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 displayed formula for methylbenzene.

[1]

ii) Draw the displayed formula for benzoic acid.

[1]

i) Name the reaction that takes place in step 1.  

[1]

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

step 1: ............................................................

step 2: ...........................................................

[2]

Describe the observations that could be made during step 1.

Describe and explain the relative acidities of benzoic acid and phenol. 

Fig. 2.1 shows three different molecules.

Fig. 2.1 

Propan-1-ol can react with sodium metal. 

Write an equation for this reaction. 

i) Give the order of the relative acidities of the propanoic acid, propan-1-ol and phenol, stating the least acidic first. 

[1]

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

[2]

Another carboxylic acid, methanoic acid is similar to propanoic acid in terms of its acidity. 

i) Name a reagent which could be used to distinguish between these two acids.

[1]

ii) Name the acid which gives a positive result in this test and describe the observations that would be made.

[1]

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

Suggest the identify of compound X. 

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

A different acyl chloride was used to synthesize ethyl butanoate. 

i) Draw the displayed formula of the acyl chloride  

[1]

ii) Name the mechanism by which ethyl butanoate is formed.

[1]

iii) Name the second produce formed in this reaction. 

[1]

Describe and explain the relative acidities of benzoic acid, phenylmethanol and 4-methylphenol shown in Fig. 1.1. 

Fig. 1.1

The ester 4-methylphenyl benzoate is used in the manufacture of perfumes and 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. 

[1]

ii) Suggest 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. 

 step 1 .........................................................

 step 2 ......................................................... 

[4]

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