Formates, HCOO

36 FORMATES, HCOO- Solubility With the exception of the lead, silver, and mercury(I) salts which are sparingly soluble, most formates are soluble in water. The free acid HCOOH, is a pungent smelling liquid (boiling point 100-5°, melting point 8°), miscible with water in all proportions, and producing blisters when allowed to come into contact with the skin. 

To study these reactions use a m solution of sodium formate, HCOONa. 

Dilute sulphuric acid formic acid is liberated, the pungent odour of which can be detected on warming the mixture. 

Concentrated sulphuric acid carbon monoxide (HIGHLY POISONOUS) is evolved on warming the gas should be ignited and the characteristic blue flame obtained. The test can be successfully carried out with solid sodium formate. 

Ethanol and concentrated sulphuric acid a pleasant odour, owing to ethyl formate, is apparent on warming (for details, see under Acetates, Section IV.35, reaction 3). 

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Formic Acid, HCOOH (in aqueous solution), and Lead Formate, (HCOO)2Pb. 

Chemical Structure and Properties. Homopolymer consists exclusively of repeating oxymethylene units. The copolymer contains alkyhdene units (eg, ethyUdene —CH2—CH2—) randomly distributed along the chain. A variety of end groups may be present in the polymers. Both homopolymer and copolymer may have alkoxy, especially methoxy (CH3 O—), or formate (HCOO—) end groups. Copolymer made with ethylene oxide has 2-hydroxyethoxy end groups. Homopolymer generally has acetate end groups. 

Photocatalytic oxidation of ethanol on Pt/ri02 and Nafion coated Ti02 catalysts were studied using in situ infrared IR techniques. Infrared studies show that the reaction produced acetaldehyde, acetic acid, acetate, formic acid, formate, and CO2/H2O. Modification of the Ti02 catalyst by Pt and Nafion slowed down the oxidation reaction through site blocking. Incorporation of Pt was found to favor formation of formate (HCOO ), indicating Pt decreases the rate of oxidation of formate more than that of its formation. 

The adsorbed acetaldehyde (CHsCHOad), adsorbed acetate (CHsCOO ad) and adsorbed formate (HCOO ad) relative IR intensity during the first 20 min of photocatalytic oxidation are presented in Figure 52.3 for the Pt/Ti02 catalyst and Ti02 catalyst (Aeroxide P25S Degussa). Results of Ti02 are included for... 

The photocatalytic oxidation of alcohols constitutes a novel approach for the synthesis of aldehydes and acid from alcohols. Modification of Ti02 catalyst with Pt and Nafion could block the catalyst active sites for the oxidation of ethanol to CO2. Incorporation of Pt resulted in enhanced selectivity towards formate (HCOO ad)-Blocking of active sites by Nafion resulted in formation of significantly smaller amounts of intermediate species, CO2 and H2O, and accumulation of photogenerated electrons. The IR experimental teclmique has been extended to Attenuated Total Reflectance (ATR), enabling the study of liquid phase photocatalytic systems. 

Fig. 20. Infrared spectra of the surface formate (HCOO) at different coverages on Cu(llO) at 300 K. Inset shows the suggested orientation. (Reproduced by permission from Hayden et...

Figure 1.9. The local aligned-bridge adsorption sites of the formate (HCOO-) species on Cu(110) and Cu(100). Also shown is the cross-bridge site on Cu(100) originally proposed as a new type of surface bond but subsequently shown to be incorrect.

Dilute sulfuric acid Formates, HCOO" Formic acid is evolved (pungent odor)... 

Decomposition of formic acid on transition and posttransition metal surfaces has drawn a great deal of interest in recent years (121-137). The process shows distinct periodic regularities and, therefore, is well suited for the BOC-MP analysis. We want to understand the mechanism of HCOOH decomposition, in particular (1) why formate HCOO is the prevailing intermediate, (2) what is the preferred coordination mode, V or t)2, for HCOO, and (3) how HCOO decomposes further into C02 and CO. 

