Aldol builder
"Aldol builder" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the NCERT section "α-Hydrogen reactions and uses" in Aldehydes, Ketones and Carboxylic Acids. Pick one or two carbonyl compounds; the sim marks α-hydrogens, forms the enolate, attacks the other carbonyl, shows the β-hydroxy product and its dehydration to the enone; with no α-H and conc. alkali it runs Cannizzaro instead. NEET has asked about this idea 5 times in 10 years of papers. JEE Main asked 60 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson α-Hydrogen reactions and uses in Aldehydes, Ketones and Carboxylic Acids. Change the values and watch what happens.
What it shows
NCERT §8.4
Pick one or two carbonyl compounds; the sim marks α-hydrogens, forms the enolate, attacks the other carbonyl, shows the β-hydroxy product and its dehydration to the enone; with no α-H and conc. alkali it runs Cannizzaro instead.
Controls
4 to try
- Selectcarbonyl 1 and 2 (ethanal, propanal, propanone, methanal, benzaldehyde)
- Toggledilute alkali / concentrated alkali + heat
- Buttonstep enolate → addition → dehydration
- Readoutsall products listed (cross-aldol gives up to four)
Try this
Cross ethanal with propanal and find all four condensation products; then make benzaldehyde react with acetone (Claisen-Schmidt)
Common mistake
The aldol –OH is on the α-carbon / aldehydes without α-H undergo aldol.
In NEET
10 years of papers
Asked 5 times in 10 years of NEET.
See the past questions: Aldol Condensation, Aldehydes, Ketones and Carboxylic Acids (chapter)
In JEE Main
42 shifts analysed
60 questions from Aldehydes, Ketones and Carboxylic Acids across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §8.4–8.5
- Hydrogens on the carbon next to C=O (α-hydrogens) are acidic: the carbonyl group withdraws electrons strongly, and the conjugate base is resonance-stabilised.
- Aldol reaction: an aldehyde or ketone with at least one α-hydrogen, with dilute alkali as catalyst, gives a β-hydroxy aldehyde (aldol) or β-hydroxy ketone (ketol). Ethanal gives 3-hydroxybutanal.
- The aldol or ketol loses water easily to give an α,β-unsaturated carbonyl compound, the aldol condensation product: 3-hydroxybutanal → but-2-enal. Ketones are included under the same name.
- Cross aldol condensation uses two different aldehydes and/or ketones. If both have α-hydrogens, four products form: ethanal with propanal gives but-2-enal, 2-methylpent-2-enal, pent-2-enal and 2-methylbut-2-enal.
- Cannizzaro reaction: an aldehyde with no α-hydrogen, heated with concentrated alkali, disproportionates. One molecule is reduced to the alcohol and another oxidised to the carboxylic acid salt: 2HCHO + conc. KOH → CH₃OH + HCOOK.
- In aromatic aldehydes and ketones the carbonyl group deactivates the ring and directs electrophiles to the meta position.
- Formalin, a 40% solution of formaldehyde, preserves biological specimens; formaldehyde also makes bakelite (a phenol-formaldehyde resin) and urea-formaldehyde glues.
- Acetaldehyde is the raw material for drugs, polymers, vinyl acetate, ethyl acetate and, mainly, acetic acid. Perfume and dye makers use benzaldehyde; acetone and ethyl methyl ketone are industrial solvents; camphor, acetophenone, vanillin and butyraldehyde are prized for their smell and taste.
Questions
5 answers
- What does the "Aldol builder" simulation show?
- Pick one or two carbonyl compounds; the sim marks α-hydrogens, forms the enolate, attacks the other carbonyl, shows the β-hydroxy product and its dehydration to the enone; with no α-H and conc. alkali it runs Cannizzaro instead.
- What mistake does the "Aldol builder" simulation fix?
- A common mistake it clears up: the aldol –OH is on the α-carbon / aldehydes without α-H undergo aldol.
- 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 Aldehydes, Ketones and Carboxylic Acids?
- Yes. JEE Main asked 60 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 "α-Hydrogen reactions and uses" in Aldehydes, Ketones and Carboxylic Acids (Class 12 Chemistry).
Embed this simulation
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Teaching this idea? Put the simulation on your own page or LMS with this code.