page 19

Question 1

Drawing Products of Nucleophilic Substitution Reactions
Key Concepts

Answer 1

Overall Effect:
The leaving group in the substrate is replaced by the nucleophile.

Steps to Draw Substitution Products:

Step 1: Find the sp³-hybridized carbon attached to the leaving group.
Step 2: Identify the nucleophile (species with a lone pair or π bond).
Step 3: Substitute the nucleophile for the leaving group.
Step 4: Assign charges (if necessary) to atoms involved in bond formation or breaking.

Proton Transfer:
For neutral nucleophiles (e.g.,
NH3, H2O):
The substitution product initially has a positive charge.
A proton transfer occurs to neutralize the product.

Question 2

Reaction Example

Answer 2

CH3CH2CH2Br +NH3 →
excess
CH3CH2CH2NH2 + NH4+ + Br−

Step 1: Identify the sp³ carbon with the leaving group:
CH3CH2CH2 − Br

Step 2: Identify the nucleophile: NH3 (ammonia).

Step 3: Substitute
NH3 for Br− to form CH3CH2CH2−NH3+ .

Step 4: Proton transfer from
NH3+ to another
NH3 molecule forms the neutral amine
CH3CH2CH2−NH2 and NH4+
.

Question 3

Leaving Groups:

Answer 3

Good leaving groups include
Cl−, Br−, I− .

Question 4

Nucleophiles:

Answer 4

Can be charged (OH−,
CN−) or neutral (
H2O, NH3).

Question 5

Products:

Answer 5

Neutral products form via proton transfer when the nucleophile is neutral.

Question 6

What is the first step in drawing a nucleophilic substitution product?

Answer 6

≈
Answer: Identify the sp³-hybridized carbon bonded to the leaving group.

Question 7

What happens to a neutral nucleophile during substitution?

Answer 7

Answer: It initially forms a positively charged product, which undergoes proton transfer to become neutral.

Question 8

In CH3CH2CH2Br + NH3, what is the leaving group?

Answer 8

Answer:
Br−

Question 9

Why does proton transfer occur in substitution with neutral nucleophiles?

Answer 9

Answer: To neutralize the positively charged product.

Question 10

What is the final product of
CH3CH2CH2Br + NH3?

Answer 10

Answer:
CH3CH2CH2NH2
(1-propylamine).