Physical properties of Alcohols, Phenols and Ethers

Alcohols, phenols, and ethers are organic compounds that are widely used in industries. Alcohols are formed by at least one hydroxyl group attached to the saturated hydrocarbon. Phenols are formed by the hydroxyl group attached to a benzene ring. Ethers are formed when oxygen atoms are connected to two aryl or alkyl groups. Let’s learn about alcohol, Phenols, and Ethers and their respective properties.

Alcohols

Alcohols are class organic compounds characterized by at least one hydroxyl group attached to the aliphatic hydrocarbon present in the alcohol. Hence, alcohol contains two parts, one is the alkyl group (R group), and the other one is the hydroxyl group (OH). Alcohols are considered derivatives of water in which one hydrocarbon atom is replaced by a hydroxyl group.

General structure: R-OH (R represents the Alkyl group)

Classification of Alcohols

Based on the presence of the hydroxyl group attached to a carbon atom, alcohols are classified into three types. The location of the hydroxyl groups will determine the physical and chemical properties of alcohols. 

• Primary alcohols: These are the types of alcohols in which the carbon atom of the hydroxyl group is attached to the primary carbon atom or only one single alkyl group. 

General structure: R-CH₂-OH  

Examples: Methanol (CH₃-OH) and ethanol (CH₃-CH₂-OH).

• Secondary alcohols: These are the types of alcohols in which the carbon atom of the hydroxyl group is attached to the secondary carbon atom or two alkyl groups on either side.

General structure: R₂-CH-OH

Examples: Isopropanol (CH₃−CH-(OH)−CH₃)

• Tertiary alcohols: These are the types of alcohols in which the carbon atom of the hydroxyl group is attached to the tertiary carbon atom or three alkyl groups.

General structure: R₃-C-OH

Examples: 2-methyl-2-propanol (CH₃)₃-C-OH

Properties of alcohols

Properties of the alcohols depend on the number of carbon atoms attached to the hydroxyl groups.

The boiling point of alcohol

Alcohols are generally possessed high boiling points compared with other hydrocarbons, which is due to the presence of intermolecular hydrogen bonding between hydroxyl groups of alcohol atoms. The boiling point of alcohols decreases with an increase in the branch of the aliphatic carbon chain, and the boiling point of alcohols increases with an increase in the number of carbon atoms in the carbon chain. Thus, the primary alcohols have a higher boiling point.

Solubility of alcohols 

The solubility of alcohols is determined by the presence of hydroxyl groups. Alcohols are more soluble in water compared to other hydrocarbons since the alcohols contain polar hydroxyl groups. The alkyl groups present in the alcohols are hydrophobic in nature. Hence, the solubility of alcohols decreases with an increase in the number of alkyl groups.

The acidity of alcohol

Alcohols are acidic in nature. They react with the metals known as potassium and sodium to form alkoxide ions. The acidic nature of alcohol is because of the polar bond between the hydrogen atom and oxygen atom presenting the hydroxyl group. Hence primary alcohols are more soluble than secondary and tertiary alcohols. The order of acidity of alcohols is as follows: 

Primary alcohols > Secondary alcohols > Primary alcohols

Physical state 

Alcohols are flammable liquids with blue flame. Alcohols are colorless, and most alcohols are generally liquids at room temperature. They generally smell sweet.

Phenols

These are also called as carbolic acids. Phenols are aromatic organic compounds that contain hydroxyl groups attached to the benzene ring. They are also called carbolic acids. They show extraordinary physical and compound properties compared with alcohols. These physical and chemical properties of phenol due to the presence of the hydroxyl group in phenols.

General structure: R-OH (R Represents Benzene)

Structure of phenols: C₆H₅-OH (Toluene)

Physical properties of phenols

Boiling point of phenols

Phenols generally have a higher boiling point when compared to the other hydrocarbons, which have an equal molecular weight, which is due to the intermolecular hydrogen bonding presence between the hydroxyl groups of the phenol molecules. In general, the boiling point of phenol increases with an increase in the number of carbon atoms in the carbon chain.

Solubility of Phenols 

The solubility of phenols is determined by the presence of hydroxyl groups. Phenols are more soluble in water due to the intermolecular hydrogen bonding between the water and phenol, which makes phenols more soluble in water. The aryl groups present in the phenols are hydrophobic in nature. Hence, the solubility of phenols decreases with an increase in the number of aryl groups.

Acidity of Phenols 

Phenols are acidic in nature. Phenols react with the metals known as potassium and sodium to form respective phenoxides. In phenol, the sp₂ hybridized carbon attached to the hydroxyl group of the benzene ring acts as an electron-withdrawing group. Consequently, it diminishes the electron density of oxygen. Because of the delocalization of the negative charge in the benzene ring, phenoxides are more stable than alkoxide particles. Subsequently, phenols are more acidic than alcohol. 

Physical state and Toxicity

Phenols exist in liquids and solids at room temperature. They are colorless. They are more toxic in nature.

Chirality of Phenols

Phenols display chirality within their structure. This chirality is due to the lack of planar and axial symmetry in the phenol atom.

Ethers

Ethers are organic compounds that contain oxygen atoms (ether group) connected to two aryl or alkyl groups. Ethers are divided into two categories which are symmetrical and asymmetrical ethers.

