What Is Formic Acid?
Formic Acid is an organic acid with one carboxy group. It was first obtained by distillation of ants (Latin: formica, hence the name). It is also known as methanoic acid.
Formic Acid in high concentrations is toxic and corrosive to the skin, so it should be handled with care.
Uses of Formic Acid
Formic Acid is used in a wide range of fields, including dyeing, rubber, leather, medicine, fragrances, and chemistry.
Specific uses include the following:
- Preservatives and antibacterial agents in livestock feed
- Metal treatment
- Rubber latex coagulant
- Semiconductor cleaning agents
- Bleaching and dyeing auxiliaries for textiles
- For leather processing
- Lime scale removers and other cleaning products
Formic acid can also be used in the chemical industry as a raw material for formic acid compounds, formic acid polymers, solvents, synthetic resin catalysts, etc. For example, by esterifying formic acid, it is used in fragrances that impart fruit aromas, as well as in pharmaceuticals and agrochemicals.
Formic acid aqueous solution is also being attempted to be used as a fuel because of its excellent safety and environmental cyclicity, with no possibility of combustion or explosion.
Properties of Formic Acid
Formic Acid is a colorless liquid with a pungent odor. Its melting point is 8.40°C and boiling point is 100.75°C. It is soluble in many polar solvents and hydrocarbons as well as water. Aqueous solutions of formic acid are the most acidic of the monovalent aliphatic carboxylic acids.
As such, it is more strongly acidic than acetic acid. Formic acid, as a carboxylic acid, has unique properties. For example, it can react with alkenes to yield formic acid esters.
Formic acid decomposes upon heating to water and carbon monoxide. Oxidation produces carbonic acid.
Structure of Formic Acid
Formic Acid has a molar mass of 46.025. It has both carboxy and aldehyde groups in its molecule, making it both acidic and reducing. It exhibits few Fehling reactions, although silver mirror reactions due to its reducing nature do occur.
When dissolved in hydrocarbons or in gas, it forms carboxylic acid dimers by hydrogen bonding.
Other Information on Formic Acid
1. How to Synthesize Formic Acid
Formic Acid is industrially obtained by synthesizing sodium formic acid by the reaction of carbon monoxide and sodium hydroxide under high pressure and acidifying it with sulfuric acid.
To concentrate, the aqueous solution is first cooled strongly to precipitate crystals of formic acid. Separated in a rectifying column and distilled with the addition of propyl formic acid, the distillate can be divided into two layers. Distillation of the propyl formate layer yields pure formic acid.
2. Synthesis of Formic Acid with Methanol and Carbon Monoxide
Formic Acid can also be produced from carbon monoxide and methanol. First, the reaction of carbon monoxide and methanol in the presence of a strong base produces methyl formic acid.
Formic acid can then be obtained by hydrolysis of methyl formate. The reaction to produce methyl esters is industrially carried out under high-pressure liquid phase. Specifically, the reaction is carried out at 80°C and 40 atmospheres using sodium methoxide.
In addition, a large excess of water is required for efficient methyl ester hydrolysis. Therefore, hydrolysis via other compounds is also possible. For example, methyl formic Acid can be reacted with ammonia to produce formamide, which can then be hydrolyzed using sulfuric acid.
2. Related Compounds of Formic Acid
Formic Acid ionizes to form the formic acid ion (HCOO-). Salts containing the formic acid ion are called formic acid salts.
Formic acid can be dehydration-condensed with alcohol to yield formic acid ester (HCOOR). Some formic acid esters are components of fruit aromas. For example:
- Ethyl formic acid (HCOOC2H5) is a component of peach, amyl
- Formic Acid (HCOOC5H11) is a component of apple, and isoamyl
- Formic Acid (HCOOCH2C2CH(CH3)2) is a component of pear aroma.