Formic acid Subject

In the presence of strong acid, formic acid decomposes to water and carbon monoxide. In the process, reactive intermediates form which are capable of direct carboxylation of carbonium ions. Since many carbonium ions are readily generated by the reaction of alcohols with strong acid, the process of elimination and carboxylation can be conveniently carried out in a single flask. The carbonium ions generated are subject to the... 

This is illustrated by the TPD spectra of formate adsorbed on Cu(lOO). To prove that formate is a reaction intermediate in the synthesis of methanol from CO2 and H2, a Cu(lOO) surface was subjected to methanol synthesis conditions and the TPD spectra recorded (lower traces of Fig. 7.13). For comparison, the upper traces represent the decomposition of formate obtained by dosing formic acid on the surface. As both CO2 and H2 desorb at significantly lower temperatures than those of the peaks in Fig. 7.13, the measurements represent decomposition-limited desorptions. Hence, the fact that both decomposition profiles are identical is strong evidence that formate is present under methanol synthesis conditions. 

Oxidation of formic acid by mercuric chloride is the subject of several early kinetic studies. Dhar showed the reaction to be first-order in oxidant and substrate and to be subject to strong retardation by added chloride ions in agreement with earlier work. The reaction is also subject to retardation by added acid and presumably involves formate ion as the principal reactant. 

Mixed condensations of esters are subject to the same general restrictions as outlined for mixed aldol reactions (Section 2.1.2). One reactant must act preferentially as the acceptor and another as the nucleophile for good yields to be obtained. Combinations that work best involve one ester that cannot form an enolate but is relatively reactive as an electrophile. Esters of aromatic acids, formic acid, and oxalic acid are especially useful. Some examples of mixed ester condensations are shown in Section C of Scheme 2.14. Entries 9 and 10 show diethyl oxalate as the acceptor, and aromatic esters function as acceptors in Entries 11 and 12. 

The decomposition of formic acid over evaporated Pd-Au alloy films has been studied by Clarke and Rafter (69) the same reaction on Pd-Au alloy wires was studied by Eley and Luetic (128). The alloy films were prepared in a conventional high vacuum system by simultaneous evaporation of the component metals from tungsten hairpins. The alloy films were characterized by X-ray diffraction and electron microscopy. The X-ray diffractometer peaks were analyzed by a method first used by Moss and Thomas (SO). It was found that alloys deposited at a substrate temperature of 450°C followed by annealing for one hour at the same temperature were substantially homogeneous. Electron microscopy revealed that all compositions were subject to preferred orientation (Section III). 

In a related approach from the same laboratory, the perfluorooctylsulfonyl tag was employed in a traceless strategy for the deoxygenation of phenols (Scheme 7.82) [94], These reactions were carried out in a toluene/acetone/water (4 4 1) solvent mixture, utilizing 5 equivalents of formic acid and potassium carbonate/[l,T-bis(diphe-nylphosphino)ferrocene]dichloropalladium(II) [Pd(dppf)Cl2] as the catalytic system. After 20 min of irradiation, the reaction mixture was subjected to fluorous solid-phase extraction (F-S PE) to afford the desired products in high yields. This new traceless fluorous tag has also been employed in the synthesis of pyrimidines and hydantoins. 

Oxidation of Formic Acid. The oxidation of formic acid on Pt has been the subject of numerous studies on polycrystalline (26) and single crystal (8-11) electrodes. However, no consensus on the mechanism has been reached so far. 

These experiments have been applied to a variety of molecules, the predominant ones being strained organic molecules such as cubane, norbornane, cyclopropane, etc. [30-33]. Recently, van der Waals complexes of formic acid have been subjected to EMS spectroscopy [34]. 

A relatively unique type of reactive metabolite is carbene, i.e., a divalent carbon, which is a proposed intermediate in the oxidation of methylene dioxy-containing compounds. A methylenedioxy group in aromatic compounds is subject to O-dealkylation, e.g., 3,4-methylenedioxyamphetamine, as shown in Figure 8.20. The process generates formic acid and the catechol metabolite as final products. However, in the course of the reaction, a... 

