人体皮脂组分角鲨烯污化棉织物的老化黄变性能

为研究纺织品老化黄变的主要原因,采用分光光度电子测色配色仪对人体皮脂组分角鲨烯污化的纯棉织物在各种老化条件（老化温度、湿度、光照强度和环境氧含量）下的黄变程度进行了系统研究,应用傅立叶变换红外光谱（FTIR）分析和场发射扫描电镜（SEM）对角鲨烯在老化过程中的结构变化及其与纯棉基质的结合状况进行了研究。结果表明：随着老化环境中温度、湿度、光照强度和氧含量的增加,织物的老化黄变程度加剧;老化前后角鲨烯的化学结构发生了明显变化,老化产物含有羟基及共轭羰基基团;角鲨烯油污多以包覆纤维及填覆纤维间凹陷的形式结合于纤维表面。     

不饱和脂肪酸结构与自动氧化关系的理论研究

利用计算化学B3LYP/6-31G(d,P)方法,以C-H键解离能(BDES)为理论参数,从分子水平研究了影响油脂氧化稳定性的结构因素.以皮革加脂剂中常含的不饱和脂肪酸棕榈油酸(9Z-,16:1)、油酸(9Z-,18:1)、蓖麻油酸(9Z-,18:1)、芥酸(13Z-,22:1)、亚油酸(9Z,12Z-,18:2)、亚麻油酸(9Z,12Z,15Z-,18:2)、α-桐油酸(9Z,11E,13E-,18:3)和二十二碳六烯酸DHA(4Z,7Z,10Z,13Z,156,19Z-,22:6)为模型,研究了不饱和脂肪酸碳链上最容易发生抽氢反应的位置,以及碳链长度、双键个数、酯化反应、取代基对不饱和脂肪酸自动氧化的影响.计算表明,紧邻不饱和脂肪酸双键(-C=C-)的α-CH2,尤其是具有双烯丙基结构的α-CH,是油脂氧化抽氢的位点,而双键上的-CH=CH-最难发生抽氢.不饱和脂肪酸的氧化稳定性不仅与双键数目有关,而且与双键的相对位置有关,在抽氢后能形成共轭结构的不饱和脂肪酸容易发生自动氧化.碳链上的取代基对不饱和脂肪酸的自动氧化有影响,吸电子基团有利于提高脂肪酸的氧化稳定性,但碳链的长短对氧化稳定性的影响并没有规律.     

Liquid-phase p-t-butyltoluene autoxidation enhanced by electrochemistry: Activation of the catalytic effect of cobalt acetate

The autoxidation of p-t-butyltoluene (TBT) at 80 °C in the liquid phase is carried out with an initial mixture of cobalt(III) and cobalt(II) acetate in an acetic acid solution. The autoxidation kinetics of TBT is appreciably accelerated by electrolysis with a anodic current density of 62.5 A m^–2. The electrolysis increases the concentration of cobalt(III) acetate, the actual catalyst of the autoxidation reaction. The end product of oxidation is p-t-butylbenzoic acid (TBBA). p-t-Butylbenzaldehyde (TBBZ) is an intermediary whose concentration passes through a maximum. The oxidation experiments with TBT were performed with total cobalt acetate concentrations ranging from 0.0188 to 0.169 mol dm^–3. An increase in total cobalt acetate concentration favours the electrochemical regeneration of Co^III and slightly improves the TBBZ selectivity. The duration of TBT oxidation into TBBA is reduced by a factor of 5 compared with a reaction without electrolysis.     

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

Non‐heme iron complexes are emerging as powerful and versatile catalysts in several oxidative transformations. The most investigated iron complex structures are based on aminopyridine ligands, but a number of imine‐based ligands have been also tested. In this review a collection of recent results obtained in oxidation catalysis with non‐heme imine‐based iron complexes is presented. Their catalytic performances in C H, CC and  S oxidation are spread over a wide range of efficiency, going from very low to quite high. Such performances are discussed, whenever possible, in light of the operating reaction mechanisms and of catalyst stability. In order to facilitate the discussion, an initial survey of the most useful mechanistic tools widely applied to distinguish a metal‐based oxidation from a radical‐chain process is also reported. Imine‐based catalysts are divided into two classes: (i) salen‐Fe complexes, and (ii) imine‐Fe complexes. In some cases clues for free‐radical oxidation mechanisms have been reported while in other cases evidence for metal‐based mechanisms has been collected. The preferred mechanistic pathway is shown to be a function of catalyst structure and features. Interestingly, some imine‐based iron complexes are able to perform stereospecific oxidation reactions, demonstrating that the imine functionality can be incorporated in ligands designed for oxidation catalysis.

