14. Hydrocarbons
A section of Chemistry, 9701
Listing 10 of 313 questions
(CH3)3CCHO is used in the synthesis of some antibiotics. Give the name of (CH3)3CCHO. State the hybridisation of the carbon atom labelled with an asterisk, *. CH3 CH3 H3C C C O H * Two reaction sequences are shown. CH3 CH3 NaBH4 H3C C S (CH3)3CCO2H A U C O H T reaction 2 reaction 3 reaction 1 O O Reaction1 is an oxidation reaction. Identify the reagentand conditions for reaction1. 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. Give the balanced equation for the reaction of (CH3)3CCHO with NaBH4 to form S. Use to represent an atom of hydrogen provided by NaBH4. Draw the structure of the organic molecule T that reacts with A, (CH3)3CCO2H, in reaction2, to form U. Suggest a catalyst for reaction2. T catalyst  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. compound observations with 2,4-DNPH observations with Fehling’s solution principal absorptions in infra-red spectrum X no reaction 1715 cm–1 Y red precipitate 1730 cm–1 Z no reaction no reaction 3200–3600 cm–1 1630 cm–1 1050 cm–1 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. Identify the functional group present in Y that causes the recorded observation with Fehling’s solution. Y has a chiral centre and exists as a pair of optical isomers. State what is meant by the term chiral centre. Draw the optical isomers of Y using the conventional three-dimensional representation.  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  Draw the skeletal formula of Z.  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. C C2H5 C2H5 HO NC  State the role of NaCN in the reaction in . 
9701_w19_qp_21
THEORY
2019
Paper 2, Variant 1
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(CH3)3CCHO is used in the synthesis of some antibiotics. Give the name of (CH3)3CCHO. State the hybridisation of the carbon atom labelled with an asterisk, *. CH3 CH3 H3C C C O H * Two reaction sequences are shown. CH3 CH3 NaBH4 H3C C S (CH3)3CCO2H A U C O H T reaction 2 reaction 3 reaction 1 O O Reaction1 is an oxidation reaction. Identify the reagentand conditions for reaction1. 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. Give the balanced equation for the reaction of (CH3)3CCHO with NaBH4 to form S. Use to represent an atom of hydrogen provided by NaBH4. Draw the structure of the organic molecule T that reacts with A, (CH3)3CCO2H, in reaction2, to form U. Suggest a catalyst for reaction2. T catalyst  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. compound observations with 2,4-DNPH observations with Fehling’s solution principal absorptions in infra-red spectrum X no reaction 1715 cm–1 Y red precipitate 1730 cm–1 Z no reaction no reaction 3200–3600 cm–1 1630 cm–1 1050 cm–1 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. Identify the functional group present in Y that causes the recorded observation with Fehling’s solution. Y has a chiral centre and exists as a pair of optical isomers. State what is meant by the term chiral centre. Draw the optical isomers of Y using the conventional three-dimensional representation.  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  Draw the skeletal formula of Z.  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. C C2H5 C2H5 HO NC  State the role of NaCN in the reaction in . 
9701_w19_qp_23
THEORY
2019
Paper 2, Variant 3
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Questions Discovered
313