A-LevelChemistryHalogen derivatives9701/42 · May/June 2021 · Q810 Marks

State and explain the relative rate of hydrolysis of acyl chlorides, alkyl chlorides and aryl chlorides. fastest ............................................................... > ............................................... > ............................................... slowest ........................................................................................................................................................... ........................................................................................................................................................... ...........................................................................................................................................................

(a)State and explain the relative rate of hydrolysis of acyl chlorides, alkyl chlorides and aryl chlorides. fastest ............................................................... > ............................................... > ............................................... slowest ........................................................................................................................................................... ........................................................................................................................................................... ...........................................................................................................................................................[3]
(b)The drug remifentanil is shown. remifentanil [Figure X.X] Remifentanil is completely hydrolysed under acidic conditions. Three different organic compounds are formed. Draw the structures for these organic compounds in the boxes.[3]
(c)Compound Y, C5H10O2, reacts with Na2CO3(aq) to evolve bubbles of gas. The proton (1H) NMR spectrum of compound Y in D2O is shown. [Figure showing proton NMR spectrum] 2 1 0 δ/ppm
(c)(i)Use this information to suggest a structure for Y.[1]
(c)(ii)Use the Data Booklet, the proton (1H) NMR spectrum and your answer to (c)(i) to complete the table. chemical shift (δ) environment of proton splitting pattern number of 'H atoms responsible for the peak 0.95 1.90 2.20[3]

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Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[3] M1: acyl chlorides > alkyl chlorides > aryl chlorides (fastest to slowest) M2/3: Any two from: • acyl chlorides: carbon in C-Cl bond is more electron deficient since it is also attached to an oxygen atom OR C-Cl bond is weakest / weakened in acyl chlorides since it is also attached to an oxygen atom / two electronegative atoms • aryl chlorides: C-Cl bond is part of delocalised system / partially double bond character (so C-Cl bond is stronger) OR lone pair/p-orbital on Cl delocalises with π ring (so C-Cl bond is stronger) • alkyl chlorides: C-Cl bond strengthened by electron donating effect / positive inductive effect of alkyl / R group (as compared to acyl chlorides) OR carbon atom has a smaller δ+ and the C-Cl bond is stronger (than the C-Cl bond in COCl) due to (the carbon) being only attached to one electronegative atom
[3] Structures of the three organic products: 1. CH₃OH (methanol) 2. CH₃CH₂COOH (propanoic acid) 3. (Piperidine ring with N-CH₂-C₆H₅ and N-CH₃ at N1, and C4-COOH and C4-NH₂. So, 4-amino-1-benzyl-1-methylpiperidine-4-carboxylic acid)
[1] (Structure of 3-methylbutanoic acid: (CH₃)₂CHCH₂COOH)
[3] (Table completion for 3-methylbutanoic acid): 0.95: alkane / CH₃, doublet, 6 1.90: alkane / CH, multiplet, 1 2.20: R/alkyl / CH₂, next to C=O/COOH, doublet, 2

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