Kinetic evidence for synergic adsorption of carbon monoxide and water on the low-temperature shift catalyst Cu/ZnO/Fe203 was obtained by van Herwijnen and deJong (113), and IR spectra of surface formate were detected on several oxide catalysts, including CuO/MgO, at temperatures as low as 20 JC and pressures of 20 Torr, as reported by Davydov et al. (104). Decomposition of the surface formate to C02 and H2 occurred at 100-150°C over the Cu/MgO catalyst and at 250 300°C over the MgO catalyst, and the promotion effect of copper was attributed to the formation and decomposition of a labile surface formate (HCOO)2Cu. Ueno et al. (117) have shown earlier that surface formates are formed on zinc oxide, from CO and H20 as well as from C02 and H2, and hence an associative mechanism of the shift and reverse-shift reaction, involving formate intermediate, is believed to operate on many oxide catalysts. 

Another early effort in this direction [51] considered the competition for the bridging proton within the H-bond connecting a formate HCOO anion and an imine base of the sort HN=CH2. In the gas phase, it was found that the neutral pair HCOOH NHCH2 was preferred over an ion pair. However, again as in the aforementioned XH-amine complexes, the ion pair is progressively more favored as the dielectric constant of the medium rises. More specifically, in an in vacuo situation, the neutral pair in which the proton resides on the carboxylate rather than the imine... 

In order to understand the bewildering variety of reactions involving tetrahydrofolate, it is essential to realize that in biological systems, one-carbon compounds may exist in five different oxidation states. The most reduced form is methane, CH4, and the most oxidized form is C02. In between these two extremes are methanol (CH3OH), formaldehyde (CH20), and formate (HCOO ). 

E5-2 When 13C-labelled formaldehyde, 13CH20, is fed to live cultures of bacteria in an NMR spectrometer, the metabolism of the label can be followed by 13C NMR. Many bacterial species produce roughly equal amounts of formate (HCOO ) and methanol (CH3OH). This is reminiscent of the purely chemical Cannizzaro reaction in which a hydride ion (H ) is transferred directly from one formaldehyde molecule to another. The accompanying 61 MHz deuterium NMR spectra are of methanol that results from the metabolism of deuterium-labelled formaldehyde, CD2O, by Escherichia coli and Pseudomonas putida. What do they tell us about possible Cannizzarase enzymes in those organisms ... 

How do you account for the following facts formic acid, HCOOH, contains one carbon-oxygen bond of 1.36 A and another of 1.23 A, yet sodium formate, HCOO Na, contains two equal carbon-oxygen bonds, each of 1.27 A. (Check your answer in Sec. 18.13.)... 

Fig. 11.16 (a) Two-dimensional model showing the c(2 x 2)-formate/acetate structure, (b) Three-dimensional representation of a reaction sequence between formate (HCOO) and an added Ni atom. The interaction between the HCOO and the added Ni atom may facilitate the decomposition of formate to CO Cg) and Ni-H. Reprinted with permission from [21]. Copyright 2004 American Chemical Society... 

Formate, HCOO Ruthenate, Ru04 Ammonium, NH4+ Mercury(l), Hg2 +... 

Formate, HCOO Phosphite, HPOg Neptunyl(V), Np02 Neptunyl(Vl), Np02 ... 

Carboxylic Acids Both formic and acetic acid dissociate at room temperature and below on (100) terraces giving surface hydroxide and the formate (HCOO-) and acetate (CH3COO-) species (Peng and Barteau, 1991). 

In an oxygenated formate (HCOO-) solution the following reactions occur to produce 02 (Eq. 14-17) [35,112]. 

Recall that the formation of HjCO and CO result from the decomposition of the surfrice methoxy, CH3O, and the surface formate, HCOO, intermediates, respectively. The surfrice formate is produced by readsorption of formaldehyde product on the surface vanadia sites... 

They exist with relatively low activity in peroxisomes in the liver and kidney. The most important D-amino acid oxidase is glycine oxidase, an FAD-containing enzyme that catalyzes the formation of glyoxylate and also acts on D-amino acids to form their corresponding 2-oxoacid. Glyoxylate is further oxidized to COj and formate, HCOO , which is used in one-carbon (Cl) metabolism. 

Carboxylate salt The salt of a carboxylic acid, such as sodium formate, HCOO Na+. 

Later, we will see that NO2 will again be converted to nitrite (5.206) via electron transfer processes independent of the reaction chain (5.201) to (5.203), thereby establishing dynamic equilibria. In the presence of formate HCOO , which is an efficient OH radical scavenger, it not only prevents nitrite losses via reaction (5.191), but actually converts NO2, the major product of nitrate photolysis, into additional nitrite via the following reaction sequence = 4.3 10 L mol s and ks 202 = 2.4 10 L mol s ... 

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