Carboxylic Acids (Cambridge (CIE) A Level Chemistry): Exam Questions

Benzoic acid can be formed from methylbenzene. 

This process occurs in two stages. 

methylbenzene          potassium benzoate      benzoic acid        

i) Draw the skeletal formula for methylbenzene.

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ii) Draw the skeletal formula for benzoic acid.

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i) State the type of reaction that takes place in step 1.

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ii) State the reagents and conditions needed for step 1 and step 2 of this reaction.

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State two observations that could be made during step 1.

State the relative acidities of benzoic acid and phenol. Explain your reasoning.

Fig. 2.1 shows three different molecules.

Fig. 2.1

Propan-1-ol can react with sodium metal.

Construct an equation for this reaction.

i) State the relative order of acidity of propanoic acid, propan-1-ol and phenol, starting with the least acidic.

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ii) Explain your answer to part (b)(i).

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Methanoic acid and propanoic acid can be distinguished by a simple chemical test.

i) State the name of a reagent that could be used for this test.

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ii) State which of these two acids gives a positive result with your chosen reagent, and state the observation you would make.

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The acyl chloride, ethanedioyl dichloride is shown in Fig. 3.1.

This can be synthesised from compound X in a single step.

Fig. 3.1

Deduce the identity of compound X.

State the reagents and conditions needed to convert X into ClCOCOCl.

A different acyl chloride was used to synthesise ethyl butanoate.

i) Draw the displayed formula of the acyl chloride.

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ii) State the name of the mechanism by which ethyl butanoate is formed.

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iii) State the name of the other product formed in this reaction.

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State the relative order of acidity of benzoic acid, phenylmethanol and 4-methylphenol shown in Fig. 1.1, starting with the most acidic. Explain your reasoning.

Fig. 1.1

The ester 4-methylphenyl benzoate can be formed in two steps from two of the compounds shown in Fig. 1.1 in part (a).

i) Draw the skeletal formula of 4-methylphenyl benzoate.

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ii) State the two-step route for the synthesis of 4-methylphenyl benzoate. Include reagents and conditions for each step and the structure of the intermediate compound.

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State the reagents and conditions required to form benzoic acid from methylbenzene.

Acyl chlorides, amino acids, and polyamides are important nitrogen-containing organic compounds.

Ethanoyl chloride, CH₃COCl, reacts vigorously with ammonia, NH₃, to form an amide.

i) State the name of the mechanism of this reaction.

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ii) Draw the mechanism for this reaction. Include all relevant curly arrows, lone pairs, and dipoles.

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Alanine, H₂​NCH(CH₃​)COOH, is an amino acid that exists as a zwitterion in the solid state.

Draw the structure of the zwitterion of alanine.

1,6-diaminohexane reacts with hexanedioic acid to form a polyamide called Nylon 6,6.

i) Draw the structure of the repeat unit of Nylon 6,6.

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ii) Polyesters and polyamides are biodegradable polymers, whereas polyalkenes are generally non-biodegradable.

Explain this difference in terms of the structure and reactivity of the polymer chains.

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