Gabriel phthalimide synthesisगैब्रिएल थैलिमाइड संश्लेषणGabriel phthalimide synthesis

Class 12 Chemistry · Chapter 9 · interactive diagram

Parts and what they mean

• Phthalimide (थैलिमाइड) — A cyclic imide: the N–H between two C=O groups is acidic.
• Ethanolic KOH (एथेनॉलिक KOH) — Removes the acidic H as water and forms the potassium salt.
• Potassium phthalimide (phthalimide anion) (पोटैशियम थैलिमाइड (थैलिमाइड ऋणायन)) — The N⁻ is the nucleophile that attacks the alkyl halide.
• Alkyl halide, heat (ऐल्किल हैलाइड, गर्म) — Nucleophilic substitution; KX is removed.
• N-Alkylphthalimide (N-ऐल्किलथैलिमाइड) — Only ONE alkyl group can attach — so no 2°/3° amines form (unlike ammonolysis).
• Alkaline hydrolysis, NaOH(aq) (क्षारीय जल-अपघटन, NaOH(aq)) — Breaks both C–N bonds of the imide.
• Disodium phthalate (by-product) (डाइसोडियम थैलेट (उप-उत्पाद)) — C₆H₄(COONa)₂ — the phthalimide part ends up here.
• Primary amine R–NH₂ (प्राथमिक ऐमीन R–NH₂) — Gabriel synthesis gives only 1° amines.
• No aromatic amines by Gabriel (गैब्रिएल से ऐरोमैटिक ऐमीन नहीं) — Aryl halides do not undergo nucleophilic substitution with the phthalimide anion.

Steps

1. Phthalimide + ethanolic KOH → potassium phthalimide (the N–H is acidic, flanked by two C=O).
2. Heat with an alkyl halide: the phthalimide anion substitutes X → N-alkylphthalimide.
3. Alkaline hydrolysis (NaOH(aq)) → primary amine + sodium phthalate.

Original diagram drawn by Simple Learning Hub, based on the NCERT textbook. Report a mistake