Alcohols Phenols And Ethers

i) Ethyl alcohol from Grignard's reagent:

ii) Tertiary alcohol from Grignard's reagent:

iii) Ethyl alcohol from Methyl alcohol:

iv) Diethyl ether from Ethyl alcohol:

v) Ethyl acetate from Ethyl alcohol:

Preparation of phenol:
One important laboratory method is from diazonium salts (benzene diazonium chloride).
Thus, phenol is obtained by hydrolysis of benzene diazonium chloride.
Reactions of phenol:
(i) With conc. HNO (Nitration):
Phenol reacts with concentrated nitric acid to give picric acid (2,4,6-trinitrophenol).
(ii) With bromine water (Bromination):
Phenol reacts with bromine water to give a white precipitate of 2,4,6-tribromophenol.
(iii) With zinc (Reduction):
Phenol reacts with zinc on heating to give benzene.

i) Reaction of dilute HNO with phenol:
Phenol undergoes nitration with dilute HNO to form ortho- and para-nitrophenol.

ii) Reaction of phenol with chloroform in the presence of NaOH (aq.):
This is the Reimer-Tiemann reaction. Phenol reacts with chloroform and NaOH to give salicylaldehyde (o-hydroxybenzaldehyde).

Dehydration reaction: Alcohols on heating with concentrated H SO or H PO undergo dehydration to give alkenes.
(i) Primary alcohol:
Example: Ethanol
(ii) Secondary alcohol:
Example: 2-propanol
(iii) Tertiary alcohol:
Example: tert-butanol
Mechanism of dehydration of primary alcohol (Ethanol):

Step 1: Protonation of alcohol.

Step 2: Formation of carbocation (slow step).

Step 3: Deprotonation to form alkene.
Thus, the product is ethene.

(i) Preparation of 4-Nitrophenol:
Phenol undergoes nitration with dilute HNO at room temperature.
Para product (4-nitrophenol) is the major one due to steric effects.
(ii) Preparation of Picric acid (2,4,6-trinitrophenol):
On treatment with concentrated HNO in presence of concentrated H SO , phenol gives picric acid.
(iii) Preparation of 4-Bromophenol:
Phenol reacts with bromine water to give 2,4,6-tribromophenol. But to obtain monobromo derivative, phenol is treated with bromine in CS at low temperature.
(iv) Preparation of Salicylaldehyde:
This is obtained by the Reimer–Tiemann reaction. Phenol is treated with chloroform (CHCl ) and alkali (KOH/NaOH).
(Main product is salicylaldehyde at ortho-position.)
(v) Preparation of Benzoquinone:
Phenol is oxidised by strong oxidising agents like Na Cr O /H SO .

Step 1: Raw material.
Molasses, a by-product of sugar industry, contains about 30–40% sucrose.

Step 2: Fermentation process.
Molasses is diluted with water and yeast (Saccharomyces cerevisiae) is added.
The enzyme invertase converts sucrose into glucose and fructose.
Then the enzyme zymase converts glucose/fructose into ethanol and carbon dioxide.

Step 3: Distillation.
The fermented solution is distilled to obtain ethanol of higher purity.

Alcohols are more soluble in water compared to hydrocarbons of similar molecular weight due to the presence of the hydroxyl group (-OH), which allows alcohols to form hydrogen bonds with water molecules. The following points explain this in detail:
1. Hydrogen Bonding:
Alcohols contain a hydroxyl group (-OH), which can form hydrogen bonds with water molecules. Water is a polar solvent, and the hydroxyl group in alcohols is also polar, making it capable of forming hydrogen bonds. These interactions increase the solubility of alcohols in water. On the other hand, hydrocarbons are non-polar and cannot form hydrogen bonds with water, making them much less soluble.
2. Polarity:
The hydroxyl group in alcohols makes them polar, while hydrocarbons are non-polar. Water is a polar solvent, and polar substances tend to dissolve more easily in polar solvents. This is the main reason why alcohols are more soluble in water than hydrocarbons of similar molecular weight.
3. Hydrophilic and Hydrophobic Parts:
In alcohols, the -OH group is hydrophilic (water-loving) and can interact with water molecules, whereas the hydrocarbon chain is hydrophobic (water-repelling). However, the hydrophilic nature of the hydroxyl group overcomes the hydrophobic nature of the hydrocarbon part, making alcohols more soluble than hydrocarbons in water.
4. Size of the Alcohol:
The solubility of alcohols in water decreases with increasing size of the hydrophobic hydrocarbon chain. Larger alcohols, such as octanol, are less soluble in water compared to smaller alcohols, like methanol or ethanol. However, alcohols are still more soluble than hydrocarbons of comparable molecular weight due to the presence of the -OH group.
5. Hydrogen Bond Formation:
In water, the hydroxyl group of alcohols can form hydrogen bonds not only with other alcohol molecules but also with water molecules. This significantly increases the solubility of alcohols. Hydrocarbons, lacking the ability to form hydrogen bonds with water, are much less soluble in water. Thus, alcohols are more soluble in water because of their ability to form hydrogen bonds with water molecules, whereas hydrocarbons lack this ability.

