Chemistry_2018_STPM term 3_Objectives

The three atoms of an organic compound are labelled p, q and r, and the structural formula of the compound ais shown in the diagram. What are types of hrbridisation of each atom?

• p : sp²

  q : sp¹

  r : sp³

• p : sp²

  q : sp³

  r : sp

• p : sp³

  q : sp³

  r : sp

• p : sp²

  q : sp³

  r : sp³

Answer explanation

The carbon atoms in the benzene ring undergoes sp² hydridisation.

The saturated carbon atom (q) undergoes sp³ hybridisation.

The saturated oxygen atom (r) undergoes sp³ hybridisation.

Which statement is true about methyl methacrylate, CH₂=C(CH₃) COOCH₃?

• It has one chiral carbon.

• It exists cis-trans isomerism.

• Its structural isomer is 2-methyl-2-butenoic acid.

• It undergo condensation polymerisation reaction.

Answer explanation

Two hydrogen atoms bonded to the unsaturated carbon atom cannot exhibit cis-trans isomerism. The structure isomer is shown in the diagram. Due to the presence of C=C bond, it undergoes addition polymerisation.

Which is not true about a nucleophile?

• It is a Lewis base.

• It is an electron pair donor.

• It is involved in the Friedel-Crafts reaction.

• It is formed during heterolytic fission of covalent bond.

Answer explanation

Ethanoic acid, CH₃COOH and chloroethanoic acid, CICH₂COOH undergo ionisation in aqueous solutions. Which statement is true about the acids or their ions?

• CICH₂COO^- ion is more stable than CH₃COO^- ion.

• The pK_a value of CICH₂COOH is higher than that of CH₃COOH.

• The O—H bond in CICH₂COOH is stronger than that in CH₃COOH.

• The charge density on the oxygen atoms in CICH₂COO^- ion is higher than that in CH₃COO^- ion.

Answer explanation

Compound S reacts with hot acidified KMnO₄ solution to form a carboxylic acid and compound S also reacts with HBr to form an optically active compound. What is compound S?

• CH₂=C(CH₃)CH₂

  CH₂CH₃

• CH₂= CHCH₂CH₂CH₂CH₃

• CH₃CH₂CH=

  C(CH₃)₂

• CH₂=C(CH₃)CH

  (CH₃)₂

Answer explanation

Toluene reacts with hot acidified KMnO₄ solution followed by concentrated HNO₃/H₂SO₄. What is the structural formula of the product of the reaction?

• 
• 
• 
• 

Answer explanation

Oxidation of toluene produces benzoic acid.

—COOH is a para-director (position 3 director). Nitration of benzoic acid would produce 3-nitrobenzoic acid.

Halogenated compounds undergo nucleophilic substitution reaction with an aqueous solution of sodium hydroxide. Which is the correct order of increasing reactivity towards the reaction?

• Ⅰ , Ⅱ , Ⅳ , Ⅲ

• Ⅰ , Ⅳ , Ⅱ , Ⅲ

• Ⅱ , Ⅳ , Ⅲ , Ⅰ

• Ⅳ , Ⅱ , Ⅲ , Ⅰ

Answer explanation

Chlorobenzene is the least susceptible to electrophilic substitution followed by chloroarenes. For the haloalkanes, the reactivity increases in the order 1° < 2° < 3°.

The structural formula of menthol is shown in the diagram. Which statement is true about menthol?

• It is optically in active.

• It is in soluble in ethanol.

• It is secondary alcohol.

• It exhibits geometrical isomerism.

Answer explanation

The chiral centres are marked as ( * ) in the diagram.

Due to the presence of a large hydrocarbon groups it is soluble in organic solvent such as ethanol.

The structure formula of atenolol, a drug used to treat high blood pressure, is shown in the diagram. Which is true about the molecule?

• It is a primary amine.

• It is optically inactive.

• It reacts with sodium carbonate to liberate carbon dioxide.

• It reacts with concentrated sulphuric acid to form two different alkenes.

Answer explanation

Which reagents could be used to differentiate between phenol and benzoic acid?

Ⅰ. Aqueous solution of sodium hydroxide

Ⅱ. Bromine water

Ⅲ. Aqueous solution of iron (Ⅲ) chloride

Ⅳ. Acidified potassium manganate (Ⅶ)

• Ⅰ and Ⅱ

• Ⅰ and Ⅳ

• Ⅱ and Ⅲ

• Ⅲ and Ⅳ

Answer explanation