Insertion reactions of C02 into the metal-hydride and metal-alkyl bonds are of considerable importance, since these reactions are involved not only in the catalytic cycle of the hydrogenation of C02 into formic acid but also in the catalytic cycle of co-polymerization of C02 and epoxide. In this regard, insertions of C02 into various metal-hydride, metal-alkyl, and similar bonds have been the subject of intense experimental investigation. For instance, C02 insertions into Cu(I)-CH3, Cu(I)-OR, Cu(I)-alkyl [26-28], Ru(II)-H [29], Cr(0)-H, Mo(0)-H, W(0)-H [30], Ni(II)-H and Ni(II)-CH3 bonds [31, 32] have been so far reported. 

Electrodes modified by underpotential deposition of metal were subjected as electrocatalysts to reduction of oxygen,oxidation of formic acid, and other processes in which polycrystalline metal substrates were used (see review in Ref. 151). Electrocatalysis of single-crystal electrodes modified by underpotential deposition was also investigated, as reviewed by Ad2iC. ... 

The decomposition of formic acid is one of the most extensively studied catalytic reactions. Several excellent review articles have been written on the subject (76- 78). From a large number of studies on supported metal catalysts the following, and sometimes contradictory, observations were made ... 

Formic acid was formed when acetaldehyde in the presence of oxygen was subjected to continuous irradiation (X >2200 A) at room temperature (Johnston and Heicklen, 1964). 

Ozonization of phenol in water resulted in the formation of many oxidation products. The identified products in the order of degradation are catechol, hydroquinone, o-quinone, cis,ds-muconic acid, maleic (or fumaric) and oxalic acids (Eisenhauer, 1968). In addition, glyoxylic, formic, and acetic acids also were reported as ozonization products prior to oxidation to carbon dioxide (Kuo et al, 1977). Ozonation of an aqueous solution of phenol subjected to UV light (120-W low pressure mercury lamp) gave glyoxal, glyoxylic, oxalic, and formic acids as major products. Minor products included catechol, hydroquinone, muconic, fumaric, and maleic acids (Takahashi, 1990). Wet oxidation of phenol at 320 °C yielded formic and acetic acids (Randall and Knopp, 1980). 

The stability of the uracil dimer is the subject of conflicting reports. Ishihara reports33 that it is destroyed by IN NaOH at 100°C, and Wacker states that it is unstable in acid, alkali, or even in boiling water. Setlow et al.46 report that 50% of the uracil dimer is destroyed by formic acid hydrolysis (presumably at 175°C). But Smith32 found it to be stable to boiling water, IN NH4OH, IN HC1, and trifluoracetic acid both at room temperature and at 155°C. 

Collection Method. The goal of the initial phase of our work was to determine the concentration of formic acid in engine exhaust subject to different forms of control, e.g., catalytic oxidation. Initially, samples were collected from diesel engine... 

In a later phase of work, the formic acid concentration in mine air subject to diesel emissions was measured. The expected concentrations were about one hundred times lower than those found in engine exhaust. The efficiency of the collection scheme was again measured under these conditions of challenge concentration (0.06 mg/m3). The collection efficiency was found to be 92.2% at this level (Table IV). 

Two ion chromatographic techniques were utilized to quantify formic acid in both diesel engine exhaust and mine air subjected to diesel emissions. A commonly used anion separation system utilizing a weak borate eluent adequately separated the acids of interest in diesel exhaust. It was, however, affected by the presence of strong acids during subsequent consecutive analyses. 

Results of analysis of formic acid in diesel engine exhaust subjected to various forms of post-combustion control, i.e., catalytic oxidation and water conditioning, indicate both a reduction of formic acid due to oxidation in the catalyst and dissolution in the water scrubber. In-mine analysis of formic acid at increasing distances from a source of diesel exhaust indicates that no significant change in concentration occurs. This finding contradicts a hypothesis that formaldehyde concentration decreases with increasing distance due to gas phase oxidation to formic acid. Surface reactions may, however, be important sinks for formaldehyde. 

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