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This question is about 2-bromopropane - AQA - A-Level Chemistry - Question 5 - 2020 - Paper 2
Question 5
This question is about 2-bromopropane. 1. Define the term electronegativity. 2. Explain the polarity of the C–Br bond in 2-bromopropane. Electronegativity ______... show full transcript
Worked Solution & Example Answer:This question is about 2-bromopropane - AQA - A-Level Chemistry - Question 5 - 2020 - Paper 2
Step 1
Step 2
Explain the polarity of the C–Br bond in 2-bromopropane.
Answer
The C–Br bond in 2-bromopropane is polar due to the difference in electronegativity between carbon and bromine. Bromine is more electronegative than carbon, leading to an unequal sharing of electrons. As a result, the electrons are drawn closer to the bromine atom, creating a dipole where the bromine atom gains a partial negative charge (δ-) and the carbon atom gains a partial positive charge (δ+).
Step 3
Outline the mechanism for the reaction of 2-bromopropane with an excess of ammonia.
Answer
The mechanism proceeds as follows:
- The nucleophilic nitrogen atom in ammonia (NH3) attacks the electrophilic carbon atom in 2-bromopropane, forming a bond and resulting in a carbocation.
- A curly arrow indicates the movement of the electron pair from the C-Br bond to the Br atom, leading to the departure of bromide (Br-).
- The resulting ammonia-subsituted intermediate can then lose a hydrogen ion (H+) to form the final amine product.
Step 4
Draw the skeletal formula of the main organic species formed in the reaction between a large excess of 2-bromopropane and ammonia.
Answer
The skeletal formula of the main organic species formed is presented as follows:
H3C- C – NH2
| |
H H
H Br
This indicates that the product is an amine, specifically isopropylamine.
- A use for the organic product.
A practical use for isopropylamine is its application as a hair conditioner, surfactant, or disinfectant.