Degradative oxidation

Strecker Degradation (Oxidative Deamination), Mild oxidizing agents such as aqueous sodium hypochlorite or aqueous A-bromosuccinimide, cause decarboxylation and concurrent deamination of amino acids to give aldehydes. 

RUFF - FENTON Degradation Oxidative degradation of aldoses via a-hydroxy acids to lower chain aldoses. 

The author is unaware of any commerical polymers that are specifically designed to degrade oxidatively, although oxidation may be involved in association with hydrolytic and biological degradation. It may be of interest to note that before World War II products known as rubbones were produced by degrading natural rubber with cobalt linoleate in the presence of cellulosic materials to produce low molecular weight, fluid oxidised natural rubber (Section 30.4). 

Brittleness with age. Degradative oxidation can be produced, even after vulcanization, due to oxygen and ozone attack to the carbon-carbon double bonds. Adequate antioxidants must be added if ageing is a key factor in performance. 

A few relatively recent published examples of the use of NMR spectroscopy for studying polymer degradation/oxidation processes will now be discussed briefly. At the early stages of degradation, the technique can be used to provide chemical identification and quantification of oxidised species for polyolefins, oxidation sites can be identified by the chemical shifts of -CH2- groups a and ji to carbons bonded to oxygen [85]. Spin-spin relaxation times may be determined by a pulse sequence known as the Hahn spin-echo pulse sequence. 

Liquid chromatography (LC) encompasses several techniques, which includes HPLC and SEC (sometimes referred to as GPC). Many variants of and developments from these techniques exist, and are used in the study and analysis of polymer degradation/oxidation. As discussed earlier, SEC is often coupled with MALDI-ToF-MS to facilitate the identification of the products of polymer degradation. SEC has also been coupled with mid-infrared detection and similarly used for studies of polymer degradation. SEC/GPC is discussed further below. 

As is evident in the many examples selected in this chapter to illustrate the molecular characterisation and analysis of polymer degradation and oxidation processes, almost, without exception, each study or investigation cited has involved use of more than one analytical method or characterisation technique, often many more than two. This clearly emphasises the importance of using a multi-technique approach to provide supportive, complementary and confirmatory information, since each technique or method yields a different aspect of the degradation/oxidation process in polymers. 

Nitroalkenes with Chiral Auxiliaries The use of carbohydrates as chiral auxiliary in Diels-Alder reactions for the stereoselective preparation of carbocyclic and heterocyclic chiral rings is well documented.48 For example, D-manno-nitroalkene reacts with 2,3-dimethyl-1,3-butadiene to give a 65 35 mixture of adducts, as shown in Eq. 8.29. The configurations at C-4 and C-5 have been determined to be (4R,5R) and (45,55), respectively. Hydrolysis of the product followed by degradative oxidation of the sugar side chains leads to enantiomerically... 

Another dictyotalean genus, Dictyopteris, has been reported to produce an array of Cu cyclic or acyclic acetogenins derived from higher fatty acids (Stratmann et al. 1992). Examples include the hydrocarbons dictyopterene A (Fig. 1.6e) (Moore et al. 1968) and dictyopterene D [B1] (Fig. 1.6f) (Moore and Pettus 1971), which act as pheromones in sexual reproduction (Stratmann et al. 1992). The compounds are short lived and undergo facile degradative oxidation to yield compounds such as dictyoprolene (Fig. 1.6g) (Yamada et al. 1979) and dihydrotropone (Fig. 1.6h) (Moore and Yost 1973). In a tme exhibition of efficiency, these degradative products have also been shown to act as a chemical defense (Hay et al. 1998). 

This substance undergoes degradation, oxidation, and cyclization reactions to form the first steroid "lanosterol", which is transformed into cholesterol after several steps. Schematic outlines of these biosynthetic pathways are well illustrated in the literature [56-59]. 

In the radiolysis of nitric acid, HNO2 and H2O2 are formed. They strongly affect the solvent degradation, oxidation states of metal ions, and corrosion condition of the material. However, HNO2 and H2O2 are not coexisting because the next reaction will take place. 

The oxidant is seeking electrons and is therefore an electrophile. As a side reaction, the oxidant can attack and destroy the ring. The NO, deactivates the ring toward electrophilic attack, thereby stabilizing it toward degradative oxidation. 

New International Dictionary, Merriam Co, Springfield, Mass(195I), 73 Alperox C. Trade name for tech lauroyl peroxide manufd by the Lucidol Division of Wallace Tieraan, Inc, Buffalo, NY Alpha-Cellulose is that portion of cellulosic materialfpulp, paper, etc) which,after treatment with 17,5% NaOH(mercerized strength) at 20° and diln to 7.3% NaOH,can be separated by filtration. The residue of alpha-cellulose is a good index of the undegraded cellulose content of the material. The alkali treatment removes degraded(oxidized or hydrolyzed) cellulose and short chain material. Some pentosans and hexosans may... 

Pure homoallylic alcohols are converted into y-amino-p-hydroxy acids by protection as the TBDMS ether or A(0-acetonide followed by degradative oxidation of the terminal alkene using a catalytic amount of ruthenium(III) chloride and sodium periodate (Scheme... 

Chromones are readily oxidized by permanganate or dichromate with opening of the pyran ring and the formation of a salicylic acid (402). Flavones and isoflavones are also degradatively oxidized for example oxidation of munetone (403) with alkaline hydrogen peroxide yields 2-methoxybenzoic acid and 4-hydroxy-2-isopropylbenzofuran-5-carboxylic (isotubaic) acid. 

The results of the oxidations of polyfluoropropanes and higher alkanes are strongly dependent both on the structure of the substrate and the oxidation agent. Shorter chain compounds formed by degradative oxidation are usually present in the reaction mixture as byproducts. Thus, 1,1,1 -trifluoropropanecan be converted by nitric acid and oxygen into a mixture of trifluoroacetaldehyde (5) and l,l,l-trifluoro-3-nitropropane (6).8... 

Less is known about the combustion pathway. Using IR spectroscopy, formate, carboxylate, bidentate carbonate, monodentate carbonate, and acetate bands have been observed when butene is adsorbed on Surface degradation (oxidation) of butadiene has also been observed on a-Fe203 at room temperature (34). 

Degradative oxidation of aromatic rings into carboxylic acids4b and oxidation of aromatic compounds to quinones2a... 

Thus, the degradative oxidation of chlorophenols proceeds by a hydroxy-lated species (Equation 6.99 and Equation 6.100), followed by ring opening to yield aldehydes and ultimate degradation of C02 and CP. It was suggested that the first step is the formation of radical cation by acid-catalyzed dehydration of radicals formed due to the interaction of OH with chlorophenols. 

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