Organic Reactions

Step 1: In Etard's reaction, toluene is selectively oxidized to benzaldehyde using chromyl chloride ( ).

Step 2: The reaction proceeds as:

(b) What happens when – (write chemical equations only)

(i) Mixture of calcium acetate and calcium formate is dry distilled?

(COO)_2Ca + HCOO_2Ca → CH_3CHO + CaCO_3

(ii) Acetone is distilled with conc. H₂SO₄?

2 CH_3COCH_3 → CH_3CH=CH_2 + CH_3COOH

(iii) Acetone is heated with chloroform in presence of alkali?

CH_3COCH_3 + CHCl_3 + NaOH → CH_3CCl_3OH + NaCl

(iv) Formic acid is heated with Fehling’s solution?

HCOOH + 2Cu²⁺ + 5OH^- → CO_2 + Cu_2O + 3H_2O

(v) Formaldehyde is heated with conc. NaOH solution?

HCHO + NaOH → HCOONa + H_2

OR

(b) Explain the following:

(i) Benzoin condensation

Solution:

Step 1: In benzoin condensation, two aldehyde molecules condense in presence of cyanide ion.

Step 2: Reaction:

2 C_6H_5CHO + CN^- → C_6H_5CH(OH)C(=O)C_6H_5

Benzoin is formed.

(ii) Perkin’s reaction

Solution:

Step 1: Perkin’s reaction involves condensation of aromatic aldehydes with acid anhydrides.

Step 2: Reaction:

C_6H_5CHO + (CH_3CO)_2O → C_6H_5CH=CHCOOH

It forms cinnamic acid.

(iii) Cross Cannizzaro reaction

Solution:

Step 1: Cross Cannizzaro reaction occurs between two different aldehydes, one undergoing oxidation and the other reduction.

Step 2: Example:

HCHO + C_6H_5CHO + NaOH → HCOONa + C_6H_5CH_2OH

Preparation of Benzene Diazonium Chloride: Conversions:

(i) Benzene

(ii) Chlorobenzene

(iii) Nitrobenzene

Solution:

(i) Preparation of ethanol from fermentation of sugar

C₆H₁₂O₆ ⟶ (Yeast) 2C₂H₅OH + 2CO₂

(ii) Reimer-Tiemann Reaction

C₆H₅OH + CHCl₃ + NaOH ⟶ o-Hydroxybenzaldehyde + p-Hydroxybenzaldehyde

(iii) Williamson’s Synthesis

R-O⁻ + R'-X ⟶ R-O-R' + X⁻

OR

(i) Preparation of alcohols from Grignard’s reagent:

Primary Alcohol:

R-MgX + HCHO ⟶ (H₂O) R-CH₂OH + Mg(OH)X

Secondary Alcohol:

R-MgX + CH₃CHO ⟶ (H₂O) R-CHOH-CH₃ + Mg(OH)X

Tertiary Alcohol:

R-MgX + R'CO-R'' ⟶ (H₂O) R-C(OH)-R'R'' + Mg(OH)X

Solution:

Step 1: Resonance Effect in Haloarenes:

Haloarenes (e.g., chlorobenzene) show resonance due to delocalization of lone pair electrons on the halogen. This results in partial double bond character, reducing reactivity towards nucleophilic substitution.

Step 2: Wurtz-Fittig Reaction:

• This reaction involves the coupling of aryl halides with alkyl halides using sodium in dry ether.
• Reaction:

Step 3: Friedel-Crafts Reaction:

• Aromatic compounds undergo electrophilic substitution with alkyl halides in the presence of a Lewis acid catalyst ( ).
• Example:

What happens when – (write chemical equations only)?

(i) Ethyl bromide reacts with sodium ethoxide?

(ii) Ethyl chloride reacts with alcoholic KCN?

(iii) Chlorobenzene reacts with nitric acid?

(iv) n-butyl chloride reacts with alcoholic KOH?

(v) Ethyl bromide reacts with magnesium metal in the presence of dry ether?

Step 1: Paramagnetic Behaviour: - Transition metals exhibit paramagnetism due to the presence of unpaired electrons in d-orbitals. - Magnetic moment: where is the number of unpaired electrons.

Step 2: Formation of Coloured Ions: - Colour in transition metal ions arises due to d-d transitions when electrons absorb visible light and jump between d-orbitals. - Example:

Step 1: Basicity and Lanthanoid Contraction: - As we move across the lanthanide series, atomic size decreases due to lanthanoid contraction.
- has a larger ionic radius, making it more basic than .

Step 2: Explanation: - Larger ionic size in leads to weaker bond strength in , making hydroxide ions ( ) more available.
- has a smaller radius, leading to a stronger attraction between and , reducing basicity.