QUESTION 147 (4 marks)
Ethanoic acid and methylamine undergo a condensation reaction under suitable heated, dehydrating conditions to form an amide. Treat the stated condensation as complete for the equation; do not model the initial acid–base salt.
(a) Draw the condensed structural formula of the amide. [2 marks]
(b) Write the balanced equation, including the small molecule eliminated. [1 marks]
(c) Identify the bond that distinguishes this amide from an ester. [1 marks]
Practice marking scheme
Answer
Amide: . . Its carbonyl carbon is bonded to nitrogen rather than an ester oxygen.
Working
The acid’s carbonyl carbon forms a bond to the amine nitrogen. Remove OH from the carboxyl group and H from the amino group to form water. The product retains a C=O group bonded directly to N, giving an amide linkage.
Marking criteria
- Shows the retained ethanoic-acid carbonyl carbon and methyl group. [1 mark]
- Connects that carbonyl carbon to NHCH₃ to give CH₃CONHCH₃. [1 mark]
- Writes the balanced condensation equation with water. [1 mark]
- Identifies the carbonyl C–N bond, contrasting it with carbonyl C–O in an ester. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusCompare your working with the guide above.