Difference Between Alcohol and Phenol

Main Difference – Alcohol vs Phenol

Alcohols and phenol are important hydrocarbons that contain at least one hydroxyl (–OH) group attached to a saturated or an aryl carbon.  Phenol is often categorized under the broad term alcohols due to this presence of the hydroxyl group. The key difference between alcohols and phenol is that the hydroxyl group of phenol is bonded directly to a carbon atom of an aromatic ring, whereas in other alcohols, the hydroxyl group is bonded to a saturated carbon atom. This –OH group also determines various properties of these compounds. For example, alcohols and phenol are known as weak acids due to the presence of hydroxyl group. Alcohols and phenols are important to humans in many ways. For example, alcohols like ethanol are used in alcoholic beverages, while phenols are mainly applied as antiseptic agents.

1. What is Alcohol
      – Definition, Structure, Use
2. What is Phenol
      – Definition, Structure, Use
3. What is the difference between Alcohol and Phenol

What is Alcohol

Alcohol is an organic compound whose molecule contains one or more hydroxyl groups attached to a carbon atom. Hence, alcohol is a molecule that contains one or more hydroxyl groups. Alcohols are classified into three major categories based on the structure of their molecule as primary alcohol, secondary alcohol and tertiary alcohol. The general formula of alcohol is written as R-OH, where R is the hydrocarbon group called alkyl group. The simplest alcohol is methanol; R is its methyl group (-CH₃). Usually, when compared with analogous alkanes, their alcohols have significantly high boiling points. Moreover, the boiling point of alcohol increases when the number of carbon atoms in the molecule is increased. Due to the presence of hydroxyl groups, alcohols molecules form hydrogen bonds with surrounding other alcohols molecules, forming intermolecular attractions. Alcohols with simple structures are soluble in water. However, solubility decreases with increasing the length of an alkyl group of the alcohol. High concentration solutions of alcohols are usually poisonous. Therefore, alcohols are usually used as diluted solutions. Alcohols are widely applied in many industries such as pharmaceutical industry, microbiological application, and alcoholic beverage production.

Figure 1: Methanol, the simplest alcohol

What is Phenol?

Even though phenol comes under a type of alcohol, phenol is often considered as a different type of hydrocarbon due to its unique chemical behavior. Unlike in alcohols, the hydroxyl group is directly bonded to an aromatic ring. Due to this presence of an aromatic ring, phenol is considered as an aromatic compound, whereas alcohols can be either aliphatic or aromatic depending the presence of aromatic rings.  Phenol is best known for their antiseptic properties. Hence, it is used in surgeries and pharmaceutical industry as an antiseptic agent. However, highly concentrated/ pure phenol cannot be used in above-mentioned applications as it burns healthy tissues as well. Even the diluted phenol is still too strong to be used on biological tissues. Because of this reason, phenol is replaced by other compounds such as 4-n-hexylresorcinol. Due to the presence of the aromatic ring, phenols are more acidic in nature than alcohols. Phenol has a low melting point and a characteristic pungent odor. Phenol is soluble in most organic solvents such as aromatic hydrocarbons, alcohols, ketones, ether, acids, etc.

Figure 2: Phenol

Difference Between Alcohol and Phenol

Definition

Alcohol: Alcohol is an organic compound whose molecule contains one or more hydroxyl groups attached to a carbon atom.

Phenol: Phenol is a compound consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group.

Nature

Alcohol: Alcohols are generally aliphatic hydrocarbons.

Phenol:  Phenols are aromatic hydrocarbons.

Acidity

Alcohol: Aliphatic alcohols are less acidic than phenol.

Phenol:  Phenols are acidic and should always be diluted before use.

Applications

Alcohol: Alcohols are used in the alcoholic beverage industry, pharmaceutical, ink and many more industries.

Phenol:  Phenols are mainly used as antiseptic agents.

Denotation

Alcohol: R-OH, where R is the alkyl group.

Phenol: Ph-OH, where Ph is the phenolic ring.

Type

Alcohol: Alcohols are a group of compounds.                                            

Phenol:  Phenol is a specific compound

Summary

Alcohols are a major type of aliphatic hydrocarbons that contains one or more hydroxyl groups attached to a saturated carbon of the molecule, whereas phenol is an aromatic hydrocarbon that contains a hydroxyl group directly bonded to a phenolic ring (benzene ring). This is the main difference between alcohol and phenol.

Reference:
1. Properties of Alcohols and Phenols. (2016, July 21). Retrieved May 15, 2017, from https://chem.libretexts.org/LibreTexts/Athabasca_University/Chemistry_360%3A_Organic_Chemistry_II/Chapter_17%3A_Alcohols_and_Phenols/17.02_Properties_of_Alcohols_and_Phenols
2. Rappoport, Z. (2004). The Chemistry of Phenols, 2 Volume Set. John Wiley & Sons.
3. Competition Science Vision, 2003, Vol.5, Pratiyogita Darpan Group, India

Image Courtesy:
1. “Einfachste Alkohol Metanol-Seite001” By Poyraz 72 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Aryl=Phenyl=Phenol” By Jü – Own work (Public Domain) via Commons Wikimedia