The general formula of ethers: R-O-R’

• Symmetrical ethers: These contain the same alkyl groups or aryl groups on both sides of the oxygen atom. 

Examples: CH₃-O-CH₃ (Dimethyl ether)

• Asymmetrical ethers: These contain different alkyl or aryl groups at both sides of the oxygen atom.

Examples: CH₃-O-CH₂-CH₃ (Ethyl Methyl ether)

Physical properties of Ethers

Polarity of ethers

Ethers are dipolar in nature. The C – O bonds in the ether are polar, and thereby, ethers show a net dipole moment due to the electronegativity between oxygen and a carbon atom. Ethers are more polar than alkenes but not polar when compared with alcohols, esters, or amides with similar structures.

Boiling point

Ethers have much lower boiling points as compared to isomeric alcohols since they do not contain intramolecular hydrogen bonding. The boiling point of ethers is practically identical to the alkanes; however much lower than that of alcohols of the same atomic mass in spite of the extremity of the C-O bond.

Physical state

Ethers are generally colorless, sweet-smelling, and volatile in nature.

Solubility

Ethers are comprised of two sorts of particles: the nonpolar hydrophobic hydrocarbon chain and the polar hydrophilic oxygen end. The solubility of ethers is the same as alcohols. They are miscible in water. As the size of the alkyl group increases, the solubility of ether in water decreases.

Acidity of ethers

Ethers act as Lewis bases on account of the presence of two sets of electrons on the oxygen molecule. Consequently, they form salts with strong acids. 

FAQs on Alcohols, Phenols, and Ethers

Question 1: What are the properties and uses of alcohol?

Answer:

Alcohols are colorless liquids at room temperature. Methyl alcohol, ethyl alcohol, and isopropyl alcohol are free-streaming liquids with fruity odors. Alcohols are used in alcoholic drinks and methylated industrial spirits. Isopropyl liquor is broadly utilized in the industry as a solvent for paints and compound cycles, and ethanol is utilized as a solvent for food concentrates like vanilla, fragrances, and a few kinds of paints and veneers. Methanol is used as a solvent in the pharma industries.

Question 2: What are the properties of phenols?

Answer:

Phenols are natural aromatic compounds containing a hydroxyl functional group attached to the benzene ring. As alcohols, Phenols are either colourless liquids or solids. Phenols are generally utilized as sterile, sanitizer, sedative and family cleaning items. Phenol is likewise utilized as a beginning material or produced halfway in industry. The boiling point of phenols are higher than the boiling point of alcohols with the same molecular weight. Phenols are more acidic than alcohols but less acidic than a carboxylic acid.

Question 3: What are the uses of phenols?

Answer:

Phenols are used as disinfectants, antiseptics, anesthetics, and also used in cleaning products. Phenols can be used against fungi and viruses. In small quantities, these can be used as disinfectants in mouthwash and household cleaning products. Concentrated phenol is toxic and can harm skin with next to no aggravation.

Phenol is likewise utilized as a beginning material or produced as a transitional in industry. Plastics, touchy, picric corrosive and various medications are produced using phenol. In the color industry, phenols are generally used to make azo colors. As wood additives, phenols (like cresols) are additionally utilized.

Question 4: Explain the solubility of ethers.

Answer:

Ethers with up to three carbon molecules are miscible in water because lesser ethers form simple hydrogen bonds with water. Ethers are comprised of two sorts of particles: the nonpolar hydrophobic hydrocarbon chain and the polar hydrophilic oxygen end. The dissolvability of ether in water diminishes as the size of the alkyl bunch increments. This is attributable to the hydrocarbon part’s non-polar nature, which hinders hydrogen bonds with the polar water atoms from framing. 

Question 5: Explain the acidity of alcohols.

Answer:

Alcohols react with dynamic metals, for example, sodium, potassium, and so on, to frame the relating alkoxide. These reactions of alcohol demonstrate their acidic nature. The acidity of alcohols is because of the extremity of the – OH bond. The acidity of alcohols diminishes when an electron-giving gathering is connected to the hydroxyl bunch as it builds the electron thickness on the oxygen ion. Along these lines, essential alcohols are, for the most part, more acidic than optional and tertiary alcohols. Because of the presence of unshared electrons on the oxygen particle, alcohols go about as Bronsted bases as well.

Question 6: Explain the hydrogen bonding of ethers.

Answer:

Ethers do not contain hydrogen bonding between the molecules since the hydrogen atom in the ethers do not directly attached to the oxygen. However, they show hydrogen bonding with water molecules since oxygen atoms are having 2 lone pair of electrons.

Question 7: Explain the boiling point of alcohols.

Answer:

Alcohols have higher boiling points when compared with other hydrocarbons having the same molecular weight, which is due to the presence of intermolecular hydrogen bonding between hydroxyl groups present in the alcohol molecules. The boiling point of alcohols decreases with an increase in the branch of the aliphatic carbon chain, and the boiling point of alcohols increases with an increase in the number of carbon atoms in the carbon chain. Thus, the primary alcohols have a higher boiling point. Thus primary alcohols have a higher boiling point.