
ORGANIC CHEMISTRY
Instructors: Dr. Lê Vũ Hà & Dr. Nguyễn Đăng Khoa
Office: 211B2
Tel: 02838647256 ext. 5681
Email: lvha@hcmut.edu.vn
khoand1989@hcmut.edu.vn
Main compiler: Prof. Dr. Phan Thanh Sơn Nam
Ho Chi Minh University of Technology –VNU HCMC
Department of Chemical Engineering
Division of Organic Chemistry

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CHAPTER 3 –REACTION MECHANISM
1. Nucleophilic substitution –SN
2. Electrophilic substitution –SE
3. Nucleophilic addition –AN
4. Electrophilic addition –AE
5. Elimination –E
Popular organic reaction mechanisms
Note: Details of these reaction mechanism will be mentioned one more time in the next
chapters of functional groups.

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Substitution reaction: chemical reaction in which an atom/group
replaces another atom/group in the structure of a molecule
Nucleophile: any negative/neutral molecule that has an unshared
electron pair and can form a covalent bond to positive center (anion,
Lewis base).
→Some popular nucleophiles: OH-, RO-, RC≡C-, X-, CN-, CH3COO-, H2O,
ROH (alkyl), NH3, RNH2(alkyl)…
Nucleophilic substitution –SN
d-
d+
+X-
+
Nu-

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Nucleophilic substitution –SN
d-
d+
+X-
+
Nu-
++
++
++
In a nucleophilic substitution reaction, a nucleophile attacks/bonds
with the positive center to form a NEW substituted product.

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Nucleophilic substitution –SN
•Bimolecular nucleophilic substitution reaction SN2: in slow step, in
which there is the presence of Nü and R-X
•Unimolecular nucleophilic substitution reaction SN1: in slow step, in
which there is only the presence of R-X

