A-LevelChemistryHalogen derivatives9701/42 · May/June 2023 · Q815 Marks

Compound T, C5H9O2Cl, is a useful synthetic intermediate. Fig. 8.1 shows some reactions of T. [Figure 8.1]

(a)Describe the difference in reactivity between chloroethane and chlorobenzene with OH-(aq). Explain your answer.[2]
(b)(i)Give the systematic name for T.[1]
(b)(ii)Draw the structures of W, X, Y and Z in Fig. 8.1.[4]
(b)(iii)State the reagents and conditions for steps 1 and 2 in Fig. 8.1. step 1 step 2[2]
(c)(i)The proton (1H) NMR spectrum of compound T, C5H9O2Cl, in CDCl3 is shown in Fig. 8.2. [Figure 8.2] Table 8.1 [Table 8.1, chemical shift ranges] Suggest why CDCl3 is used as a solvent instead of CHCl3 for the proton (1H) NMR spectrum.[1]
(c)(ii)Complete Table 8.2 for the proton (1H) NMR spectrum of T. [Table 8.2, chemical shifts 1.2, 2.8, 3.7, 3.9][4]
(c)(iii)Explain the splitting pattern of the peak at δ 3.9 ppm.[1]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[1] chlorobenzene is less reactive than chloroethane OWTTE
[1] p-orbital/lone pair on Cl will overlap / delocalise into the ring
[1] due to partial double C-Cl bond OWTTE OR C-Cl bond strengthened (more)
[1] ethyl 3-chloropropanoate
[1] Structure of W: Cl-CH2CH2COO-Na+ (sodium 3-chloropropanoate)
[1] Structure of X: CH3CH2OH (ethanol)
[1] Structure of Y: NC-CH2CH2COOCH2CH3 (ethyl 3-cyanopropanoate)
[1] Structure of Z: H2N-(CH2)5-COOH (6-aminohexanoic acid)
[1] M1 step 1: NaCN / KCN in ethanol (heat)
[1] M2 step 2: H2 + Ni / H2 + Pt ALLOW LiAlH4
[1] (because solvent / D / CDCl3) doesn't give a signal / peak / absorption ORA
[1] For chemical shift 1.2: environment alkyl / alkane / (R-)CH(3), splitting triplet, number of 1H atoms 3
[1] For chemical shift 2.8: environment alkyl next to C=O / CH(2)C=O, splitting triplet, number of 1H atoms 2
[1] For chemical shift 3.7: environment alkyl next to electronegative atom / CH(2)-Cl, splitting triplet, number of 1H atoms 2
[1] For chemical shift 3.9: environment alkyl next to electronegative atom / CH(2)-O, splitting quartet/quadruplet, number of 1H atoms 2
[1] (δ = 3.9) three H on neighbouring / adjacent C / it's next to a CH3

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