INChO — Indian National Chemistry Olympiad — Answer Writing
INChO asks for the reasoning that multiple choice hides: the arrow-pushing, the intermediate, the equilibrium worked to a number. The product alone is rarely the answer.
Answer all questions. Show mechanisms with curved arrows where asked. Use of a non-programmable calculator is permitted.
- 1.Predict the major product when 2-bromo-2-methylbutane is treated with sodium ethoxide in ethanol, and explain the mechanism and regiochemistry.10
- 2.Calculate the pH of the buffer described above and the change on adding 0.01 mol of strong acid.10
- 3.Explain the splitting of d-orbitals in an octahedral field and predict the magnetic behaviour of the given complex.12
One INChO answer, from question to marked report
A real question, an attempt with the weaknesses a real attempt has, and the report an AI examiner hands back — in the marking unit INChO genuinely uses. This is the whole product; there is nothing else to sign up for.
Scoped to the paper and topic you pick, at the marks it is genuinely set at.
Predict the major product when 2-bromo-2-methylbutane is treated with sodium ethoxide in ethanol, and explain the mechanism and regiochemistry.
Type it, dictate it, or write on paper and photograph the page — your handwriting is read.
Photographed, read, and marked in red — every expected step scored down the right margin and the omissions written in.
The product is 2-methyl-2-butene. Sodium ethoxide is a strong base so elimination takes place by E2 mechanism. The more substituted alkene is formed as per Zaitsev rule.? 2-bromo-2-methylbutane is a tertiary halide and the carbon carrying the bromine has three alkyl groups attached to it. Ethoxide can remove a proton from either of two different beta carbons, so two alkenes are possible. Removal from the methyl group would give 2-methyl-1-butene, the less substituted alkene, while removal from the CH2 group gives 2-methyl-2-butene. The more substituted alkene is more stable because of hyperconjugation and the greater number of alkyl groups on the double bond, and the transition state leading to it is lower in energy. Therefore 2-methyl-2-butene is the major product and 2-methyl-1-butene is formed only in a small amount.
- The concerted anti-periplanar transition state, described step by step
- Why E2 rather than E1 or SN2 on this substrate with this base
- The Hofmann contrast with a bulky base such as potassium tert-butoxide
Model answer for this question
Identify the substrate as tertiary and ethoxide as a strong, small base, so E2 dominates over E1 and SN2 is blocked sterically. Describe the concerted step: base removes a beta hydrogen anti-periplanar to the leaving bromide, with C-H bond breaking, pi bond forming and C-Br breaking in one transition state. Compare the two available beta positions and explain that the more substituted alkene is favoured by hyperconjugative stabilisation in the transition state, giving 2-methyl-2-butene. Add the contrast: a bulky base gives the Hofmann product.
Photograph the page from your phone and the Studio reads your handwriting — the only way to practise the speed and layout the paper actually tests.
Fast enough to write, read the report and rewrite the same answer in one sitting — which is where the improvement actually comes from.
The scoring behind those pen marks: every expected step, what it was worth, what you earned, and a model answer.
- Major product identified2/2
Correct.
- Mechanism identified and justified2/3
E2 named correctly; the tertiary substrate and strong base as the reasons are not stated.
- Mechanism drawn — anti-periplanar arrangement and concerted arrows0/3
Not drawn or described. The arrows are the mechanism.
- Regiochemistry explained rather than named1/2
Zaitsev named without the stabilisation argument, and the Hofmann alternative with a bulky base is not contrasted.
INChO at a glance
| Conducting body | Homi Bhabha Centre for Science Education (HBCSE) |
|---|---|
| Mode | Handwritten solutions |
| Papers | 3 |
| Marking | INChO — step marking |
What INChO sets
The papers you sit, and what each is worth.
- Marked to the INChO scheme
- Model answer, every time
- Handwriting read from a photo
- AI viva on any topic
- Full timed papers
- Every attempt kept in your archive
- WriteA question, answered and marked.
- VivaQuestioned on Reaction mechanisms and more.
- Full paperA timed paper, one scorecard.