Lesson Plan for Calss XII Chemistry of NCERT Lesson CBSE This lesson plan covers Nucleophilic substitution reaction, SN1 and SN2 reaction,Factors affecting nucleophilic substitution reaction, sterric hindrance,

1. Mechanism of nucleophilic
substitution reaction of alkyl halide
A.K.Gupta
PGT Chemistry
Kendriya Vidyalaya Ballygunge
Kolkata 700019
ashokkgupta62@rediffmail.com

2. Learning Objectives
At the end of this class, pupil should be able to-
•Understand the meaning of Nucleophilic
substitution(SN) reaction.
•Explain the factor affecting SN reaction
•Differentiate between SN1 and SN2 reaction
•Predict whether the given halide will undergo SN1
and SN2 reaction

3. (a) Substitution nucleophilic
bimolecular (SN2
)

4. SN1 - Racemization - Inversion

5. SN1 - Racemization - Retention

6. SN2 concerted reaction inversion

7. SN2 Inversion

8. Steric effects in SN2
reaction-
The relative rate of SN2
reaction
is given in parenthesis

9. (b) Substitution nucleophilic
unimolecular (SN1
)

10. We can sum up the order of
reactivity of alkyl halides towards
SN1
and SN2
reactions as follows:

11. Compare the reactivity of allylic
and benzylic halides towards
the SN1
reaction-
Allylic Halide Benzylic Halide

12. The carbocation formed gets
stabilised through resonance as
shown below-

13. What order do you expect
regarding the reactivity of alkyl
halide for a given Alkyl group ?
• R–I> R–Br>R–Cl>>R–F

14. 1 . Which statement best describes
a carbon-chlorine bond?
A.The bond is covalent and polar, with chlorine
carrying a partial positive charge.
B.The bond is ionic and polar, with chlorine
carrying a full positive charge.
C.The bond is covalent and nonpolar.
D.The bond is covalent and polar, with chlorine
carrying a partial negative charge.
E.The bond is ionic and polar, with chlorine
carrying a full negative charge.

15. 2 . Which of the following does
not affect the mechanism of a
nucleophilic substitution reaction?
A. the intensity of the light present
B. the structure of the alkyl halide
C. the polarity of the solvent the
concentration of the nucleophile
D. the reactivity of the nucleophile

16. 4 . Which type of reactant shows
the greatest reactivity in an SN2
reaction?
A. quaternary alkyl halides
B. methyl halides
C. tertiary alkyl halides
D. secondary alkyl halides
E. primary alkyl halides

17. 6 . Which of the following
represents the relative leaving
group abilities of the halide ions?
A. iodide < bromide < chloride > fluoride
B. iodide > chloride > bromide > fluoride
C. iodide < bromide < chloride < fluoride
D. iodide > bromide > chloride > fluoride
E. iodide < bromide > chloride > fluoride

18. 7 . Which statement best
describes the mechanism of an SN2
reaction?
A. front side and back side attack with
racemization
B. front side attack with inversion of configuration
C. back side attack with retention of configuration
D. back side attack with inversion of
configuration
E. front side attack with retention of configuration

19. 8 . Which of the following is not
a correct statement?
A. Alkyl halides react with -NH2 to form amines.
B. Alkyl halides react with RS- to form thiols.
C. Alkyl halides react with RCΞC- to form
alkynes.
D. Alkyl halides react with HO- to form alcohols.
E. Alky halides react with RO- to form ethers.

20. Which of the following is the rate
law for an SN1
reaction?
A. Rate = k[nucleophile]2
B. Rate = k[alkyl halide][nucleophile]
C. Rate = k[alkyl halide]2
D. Rate = k[alkyl halide]
E. Rate = k[nucleophile]

21. Which of the following is the rate-
limiting step for the hydrolysis of
tert-butyl bromide?
A. loss of water from the carbocation
B. addition of water to the carbocation
C. deprotonation of the addition product formed
by addition of water to the carbocation
D. dissociation of the alkyl halide into a
carbocation and a bromide ion
E. reaction of the carbocation with bromide ion

22. Which of the following alkyl
bromides is the most reactive in an
SN1
reaction?
A. 1-bromopropane
B. bromomethane
C. 1-bromo-2-methylpropane
D. 2-bromopropane
E. 2-bromo-2-methylpropane

23. Which of the following is the most
nucleophilic towards CH3I?
A. NH3
B. -CN
C. F-
D. CH3S-
E. H2O

24. Home work Assignment:
TBQ 10.9 Which compound in each of the
following pairs will react faster in SN2
reaction
with –OH?
(i) CH3Br or CH3I (ii) (CH3)3CCl or CH3Cl
TBQ 10.16 Arrange the compounds of each set in
order of reactivity towards SN2
displacement:
(i) 2-Bromo-2-methylbutane, 1-Bromopentane,
2-Bromopentane
(ii) 1-Bromo-3-methylbutane,
2-Bromo-2-methylbutane,