Bromine-formic acid reaction

The rate of the bromine-formic acid reaction also depends on the concentration of formic acid. However, by adding a large excess of fonnic acid to the reaction mixture we can ensure that the concentration of formic acid remains virtually constant throughout the course of the reaction. Under this condition the change in the amount of formic acid present in solution has no effect on the measured rate. 

In its reactions SsO shows properties typical for both sulfur homocycles and sulfoxides. With elemental chlorine SOCI2 and S2CI2 are formed, with bromine SOBr2 and S2Br2 are obtained. Water decomposes SsO to H2S and SO2 besides elemental sulfur while cyanide ions expectedly produce thiocyanate. The reaction with iodide in the presence of formic acid is used for the iodometric determination of the oxygen content [70] ... 

To provide an example of a reaction that is very different to electrophilic aromatic substitution, the oxidation of formic acid by bromine was also studied. This reaction, which involves electrophilic attack on the formate anion (15) (Cox and McTigue, 1964 Smith, 1972 Herbine et al., 1980 Brusa and Colussi, 1980), is catalysed by a-CD (/c /k2u = 11) (Tee et al., 1990a), and the degree of transition state stabilization (Xts = 0.18 mM) is similar to that for phenols (Table A4.2) and most of the other substrates (Table A4.4). 

A. Tri-O-acetyl-D-xylono-l,4-lactone 2. a) Bromine oxidation. A 250-mL, threenecked, round-bottomed reaction flask equipped with a magnetic stirrer, thermometer, and an addition funnel is charged with 30.0 g (0.20 mol) of D-xylose and 80 mL of water. After the clear aqueous solution is cooled with an ice-water bath, 34.0 g 0.23 mol) of potassium carbonate is added in portions, keeping the temperature below 20°C. After the mixture is cooled to below 5°C, 12 mL (0.22 mol) of bromine is added dropwise over 90 min, keeping the temperature of the reaction mixture below 10°C (Note 1). The orange solution is stirred at that temperature for 30 min, then at room temperature overnight. The reaction is quenched by careful addition of 88% formic acid (2.5 mL) to afford a colorless solution (Note 2). The solution is concentrated at 50°C on a rotary evaporator and 20 mL of acetic acid is added. The mixture is Concentrated again at 50°C to remove any residual water (Note 3). 

A compound that includes an aminopyrimidine ring as well as the quaternary salt present in thiamine shows preferential inhibition of absorption of that co-factor by coccidia parasites over uptake by vertebrates. The compound is thus used in poultry where coccidiosis is an economically important disease. Condensation of ethoxymethylenemalononitrile (42-1) with the amidine (42-2) leads to the aminopyrimidine (42-4), probably via the intermediate addition-elimination intermediate (42-3). The nitrile group is then reduced to the methylamino derivative (42-5) by means of hthium aluminum hydride. Exhaustive methylation, for example by reaction with formaldehyde and formic acid, followed by methyl iodide leads to the quaternary methiodide (42-6). The quaternary salt is then displaced by bromine, and the resulting benzyhc-like cylic halide (42-7) is displaced by 2-picoline (42-8). There is thus obtained amprolium (42-9) [43]. 

T FIGURE 12.4 The reaction of formic acid (HC02H) and bromine (Br2). As time passes (left to right), the red color of bromine disappears because Br2 is reduced to the colorless Br ion. The concentration of Br2 as a function of time, and thus the reaction rate, can be determined by measuring the intensity of the color. 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by inhalation. A corrosive irritant to the eyes, skin, and mucous membranes. With the appropriate conditions it undergoes hazardous reactions with formic acid, hydrogen fluoride, inorganic bases, iodides, metals, methyl hydroperoxide, oxidants (e.g., bromine, pentafluoride, chlorine trifluoride, perchloric acid, oxygen difluoride, hydrogen peroxide), 3-propynol, water. When heated to decomposition it emits toxic fumes of POx. 

The method (16) describes the titrimetric microdetermination of salicylic acid, aspirin and p-hydroxybenzoic acid by amplification reactions. The cited acids are brominated with Br to form tribromophenyl hypobromite, which after removal of unconsumed Br wtih formic acid, is treated with iodide to give tribromophenol and free iodine. The liberated iodine is extracted with CHCI3 and reduced to iodide, which is determined by oxidation with Br and iodimetric titration of the iodate produced with Na2S203 solution. This six fold amplification... 

Alkyl- and aryl-substituted carboxylic acid derivatives such as ethyl 4-methoxybenzoate, diethyl phthalate,104 aryl- and alkylcarboxylic add halides or anhydrides10,2 5 8 give benzoxazinones (193). When IA was brominated in glacial acetic acid, 193 (R2 = CHBr2) was obtained.259 Anthranilic acid (4) with A-methyl IA (24) leads to 194, which cyclizes in sulfuric acid to the benzoxazinone 195134 (Scheme 33). Reaction of /V-formylanthranilic acid (196) (available from 1A and formic acid) with IA again yields the quina-zolinone 19710 260 (Eq. 19). 

The reagent is prepared just as the corresponding trichloride is prepared by reaction of catechol with PBr, and then bromine. It reacts with formic acid esters to give a,a-dibromomethyl alkyl ethers 1... 

TABLE 13.1 Rates of the Reaction between Molecular Bromine and Formic Acid at 25°C... 

FIGURE 13.5 The instantaneous rates of the reaction between molecular bromine and formic acid at t = 100 s, 200 s, and 300 s are given by the slopes of the tangents at these times. 

FIGURE 13.6 Plot of rote versus moleculor bromine concentration for the reaction between molecular bromine and formic acid. The straight-line relationship shows that the rate of reaction is directly proportional to the molecular bromine concentration. 

As formic acid has not been detected in the solution either, it should undergo further reactions, for example oxidation by bromine ... 

OXALIC ACID (144-62-7) CjHjO. HOOCCOOH Combustible solid heat-sensitive. (combustible <215 F/101°C. Fire Rating 1). Exposure to elevated temperatures, hot surfaces, or flames causes decomposition and the formation of toxic and flammable formic acid and carbon monoxide. Hygroscopic the solution in water is a medium-strong acid. Violent reaction with strong oxidizers, acid chlorides alkali metals bromine, furfuryl alcohol hydrogen peroxide (90%) phosphorus trichloride silver powders sodium, sodium chlorite sodium hypochlorite urea + heat (forms NHj gas, CO2 and CO may explode). Mixture with some silver compounds forms explosive salts of silver oxalate. Incompatible with caustics, mercury, urea. On small fires, use dry chemical powder (such as Purple-K-... 

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