Difference Between Alcohol and Phenol

Alcohols and phenols are both classes of organic compounds containing a hydroxyl (-OH) functional group. However, while they both feature hydroxyl groups, they differ fundamentally from each other. Alcohols have hydroxyl groups attached to alkyl carbon atoms, whereas phenols have the hydroxyl group directly attached to an aromatic benzene ring.

The difference between alcohol and phenol is very important from the perspective of class 11 and 12 students, especially for those preparing for the NEET exam. In this article, we will explore the differences between alcohol and phenol, including their definitions, properties, types, and many other important terms.

What are Alcohols is Chemistry?

Alcohol is a common organic compound that consists one or more hydroxyl (OH) groups. The general formula of alcohol is R-OH, where R represents the alkyl group. The molecules of alcohol attached to the carbon atom of alkyl groups or hydrocarbon chain. Most of the alcohols are colorless liquid. Based on the bonding of carbon atoms to the hydroxyl groups, alcohol can be classified in three types namely – primary, secondary and tertiary. Alcohol is widely used in industries for manufacturing beverages and preparing perfumes.

Types of Alcohols

Alcohol can be classified based on the hydroxyl group attached as primary, secondary, and tertiary. Let’s discuss these types in detail as follows.

• Primary Alcohols

Primary alcohols can be defined as the carbon atom that contains -OH group is attached only to an alkyl group. The examples of primary alcohols are Methanol (propanol), ethanol, butanol etc.

• Secondary Alcohols

Secondary alcohols can be defined as a hydroxyl group attached to carbon atom which is connected to two alkyl groups. The examples of secondary alcohols are propan-2, butan-2-ol etc.

• Tertiary Alcohols

Tertiary alcohols can be defined as the carbon atom that carries -OH group, is attached directly to three alkyl groups. The groups may be same or different. The examples of tertiary alcohols are 2-methypropan-2-ol, 2-methylbutan-2-ol etc.

What are Phenols?

Phenols are a class of organic compounds characterized by a hydroxyl (OH) group attached directly to an aromatic benzene ring. Chemically, they are aromatic compounds with a hydroxyl group bonded to one of the carbon atoms in the benzene ring. Phenols are often referred to as derivatives of benzene with one or more hydroxyl (-OH) groups attached.

Some examples of phenols include: Phenol (C₆H₅OH), Cresols, Bisphenol A(BPA), Resorcinol (1,3-dihydroxybenzene), Gallic Acid( trihydroxybenzoic acid), Flavonoids, Quinones and Stilbenes.

Phenol as Special Type of Alcohol

Phenol has -OH group that is attached to two carbon atoms like a secondary alcohol. ​ So sometimes phenol is called as a secondary alcohol. But for some reasons it is not considered as an alcohol. Phenol consists -0H group similar to alcohol, but the -OH group of phenol is attached to a benzene ring. In addition to, phenol is more acidic nature than alcohol.

Physical Properties Comparison

Comparison table outlining some key physical properties of alcohols and phenols is given as:

Property	Alcohols	Phenols
Molecular Structure	R-OH	Ar-OH
Hydrogen Bonding	Form hydrogen bonds with water and themselves	Form hydrogen bonds with water and themselves
Solubility in Water	Soluble in water, with shorter chains being more soluble	Soluble in water, but less so than alcohols due to the presence of the aromatic ring
Boiling Point	Generally lower boiling points compared to phenols	Generally higher boiling points compared to alcohols due to stronger intermolecular hydrogen bonding
Odor	Typically have a characteristic odor, often described as “alcoholic”	Less odor compared to alcohols, often described as “sweet”
Acidity	Less acidic compared to phenols	More acidic compared to alcohols due to the resonance stabilization of the phenoxide ion
Reactivity	Undergo reactions such as oxidation, dehydration, and esterification	Reactivity influenced by the aromatic ring, undergo reactions such as electrophilic aromatic substitution and oxidation
Toxicity	Generally less toxic compared to phenols	Phenols can be toxic, especially in higher concentrations

Chemical Properties Comparison

Comparision of different chemical propertes such as oxidation, esterification, reaction with metlas, etc. are given in the following table:

