Cyclopentanone, degradation product

Four groups of degradation products, cyclic imides, pyridines, chain fragments and cyclopentanones were identified in thermo-oxidised PA 6,6. After 1,200 h of thermooxidation, l-pentyl-2,5-pyrrolidinedione (denoted by R3 in Figure 2.2) was the most abundant degradation product. Approximately four times more 1-pentyl-2,5-... 

In contrast to PVA, it was found [199-201] that when nylon-6,6 was subjected to temperatures above 300°C in an inert atmosphere it completely decomposed. The wide range of degradation products, which included several simple hydrocarbons, cyclopentanone, water, CO, COj and NHj suggested that the degradation mechanism must have been highly complex. Further research has led to a generally accepted degradation mechanism for aliphatic... 

Figure 3.3 Volatile degradation products in two oxidized polymers monitored by head-space GC. (a) Photo-oxidized LDPE with iron dimethyl dithiocarbamate and carbon black 1 = acetaldehyde 2 = methanol 3 = acetone 4 = 1-butanol 5 = butanol 6 = 3-pentanol. (b) Thermo-oxidized nylon 66 1 = acetaldehyde 2 = Cu-acetate 3 = cyclopentanone 4 = aniline.

Soto-Valdez H, Gramshaw JW. Cyclopentanone and cyclopentanone derivatives as degradation products of polyamide 6,6. J Mater Sci Lett 2000 19(10) 823-5. 

Fig. 5. Volatile degradation products of thermo-oxidised nylon 66 monitored by HS-GC. 1 = acetaldehyde, 2 = Cu-acetate, 3 = cyclopentanone, 4 = aniline...

Degradatiou. Heating of succinic acid or anhydride yields y-ketopimehc ddactone, cyclohexane-1,4-dione, and a mixture of decomposition products that include acetic acid, propionic acid, acryUc acid, acetaldeide, acrolein, oxaUc acid, cyclopentanone, and furane. In argon atmosphere, thermal degradation of succinic anhydride takes place at 340°C (123). Electrolysis of succinic acid produces ethylene and acetylene. 

Baeyer-Villiger oxidation is also a common feature during the catabolic degradation of a variety of other compounds, including monocyclic, bicyclic or polycyclic molecules. For monocyclic compounds, one of the first reports describing formation of a lactone from racemic a-substituted cyclopentanone by various Pseudomonas sp. was by Shaw1341. This could be regarded as the first indication that these reactions were to prove of interest for asymmetric synthesis since the lactone product displayed some optical activity (Fig. 16.5-6). 

One set of degradation studies on cholanic acid (9-1) (Scheme 1.9) led to scission of what are now known as ring A and ring C. One pair of the four new carboxylic acids led to a cyclopentanone and the other to an anhydride. On the basis of this, it was then inferred that ring A was six-membered whereas ring C comprised a cyclopentane (see also 8-1). It was later recognized that carboxylic acids attached directly to rings as in 9-2 cannot form a cyclopentanone. This exception was later attributed to steric strain in the hypothetical product. 

Methyl 4,6-O-methylene-o-D-mannopyranoside was the only product isolated from the LiBr-catalised transacetalation of the unprotected methyl glycoside with dimethojqmiethane. Cyclopentylidene derivatives of pentoses have been prepared in moderate yields by treatment of the free sugars with cyclopentanone in the presence of copper (II) sulphate and sulphuric acid. D-Xylose formed the diacetal (11) (also used in Scheme 3 below), whereas from D-ribose the 2,3-monoacetal (12) was obtained. A novel, selective synthesis of (5)-configurated 4,6-pyruvate acetals of methyl D-hexopyranosides is illustrated in Scheme 1. It relies on transacetalation from the dimethyl acetal of 3,4-dimethoxybenzophenone to give, after acetylation, preferentially the intermediate (13) with an axial aryl substituent which, on oxidation, suffers rapid degradation to a carboxylic acid group. ... 

Di Pasquale and co-workers [15] applied TGA and on-line flash Py-GC-MS to a study of thermal decomposition processes in glass hardened polyamides. The thermal decomposition of each polymer was found to begin at about 350 °C and proceeded with a weight loss of 100% for the non-glass fibre-reinforced polymers, under a nitrogen atmosphere. The analysis of the pyrolysate compounds showed that from polyamide-6,6 the most common volatile product at degradation temperatures was cyclopentanone, while from polyamide-6 there was a significant yield of e-caprolactam. 

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