Knowing Your Alcohol Chemical & Physical Properties

August 15, 2021

Alcohols are organic compounds that are characterized by the presence of one, two, or more hydroxyl groups (−OH) attached to the carbon atom in an alkyl group or hydrocarbon chain. If you’re just learning about alcohol in the Midwest, or you’re in need of a refresher, here’s a primer from Mid-West Instrument.

What is Alcohol?

Alcohol comes in different structures and forms and is considered to be a derivative of water, where one amongst the hydrogen atoms of water are replaced by an alkyl group, which is typically represented by the letter R in an organic structure. Alcohols are one of the most commonly occurring organic compounds and thus are found in a variety of places. For example, alcohols are utilized in the form of sweeteners, in the preparation of perfumes, and in the process of synthesizing other compounds. Moreover, some alcohols are manufactured in organic chemicals coming from various industries.

Main Types of Alcohol

Alcohols are differentiated based upon the presence of the hydroxyl group attached and the location of this hydroxyl group, which will change the physical and chemical properties of any alcohol. There are three types of alcohol: primary, secondary, and tertiary. The classification is done in accordance with where the carbon atom of an alkyl group is attached to the hydroxyl group. Most alcohols are colorless liquids, but some are known to behave as a solid when at room temperature. Alcohols with less molecular weight can be highly soluble in water, while those alcohols that increase in molecular weight tend to become less soluble and demonstrate increasing vapor pressures, boiling points, densities, and viscosities. Additionally, alcohols can be measured by gauges, for example, hexyl measurement or isobutyl measurement.

Primary Alcohols

Primary alcohols are alcohols where the carbon atom of the hydroxyl group (OH) is attached to only one single alkyl group. Two of the most common examples of primary alcohols are methanol and ethanol. The complexity of this alkyl chain plays no role in the classification of any alcohol considered as primary–only the existence of the single linkage among –OH group and an alkyl group is what qualifies an alcohol as a primary. These types of alcohol are easily oxidized to an aldehyde and can further be oxidized to carboxylic acids too.

Secondary Alcohols

Secondary alcohols are those where the carbon atom of the hydroxyl group is attached to two alkyl groups on either side. The two alkyl groups present may be either structurally identical or different. Notable examples of secondary alcohols are propanol and butanol. Secondary alcohols get easily oxidized to ketone, but further oxidation is impossible.

Tertiary Alcohols

Tertiary alcohols are those where the carbon atom of the hydroxyl group is connected to three alkyl groups. The physical properties of these alcohols mainly depend on their structure. The presence of this -OH group allows the alcohols in the formation of hydrogen bonds with their neighboring atoms. The bonds formed are weak, which makes the boiling points of these alcohols higher than others. Tertiary alcohols don’t oxidize in the presence of sodium dichromate. Examples of tertiary alcohols include benzilone and isophytol.

Check Compatibility When Working With Alcohols.

Alcohols have a diverse range of uses, from pressure monitoring and as an anti-freezing agent, to internal combustion engine power and preservatives in the field of medicine.  For information about alcohols compatibility with other materials see our online chemical compatibility database.