CAIE A-Level Chemistry 34.1.2 Amide Formation from Amines

Practise forming amides when ammonia or an amine reacts with an acyl chloride at room temperature.

Exam points

replace the acyl chloride’s Cl by –NH2 when ammonia is used, forming a primary amide
retain one or two carbon substituents on nitrogen when a primary or secondary amine is acylated
draw every amide link when a diacyl chloride reacts with excess amino compound and include HCl formation

[Maximum number: 3]

Asparagine and aspartic acid are two naturally occurring amino acids. Their structures and isoelectric points are shown in Table 8.1.

Table 8.1

(a)

Propanedioic acid, $\mathrm{HOOCCH}_{2} \mathrm{COOH}$ , is treated with an excess of thionyl chloride, $\mathrm{SOCl}_{2}$ . Propanedioyl chloride, $\mathrm{ClOCCH}_{2} \mathrm{COCl}$ , is formed.

[ 3 ]

(i)

Write an equation for this reaction.

[ 1 ]

$\mathrm{HOOCCH}_{2} \mathrm{COOH}+2 \mathrm{SOCl}_{2} \rightarrow \mathrm{ClOCCH}_{2} \mathrm{COCl}+2 \mathrm{SO}_{2}+2 \mathrm{HCl}$

(ii)

Propanedioyl chloride reacts with an excess of asparagine to form compound G with molecular formula $\mathrm{C}_{11} \mathrm{H}_{16} \mathrm{~N}_{4} \mathrm{O}_{8}$ .

Each molecule of compound G has four amide groups.
Draw the structure of compound G.

\text { Compound G, } \mathrm{C}_{11} \mathrm{H}_{16} \mathrm{~N}_{4} \mathrm{O}_{8}

[ 2 ]

Figure for Answer to Question (ii) — CAIE A-Level Chemistry A2

$\mathrm{HOOCCH}\left(\mathrm{CH}_{2} \mathrm{CONH}_{2}\right) \mathrm{NHCOCH}_{2} \mathrm{CONHCH}\left(\mathrm{CH}_{2} \mathrm{CONH}_{2}\right) \mathrm{COOH}$

M1: three molecules joined, with four correct amide groups only

M2: whole structure correct as above, displayed formula accepted, skeletal formula as below accepted

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34.1.2—Amide formation from amines question 1

Question (a)

Question (i)

Question (ii)