AQA A2 Chemistry C26 Compound Containing Carbonyl Group Kerboodle Answers

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C26.1 Introduction to aldehydes and ketones AQA A2 Compount Containing Carbonyl Groups: Page No.  157

1: a Pentan-3-one b Propanal 2

A ketone must have a C= O group with two carbon-containing groups attached to it, so at least three carbon atoms are required.

The C=O group can only be on carbon 2, otherwise the compound would be an aldehyde. c The C=O group must always be on the end of the chain. 3 A hydrogen bond requires a molecule with a hydrogen atom covalemly bonded to an atom of fluorine, oxygen, or nitrogen. There is no such carbon atom in propanone. 4 The hydrogen atom in a.n -OH group in a water molecule can hydrogen bond with the oxygen atom in the C=O bond of propanone.

26.2 Reactions of the carbonyl group in aldehydes and ketonesAQA A2 Compount Containing Carbonyl Groups: Page No. 160

1 w, cr, Cl • Cl^– 2 a No b A negatively charged nucleophile will be repelled by the high electron density in the C= C. c 3 4 The cN-ions can at.tack the planar C= O group from above or below. In the case of CHCHO this will produce a compound with a chiral centre (four different groups attached to it). This will be a pair of optical isomers. As attack from above or below is equally likely it will be a 50:50 mixture (racemic). In the case of CH₃COCH3′ the product will not have a carbon atom with four groups attached to it. It will not therefore be chiral and will be a single compound.

26.3 Carboxylic acids and esters AQA A2 Compount Containing Carbonyl Groups : Page No. 163

1 3-brornobutanoic acid 2 3 The carboxylic acid must be at the end of a chain and therefore in the 1 position. 4 Ethyl ethanoate; methyl propanoate

26.4 Reactions of carboxylic acids and esters AQA A2 Compount Containing Carbonyl Groups: Page No. 167

1. They react with carbonates and hydrogencarbonates to give carbon dioxide, metal oxides to give salts, and alkalis to give salts.

2 Methanol and ethanoic add 3 Ethanol and methanoic acid 4 They have the same molecular formula but have a different arrangement of their atoms in space.

26.5 Acylation AQA A2 Compount Containing Carbonyl Groups: Page No. 172

1 The carbon of the C= O group is strongly cO+ because, as well as oxygen, it is also bonded to an electronegative chlorine atom whid1 draws electrons away from it. 2 OH-, because it is negatively charged and contains a lone pair of electrons. 3 Because the nucleophile and the acylating agent join together and then a small molecule is lost. 4 Banner 2

Practice questions: Page No. 173

1 (a) CH₃OH + CH₃CH₂COOH → CH₃CH₂COOCH₃ + H₂O (b) Nucleophilic addition–elimination (c) (d) (i) A selection of answers are correct here. These are : faster/ not reversible/ bigger yield /purer product/ no acid catalyst required (ii) Anhydride less easily hydrolysed or reaction less exothermic. 2 (a) Nucleophilic addition (b) (i) Name compound Q. 2-hydroxybutanenitrile (ii) (c) (i) methanol in the presence of a few drops of concentrated sulfuric acid; (ii) (iii) CH₃CH=CHCOOH 3 (a) (Nucleophilic) addition – elimination; (b) 4 (a) Propan(e)-1,2,3-triol (b) CH₃(CH₂)₁₆COONa or C₁₇H₃₅COONa Banner 3

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