Dehydration reaction: A dehydration reaction is a chemical reaction in which a molecule of water ( ) is eliminated from the reacting molecule. In the case of alcohols, when heated with a strong acid catalyst (such as conc. H SO or H PO ), alcohols undergo dehydration to form alkenes.
This reaction follows the mechanism of E1 elimination for secondary and tertiary alcohols and E2 elimination for primary alcohols.
Mechanism of Dehydration of Alcohol (E1 for 2 or 3 alcohols):

Step 1: Protonation of alcohol.
The lone pair of electrons on the oxygen atom of the alcohol attacks a proton ( ) from the acid catalyst, converting the hydroxyl group into a better leaving group (water).

Step 2: Formation of carbocation.
The protonated alcohol loses a water molecule, forming a carbocation intermediate.

Step 3: Elimination of proton.
A base (often ) abstracts a -hydrogen atom from the carbon adjacent to the carbocation, leading to the formation of a double bond (alkene). Overall reaction:

(i) Kolbe Reaction:
The Kolbe reaction involves the electrolysis of sodium or potassium salts of carboxylic acids, resulting in the decarboxylation and coupling of alkyl radicals to form alkanes.
Example:
Electrolysis of sodium acetate gives ethane: (ii) Reimer–Tiemann Reaction:
The Reimer–Tiemann reaction introduces a formyl group ( ) into the aromatic ring of phenols, mainly at the ortho position, using chloroform ( ) and alkali (NaOH/KOH).
Example:
Phenol reacts with chloroform in alkaline medium to give salicylaldehyde (2-hydroxybenzaldehyde). (iii) Williamson Ether Synthesis:
The Williamson ether synthesis involves the reaction of a sodium alkoxide with a primary alkyl halide to form ethers. It is a nucleophilic substitution ( ) reaction.
Example:
Sodium ethoxide reacts with methyl iodide to give ethyl methyl ether:

Step 1: Nature of forces in butane.
Butane (C H ) is a hydrocarbon and non-polar in nature. The only intermolecular forces present in butane are weak Van der Waals (London dispersion) forces. These forces require relatively little energy to overcome, so butane has a low boiling point.

Step 2: Nature of forces in propanol.
Propanol (C H OH) is an alcohol containing an –OH group. The hydroxyl group allows molecules of propanol to form intermolecular hydrogen bonds. Hydrogen bonds are much stronger than Van der Waals forces. Breaking these bonds requires more energy, which raises the boiling point of propanol significantly.

Step 3: Comparison.
Because propanol forms hydrogen bonds while butane does not, the boiling point of propanol is much greater than that of butane.

The preparation of phenol can be done via several methods. One common method is the **Caustic soda method**, where chlorobenzene reacts with sodium hydroxide. Here, chlorobenzene (C H Cl) reacts with sodium hydroxide (NaOH) in the presence of heat (Δ) to form phenol (C H OH) and sodium chloride (NaCl). Final Answer:

Analysis of the Reaction:
This question deals with the Nitration of Phenol. The product depends on the concentration of the acid used.

• Reaction with Dilute :
  When phenol is treated with dilute nitric acid at low temperature (298 K), it undergoes mono-nitration to yield a mixture of ortho- and para- isomers.
  • (A) o-Nitrophenol: The group attaches at the ortho position (adjacent to ).
  • (B) p-Nitrophenol: The group attaches at the para position (opposite to ).
• Reaction with Concentrated :
  With concentrated nitric acid, the reaction is vigorous, and poly-nitration occurs at all activating positions (ortho and para).
  • (C) 2,4,6-Trinitrophenol: Commonly known as Picric Acid.

Structures:

• (A): o-Nitrophenol ( - ortho isomer)
• (B): p-Nitrophenol ( - para isomer)
• (C): 2,4,6-Trinitrophenol (Picric Acid)