AL Examination – Nitrogen compounds
1.
(i) Give the reaction conditions and the necessary chemicals/reagents required for the formation of
benzenediazonium ion from phenylamine.
(ii) Benzenediazonium ion reacts with naphthalen-2-ol to give compound T. Give the structure of T.
2. Write an essay on the chemistry of amines.
3.
1
3M-97
20M-97
The following equation represents the acid hydrolysis of a dipeptide D to produce compounds E and F,
one of which is a chiral compound.
(i) Name all functional groups in D.
(ii) Give one structure for E and one for F. Draw a suitable representation for the chiral product.
(iii) Suggest a method to separate E and F from the reaction mixture.
4.
Write an essay on the compound, CH3CH(NH2)CO2H.
Your essay should include such topics as its expected chemical reactions and physical properties, and
how the compound may be obtained from natural sources.
5.
20M-98
Consider the amino acids, F and G.
Draw three-dimensional structures of all dipeptides formed from F and G.
6.
5M-97
2M-99
Aspartame, a sweetener, has the structure below:
(i) Name all functional groups in aspartame.
(ii) Upon hydrolysis, aspartame gives two amino acids. Draw their structures.
(iii) Two electrodes are dipped into an aqueous solution containing the two amino acids in a pH 12
buffer, and are connected to the two poles of a battery. Which species derived from these amino
acids will move faster towards the anode? Explain your answer.
7M-00
AL Examination – Nitrogen compounds
2
7.
Arrange the compounds, B, C, D and E, in order of increasing basicity. Explain your arrangement.
4M-00
8.
The compounds below are the monomers of some polymers.
These compounds react in the presence of an inorganic reagent U to give compound V.
(i) What is reagent U?
(ii) The flow diagram below illustrates the reaction sequence for the transformation of B to compound
W with four aromatic rings. What are reagents X and Y?
(iii) In the reaction sequence as in (ii), V is replaced by W- that is, W is allowed to react with reagents
X and Y, and the products react in the presence of U to form a polymer Z. Draw the structure of Z.
5M-00
AL Examination – Nitrogen compounds
9.
3
(a) Give the reagent(s) and conditions for Step 1 and Step 2 in the reaction sequence below:
(b) 4-nitrobenzoic acid can be converted to benzocaine, and anaesthetics, is not more than three steps.
Use equations to show how you would carry out the conversion.
conditions and structure of the product.
In each step, give the reagent(s),
5M-01
10 Alanine, an amino acid, can be synthesized from ethanal into two steps:
(a) In step 1, ethanal reacts with NH4Cl to give an intermediate L (CH 3CH=NH).
NaCN to give K. Outline a mechanism for the formation of K from L.
(Hint:
L then reacts with
N is more electronegative than C.)
(b) Give the reagent(s) and conditions for Step 2.
(c) Hydrolysis of a protein gives a mixture of amino acids including alanine.
separate alanine from the mixture.
Suggest a method to
(d) The alanine obtained from the hydrolysis of natural proteins and that synthesized from ethanal
have different melting points. Why?
11. The equation below shows the complete hydrolysis of a pentapeptide M.
6M-01
AL Examination – Nitrogen compounds
4
Under mild conditions, M undergoes partial hydrolysis to give, among other products, two dipeptides:
Deduce the amino acid sequence of M.
3M-01
12. Based on the fact that the pKa of carboxylic acids (RCO2H) is about 5 and that the pKb of amines
(RNH2) is about 10, answer the questions below:
(a) For each of the compounds G, H and J below,
(i) draw the structure of the predominant species in a pH 3 buffer solution, and
(ii) draw the structure of the predominant species in a pH 11 buffer solution.
(b) Two electrons are dipped into an aqueous solution of G, H and J maintained at pH 7, and are
connected to the two poles of a battery. Which of these compounds, under such conditions, will
remain almost stationery? Explain your answer.
6M-02