Organic-based inhibitors

In the days of riveted boilers, concentration of caustic took place through the seepage or leakage of BW into rivet holes or seams. Sodium nitrate was the classic SCC inhibitor and was applied at 20 to 40% of the caustic alkalinity (2P-M). It is still used today in certain older facilities, although alternative organic-based inhibitors are now available. 

Metal- Working and Hydraulic Fluids. In the preparation of fluids for metal-working and hydrauflcs, the trend has been to replace organic-based materials with aqueous-based materials. Neodecanoic acid has found apphcation in these newer fluids as a corrosion inhibitor and a viscosity improver. For example, neodecanoic acid is used in an aqueous hydrauflc fluid concentrate for corrosion inhibition and improved antiwear properties (101), in the preparation of a thickened aqueous hydrauflc fluid to reduce viscosity loss (102), and in a water-soluble metal working oil to reduce corrosion (103). In a similar vein, neodecanoic acid has been used in antifreeze concentrates for corrosion inhibition (104). 

The alcohol is a mobile liquid, light in colour, with a boiling point of 170°C. It is very reactive and will resinify if exposed to high temperatures, acidity, air or oxygen. Organic bases such as piperidine and n-butylamine are useful inhibitors. 

Chemical Reactivity - Reactivity with Water A non violent reaction occurs forming carbon dioxide gas and an organic base Reactivity with Common Materials No reactions Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Slow polymerization occurs at temperatures above 113 of. The reaction is not hazardous Inhibitor of Polymerization Not pertinent. 

A variety of inorganic (31,87) and organic bases have been added to the catalyst to improve selectivity. The effectiveness of organic bases is very sensitive to structure. Morpholine is an effective inhibitor, more so than /Si-melhylmorphollne > N-elhylmorpholine > 3,5-dimethylmorpholine (55). Piperazine is effective, but ethanolamine and ethylenediamine are poisons. 

Although azoles are commonly thought of as only yellow metal inhibitors, they are, in fact, used for corrosion inhibition in a wider range of metals such as steel and aluminum. They also are often incorporated in molybdate-based programs to both provide some synergism and reduce the level of molybdate required. Azoles also are employed in many types of organic-based formulations, where they improve the overall protection of steel and reduce the risk of corrosion of yellow metals due to the corrosive action of some common phosphonates. 

Irreversible inhibitors may be classified for convenience as active site directed inhibitors and suicide or irreversible mechanism based inhibitors (IMBIs). They bind to the enzyme by either strong non-covalent or strong covalent bonds. Inhibitors bound by strong non-covalent bonds will slowly dissociate, releasing the enzyme to carry out its normal function. However, whatever the type of binding, the enzyme will resume its normal function once the organism has synthesized a sufficient number of additional enzyme molecules to overcome the effect of the inhibitor. 

An unprecedented example of the application of an organic azide as an enzyme inhibitor derives from the elegant studies of Stubbe and coworkers at MIT, who have investigated the mechanism of action of ribonucleotide reductase (RNR) using several mechanism-based inhibitors including 2 -azido-2 -deoxyuridine-5 -diphosphate (NjUDP) (71) [82]. RNR plays a... 

It should be emphasized that the organic cosolvent concentration should be kept to a minimum as it may alter the basal enzyme activity. Also, a compound could be a weak direct inhibitor but a potent metabolism/mechanism-based inhibitor. Therefore, it is important to evaluate both types of inhibition [52],... 

Merrill, A.H. Jr. and Schmelz, E. (2001) Sphingolipids metabolism-based inhibitors of carcinogenesis produced by animals, plants, and other organisms, in Handbook of Nutraceuticals and Functional Foods (ed R.C. Wildman), CrC Press, New York, NY, pp. 377-392. 

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