Copper inhibitor compounds effect

The copper(II) complexes of 3-ethoxy-2-oxobutyraldehyde bis(thiosemicarbazone) and related compounds are active in vivo agents [151, 158, 159]. The metal complexes of 2-heterocyclic thiosemicarbazones were evaluated for their cytotoxicities [160, 161]. Further studies have revealed that these ligand s iron and copper complexes are effective inhibitors of DNA synthesis at much lower concentrations than the free thiosemicarbazones without apparent cytotoxicity [127]. Although the iron(III) complex of 2-isoformylquinoline thiosemicarbaz-one, 21, is considerably more active than free 21, the copper(II) complex is only moderately more active [127]. 

Analogous cycles are observed in the polyacetal-steel and polyolefin-steel friction pairs. Physical-chemical processes can exert a favorable effect on the metal-polymer friction pair as well. For instance, metal-containing compounds of copper stearate and oleate types are formed in the contact zone as a result of tribochemical reactions when CFD copolymer rubs against copper. These compounds retard thermally destruction processes in CFD, serving as wear inhibitors (WI) for this system. 

The efficiency of benzo-hydroxamic acid derivatives, which are effective copper inhibitors for pitting and general corrosion processes, increases with increasing hydro-phobicity. The adsorption model of these compounds can be described as follows The molecule is attached to the metal surface by the unpaired electrons of the nitrogen and oxygen atoms of the hydroxamic moiety and by the n electron cloud of the phenyl ring, which may interact with the empty d-orbital of iron. 

DNPD is a member of the p-phenylenediamine family of AOs however, it is used more as an effective antioxidant and copper inhibitor (to prevent copper from degrading the cured rubber compound) than it is as an antiozonant (which is how most p-phenylenediamines are used). One to two parts per hundred rubber (phr) of DNPD will impart good heat and oxidative aging resistance with many different types of rubber. DNPD is relatively low staining compared to many other amine AOs. But DNPD can cause some discoloration with bright light exposure. 

Copper Corrosion Inhibitors. The most effective corrosion inhibitors for copper and its alloys are the aromatic triazoles, such as benzotriazole (BZT) and tolyltriazole (TTA). These compounds bond direcdy with cuprous oxide (CU2O) at the metal surface, forming a "chemisorbed" film. The plane of the triazole Hes parallel to the metal surface, thus each molecule covers a relatively large surface area. The exact mechanism of inhibition is unknown. Various studies indicate anodic inhibition, cathodic inhibition, or a combination of the two. Other studies indicate the formation of an insulating layer between the water surface and the metal surface. A recent study supports the idea of an electronic stabilization mechanism. The protective cuprous oxide layer is prevented from oxidizing to the nonprotective cupric oxide. This is an anodic mechanism. However, the triazole film exhibits some cathodic properties as well. 

The inhibition of lipid peroxidation by metalloporphyrins apparently depends on metal ions because only compounds with transition metals were efficient inhibitors. Therefore, the most probable mechanism of inhibitory effects of metalloporphyrins should be their disuniting activity. Manganese metalloporphyrins seem to be more effective inhibitors than Trolox (/5o = 204 pmol I 1) and rutin (/50 112 pmol I 1), and practically equal to SOD (/50= 15 pmol I 1). The mechanism of inhibitory activity of manganese and zinc metalloporphyrins might be compared with that of copper- and iron-flavonoid complexes [167,168], which exhibited enhanced antiradical properties due to additional superoxide-dismuting activity. 

As a consequence of the detection of catalytic pathways for formation of PCDD/F, special inhibition methods have been developed for PCDD/F. By this approach the catalytic reactions are blocked by adding special inhibitors as poisoning compounds for copper and other metal species in the fly ash. Special aliphatic amines (triethylamine) and alkanolamines (triethanolamine) have been found to be very efficient as inhibitors for PCDD/F, and have been used in pilot plants. The effect can be seen in Figure 8.6. The inhibitors have been introduced into the incinerator by spraying them into the postcombustion zone of the incinerator at about... 

There are several such toxic agents that cause considerable medical, public and political concern. Two examples are discussed here the heavy metal ions (e.g. lead, mercury, copper, cadmium) and the fluorophosphonates. Heavy metal ions readily form complexes with organic compounds which are lipid soluble so that they readily enter cells, where the ions bind to amino acid groups in the active site of enzymes. These two types of inhibitors are discussed in Boxes 3.5 and 3.6. There is also concern that some chemicals in the environment, (e.g. those found in industrial effluents, rubbish tips and agricultural sprays), although present at very low levels, can react with enhanced reactivity groups in enzymes. Consequently, only minute amounts concentrations are effective inhibitors and therefore can be toxic. It is suggested that they are responsible for some non-specific or even specific diseases (e.g. breast tumours). 

With the recognition in the late 1960s that there are two forms of MAO (Section 1.1.1), potential therapeutic implications related to isozyme selectivity needed to be considered in MAO inhibitor development. (The early literature also reveals some lack of distinction between copper-containing and flavin-containing MAOs.) An important case in point involves the clinical side effects associated with the cheese effect (Section 1.2.1) that made clear that there would be important clinical advantages to having available isozyme-selective inhibitors [115]. Follow-up studies with the well-known cyclopropylamine inhibitor trans-2-phenylcyclopropylamine (8a) demonstrated that this clinically useful compound is an irreversible inhibitor of MAO, but that it had no selectivity toward either MAO A or B [116]. 

TraA7s-2-phenylcyclopropylamine (8a) and its c/ s-isomer (8b) are competitive inhibitors of microbial copper-containing SSAO [37,130], Introduction of fluorine at position 2 of 8a and 8b had dramatic effects on the inhibition of microbial tyra-mine oxidase from Arthrobacter sp. by these compounds [130], Compound 60a with a cis arrangement of the fluorine substituent and the amino group was 10 times more potent an inhibitor than compound 8a. In contrast, the corresponding diastereomer 61a with a trans arrangement of the two substituents was five times less active than 8a (Table 3). 

A detailed study of the inhibition of MAOs by fluorophenyl cyclopropyl amines shows that the presence of fluorine has very important effects on this inhibition. While some of the regioisomers are inhibitors of the CAO (copper-containing amine oxidase), some other ones, such as 2-fluoro-l-arylcylopro-pyl amines, are excellent selective and irreversible inhibitors of MAO A. In this latter case, the nonfluorinated parent compound is a poor inhibitor of MAO B (Figure 7.55). ° " ... 

Use a copper corrosion inhibitor these compounds are typically effective in most fuel applications at treat rates from 5 to 25 ppm... 

Sodium petroleum sulphonates or calcium dinonylnaphthalene sulphonate can be applied as rust preventing additives and the catalytic effect of copper can be retarded by 2-mercaptobenzothiazole. Depending on operating temperature, various oxidation inhibitors may be used. Thus, 2,6-di-fert-butyl-4-methyl phenol is an effective inhibitor below 120 C while phenyl-alpha-naphthylamine is widely used in greases at low temperatures and above 120" C and phenothiazine is effective especially at temperatures above 150" C. Special compounds used as oxidation inhibitors for greases in the food industry are dilauryl thiodipropionate or citric acid. 

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