Dimethylamine ((CH3) 2NH) structure, properties, uses, risks

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Egbert Haynes
Dimethylamine ((CH3) 2NH) structure, properties, uses, risks

The dimethylamine is an organic compound formed by two methyl groups -CH3 attached to a -NH group. Its chemical formula is (CH3)twoNH. It is a colorless gas. When it is in the air at low concentrations a fishy odor is perceived. However, if it is in high concentration it has the smell of ammonia NH3.

Dimethylamine is present in plants and animals. It is believed that in humans it comes from the breakdown of certain enzymes but also from the ingestion of some foods such as fish. If dimethylamine gas dissolves in water, it forms highly alkaline and corrosive solutions..

Dimethylamine. Ring0 [Public domain]. Source: Wikimedia Commons.

It has various industrial uses such as to produce solvents, to accelerate the vulcanization of rubber, to inhibit the corrosion of pipes, to make soaps, to prepare colorants and to absorb acid gases in certain processes..

Dimethylamine is a highly flammable gas. Containers should not be exposed to heat or fire as they may explode. In addition, its vapors are irritating to the eyes, the skin and the respiratory tract..

It is a compound that may be part of atmospheric aerosols, that is, very fine droplets found in the atmosphere.

Article index

  • 1 Structure
  • 2 Nomenclature
  • 3 Properties
    • 3.1 Physical state
    • 3.2 Molecular weight
    • 3.3 Melting point
    • 3.4 Boiling point
    • 3.5 Flash point
    • 3.6 Autoignition temperature
    • 3.7 Density
    • 3.8 Solubility
    • 3.9 pH
    • 3.10 Dissociation constant
    • 3.11 Chemical properties
    • 3.12 Other properties
    • 3.13 Biochemical reactions
  • 4 Obtaining
  • 5 Presence in nature
    • 5.1 Patients with excess dimethylamine
  • 6 Uses
  • 7 Risks
  • 8 Influence of DMA on the atmosphere
  • 9 References

Structure

Dimethylamine is a secondary aliphatic amine. This means that the nitrogen substituents (N) are aliphatic (-CH3), which means that they are not aromatic, and that they are two. Therefore they are two methyls -CH3 attached to nitrogen, which also has a hydrogen (H).

In the dimethylamine molecule, nitrogen (N) has a pair of free electrons, that is, a pair of electrons that are not bound to any other atom..

Structure of dimethylamine. Author: Benjah-bmm27. Source: Wikimedia Commons.

Nomenclature

- Dimethylamine

- N, N-Dimethylamine

- N-methylmethanamine

- DMA (acronym for Di-Methyl-Amine).

Properties

Physical state

Colorless gas.

Molecular weight

45.08 g / mol

Melting point

-93 ºC

Boiling point

7.3 ºC

Flashpoint

-6.69 ºC (closed cup method).

Autoignition temperature

400 ° C

Density

Liquid = 0.6804 g / cm3 at 0 ºC.

Vapor = 1.6 (relative density with respect to air, air = 1).

Solubility

Very soluble in water: 163 g / 100 g of water at 40 ° C. Soluble in ethanol and ethyl ether.

pH

Aqueous dimethylamine solutions are strongly alkaline.

Dissociation constant

Kb = 5.4 x 10-4

pKto conjugated acid = 10.732 at 25 ° C. The conjugated acid is the dimethylammonium ion: (CH3) NHtwo+

Chemical properties

Liquid Dimethylamine can attack some plastics, rubbers, and coatings.

When dissolved in water, nitrogen's free electron pair (N) takes on a proton (H+) from the water, leaving an OH free-, so it forms very alkaline and corrosive solutions:

Dimethylamine + Water → Dimethylammonium Ion + Hydroxyl Ion

(CH3)twoNH + HtwoO → (CH3)twoNHtwo+ + Oh-

With nitric acid you get a nitrate salt, that is, dimethylammonium nitrate:

Dimethylamine + Nitric Acid → Dimethylammonium Nitrate

(CH3)twoNH + HNO3 → (CH3)twoNHtwo+NOT3-

Other properties

When it is in low concentration in the air it has a fish-like odor, while in high concentrations it smells like ammonia (NH3).

Biochemical reactions

In the body, dimethylamine can undergo nitrosation under weakly acidic conditions to give dimethylnitrosamine a carcinogenic compound (CH3)twoN-NO.

The formation of dimethyl nitrosamine occurs from dimethylamine and nitrite (sodium nitrite) in the stomach (at pH 5-6) by the action of bacteria in the gastrointestinal tract. Sodium nitrite is present in some foods.

Dimethylamine + Sodium Nitrite → Dimethylnitrosamine + Sodium Hydroxide

(CH3)twoNH + NaNOtwo → (CH3)twoN-NO + NaOH

Obtaining

Dimethylamine is prepared commercially by reacting methanol (CH3OH) with ammonia (NH3) at 350-450 ° C in the presence of a silica-alumina catalyst (SiOtwo/To thetwoOR3).

