JEE (Advanced) 2026, Paper 1, Chemistry, Section 4 — matching list set, one correct option: +4 if it is chosen, 0 if unanswered, −1 otherwise. The structures below are drawn from the lab's own molecule graphs, laid out as printed; the compound names under them are added by PrayogX and are not part of the question.
Q.16 Match the major products obtained in the reactions given in List-I with the corresponding structures in List-II and choose the correct option.
Four flasks on one bench, two levels at once — what you would see in the flask on the left, the electrons moving between the atoms on the right. Press START EXPERIMENT: load → reach scan → flasks P, Q, R, S → analysis bench → List-II → test options A–D → answer.
Four flasks, one ring. The question's conditions are loaded — press START EXPERIMENT.
Pink arrows move one electron pair each; gold dots are the attacking lone pair. Red dashes: a bond breaking; green: a bond forming. A₃₈₀ is the yellow of the 2-cyano-4-nitrophenoxide ion (representative absorbance).
O···C2 distance as the side chain turns about the ring–C bond; the dashed line is C + O van der Waals contact (3.22 Å); rigid-rotation model — a dip below it means the atoms can meet, not a real distance
only a phenoxide with a para-nitro group absorbs strongly at 380 nm; representative values, time compressed
not yet examined
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Nothing investigated yet.
Build the oxime, choose its geometry and what sits on the oxygen, then turn the side chain yourself. Drag the model (or use the arrow keys) to look at it from any side. The lab says whether the oxygen can reach the C–Br carbon — and what the flask would give.
The complete worked solution — every structure, arrow and reason. The mechanism figures are drawn from the same steps the lab animates.
The experiment has not finished yet.
An oxime's C=N does not rotate. Z and E are different compounds. Only the single bond from the ring to C7 turns.
A nucleophile adds to the carbon carrying the leaving group; the negative charge must spread onto an electron-withdrawing group ortho or para to it (Meisenheimer complex).
A 1,2-benzisoxazole with an H on C3 is opened by base: C3–H is removed, C≡N forms and the weak N–O bond breaks, giving a 2-cyanophenoxide.
An O-acetyl aldoxime loses AcOH by anti elimination to a nitrile. An O-acetyl ketoxime has no C–H to lose; aqueous base only removes the acetyl.
tests/verify_p1q16.py.The whole question turns on where the oxime oxygen can reach. Once it is an anion (after base removes its proton), the oxime oxygen is a good nucleophile sitting one bond-turn away from the carbon that carries bromine. If it is on the ring's side of the C=N bond (Z) it can swing into contact and, because the nitro group para to bromine can take the negative charge, it displaces bromide and closes a five-membered ring — a 1,2-benzisoxazole. What happens next depends on C3: with a hydrogen there (the aldoxime, P) base tears the ring open again to a nitrile and a phenoxide (the Kemp elimination); with a methyl there (R) the ring stays. Acetylating the oxygen first (Q) takes the nucleophile away and turns the C–H into the thing base removes — a nitrile, with bromine untouched. And an oxygen that points the wrong way (S) can never reach, so mild base only cleaves the ester.
For a student opening it for the first time. The whole investigation runs by itself after one press.
Four reactions, five possible products. Which product comes from which reaction — and which option lists all four correctly?
The question's substrates and reagents are loaded. You do not need to change anything. The answer is shown above the experiment.
Move the nitro group, skip Q's acetylation, flip S to Z or treat S with acid, and see which products change. ↺ RESTORE QUESTION CONDITIONS puts everything back.
Press ▶ START EXPERIMENT under the experiment screen. Nothing else to click (about a minute and a half; SLOW MOTION or 2× changes the pace).
The side chain turns in 3-D. Watch the dashed O···C distance: the Z oxime dips into contact, the E oxime never does.
Each flask shows its reagents going in; beside it every electron pair moves as a curved arrow. The instrument panel checks the charge and octets after each step.
The analysis bench tests for bromide, nitrile and the yellow phenoxide; each product is compared atom by atom with List-II, then every option is tested.
In the Reach explorer build any of the oximes and turn the bond yourself. Press ▶ REPLAY, or change a condition and run a custom experiment. CLASSROOM MODE enlarges everything for a projector.
| Exam | JEE Advanced 2026, Paper 1, Chemistry, Section 4, Q.16 |
|---|---|
| Chapter | Aldehydes, Ketones and Carboxylic Acids |
| Topic | Reactions of oximes — intramolecular nucleophilic aromatic substitution, Kemp elimination, dehydration of O-acyl aldoximes to nitriles |
| Also uses | Haloarenes (SNAr, activation by NO₂) · stereochemistry of C=N (E/Z) · Beckmann rearrangement (distractor) |
| Difficulty | Difficult |
| Answer | — |