TOPIC 19 & 20: CARBOXYLIC ACIDS AND DERIVATIVES & IR SPECTROSCOPY

1. The structural formulae of two compounds are shown below

Which statements about these compounds are correct?

1 The two compounds are structural isomers of each other.
2 The empirical formula of both compounds is C3H6O.
3 Both compounds are carboxylic acids.
A 1, 2 and 3 are correct B 1 and 2 only are correct
C 2 and 3 only are correct D 1 only is correct

2. Alcohols, aldehydes and nitriles can each be converted into carboxylic acids. Which descriptions
of their conversions into carboxylic acids are correct?
alcohols aldehydes nitriles
A hydrolysis hydrolysis hydrolysis
B hydrolysis hydrolysis oxidation
C oxidation oxidation hydrolysis
D oxidation oxidation oxidation

3. Which compound can be used to make propanoic acid by treatment with a single reagent?
A CH2=CHCH2CH3 B CH3CH2CH2CN
C CH3CH(OH)CN D CH3CH(OH)CH3

4. A student carried out a two-stage synthesis in which CH3CH2CH2Br was converted into
CH3CH2CH2CO2H. Which compound could have been formed by the first stage of this synthesis?
A CH3CH2CH2OH B CH3CH2CH2CHO
C CH3CH2CN D CH3CH2CH2CN

5. Four reactions of propanoic acid to form salts and other products are shown. Which reaction does
not show the formulae of all the correct products?
6. Which reagents, when used in an excess, can be used to make sodium lactate,
CH3CH(OH)CO2Na, from lactic acid, CH3CH(OH)CO2H?
1 Na 2 NaHCO3 3 NaOH
A 1, 2 and 3 are correct B 1 and 2 only are correct
C 2 and 3 only are correct D 1 only is correct

7. Ethanedioic acid, HO2CCO2H, is reduced using an excess of lithium aluminium hydride, LiAlH4.
What is the organic product of the reaction?
A ethanol B ethane-1,2-diol
C ethanedial D methane

8. How many isomeric esters, including structural isomers and stereoisomers, can be made with the
molecular formula C5H10O2, if methanoic acid is one of the two reactants used?
A2 B3 C4 D5

9. Which mixture could be used to produce propyl methanoate?

A CH3CH2CO2H and CH3OH B CH3CH2CH2CH2OH and HCO2H
C CH3CH2CH2OH and HCO2H D CH3CH2CH2CO2H and CH3OH

10. The fragrance compounds of perfumes are often dissolved in solvent Y, which has a molecular
formula C7H12O4. It is made by reacting propane-1,2-diol with ethanoic acid in the presence of an
acid catalyst.

propane-1,2-diol
What is the structure of solvent Y?

11. An ester X has the structural formula CH3CO2CH(CH3)CH2CH3. X can be prepared by heating
an alcohol Y, under reflux, with ethanoic acid and an acid catalyst. What is the correct name for Y?
A butan-1-ol B butan-2-ol
C butan-3-ol D methylpropan-2-ol
12. The ester CH3CH2CH2CO2CH2CH(CH3)2 was hydrolysed under acidic conditions. What are the
organic products of this hydrolysis?
A butanoic acid and 2-methylpropan-1-ol B butanoic acid and 2-methylpropan-2-ol
C butan-1-ol and 2-methylpropanoic acid D propanoic acid and 2-methylpropan-1-ol

13. The ester, CH3CH2CO2CH3, is hydrolysed by boiling with aqueous sodium hydroxide. Which
compound is one of the products?
A ethanol B propan-1-ol
C sodium methanoate D sodium propanoate

14. How many structural isomers with the molecular formula C4H10O give infra-red absorptions
both at approximately 1200 cm–1 and at approximately 3400 cm–1?
A2 B4 C6 D7

15. Compound X contains three carbon atoms. Part of a simplified infra-red spectrum of compound
X is shown.

Which compound could be X?

A CH3CH2CHO B CH3CH2CO2H C CH3CH2CH2OH D CH3CO2CH3

16. J is a branched-chain alcohol, C5H12O. J is heated under reflux with an excess of Cr2O72– /H+ until
no further reaction occurs. An organic compound K is formed in good yield. The infra-red spectrum
of K is shown.
What are the structures of the branched-chain alcohol J and compound K?
J K
A CH3CH(CH3)CH2CH2OH CH3CH(CH3)CH2CHO
B CH3CH2CH(OH)CH2CH3 CH3CH2COCH2CH3
C CH3CH(CH3)CH(OH)CH3 CH3CH(CH3)COCH3
D CH3CH(CH3)CH2CH2OH CH3CH(CH3)CH2COOH

17. Acetoin, CH3COCH(OH)CH3, and diacetyl, CH3COCOCH3, are two of the compounds that
give butter its characteristic flavour. Their skeletal formulae are shown.

(a) Give the systematic name for acetoin.

3 - hydroxybutan-2-one
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(b) Identify the reagents and conditions necessary for the conversion of acetoin into diacetyl.
acidified potassium manganate under reflux
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(c) The infra-red spectrum for acetoin is shown.

(i) Explain the main features of this spectrum, with reference to the peaks with wavenumbers greater
than 1500 cm–1.
absorption at 1670 - 1740 --> C = O carbonyl
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absorption at 2850 - 2950 --> CH2-H alkanes
absorption at 3200 - 3600 --> R - OH alcohol
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(ii) State and explain how the infra-red spectrum for diacetyl would differ from the infra-red
spectrum for acetoin.
no absorption at 3200 - 3600 because diacetyl has no alcohol group
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(d) If a sample of acetoin is reacted with concentrated sulfuric acid, a single product is formed that
does not exhibit stereoisomerism. However, if a sample of acetoin is reacted with HBr, a mixture
of a pair of stereoisomers is produced.
(i) Give the structural formula of the product of the reaction of acetoin with concentrated sulfuric acid.

(ii) Explain why the product in (i) does not exhibit stereoisomerism.
carbon with the double bond is bonded to 2 H
………………………………………………………………………………………………………
(iii) Explain why the product of reaction of acetoin with HBr does exhibit stereoisomerism.
the product contains a chiral center
………………………………………………………………………………………………………
carbon bonded to 4 different groups or atoms
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--> optical isomer
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(iv) Draw the two stereoisomers from (iii) using the conventional representation.