Page 35 - Q & A STPM 2022 Chemistry

Chemistry Term 3 STPM Chapter 14 Introduction to Organic Chemistry
Question 2

Which of the following statements regarding electrophiles is not correct?
A It is formed by the homolytic fission of a covalent bond.
B It has an electron-deficient site.
C It is a Lewis acid.
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D It acts as an electron-pair acceptor.
Answer: A
+
Electrophiles are usually represented by E . It is electron deficient. It accepts a
lone pair of electrons from another species and thus is also a Lewis acid.
Homolytic fission of a covalent bond results in the production of free radicals.

Question 3
Which order shows the correct relative stability of a free radical?
A 1°> 2° > 3° C 2° > 3° > 1°

B 1° > 3° > 2° D 3° > 2° > 1°

Answer: D
Free radicals are stabilised by electron-releasing groups. Alkyl groups are
electron-releasing groups. As a result, the stability of the free radicals increases
with the number of alkyl groups in the species.

Section B Structured Questions

Question 4
(a) What do you understand by stereoisomerism?
(b) Name the two main types of stereoisomerism.
(c) Draw all possible stereoisomers of the following compound.
CH 3 CH 2 !CH!CH"CH!COOH
&
OH

Answer:
(a) Different compounds having the same molecular formula, the same
structural formula, but have different spatial arrangement of the atoms/
groups. Term

Common Errors
3
Stereoisomers cannot have different structural formula. Otherwise they will
be called structural isomers.

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14 Q&A STPM Chem T3 Layout.indd 351 4/19/19 5:29 PM