An organic compound “P” of molecular formula C₆H₁₂O₃$C_{6}H_{12}O_{3}$ gives positive Iodoform test but negative Tollen’s test. When “P” is treated with dilute acid, it produces “Q”. “Q” gives positive Tollen’s test and also iodoform test. The structure of “P” is :

Related Formula

Core Logic

The reaction depicts the partial reduction of an acid chloride (benzoyl chloride) to an aldehyde (benzaldehyde) using hydrogen gas in the presence of a poisoned palladium catalyst (Pd supported on BaSO₄$BaSO_4$).

Pattern Recognition

Acid Chloride + H₂, Pd/BaSO₄$H_2, Pd/BaSO_4$ arrow$\rightarrow$ Aldehyde is strictly the Rosenmund reduction. The BaSO₄$BaSO_4$ poisons the catalyst to prevent over-reduction to an alcohol.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Core Logic

Decode the IUPAC name: 4-Methylpent-2-enal

• Word root: 'pent' arrow$\rightarrow$ 5 carbon principal chain.
• Primary suffix: '2-en' arrow$\rightarrow$ Double bond starting at carbon 2.
• Secondary suffix: 'al' arrow$\rightarrow$ Aldehyde group (-CHO) at carbon 1.
• Substituent: '4-Methyl' arrow$\rightarrow$ A methyl group (-CH3) at carbon 4.

Step 1: Drafting the structure

Numbering starts from the aldehyde carbon.

Attach the methyl at C⁴$C^4$:

This matches Option 4.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

Core Logic

Pathway 1 (Upper): Toluene is treated with Reagent 'A' and acetic anhydride (CH₃CO)₂O$(CH_3CO)_2O$ to form an intermediate (benzylidene diacetate), which on hydrolysis gives benzaldehyde. The reagent used here is Chromic oxide (CrO₃$CrO_3$). Thus, A is CrO₃$CrO_3$.

Pathway 2 (Lower): Toluene is treated with Reagent 'B' in CS₂$CS_2$ to form a chromium complex intermediate, which on hydrolysis yields benzaldehyde. This is the Etard reaction, and the reagent used is Chromyl chloride (CrO₂Cl₂$CrO_2Cl_2$). Thus, B is CrO₂Cl₂$CrO_2Cl_2$.

Step 1: Selection

Therefore, A = CrO₃$CrO_3$ and B = CrO₂Cl₂$CrO_2Cl_2$.

Pattern Recognition

Etard reaction always uses Chromyl chloride (CrO₂Cl₂$CrO_2Cl_2$). Oxidation of toluene with acetic anhydride uses Chromic acid (CrO₃$CrO_3$). Both stop the oxidation at the aldehyde stage via intermediate formation.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Related Formula

Core Logic

Ethanal (CH₃CHO$CH_3CHO$) reacts with semicarbazide (H₂N-NH-CO-NH₂$H_2N-NH-CO-NH_2$) via nucleophilic addition followed by elimination of water to form a semicarbazone.

Step 1: Product Analysis

The product is Ethanal semicarbazone: CH₃-CH=N-NH-CO-NH₂$CH_3-CH=N-NH-CO-NH_2$. Counting the nitrogen atoms in this structure:

• The imine nitrogen (=N-$=N-$)
• The amine nitrogen (-NH-$-NH-$)
• The amide nitrogen (-NH₂$-NH_2$)

Total = 3 Nitrogen atoms.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Core Logic

The reaction of benzene with carbon monoxide (CO$CO$) and hydrogen chloride (HCl$HCl$) in the presence of anhydrous aluminium chloride (AlCl₃$AlCl_3$) and cuprous chloride (CuCl$CuCl$) to give benzaldehyde is known as the Gatterman-Koch reaction.

Pattern Recognition

CO + HCl arrow$CO + HCl \rightarrow$ Formyl chloride intermediate (in situ) with Lewis acid arrow$\rightarrow$ formylation of benzene. This is definitively the Gatterman-Koch formylation.

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids