Formic acid (HCO2H), also called methanoic acid, the simplest of the carboxylic acids, used in processing textiles and leather. Formic acid was first isolated from certain ants and was named after the Latin formica, meaning “ant.” It is made by the action of sulfuric acid upon sodium formate, which is produced from and sodium hydroxide.

Formula: CH₂O₂ IUPAC ID: Formic acid Molar mass: 46.03 g/mol Density: 1.22 g/cm³ Boiling point: 100.8 °C Melting point: 8.4 °C

Properties:-

Formic acid is a colorless liquid having a pungent, penetrating odor at room temperature, not unlike the related acetic acid. It is miscible with water and most polar organic solvents, and is somewhat soluble in hydrocarbons. In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law. Solid formic acid, which can exist in either of two polymorphs, consists of an effectively endless network of hydrogen-bonded formic acid molecules. Formic acid forms a low-boiling azeotrope with water (22.4%). Liquid formic acid tends to supercool.

Preparation:-

From methyl formate and ormamide- When and carbon monoxide are combined in the presence of a strong base, the result is methyl formate, according to the chemical equation:[6]

CH3OH + CO → HCO2CH3 In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80 °C and 40 atm. The most widely used base is sodium methoxide. Hydrolysis of the methyl formate produces formic acid:

HCO2CH3 + H2O → HCOOH + CH3OH

Niche chemical routes:- By-product of acetic acid production:- A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals. At one time, acetic acid was produced on a large scale by oxidation of alkanes, by a process that cogenerates significant formic acid. This oxidative route to acetic acid is declining in importance, so that the aforementioned dedicated routes to formic acid have become more important.

Hydrogenation of

The catalytic hydrogenation of CO2 to formic acid has long been studied. This reaction can be conducted homogeneously. Oxidation of biomass Formic acid can also be obtained by aqueous catalytic partial oxidation of wet biomass by the OxFA process. A Keggin-type polyoxometalate (H5PV2Mo10O40) is used as the homogeneous catalyst to convert sugars, wood, waste paper, or cyanobacteria to formic acid and CO2 as the sole byproduct. Yields of up to 53% formic acid can be achieved.

Laboratory methods In the laboratory, formic acid can be obtained by heating oxalic acid in glycerol and extraction by steam distillation. Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, allyl alcohol results. The net reaction is thus:

C2O4H2 → CO2H2 + CO2 Another illustrative method involves the reaction between lead formate and hydrogen sulfide, driven by the formation of lead sulfide.

Pb(HCOO)2 + H2S → 2HCOOH + PbS

Electrochemical production It has been reported that formate can be formed by the electrochemical reduction of CO 2 (in the form of bicarbonate) at a lead cathode at pH 8.6: − - − − HCO 3 + H2O + 2e → HCO 2 + 2OH or - − − CO2 + H2O + 2e → HCO 2 + OH

If the feed is CO2 and oxygen is evolved at the anode, the total reaction is: − − CO2 + OH → HCO 2 + 1/2 O2 This has been proposed as a large-scale source of formate by various groups. The formate could be used as feed to modified E. coli bacteria for producing biomass. There exist natural microbes that can feed on formic acid or formate (see Methylotroph). Chemical Reaction:-

Formic acid is about ten times stronger than acetic acid. It is used as a volatile pH modifier in HPLC and capillary electrophoresis. Formic acid is a source for a formyl group for example in the formylation of methylaniline to N-methylformanilide in toluene. In synthetic organic chemistry, formic acid is often used as a source of hydride ion. The Eschweiler-Clarke reaction and the Leuckart-Wallach reaction are examples of this application. It, or more commonly its azeotrope with triethylamine, is also used as a source of hydrogen in transfer hydrogenation.

As mentioned below, formic acid readily decomposes with concentrated sulfuric acid to form carbon monoxide.

CH2O2 + H2SO4 → H2SO4 + H2O + CO

Uses:-

A major use of formic acid is as a preservative and antibacterial agent in livestock feed. it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. Formic acid arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely used to preserve winter feed for cattle. Use as preservative for silage and (other) animal feed constituted 30% of the global consumption in 2009. Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009), and in dyeing and finishing textiles (9% of the global consumption in 2009) because of its acidic nature. Use as a coagulant in the production of rubber[6] consumed 6% of the global production in 2009. Formic acid is also used in place of mineral acids for various cleaning products, Some formate esters are artificial flavorings and perfumes. Formic acid application has been reported to be an effective treatment for warts. Formic acid can be used as a fuel cell (it can be used directly in formic acid fuel cells and indirectly in hydrogen fuel cells). It is possible to use formic acid as an intermediary to produce isobutanol from CO2 using microbes.