Unlike hydrocarbons, oxygen-containing organic substances have a complex of atoms called a functional group. Methanol is a saturated alcohol that has a hydroxyl group in its molecule. It defines the main characteristics of this compound. In our article, we will look at methods for producing methyl alcohol, the most important chemical reactions and the use of methanol.
The structure of the molecule
In order to find out the structure of methyl alcohol, you need to remember what kind of molecule has the simplest saturated hydrocarbon - methane. It is expressed as CH4 and contains one carbon atom bonded via simple sigma bonds to hydrogen atoms.
If one of them is replaced by the hydroxyl group –OH, we get the formula CH3OH. It's methanol. The bond angle constructed by the direction of the C-O-H bond is approximately 110⁰, so the molecules of monohydric alcohols have an angular shape. Owing to the fact thatthe electronegativity of oxygen (3.5 eV) is greater than that of carbon (2.5 eV), the oxygen-carbon bond is very polarized, and the hydroxo group plays the role of a substituent having a negative inductive effect. Thus, methanol is an alcohol whose dipole moment is 1.69D.
Nomenclature
Let's consider three ways to form the name of a substance with the formula CH3OH. Historically, it is derived from the name of the hydrocarbon radical to which the hydroxyl group has attached. The radical CH3 is methyl, so CH3OH is called methyl alcohol. According to the Geneva nomenclature, the suffix -ol is added to the name of the corresponding hydrocarbon - an alkane. The compound will be referred to as methanol. This name is the most common and is used quite often. In rational nomenclature, the compound we are considering is called carbinol.
Physical properties
Lower alcohols containing up to three carbon atoms, which includes methanol, are liquids that mix with water in any proportions. Carbinol has a pronounced alcoholic smell, but is completely unsuitable for ingestion, as it is the strongest neurotoxic compound. Its density is less than unity and is 0.791 D420. The melting and boiling points are -97.9 ⁰C and +94.5 ⁰C respectively.
Production of methanol
Hydrolysis of the corresponding haloalkyls in the presence of hydroxides of active metals, for example, alkali or alkaline earth, and when heated -this is a common method for obtaining carbinol. Chlorine or bromomethane is taken as the starting materials, the result of the reaction will be the replacement of the halogen atom with the functional group –OH and the production of methanol.
Another method leading to the formation of primary saturated alcohols is the reduction of aldehydes or carboxylic acids. For this redox reaction, strong reducing agents such as sodium borohydride or lithium aluminum hydride are used. The starting compounds are formic acid or formaldehyde. One of the modern methods for obtaining carbinol is its synthesis from carbon, water, hydrogen and carbon monoxide. The process takes place at a temperature of +250 °C, elevated pressure and in the presence of zinc and copper oxides as catalysts. New, but economically justified, is the method of obtaining alcohol from microscopic algae of the oceans and seas, the biomass of which is really huge. The plant substrate is fermented, the liberated methane is collected and further oxidized to methanol. The big advantages of biomethanol production are the absence of the need to use fresh water reserves, electricity and the purity of the technology.
Organometallic synthesis
If organic compounds with a carbonyl group in the molecules are treated with organomagnesium compounds, monohydric alcohols can be obtained. Organometallic reagents are produced by the interaction of magnesium metal chips and bromine-containing alkane derivatives in a dry diethylether. From formic aldehyde, this reaction can be used to obtain not only methanol, the use of which is limited, but also other primary saturated alcohols.
Chemical characterization
Carbinol does not have pronounced properties of acids or bases, moreover, an aqueous solution of a substance does not affect indicators. Typical reactions of methanol are interaction with active metals and carboxylic acids. In the first case, metal alcoholates are formed, in the second - esters. For example, sodium displaces hydrogen atoms in the functional hydroxyl group of an alcohol:
2CH3OH + 2Na=2CH3ONa +H2.
Reaction between methyl alcohol and acetic acid leads to the formation of methyl acetate, or acetic acid methyl ester:
CH3COOH+CH3OH<--(H2SO 4)CH3COOCH3+H2O.
The above reaction is called esterification and is of great practical importance.
Oxidation of alcohols
Reactions of methanol leading to the production of aldehydes, consider the example of its interaction with copper oxide. If a red-hot copper wire coated with oxide is lowered into a methanol solution, then a special unpleasant odor of formaldehyde is felt. And the dull surface of the wire becomes bright and shiny due to the reduction of pure copper.
Dehydration
When heated and in the presence of hygroscopic substances, particles are split off from alcohol moleculeswater. Unsaturated hydrocarbons of the ethylene series can be found in the products. Under conditions of high water concentration and at low temperature, ethers can be obtained. So, dimethyl ether can be obtained from methanol.
Use of methyl alcohol
Methyl alcohol is used as an inhibitor of hydrates formed in gas pipelines, since the important properties of methanol are good solubility in water and low freezing point. The main volume of methyl alcohol is used in the production of phenol-formaldehyde resins. The high octane number characteristic of carbinol makes it possible to use it as an environmentally friendly fuel for cars. In the paint industry, carbinol is used as a solvent.
Effect of methanol on the human body
Wood alcohol is absolutely unsuitable for use as an alcoholic beverage, as it is the strongest toxic substance. Once in the gastrointestinal tract, it begins to oxidize to formic acid and formic aldehyde. Oxidation products affect the optic nerves and the retina, which contains receptors. Blindness sets in. Formic acid, which has a high cumulative capacity, is carried by the blood to the liver and kidneys, destroying these vital organs. As a result of methanol poisoning, a fatal outcome occurs, since methods for cleaning the blood from metabolites are ineffective.
In our article, we got acquainted with the properties, application andways to obtain methanol.
