4 (CH3)3CCHO is used in the synthesis of some antibiotics. (a) (i) Give the name of (CH3)3CCHO. (ii) State the hybridisation of the carbon atom labelled with an asterisk, *. [Figure 4.1] (b) Two reaction sequences are shown. [Figure 4.2] (i) Reaction 1 is an oxidation reaction. Identify the reagent(s) and conditions for reaction 1.

1. (a)(i)Give the name of (CH3)3CCHO.[1]
2. (a)(ii)State the hybridisation of the carbon atom labelled with an asterisk, *.[1]
3. (b)(i)Reaction 1 is an oxidation reaction. Identify the reagent(s) and conditions for reaction 1.[1]
4. (b)(ii)A, (CH3)3CCO2H, is a solid at room temperature. B, CH3CO2(CH2)2CH3, is an isomer of A. B is a liquid at room temperature. Explain the difference in the physical states of A and B, with reference to any intermolecular forces that may exist.[3]
5. (b)(iii)Give the balanced equation for the reaction of (CH3)3CCHO with NaBH4 to form S. Use [H] to represent an atom of hydrogen provided by NaBH4.[1]
6. (b)(iv)Draw the structure of the organic molecule T that reacts with A, (CH3)3CCO2H, in reaction 2, to form U. Suggest a catalyst for reaction 2. catalyst[2]
7. (c)(i)X, Y and Z are all isomers of (CH3)3CCHO. A summary of some of the reactions and properties of X, Y and Z is shown in the table. [Figure 4.3] X and Y each contains a carbonyl group. Complete the table with the expected observations for the reactions of X and Y with 2,4-DNPH.[1]
8. (c)(ii)Identify the functional group present in Y that causes the recorded observation with Fehling’s solution.[1]
9. (c)(iii)Y has a chiral centre and exists as a pair of optical isomers. State what is meant by the term chiral centre.[1]
10. (c)(iv)Draw the optical isomers of Y using the conventional three-dimensional representation.[2]
11. (c)(v)Z, C5H10O, has a branched carbon chain. It shows geometrical isomerism. Complete the table with the bond responsible for each of the principal absorptions seen in the infra-red spectrum of Z. principal absorptions in infra-red spectrum | bond responsible 3200–3600 cm–1 1630 cm–1 1050 cm–1[1]
12. (c)(vi)Draw the skeletal formula of Z.[3]
13. (c)(vii)X contains a carbonyl group. X reacts with HCN, in the presence of a small amount of NaCN, to form (C2H5)2C(OH)CN as shown. X + HCN → (C2H5)2C(OH)CN Draw the mechanism of the reaction of X with HCN. • Draw the structure of X and the intermediate. • Include all charges, partial charges, lone pairs and curly arrows.[3]
14. (c)(viii)State the role of NaCN in the reaction in (c)(vii).[1]

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