     

Hydroperoxide formation during autoxidation of conjugated linoleic acid methyl ester

The aim of this study was to investigate whether hydroperoxides are formed in the autoxidation of conjugated linoleic acid (CLA) methyl ester both in the presence and absence of α‐tocopherol. The existence of hydroperoxide protons was confirmed by D₂O exchange and by chemoselective reduction of the hydroperoxide groups into hydroxyl groups using NaBH₄. These experiments were followed by nuclear magnetic resonance (NMR) spectroscopy. The ¹³C and ¹HNMR spectra of a mixture of 9‐hydroper‐oxy‐10‐trans,12‐cis‐octadecadienoic acid methyl ester (9‐OOH) and 13‐hydroperoxy‐9‐cis, 11‐trans‐octadecadienoic acid methyl ester (13‐OOH), which are formed during the autoxidation of methyl linoleate, were studied in detail to allow the comparison between the two linoleate hydroperoxides and the CLA methyl ester hydroperoxides. The ¹³CNMR spectra of samples enriched with one of the two linoleate hydroperoxide isomers were assigned using 2D NMR techniques, namely Correlated Spectroscopy (COSY), gradient Heteronuclear Multiple Bond Correlation (gHMBC), and gradient Heteronuclear Single Quantum Correlation (gHSQC). The ¹³C and ¹H NMR experiments performed in this study show that hydroperoxides are formed during the autoxidation of CLA methyl ester both in the presence and absence of α‐tocopherol and that the major isomers of CLA methyl ester hydroperoxides have a conjugated monohydroperoxydiene structure similar to that in linoleate hydroperoxides.     

Anti- and Prooxidant Properties of Carotenoids

Carotenoids can be effective singlet oxygen quenchers and inhibit free-radical induced lipid peroxidation. A remarkable property of β-carotene ( 1a ) is the change from an antioxidant to a prooxidant depending on oxygen pressure and concentration. In the present study a considerable number of carotenoids ( 1a , 2c , 2d , 2e , 3a , 4a , 5a , 6a , 7a , 8a , 8h , 8i , 8j , 9f , 10a , 11a , 12g ) was investigated using two independent approaches: 1. Comparison of their effects on inhibition of the free-radical oxidation of methyl linoleate, and 2. The direct study of the effect of oxygen partial pressure upon their rates of oxidation. It is shown that some carotenoids ( 7a , 8a ) are even more effective than the well-known compounds β-carotene ( 1a ) and astaxanthin ( 5a ) and are powerful antioxidants without any prooxidative property. Different carotenoids display different behaviour depending on chain length and end groups. The influence of these functional groups on the antioxidative reactivity is discussed.     

Aging of oily soils on textile materials: A literature review

Literature covering the problems of oily soil aging on textile materials is reviewed. Difficulty of soil removal and discoloration of oily soiled fabrics were the main problems of aged oily soil reported by researchers. Yellowing of fabrics is attributed mainly to residual oily soils although there are other causes. Oxidation of unsaturated oils was suggested as the cause of problems related to aging of oily soils; thus, the autoxidation mechanisms of unsaturated lipids are an important part of this review. The effects of aging on oily soil removal are attributed to this oxidation of unsaturated oils, wicking of oils into small capillaries within the yarn structure, and possible chemical linkages of aged oils with fibers. Thus, included in this review are studies on the interactions between lipid oxidation products and proteins that suggest interaction between aged oily soils and fiber substrates.     

Effects of α- and γ-tocopherols on formation of hydroperoxides and two decomposition products from methyl linoleate

The antioxidant effects of α-and γ-tocopherols (at 0, 10, 100, 500, and 1000 ppm) were evaluated in a model system based on the autoxidation of methyl linoleate in bulk for 4 d at 40°C. Samples were collected every 24 h and analyzed for the 9 cis,trans, 9 trans,trans, 13 cis,trans, and 13 trans,trans isomers of hydroperoxide, hydroxy, and ketodiene oxidation products by high-performance liquid chromatography. Results showed that both α- and γ-tocopherols are effective hydrogen donors as evidenced by their abilities to inhibit the formation of hydroperoxides, hydroxy compounds, and ketodienes and the cis,trans to trans,trans isomerization of hydroperoxides. Compared with γ-tocopherol, α-tocopherol was a more efficient antioxidant at very low concentrations (10 ppm) but a less efficient antioxidant at the high concentrations (100–1000 ppm). This paradoxical behavior is explained on the basis of differences in ease of hydrogen donation between the two tocopherol homologs. Although α-tocopherol shows some loss of efficiency with increasing concentration, it is not a prooxidant when compared to the control void of antioxidants.     

Antioxidant activity of oat extract in soybean and cottonseed oils

A previously published method for extracting antioxidants from Noble oats with methanol was modified to improve the antioxidant activity. The extract was tested in soybean and cottonseed oils held at 30 and 60°C in the dark and at 30°C in the light. During storage, the peroxide values (PV) of the oils were generally significantly lower (P≤0.05) with the addition of the extract than was the control (no additives), and the PV were slightly higher than for oils containing TBHQ. In addition, the extract was added to emulsions of the same oils and held at 30°C in the light and at 60°C in the dark. The PV of the emulsions containing the extract were significantly lower (P≤0.05) than were the PV of those containing tertiary butylhydroquinone and the control.