Choichiro Shimasaki

Determination of melamine derivatives, melame, meleme, ammeline and ammelide by high-performance cation-exchange chromatography

Abstract The thermal decomposition of melamine produces melame and meleme, while alkaline hydrolysis of melamine produces ammeline and ammelide. These four melamine derivatives were determined by high-performance cation-exchange chromatography using phosphate buffer as the eluent. The elution behavior during the isocratic and gradient elutions was examined and the determination was simultaneously achieved using photodiode array UV–Vis detection. An isocratic elution with 50 mM phosphate buffer (pH 2.5) seemed most suitable for the rapid and quantitative analysis. Three types of gradient elutions involving phosphate- and NaCl-concentrations, and pH also showed satisfactory separations for the melamine derivatives.

Effect of the fire-retardant, melamine, on the combustion and the thermal decomposition of polyamide-6, polypropylene and low-density polyethylene

Abstract Combustion tests show that polyamide-6 (PA-6) mixed with melamine is self-extinguishing. The thermal degradation process in PA-6 is modified strongly by the presence of melamine, so that the temperature of decomposition is lowered and the composition of the resulting volatile products is changed. On the other hand, melamine is not effective for either polypropylene (PP) or low-density polyethylene (LDPE). Activation energies based on thermogravimetry (TG) curves for the thermal decomposition of each sample at different heating rates are in the range of about 88.1 to 263 kJ mol −1 . The fluctuations found in activation energies indicates that a charring mechanism may contribute to the overall process. Minor amounts of thermal decomposition products other than ϵ-caprolactam were also evolved from the pure PA-6, their formation being suppressed in mixtures with melamine. The charring process occurs in parallel with the volatilization of decomposition products of PA-6, on which melamine seems not to have a significant effect. It appears evident that, compared with PP and LDPE, PA-6 is much more susceptible to thermal decomposition in the presence of melamine.

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from cottonseed oil and valeric acid in batch culture of Ralstonia sp. strain JC-64

A Ralstonia sp. strain JC-64 that is capable of accumulating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[3HB-co-3HV]) from cottonseed oil and valeric acid was isolated. By using a high limiting-nitrogen (HLN) mineral medium as the medium for the second stage of the fermentation process and by adding the two carbon sources at different times, a range of copolymers with 12–62 mol% of 3HV were produced from a series of HLN mineral mediums containing different compositions of cottonseed oil and valeric acid by Ralstonia sp. JC-64. The melting temperature (Tm) of polyhydroxybutyrate from cottonseed oil was 174°C and that of P(3HB-co-3HV) with the highest 3HV-mol fraction (62%) was 81°C.

Formation of S,S-diphenyl-S-methoxythiazyne Ph2S(OMe)(≡N) in the alkaline hydrolysis of S,S-diphenyl-N-halosulfilimines

Abstract The structure of a compound formed during the alkaline hydrolysis of S,S-diphenyl-N-halosulfilimines to the corresponding sulfoximine in methanol was assigned to PhS(OMe)(≡N)Ph, S,S-diphenyl-S-methoxythiazyne, on the basis of spectroscopic analyses and chemical reactions.

Syntheses and structural analysis of 10-monoxy- and -dioxy-5-N-substituted iminothianthrene derivatives and the stereochemical change on their sulfur atom under acidic and thermal conditions.

5-(N-p)-Toluenesulfonyl)iminothianthrenes, whose sulfur atoms are oxidized to a sulfoxide or sulfone at the 10-position, were hydrolysed readily in high yield to N-unsubstituted-sulfilimines by using concentrated H2SO4. During hydrolysis, 10-monoxy-5-N-unsubstituted-sulfilimines were obtained as a separable mixture of the cis and trans isomers. The stereochemical interconversion of these compounds was studied under both hydrolytic and thermal conditions and their structures were elucidated by using X-ray crystallography.

Thiapyran formation via an unexpected thioaldehyde intermediate by the thermal decomposition of phenacyl sulfoxides bearing some heterocycles

Thermolysis of phenacyl sulfoxide bearing some nitrogen-containing heterocycles in the presence of 2,3-dimethyl-1,3-butadiene led to 6-benzoyl-5,6-dihydro-3,4-dimethyl-2H-thiapyran. This product was considered to be formed by the Diels-Alder reaction of the diene with thioaldehyde formed initially by the thermal decomposition of the sulfoxide.

Pyrolysis of tetraphenyl imidodiphosphate

The pyrolysis of tetraphenyl imidophosphate (1) was investigated by DTA—TG, IR, 1H- and 31P-NMR, mass spectroscopy, and TG—GC/MS. The DTA—TG/DTG curve showed that the pyrolysis of 1 occurred in one stage. Compound 1 melted at about 110°C and pyrolyzed to polyphosphates accompanied by a weight loss of about 70% in the temperature region from 250 to 450°C. The results of IR, 1H and 31P NMR and TG—GC/MS confirmed that this weight loss could be attributed to the cleavage of the PN bond accompanying the formation of diphenyl phosphoramidate (2) and to the liberation of pyrolysis intermediate substances such as phenol, triphenyl phosphate (3), triphenyl N-(diphenoxyphosphoryl)imidophosphate (4), hexaphenoxycyclotriphosphazene (5), diphenyl hydrogen phosphate (6), and 2. Cleavage of PO(Ph) or (P)OPh bonds is characteristic of fragmentation in the high mass spectrum of 1. Subsequently, the fission species transform to other species forming new compounds. The activation energy of the pyrolysis of 1 was estimated to be 111 kJ mol−1, and that for 2 and 3 to be 151 and 220 kJ mol−1, respectively.

PHOSPHINECARBOTHIOAMIDE FORMATION IN THE REACTION OF TETRAZOLYLSULFINYLMETHYL(DIMETHYL)PHOSPHINE OXIDE WITH AMINES

Abstract In the study of the thermolysis of heteroaryl substituted sulfoxides, we examined the same reaction in the presence of several amines, such as aniline, benzylamine, and morpholine. In the case of 5-(1-phenyl)-1,2,3,4-tetrazolylsulfinylmethyl(dimethyl)phosphine oxide ( 1 ), the corresponding phosphinecarbothioamide 2 were unexpectedly obtained in moderate yields together with 1-phenyl-1,2,3,4-tetrazole ( 3 ). These products are considered to be formed by the addition reaction of amines to the sulfine formed initially and then elimination of H 2 O.

pH-Dependent elution behaviour of meleme in high-performance cation-exchange chromatography

Abstract Meleme, one of thermal decomposition products of melamine, ws analyzed satisfactorily by high-performance cation-exchange chromatography using 20 m M phosphate buffer as eluent. The elution behavior of meleme and melamine at various pH values (pH 2.0–6.0) was examined and the determination was accomplishes simultaneously using photodiode array UV-Vis detection.

Synthesis of a stable sulfenic acid, trans-decalin-9-sulfenic acid

Hydrolysis of trans-9-decalyl methoxymethyl sulfoxide with 7% perchloric acid in MeOH–H2O (2 : 1) gave crystalline trans-decalin-9-sulfenic acid whose structure was confirmed by IR, NMR and mass spectrometry; addition to methyl propiolate affording methyl trans-3-(trans-9-decalylsulfinyl)acrylate.