2 CH3OH + NH3 → (CH3)twoNH + 2 HtwoOR

Since monomethylamine and trimethylamine are also produced, purification is carried out in a series of four to five distillation columns..

Presence in nature

Dimethylamine is found in plants and animals. It is also present naturally and abundantly in human urine..

It is estimated that its presence in humans is due to the fact that it is produced by certain types of intestinal bacteria from some compounds found in food.

Some of these compounds are choline (a compound that is associated with the group of B vitamins) and trimethylamine oxide. It is also believed to come from an enzyme that inhibits nitric oxide (NO) that is formed in the body..

Certain sources of information indicate that the increase in dimethylamine in the urine is caused by the ingestion of fish and seafood, where the highest values ​​are obtained when squid, hake, sardines, swordfish, cod, whiting and ray are eaten..

Eating fish could increase the levels of dimethylamine in your urine. Author: Anna Sulencka. Source: Pixabay.

Patients with excess dimethylamine

Dimethylamine is considered to be a uremic toxin, that is, a substance that can cause harm if its concentration in the urine is too high. In fact, very high levels of dimethylamine have been observed in patients with end-stage renal disease..

It is believed that in these patients there may be an overpopulation of intestinal bacteria that could be producing it.

Applications

Dimethylamine or DMA is used to:

- Preparation of other compounds.

- Production of the solvents dimethylformamide and dimethylacetamide.

- Accelerate the vulcanization of certain rubbers.

- Remove hair from hides during tanning.

- Act as an antioxidant for solvents.

- Serve as a mineral flotation agent.

- Inhibit corrosion and as an anti-fouling agent for pipes.

- Function as a surfactant.

- Make soaps and detergents.

- Act as a textile chemist.

- Function as an antiknock agent in fuels and as a stabilizer for gasoline.

- Prepare colorants.

- Absorb acid gases.

- Serve as a propellant for pesticides and rockets.

- Be part of agents for water treatment.

- Act as a fungicide in agrochemical products.

- Discontinued uses such as attracting and killing weevils or insects that attack cotton.

Cotton plant. Author: ISAAA KC. Source: Pixabay.
In the past, insects that attack cotton plants were killed with dimethylamine. MarvinBikolano [CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)]. Source: Wikimedia Commons.

Risks

Dimethylamine vapors are irritating to the skin, eyes and respiratory tract..

If it comes into contact with the skin in liquid form, it can cause frostbite and chemical burns. Its inhalation has adverse health effects.

DMA gas is corrosive and can form corrosive aqueous solutions. Your aqueous solutions can become flammable unless well diluted..

Dimethylamine in gas form easily ignites producing toxic fumes of nitrogen oxides (NOx).

If the container containing this gas is exposed to fire or intense heat, it may explode..

Influence of DMA on the atmosphere

The atmospheric aerosol (very small droplets of mixture of natural compounds and / or pollutants in the atmosphere) has a profound impact on the global climate and on air quality in the various regions of the world..

The formation of the new aerosol particles is not yet fully understood.

It is estimated that dimethylamine participates together with other compounds in the formation of these particles, which seems to depend on the fact that there are strong emissions of DMA in the area..

For example, in industrial areas there is a higher concentration than in agricultural areas, and this may influence the way in which the WFD participates..

It is noteworthy that, according to some scientists, the burning of plant material containing glyphosate (one of the most widely used herbicides in the world), can lead to the formation of dimethylamine.

Atmospheric aerosols over South America. Dimethylamine could contribute to its formation. MarvinBikolano [CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)]. Source: Wikimedia Commons.

References

  1. U.S. National Library of Medicine. (2019). Dimethylamine. Recovered from pubchem.ncbi.nlm.nih.gov.
  2. Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Fourth Edition. John Wiley & Sons.
  3. Morrison, R.T. and Boyd, R.N. (2002). Organic Chemistry. 6th Edition. Prentice-Hall.
  4. Windholz, M. et al. (editors) (1983). The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. Tenth Edition. Merck & CO., Inc.
  5. Abramowitz, M.K. et al. (2010). The Pathophysiology of Uremia. Aliphatic Amines. In Chronic Kidney Disease, Dialysis, and Transplantation (Third Edition). Recovered from sciencedirect.com.
  6. Li, H. et al. (2019). Influence of atmospheric conditions on sulfuric acid-dimethylamine-ammonia-based new particle formation. Chemosphere 2019; 245: 125554. Recovered from ncbi.nlm.nih.gov.
  7. Mackie, J.C. and Kennedy, E.M. (2019). Pyrolysis of Glyphosate and Its Toxic Products. Environ. Sci. Technol. 2019: 53 (23): 13742-13747. Recovered from ncbi.nlm.nih.gov.

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