Page 34 - Q & A STPM 2022 Chemistry

Chemistry Term 3 STPM Chapter 14 Introduction to Organic Chemistry
(ii) Optical isomerism is the occurrence of two compounds having the
same molecular formula, the same structural formula, but are mirror
images of one another and cannot be superimposed.
(c) (i) H H H CH 3
C"C C"C
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CH 3 CH 2 !C!CH 3 CH 3 CH 3 CH 2 !C!CH 3 H
& &
NH 2 NH 2
Cis-isomer Trans-isomer

(ii) CH"CHCH 3 CH 3 CH"CH
& &
C C
CH 3 H 3 C CH 2 CH 3
CH 3 CH 2
H 2 N
NH 2
(d) The optical isomers can be differentiated using a polarimeter which
measures the specific rotation (α) of the plane-polarised light. One isomer
would rotate the plane-polarised light clockwise (where α is positive)
and the other isomer would rotate the light anticlockwise (where α is
negative).

14.5 Free Radicals, Nucleophiles and Electrophiles

Section A Multiple-choice Questions

Question 1
Which of the following is not a nucleophile?
A H 2 O
B NH 4
+
C Cl –
D Br 2

Answer: B
Exam Tips
Exam Tips
A positive species cannot be a nucleophile.
Term
3 Nucleophiles are either negatively charged or are species with a lone pair of
electrons. They attack centres of low electron density (with partial positive
charge).

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