Alcohols

Alcohols are classified as monohydric, dihydric, trihydric, or polyhydric based on the presence of one, two, three, or more than three hydroxyl groups, respectively.

Monohydric alcohols are further divided into:

• Compounds with a Csp3-OH bond: The hydroxyl group is connected to an alkyl group with an sp3 hybridised carbon atom in compounds with the Csp3-OH bond. Primary, secondary, and tertiary alcohols are the three types of alcohol.

  • Allylic alcohols: The hydroxyl group is connected to an sp3 hybridised carbon atom next to a carbon-carbon double bond.

  • Benzylic alcohols: The hydroxyl group is connected to an sp3 hybridised carbon atom close to the aromatic ring in benzylic alcohols.

• Compounds with a Csp2-OH bond: The hydroxyl group is connected to an sp2 hybridised carbon atom. Vinylic alcohols are another name for these alcohols.

Phenols

These are categorised as monohydric, dihydric, and polyhydric based on the number of hydroxyl groups.

Ethers

There are two types of ethers: symmetrical and unsymmetrical.

Symmetrical: O is connected to the same groups on both sides.

Unsymmetrical: Different groupings are asymmetrically attached to O.

Alcohols

“Alcohol” is a common name for a substance that belongs to the alkyl group, such as methyl alcohol, ethyl alcohol, and so on.

The suffix “ol” is applied to the alkane name, such as methanol, according to the International Union of Pure and Applied Chemistry.

Phenol

C6H5OH is the most basic phenol.

The position of the OH group is indicated by o (ortho), m (meta), p (para), or cyclic carbon numbers, among other things.

Ethers

The term “ether” follows in alphabetical order the name of the alkyl groups, for example, ethyl methyl ether, ether of diethyl, etc. 

International Union of Pure and Applied Chemistry name: Derivative of alkoxy or aryloxy hydrocarbon. The parent hydrocarbon, such as methoxymethane, methoxybenzene, and so on, is called the bulkier group.

Alcohols

• The C and O sp3 hybridised orbitals share a bond.

• The C-O-H bond angle is 108.9°, which is smaller than tetrahedral (109° 28'). It results from the repulsion between oxygen electron pairs.

• Bond length: The C-O bond length in methanol is 142 pm.

Phenols

• The aromatic ring’s C and the sp2 hybridised orbitals’ O have a bond.

• The C-O-H bond angle in phenol is 109°.

• C-O bond length: The C-O bond in phenol is 136 pm long.

• Carbon has less sp2 hybridisation than methanol, and conjugation of the pi electrons of the aromatic ring results in a partial double-bond character.

Ethers

• The angle of the C-O-C bond is 111.7° (methoxymethane).

• Owing to the repulsion between the two classes of R, it is more than tetrahedral (bulky).

• The C-O bond has a length of 141 pm, which is about the same as alcohol.

Alcohols can be made in a variety of ways.

• Acid-catalysed hydration of alkenes: In the presence of an acid, an alkene combines with water to create alcohol, according to Markovnikov’s addition.

• The hydroboration oxidation of alkenes produces trialkyl borane as an extra product when diborane is reacted with alkenes.

• Aldehyde and ketone reduction: Aldehydes and ketones are reduced by adding hydrogen in the presence of catalysts like nickel, platinum, and palladium. Primary alcohols are formed from aldehyde, while secondary alcohols are formed from ketones.

• Reduction of carboxylic acids and esters: Lithium hydrogen hydride carboxylic acids are reduced to primary alcohols in the presence of powerful reducing agents.

Phenols can be made using the following methods:

• Haloarenes are made by reacting NaOH with chlorobenzene to produce sodium phenoxide, which then reacts with an acid to produce phenol.

          C₆H₅Cl + NaOH → C₆H₅ONa + HCl → C₆H₅OH

• Sulphonation of benzene with oleum is the initial step in producing benzene sulphonic acid. With molten NaOH, benzene sulphonic acid is heated to create sodium phenoxide, which is subsequently acidified from phenol.

• Aniline (C₆H₅NH₂) is a diazonium salt that combines with NaNO₂ + HCl to generate benzene diazonium chloride (C₆H₅N₂Cl), which hydrolyses to give phenol.

• Cumene (isopropylbenzene) is oxidised and subsequently converted to phenol using dilute acid. Acetone is a byproduct of the reaction.

Ethers can be made in a variety of ways.

• Dehydration of alcohols: When primary alcohols are treated with protic acids, the nucleophilic bimolecular process yields ether (H₂SO₄, H₃PO₄). The principal products of this reaction are alkene at 443 K and ether at 413 K, depending on the circumstances. When alcohol is at 2° or 3°, the elimination process competes with SN1, resulting in alkene as the primary product.

• Synthesis by Williamson

Alcohol

As the number of carbon atoms increases, Van der Waal forces rise, raising the boiling point of alcohols.

Alcohols are water-soluble because they create hydrogen bonds with water molecules.

Phenol

When compared to other compounds like arenes, ethers, and haloarenes, phenol has a higher boiling point due to intermolecular hydrogen bonding.

Intermolecular hydrogen bonding with water is responsible for solubility. It reduces as the hydrophobic portion increases.

Ether

Due to intermolecular hydrogen bonding in ethers, their boiling point is lower than water.

Ether miscibility is equivalent to that of alcohol and greater than that of an alkane of the same molecular mass owing to the formation of a hydrogen bond with water and O of ether.

Alcohol

• Bronsted acids can help the Bronsted base by donating electrons.

• The polarity of the O-H bond causes acidity. As the electron-releasing alkyl groups diminish the acidity, the alcohol acidity order is 1° > 2° > 3°.

• Alcohols are a weaker donor of protons or a more potent acid than water.

• They also act as a proton acceptor or Bronsted base owing to the unshared electron pairs on oxygen.

Phenol

• The alcohol group on the benzene ring works as an electron-withdrawing group. The double bond of the benzene ring is linked with oxygen electron pairs, making OH oxygen positive.

• Acids stronger than water and alcohol are known as phenols.

• This could be explained by the more stable phenoxide ion and the more polar OH bond.

• The electron-withdrawing group (-NO₂) makes the substituted phenols more acidic, while the electron-donating groups (alkyl) make it less acidic.

• Nitrophenol > phenol > cresol > ethanol is the order of acidity.

Ether

Ethers are acidic, although not as much as aldehydes and ketones but more so than hydrocarbons.