Amines

Chemistry · Class 12

Simulation · Chemistry · Class 12

Count the carbons

"Count the carbons" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the NCERT section "Gabriel and Hoffmann methods" in Amines. A carbon-count tracker for amine syntheses: from a halide or amide choose ammonolysis, nitrile reduction (+1 C), Gabriel (same C, aliphatic only) or Hoffmann bromamide (−1 C) NEET has asked about this idea 5 times in 10 years of papers. JEE Main asked 57 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).

From the lesson Gabriel and Hoffmann methods in Amines. Change the values and watch what happens.

Count the carbonsChemistry · Class 12

What it shows

NCERT §9.4

A carbon-count tracker for amine syntheses: from a halide or amide choose ammonolysis, nitrile reduction (+1 C), Gabriel (same C, aliphatic only) or Hoffmann bromamide (−1 C)

Controls

3 to try

  • Selectstart (C₂H₅Br, n-C₃H₇Br, C₆H₅Br, butanamide, benzamide, CH₃CN)
  • Buttonroute (NH₃ excess, KCN then LiAlH₄, potassium phthalimide then OH⁻, Br₂/NaOH, Na/C₂H₅OH)
  • Readoutsproduct, carbon count change, route fails? (e.g. Gabriel on aryl halide)

Try this

Make propan-1-amine from a two-carbon halide, then make aniline (Gabriel will refuse; find the route that works)

Common mistake

Hoffmann keeps the carbon count / Gabriel makes aniline.

In NEET

10 years of papers

Asked 5 times in 10 years of NEET.

See the past questions: Amines and Diazonium Salts, Amines (chapter)

In JEE Main

42 shifts analysed

57 questions from Amines across the 42 JEE Main shifts Lumi has analysed (2017–2026).

See the past questions

The idea behind it

NCERT §9.4

  • Gabriel phthalimide synthesis gives primary amines only. Phthalimide with ethanolic KOH forms potassium phthalimide; heating this with an alkyl halide gives an N-alkylphthalimide, and alkaline hydrolysis releases the primary amine.
  • Gabriel synthesis cannot give aniline or any aromatic primary amine: an aryl halide will not be attacked by the phthalimide anion in a substitution.
  • Hoffmann bromamide degradation (NCERT's spelling): an amide is treated with bromine in aqueous or ethanolic NaOH. An alkyl or aryl group migrates from the carbonyl carbon to nitrogen, and the primary amine formed has one carbon fewer than the amide.
  • Equation: RCONH₂ + Br₂ + 4NaOH → RNH₂ + Na₂CO₃ + 2NaBr + 2H₂O.
  • Worked: propanamine (three carbons) comes from butanamide (four); benzamide (seven carbons) gives aniline (six).
  • Carbon count at a glance: nitrile reduction adds one carbon to the alkyl halide, Hoffmann degradation removes one from the amide, and Gabriel synthesis and ammonolysis keep the halide's carbon count.

Questions

5 answers

What does the "Count the carbons" simulation show?
A carbon-count tracker for amine syntheses: from a halide or amide choose ammonolysis, nitrile reduction (+1 C), Gabriel (same C, aliphatic only) or Hoffmann bromamide (−1 C)
What mistake does the "Count the carbons" simulation fix?
A common mistake it clears up: hoffmann keeps the carbon count / Gabriel makes aniline.
Has NEET asked about this idea?
Yes. NEET has asked about this idea 5 times in 10 years of papers.
Does JEE Main ask questions from Amines?
Yes. JEE Main asked 57 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
Is this simulation free?
Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Gabriel and Hoffmann methods" in Amines (Class 12 Chemistry).

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