Chemical properties	Alcohol	Phenol
Oxidation	R-OH + HO-NO2→ R-O-NO2	Phenols get easily oxidized to para-benzoquinone. This when reduced forms quinones.
Esterification	When the alcohol reacts with acid, it forms an ester and water. R-OH + R’-COOH + H+ ↔ R’-COOR	Phenyl esters (RCOOAr) do not form directly from RCOOH, but for this acid chlorides or anhydrides react with ArOH in the presence of a strong base. (CH3CO)2O + C6H5OH + NaOH → CH3COOC6H5 + CH3COONa + H2O C6H5COCl + C6H5OH + NaOH → C6H5COOC6H5 + Na+Cl– + H2O
Reaction with metals	Alcohol (ethanol) reacts with sodium metal and produced hydrogen gas and sodium ethoxide. 2ROH + Na→2RO+Na– + H2	Generally phenol does not react with most of the metals. In some cases it reacts with sodium, potassium, and magnesium. Phenol reacts with sodium or potassium to form phenoxide ions and hydrogen gas. 2C6H5OH + 2Na = 2C6H5O– (phenoxide ion) + H + 2Na+
Reaction with halogen group elements	When the halogen group elements ( chlorine, bromine) react with alcohol, the chlorine, bromine replace the -OH group in alcohol. ROH + HX → R-X + H2O	Phenol can react with halogens (fluorine, chlorine, bromine, iodine) to form halogenated phenols. C6H5OH + Cl2 = C6H5Cl2 + HCl + H+

Difference between Alcohol and Phenol

The key differences between Alcohol and Phenol are listed in the following table:

Parameter	Alcohol	Phenol
Functional Group	hydroxyl (OH) groups	hydroxyl ( -OH) group attached to a benzene ring
Formula/Chemical Name	R-OH	C6H5OH
Number of -OH group	Alcohol consisting one or more -OH groups.	Phenols consisting a -OH group attached to aromatic benzene group.
Aromaticity	Alcohol does not contain aromatic ring.	Phenol contains aromatic benzene ring.
Nature of compound	Alcohols are aliphatic compounds.	Phenols are aromatic compounds.
Acidity	Alcohols are less acidic than phenols.	Phenols are more acidic than alcohols.
State at Room Temperature	generally colorless and liquid	Typically solid at room temperature due to stronger intermolecular forces.
Solubility in Water	More Soluble in water.	Less Soluble in water.
Boiling point	Alcohols have less boiling point than phenols.	Phenols have higher boiling point than alcohols.
Reactivity with Metals	Reacts with active metals to produce hydrogen gas.	Phenols do not react with metals.
Reaction on Litmus	As alcohols are neutral type, they do not show any reaction in an undergoing test.	Due to acidic nature, phenol can change the litmus paper into red color.
Reaction with NaOH	Alcohols do not react with NaOH.	Phenols react with NaOH to form phenoxides.
Example	Ethanol (C2H5OH), Methanol (CH3OH).	Phenol (C6H5OH).
Usage	Used as the main component of alcoholic beverages. It is also used in pharma company, industries, to prepare perfume and ink.	It is mainly used in pharma company to manufacture medical products.

Conclusion

In conclusion, while both alcohols and phenols contain hydroxyl (-OH) groups, they exhibit distinct chemical properties due to differences in molecular structure. Alcohols feature the hydroxyl group attached to a saturated carbon atom in an alkyl chain, while phenols have the hydroxyl group directly bonded to an aromatic benzene ring.

These structural disparities result in variations in physical properties such as solubility, boiling points, and acidity. Additionally, the aromatic nature of phenols imparts unique reactivity and potential toxicity compared to alcohols.

FAQs on Alcohol and Phenol

What are alcohols and phenols?

Alcohols and phenols are classes of organic compounds containing a hydroxyl (-OH) functional group.

What are the main differences between alcohols and phenols?

Alcohols have the hydroxyl group attached to a saturated carbon atom in a hydrocarbon chain, while phenols have the hydroxyl group directly bonded to an aromatic benzene ring.

What are some common examples of alcohols?

Common examples of alcohols include ethanol (found in alcoholic beverages), methanol (used as a solvent and fuel), isopropyl alcohol (used as a disinfectant), and glycerol (found in skincare products and as a solvent).

What are some common examples of phenols?

Common examples of phenols include phenol (carbolic acid), cresols, bisphenol A (BPA), resorcinol, and gallic acid.

Are alcohols and phenols toxic?

While alcohols are generally less toxic, phenols can be toxic, especially in higher concentrations. Some phenolic compounds, such as cresols and BPA, have been associated with health concerns and are regulated in certain products.