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Lewis Acids, Lewis Bases, and Curvy Arrows. Susan F. Hornbuckle Associate Professor of Chemistry Clayton State University. Example 1. CH 3 -CH 2 -Br + - OH CH 3 -CH 2 -OH + Br - The Br formal charge changes from 0 to -1. Therefore, it is accepting electrons. - PowerPoint PPT Presentation
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Lewis Acids, Lewis Bases, and Curvy Arrows
Susan F. Hornbuckle
Associate Professor of Chemistry
Clayton State University
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH + Br-
The Br formal charge changes from 0 to -1. Therefore, it is accepting electrons.
An arrow must end at the Br.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH + Br-
The O formal charge changes from -1 to 0. Therefore, it is donating electrons. An arrow must be starting at O.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH +
Br-
A bond is formed between O and C. The arrow starting at O must end at the C where it bonds.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH +
Br-
A bond is broken between Br and C. The arrow that ends at Br must start at the bond between Br and C.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH +
Br-
-OH is the species that is donating electrons. Therefore, it is the Lewis Base.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH + Br-
Lewis Base
The bromoethane is the species accepting the electrons. Therefore, it is the Lewis Acid.
Example 1
CH3-CH2-Br + -OH CH3-CH2-OH +
Br-
Lewis Acid Lewis Base
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3
The Cl formal charge changes from 0 to +1. Therefore, it is donating electrons. An arrow must start at Cl.
+ -
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3
The Al formal charge changes from 0 to -1. Therefore, it is accepting electrons. An arrow must end at Al.
+ -
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3
A bond is formed between Al and Cl. Therefore, the arrow starting at Cl must end at Al.
+ -
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3
The chloroethane is the species that is donating electrons. Therefore, it is the Lewis Base.
+ -
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3Lewis Base
AlCl3 is the species accepting the electrons. Therefore, it is the Lewis Acid.
+ -
Example 2
CH3-CH2-Cl + AlCl3 CH3-CH2-Cl-AlCl3 Lewis Base Lewis Acid
+ -
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
The N formal charge changes from 0 to +1. Therefore, it is donating electrons. An arrow must start at N.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
The O formal charge changes from 0 to -1. Therefore, it is accepting electrons. An arrow must end at O.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
A bond is broken between C and O. The arrow that ends at O must start at the bond between C and O.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
A bond is formed between N and C. The arrow that starts at N must end at the C where it forms a bond.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
The nitrogen containing compound is the species that is donating electrons. Therefore, it is the Lewis Base.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
Lewis Base
The oxygen containing compound is the species accepting the electrons. Therefore, it is the Lewis Acid.
Example 3
CH3
C
CH3
O
+ N
CH3
CH3CH3
O
C CH3CH3
N CH3CH3
CH3
-
+
Lewis Acid Lewis Base
