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Named Reactions

Board-useful named reactions with mechanisms, conditions, and common mistakes. This public set is bundled locally for fast access. Free, no login needed.

CBSE Class XII Chemistry Part 2 (Chapters 6 to 9) · 100% Deterministic EngineNCERT Class XII Chemistry Part 2, Ch 8, Section 8.4.3 & 8.4.4

Organic Multi-Step Synthesis, Wet-Lab Distinction & Stereochemistry (R/S) Workbench

Commit multi-step reagent pathways (A -> B -> C), inspect Cahn-Ingold-Prelog (R/S) Walden inversion vs racemization, simulate wet-lab functional group distinction tubes, and compute Double Bond Equivalents (DBE) locally with zero runtime AI.

Step 1 · Select CBSE Class XII Organic Conversion & Distinction Roadmap

Multi-Step Conversion Chain (Compound A -> Intermediate B -> Product C)

Starting Material (A)

Ethanal (CH3CHO, 3 alpha-H) vs Benzaldehyde (C6H5CHO, 0 alpha-H) vs Propanone (CH3COCH3)

Intermediate / State (B)

3-Hydroxybutanal (Aldol beta-hydroxy aldehyde) vs Benzyl alcohol + Sodium benzoate (Cannizzaro)

Final Target (C)

But-2-enal (Crotonaldehyde, alpha,beta-unsaturated aldehyde after dehydration)

Compare the base-catalyzed pathways and chemical distinction tests for Ethanal (CH3CHO), Benzaldehyde (C6H5CHO), and Propanone (CH3COCH3). Commit the reagent sequence that converts Ethanal -> 3-Hydroxybutanal -> But-2-enal while explaining why Benzaldehyde undergoes Cannizzaro disproportionation instead.

Step 2 · Commit Reagent Sequence (A -> B -> C)

Active Chemical Test: Iodoform Haloform Test
Verified Roadmap + Distinction TestFSRS-5: Reinforce Soon (Next interval: 7d)

Verified: Dilute NaOH deprotonates the alpha-carbon of CH3CHO for Aldol condensation to But-2-enal, while 50% conc. NaOH drives hydride transfer in alpha-H-free C6H5CHO. Chemical Distinction Verified: Iodoform Haloform Test (I2 + aqueous NaOH (or NaOI, warm)) yields Yellow precipitate of CHI3(s).

Stereochemical & Mechanistic Rule (Cahn-Ingold-Prelog / Regioselectivity):

Alpha-Hydrogen Rule: Aldehydes/ketones with at least one alpha-H (such as CH3CHO or CH3COCH3) form resonance-stabilized enolate ions in dilute base to undergo Aldol addition, followed by E1cb dehydration on heating to yield alpha,beta-unsaturated carbonyls. Aldehydes with zero alpha-H (C6H5CHO, HCHO) cannot enolize and instead undergo hydride transfer (Cannizzaro disproportionation) in 50% concentrated alkali.

Distinction Matrix: Ethanal (CH3CHO) is the unique aldehyde with a CH3CO-H group, so it gives BOTH a positive Tollens silver mirror AND a positive yellow CHI3 Iodoform precipitate. Benzaldehyde (C6H5CHO) gives a positive Tollens silver mirror but NEGATIVE Fehling and NEGATIVE Iodoform tests. Propanone (CH3COCH3) gives a positive Iodoform precipitate but NEGATIVE Tollens test.

Retrievability R93.9%
Stability S -> S'5.2d -> 8.17d
Next Due Interval7 days

CBSE 3-Mark Stepwise Conversion & Distinction Rubric

Step 1 (1.0 mark): Identify that CH3CHO possesses 3 acidic alpha-hydrogens (sp3 C-H adjacent to C=O), forming 3-hydroxybutanal (Aldol) with dilute NaOH, which loses H2O on heating to give But-2-enal.

Step 2 (1.0 mark): State that Benzaldehyde (C6H5CHO) has zero alpha-H on the ipso ring carbon, so concentrated NaOH triggers Cannizzaro disproportionation into C6H5CH2OH + C6H5COONa.

Step 3 (1.0 mark): Distinguish the triad via Tollens and Iodoform tests: CH3CHO gives yellow CHI3(s) + silver mirror; C6H5CHO gives silver mirror only (Fehling negative); CH3COCH3 gives yellow CHI3(s) only.

Socratic Checkpoint: Count the hydrogens attached to the carbon directly bonded to the -CHO group in C6H5CHO versus CH3CHO. Why can C6H5CHO not form a nucleophilic enolate ion?

Step 3 · Wet-Lab Chemical Distinction Tube Simulator

7 Board Functional Group Tests

Select a wet-lab reagent to inspect precipitate, mirror, turbidity, or azo-dye color change.

Iodoform Haloform TestYellow CHI3 Precipitate

Reagent: I2 + aqueous NaOH (or NaOI, warm)

Target: Methyl ketones (CH3CO-) and CH3CH(OH)- alcohols (plus Ethanal CH3CHO)

Pale yellow crystalline precipitate of triiodomethane (CHI3) with characteristic antiseptic odor.

Phase / Precipitate: Yellow precipitate of CHI3(s)

Step 4 · Molecular Formula DBE Calculator (C_x H_y N_z O_w X_k)

C7H6O · DBE = 5

Formula: DBE = C + 1 - (H + X - N) / 2. Divalent oxygen (O) does not alter DBE.

DBE = 7 + 1 - (6 + 0 - 0) / 2 = 5Benzene Ring Candidate (DBE >= 4)

DBE = 5 (with >= 7 carbons): Benzene ring (4 DBE) + 1 exocyclic pi bond (C=O in Benzaldehyde, Benzoic acid, Benzamide, or Salicylaldehyde).

Matching Board Examples: Benzaldehyde (C7H6O) · Salicylaldehyde (C7H6O2) · Salicylic acid (C7H6O3) · Benzamide (C7H7NO)

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