Concept, types, nomenclature and properties

We explain to you what are the alcohols, their classification, nomenclature and properties.Besides, examples and importance in the industry.
The alcohols have one or more hydroxyl groups bonded to a carbon atom.

What are alcohols?

Alcohols are certain organic chemical compounds, which have in their structure one or more chemical hydroxyl groups (-OH) covalently linked to a saturated carbon atom (that is, with simple bonds only to adjacent atoms), thus forming a carbinol group (-C-OH).

Alcohols are organic compounds very common in nature , which play important roles in living organisms, especially in organic synthesis.

Its name comes from the Arabic al-kul , which literally translates "spirit" or "liquid distillate ”, since the old Muslim alchemists perfected its distillation methods in the 9th century.Later studies allowed to know its chemical nature, especially Lavoisier's contributions regarding the fermentation of brewer's yeast.

Alcohol intake has toxic effects on the human organism, in some cases inducing intoxication and acting as a behavior inhibitor, but also as a central nervous system depressant (in the case of ethanol).

In other cases, they have a harmful and possibly lethal effect, depending on the dose consumed.However, they also have antibacterial and antiseptic properties , which allow surface uses.

It can serve you: Organic matter

Types of alcohols

In principle, alcohols can be classified according to the number of carbonyl radicals they present, so it distinguishes between alcohols (a radical) and polyalcohols or polyols, which have two or more.

However, the main distinction between alcohols depends on their atomic structure around the carbon atom of carbinol, as follows:

• Primary alcohols .The hydroxyl group (-OH) is located in a carbon linked to another unique carbon atom.


• Secondary alcohols .The hydroxyl group (-OH) is located in a carbon linked to two different carbon atoms.


• Tertiary alcohols .The hydroxyl group (-OH) is located in a carbon in turn linked to three different carbon atoms.

Nomenclature of alcohols

Like other organic compounds, alcohols have different ways of naming, which we will explain below:

Traditional (non-systematic) method .Attention is paid, above all, to the carbon chain to which the hydroxyl (usually an alkane) adheres, to rescue the term with which it name it, put the word “alcohol” before it and then add the suffix –ilico instead of –ano.For example:

• If it is a methane chain, it will be called methyl alcohol .


• If it is an ethane chain, it will be called ethyl alcohol .


• If it is a propane chain, it will be called propyl alcohol .

IUPAC Method .Like the previous method, attention will be given to the precursor hydrocarbon, to rescue its name and simply add an ele ( L ) at the end of the suffix –ano.For example:

• If it is a methane chain, it will be called methanol .


• If it is an ethane chain, it will be called ethanol .


• If it is a propane chain, it will be called propanol .

Eventually, it will be necessary to indicate in some way the location of the hydroxyl group in the chain, for which a number will be used at the beginning of the name: 2-butanol , for example.

More in: Chemical Nomenclature

Physical properties of alcohols

Alcohols are generally liquid and colorless , although they have a characteristic odor.They are soluble in water through hydrogen bonds, although only in their simplest versions, since from hexanol begin to have oily consistency and be insoluble in water.

Similarly, The density of alcohols is higher according to the increase in the number of carbon atoms in their chain and the ramifications they introduce.The same applies to their melting and boiling points: they increase according to the greater number of hydroxyl groups are in its formula, since their hydrogen bonds are difficult to break.

Chemical properties of alcohols

The alcohols have a dipole character , similar to that of water, due to their hydroxyl molecule, which makes them polar substances (endowed with a positive and a negative pole).

Due to this, can behave as acids or as bases depending on which reagent they are in.For example, if it is a strong base, the hydroxyl group is deprotonated and oxygen retains its negative electromagnetic charge, acting as an acid.

By the hospital, if faced with a very strong acid, the electronic oxygen pairs cause the hydroxyl to protonize, having a positive charge and behaving as a weak base.

On the other hand, alcohols can:

• Halogenate by reacting with a hydrazide acid to form aquyl halides and water;


• oxidize in the presence of catalysts to produce carboxylic acids, ketones or aldehydes, depending on the type of alcohol used;


• dehydrogenating in the presence of heat and certain catalysts (only primary and secondary alcohols), to lose hydrogen and become aldehydes or ketones;


• dehydrate in the presence of a mineral acid, to extract the hydroxyl group and thus obtain an alkene by elimination processes.

Importance of alcohols

Alcohol is used to make biofuels together with other organic substances.

Alcohols are substances of high chemical value.As raw materials, are used to obtain other organic compounds , in laboratories.Also as a component of industrial products for everyday use, such as disinfectants, cleaners, solvents, perfume base.

They are also used in the manufacture of fuels, especially in the biofuel industry, an alternative to fossil fuels, often seen in hospitals, first aid kits or similar.

On the other hand, certain alcohols are for human consumption (especially ethanol), part of numerous spirits in different degrees of refinement and intensity.

Examples of alcohols

Some examples of common use are ethanol or ethyl alcohol (C2H5OH), 1-propanol (C3H7OH), methanol (CH3OH) or isobutanol (C4H9OH).

Continue with: Biomolecules