Iron stabilities

Sodium polymethacrylates are also anionic and are useful as iron oxide dispersants and iron stabilizers. Typical MWs range from 6,000 to 20,000. Examples include Polacryl F70-40S, Tamol 850, Tamol 960, and Aquatreat AR-232. 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Acrylic acid terpolymers have appeared on the market in recent years. With their broad spectrum of functions, they offer the potential for excellent waterside conditions. In particular, the terpolymers have proved to be very effective particulate iron oxides dispersants and colloidal iron stabilizers. Examples include acrylic acid/sulfonic acid/sodium styrene sulfonate (AA/SA/SSS), such as Good-Rite K781, K797, K798. A further example is acrylic acid/ sulfonic acid/substituted acrylamide (AA/SA/NI), such as Acumer 3100. 

C) for cast iron and up to 140 °F for marstenitic SS (60 °C). Not suitable for galvanizing, aluminum, or enamels. Formic acid solvents containing the appropriate corrosion inhibitors and iron stabilizers can be very successful in cleaning larger units, such as once-through boilers. 

Crowe, C.W. "Guidelines for Selecting Iron Stabilizers for Use in Acidizing Treatments," 1980 Proc. Anna. Southwest. Pet. Short Course, Lubbock, April 17-18, 39 45. 

Sodium polymethacrylates are recognized as being useful as iron oxide dispersants and iron stabilizers. A typical MW is 6000 to 10,000. More typically, polymethacrylates now tend to be used in boiler water formulations rather than in CW formulations. 

Certain acrylic acid terpolymers have proved to be effective iron oxide dispersants and iron stabilizers (an example is acrylic acid/sulfonic acid/sodium styrene sulfonate, or AA/SA/SSS). 

Dose rates for polyacrylates vary considerably, depending on particular applications and whether they are incorporated in formulations with other polymers. However, for general purposes, the dose rate will tend to be from 1.25 to 5.0 ppm as actives in the recirculating cooling water. For particular applications (such as iron stabilization), there may need to be 5.0 to 10.0 ppm actives present. 

Proximal histidine provides for iron stabilization in the higher oxidized state Fe4+. 

Phosphoras(III), with its high propensity for accepting r-electron density from coordinated iron, stabilizes complexes in lower oxidation states, but higher oxidation state complexes are also known. For example, [FeCl3(PPh3)] is obtained from Fe3(CO)i2 and PPh3 in chloroform. The reaction of iron(III) salts with tertiary phosphines yields an iron(II) bis-phosphine complex. Iron(III) complexes of bidentate phosphines are better known and are typically four coordinate and of the form [FeX2(P-P0]. The lower... 

The dehydrogenation of bis(a-bromobenzyl) sulfide (41) with Fe2(CO)9 in the presence of furan affords (43). The iron-stabilized sulfur ylide (42) has been proposed as intermediate. Reaction of C -di-phenylnitrone (44) with l,2-bis(methylene)-3,3.4,4,5,5-hexamethylcyclopentane (45) in benzene at 80 C gives a [4 -I- 3] cycloadduct (46 18%), along with some other products. Landor et al. have shown that the dehydrobromination of allenyl bromide (47) in the presence of furan affords bicyclic ketone (49) in 9% yield. Apparently, a strain alkyne intermediate reacts with r-butyl alcohol to afford an enol ether (48), which is then converted to (49) (Scheme 11). 

Fig. 4.2. Eh/pH iron stability diagram showing the natural domains of the main groups of the iron bacteria.

Another synthetically useful carbon bond-forming reaction involves reaction of diiron nonacarbonyl with halo-carbonyl compounds. Noyori found that a,a -dibromoketones (498) react with diiron nonacarbonyl [Fe2(CO)9] to give an iron stabilized alkoxy zwitterion (499). The intermediate Jt-allyl iron species reacts with alkenes in a stepwise manner (initially producing 500) to give cyclic ketones such as 501, 23 and the product is equivalent to the product of a [3-t2]-cycloaddition with an alkene (sec. 11.11). This cyclization method is now known as Noyori annulation. This reaction is related to the Nazarov cyclization previously discussed in Section 12.3.C. Enamines can react with 498, but the initially formed enamino ketone product eliminates the amino group to form cyclopentanone derivatives. Intermediates such as 499 may actually exist as cations hound to a metal rather than as the alkoxide-iron structures shown.323b-d noted that Zn/B(OEt)3 is... 

The iron complexes show two-fold reactivity. They react with both strong electrophiles and with strong nucleophiles as the iron can stabilize both the cationic and anionic intermediates. While the electron-withdrawing iron moiety activates the diene to nucleophilic attack, it deactivates it towards electrophilic attack. Electrophilic attack is still useful - the iron stabilizes the diene to all the side reactions that could go along with electrophilic attack, and stabilizes the cationic product. 

Frenier and Larson proposed a solvent that is predominantly formic acid and also contains iron stabilizers and corrosion inhibitors. This mixture was developed for cleaning once-through (OT) boilers. A dynamic loop (Figure 7) was constructed to... 

Also of interest in comparing the two organometalUc units is the difference in reactivity with alternative electrophiles. The cobalt system reacted well with electron-neutral and electron-poor substrates, but not at all with electron-rich compounds. In contrast, the iron system reacts much better with electron-rich aldehydes. This does not necessarily indicate a complete change in reaction mechanism however, it does indicate a different rate-determining step in the cobalt case, the malonate reaction attack on the aldehyde is more critical, and the more electropositive the aldehyde, the better the yield. For the iron stabilized system, it may be that that the aldehyde actually acts as a nucleophile, attacking the iron-dieneyl system before fast ring closure of the malonate onto the carbon. Taken with the stereochemical arguments... 

Iron-stabilized oxallyl cations (generated in situ (eq 25) from a,o -dibromo ketones and Fe2(CO)9) react with alkenes. Noyori used this [3 + 2] cycloaddition reaction to produce cyclopentanone or cyclopentanone derivatives, as illustrated by a single-step synthesis of (i)-a-cuparenone (43) (eq 26). The reaction of a,a -dibromo ketones with enamines and Fe2(CO)9 yields substituted cyclopentenones in 50-100% yield (eq 27), as illustrated by the reaction with the a-morpholinostyrene (44). ... 

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