Anhydrous aldehyde. Preparation of formaldehyde

Formic aldehyde, or formaldehyde, is a colorless gas with a sharp, unpleasant, specific odor. It dissolves well in water, as well as in alcohols. Formaldehyde is very toxic and can cause pathological changes in the human body. In addition, he is considered a carcinogen.

Formaldehyde - the first member of a whole homologous series, which includes aliphatic formic aldehyde. Formic acid also exhibits properties of this group.

Chemical properties

Formaldehyde is able to enter into all the reactions that are characteristic of the homologous series of aliphatic aldehydes. Including with nucleophiles. It also binds to reagents. This is mainly due to the fact that formaldehyde has a low electron density at the carbon atoms. Due to this structural feature, it very easily enters into chemical reactions even with the weakest nucleophiles. This explains the fact that in aqueous solutions formic aldehyde is found in the hydrated state.

Production receipt

This substance has a fairly simple formula. Formic aldehyde in the chemical language looks like this: HCHO. The main industrial method for its production is the oxidation of methanol. This reaction is carried out using a silver catalyst. The required temperature is 650 degrees. Oxidation of methanol occurs at atmospheric pressure.

This technological process has been used for a long time everywhere. He is well mastered. Approximately 80% of formaldehyde is produced by the oxidative reaction of methanol. However, this is not the only way. An even more promising method has recently been developed. It is based on the use of iron-molybdenum catalysts. In this case, the level of the required temperature drops to 300 degrees, and this is almost half the amount.

Also known is another industrial method - the oxidation of methane. The reaction of this rather simple formula: formaldehyde is obtained at a pressure of 1-2 MPa at a temperature of 450 degrees. The catalyst is aluminum phosphate.

Application

Methandiol is an aqueous solution of formaldehyde, which causes denaturation of proteins. This is its quality allows you to use this substance as a tanning agent in the manufacture of leather goods. He also found wide application in the manufacture of film. Because of its strong tannic properties, formaldehyde is known as an antiseptic. It is universally used in medicine. It is based on the production of such antiseptic drugs as "Formagel" and "Formidron". Already for a long time, formic aldehyde is used in biology to store biomaterials, for example, organs or corpses of animals.

Currently, the production of formic aldehyde is beneficial to the woodworking industry and, of course, to the furniture industry. It is used for the production of melamine-carbamido-formaldehyde resins. They are used in the manufacture of chipboard, plywood and other building materials.

When storing the formic aldehyde, it should be taken into account that at temperatures below 10 degrees the solution becomes turbid and a white precipitate appears. Also formaldehyde interacts with oxygen. As a result, additional initiators of the chain are formed because of the degenerate branching.

Toxic properties

So, formaldehyde is produced by oxidation of methanol and methane. Undoubtedly, it has a fairly high degree of toxicity. Formic aldehyde primarily affects the genetic material. From this substance reproductive organs suffer. But, of course, the defeat of the respiratory tract, skin and mucous eyes is more common.

Formaldehyde is also dangerous because it has a negative effect on the central nervous system.

Formaldehyde is not just toxic - 60-90 ml of substance (depending on body weight) that get inside, will cause death. Symptoms of poisoning are as follows:

• General decline of forces;
• Pallor of the skin ;
• Unconsciousness;
• Oppression of the central nervous system;
• labored breathing;
• Strong headache;
• Convulsions, especially at night.

The effect of formaldehyde on human body

The use of formaldehyde in production often causes different degrees of poisoning among the workers of the enterprise. With a strong inhalation lesion, that is, by inhaling a substance, conjunctivitis and an acute form of bronchitis, which sometimes leads to pulmonary edema, are observed. Symptomatic effects of long-term exposure to formaldehyde will only increase. After a short time there will be signs of defeat and depression of the central nervous system. It will be expressed in constant dizziness, there will be a feeling of fear, the gait will become shaky, and at night, a person may even have cramps.

If the poisoning has occurred through the mouth, the first symptom is a burn of the mucous membrane of the digestive tract. It will manifest itself in the form of pain, burning in the throat and along the esophagus. The person feels strong vomiting, the mass, torn away by the stomach, will contain blood. In severe cases, laryngeal edema develops and a reflex stop of respiration is observed.

With chronic low concentration poisoning, a person has severe weight loss, mental arousal, visual disturbances, insomnia, and persistent headaches.

Poisoning with formaldehyde vapor

Formic aldehyde is most often found in the air. Employees of enterprises engaged in the work related to the manufacture of artificial resins, in the presence of permanent and prolonged contact with formaldehyde vapor, poisoning is possible. Often already in the first working days a person has noticeable dermatitis on the face, hands. The presence of formaldehyde in the body can be seen from the deterioration of the nail condition - they soften and become brittle.

Eczema and dermatitis can be allergic. After the person has transferred a poisoning, at it the strong sensitivity is formed to formaldehyde. There is evidence that formaldehyde adversely affects the functioning of the reproductive system of the female body.

Use of formaldehyde in cosmetics

The content of formaldehyde is allowed as a preservative in cosmetic products, but its concentration should not exceed 0.1%. Formic aldehyde may be present in toothpaste, body, face and hands.

Also in pharmacology, in some means that prevent profuse perspiration, formaldehyde can be found. Its permissible concentration is 0.5%. This substance is a good antiseptic, even in such small amounts it is capable of destroying microorganisms. Strictly forbidden to apply to the face of any ointment, if it contains 5% formaldehyde. This is fraught with the appearance of dermatitis and allergic reactions. Also, formic aldehyde is not used for preserving cosmetic products, if they are sold as aerosols and sprays.

All products on their label must contain information on the content of this dangerous substance, even if its amount is 0.05%. In fact, to this day it has not been determined how the formaldehyde solution affects the skin, but it is known that in animals it blushes and flakes.

Carcinogenicity of formaldehyde

It is known that formaldehyde interacts with selenium with the participation of highly concentrated sulfuric acid. As a result, sulfoether-4-tetradecylidioxane is formed. This substance with a complex name after treatment with hydrated barium oxide becomes an excellent detergent. It would seem, what is the danger? But formaldehyde is listed as a substance with carcinogenic properties. Although the degree of its danger is not yet established, one can not ignore the fact that formaldehyde is deadly to animals. According to official data of many scientific centers of the world, the relationship between the use of formaldehyde in the production of paints, resins, textiles, plastic and the appearance of cancerous tumors in humans has been proved. Especially high risk of nasopharyngeal cancer.