of DMAPM with styrene were not proportional to the weight percent of the DMAPM unit incorporated, but the observed relation gave a downward curve. The copolymerizations DMAPM with α, β-disubstituted monomers such as maleic acid, maleimide, and N-phenylmaleimide were carried out in order to induce asymmetric center in the polymer chain. After hydrolysis of the copolymers obtained, the hydrolyzed polymers were found to be optically active, suggesting an induction of asymmetric center into the polymer chain.

ISSN:0022-233X    

DOI:10.1080/00222337808063185

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor