Acrylic acid is one of the simplest representatives of carboxylic unsaturated monobasic acids. Its formula is as follows: CH2 = CH-COOH. It is a colorless liquid with a pungent and unpleasant odor. It is soluble in water, chloroform, diethyl alcohol and ethanol, polymerizes with ease with the further formation of polyacrylic acid. Acrylic acid has other names: ethencarboxylic acid and propenoic acid.
How to get (or synthesize) acrylic acid?
1. Currently, acrylic acid is produced by vapor phase oxidation of propylene with oxygen (O2) on molybdenum, cobalt or bismuth catalysts. An example is the following reaction:
CH2 = CH – CH3 (propylene) + O2 (oxygen) = CH2 = CH – COOH (acrylic acid)
2. In the past, a reaction was used in which carbon monoxide II (CO), acetylene (CH≡CH) and water (H2O) were reacted. The chemical reaction will be as follows:
CH≡CH (acetylene) + CO (carbon monoxide II) + H2O (water) → CH2 = CH – COOH (acrylic acid).
We also used the reaction of formaldehyde with ketene:
CH2 = C = O (ketene) + H2C = O (formaldehyde) → CH2 = CH – COOH (propenoic acid).
3. Now Rohm and Haas is creating a special technology for the synthesis of ethencarboxylic acid from propane.
Chemical properties of acrylic acid
The acid under consideration can form salts, esters, anhydrides, amides, acid chlorides and other compounds. It can also enter into addition reactions that are characteristic of ethylene carbons. The addition of water, protic acids and NH3 does not occur according to the Markovnikov rule. In this case, substituted derivatives are formed. Acrylic acid is involved in the synthesis of dienes. It also condenses with various salts of aryldiazonium. Under ultraviolet irradiation, it forms polyacrylic acid.
Application of acrylic kilots
- is used as raw material in the production of a wide range of polymer products with various chemical and physical properties (for example, plastic and coatings);
- used in the manufacture of dispersions for acrylic water-based paints and varnishes; the scope of application of such paints will depend on the chemical properties of the copolymer - from the final painting of vehicles and to painting ceilings;
- acrylic acid and its derivatives are used to create an impregnation for leather and fabrics, emulsions for paints and varnishes, as raw materials for acrylate rubbers and polyacrylonitrile fibers, building adhesives and mixtures; esters of metaacrylic and acrylic acids (methyl esters of methyl methacrylate and methyl acrylate are used in most cases) are used in the production of polymers;
- often acrylic acid is used in the creation of superabsorbents.
Proper storage of acrylic acid
When storing this substance, an inhibitor, hydroquinone, is added to avoid polymerization. Before use, the acid must be distilled with caution, since the development of explosive polymerization is possible.
Safety when using
When working with acrylic acid, it should be noted that this substance has an irritating effect on the skin and mucous membranes. The acid irritation threshold is 0.04 mg / liter. If it enters the mucous membrane of the eyeballs, as a rule, it causes severe burns to the cornea and can lead to irreversible changes (damage that cannot be treated). Inhalation of acrylic acid vapors can cause headache, respiratory tract irritation, and in excessive doses, the development of pulmonary edema. In rooms where work with acrylic acid is carried out, constant air control is necessary. The MPC for this acid is 5 mg / meter³. Safety measures must be observed when working with other derivatives. An example is nitrile of acrylic acid.