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Figure 1 shows some compounds made from a halogenoalkane - AQA - A-Level Chemistry - Question 1 - 2017 - Paper 2
Question 1
Figure 1 shows some compounds made from a halogenoalkane. Figure 1 Compound J Reaction 1 CH3CH2CH2Br NaOH(aq) Reaction 2 NH2 Reac... show full transcript
Worked Solution & Example Answer:Figure 1 shows some compounds made from a halogenoalkane - AQA - A-Level Chemistry - Question 1 - 2017 - Paper 2
Step 1
Step 2
Name the mechanism for Reaction 2 and give an essential condition used to ensure that CH3CH2CH2NH2 is the major product.
Answer
The mechanism for Reaction 2 is Nucleophilic substitution.
The essential condition to ensure that CH3CH2CH2NH2 is the major product is to use excess NH2, which drives the reaction forward towards amine production.
Step 3
Calculate the mass, in grams, of CH3CH2CH2NH2 produced from 25.2 g of CH3CH2CH2Br in Reaction 2 assuming a 75.0% yield.
Answer
First, find the molar mass of CH3CH2CH2Br:
- Molar mass of C3H7Br = 3(12.01) + 7(1.008) + 79.904 = 155.91 g/mol.
Then calculate the moles of CH3CH2CH2Br:
- Moles = mass / molar mass = 25.2 g / 155.91 g/mol ≈ 0.162 moles.
Assuming a 1:1 molar ratio for the reaction, the theoretical mass of CH3CH2CH2NH2 would be:
- Molar mass of C3H9N = 3(12.01) + 9(1.008) + 14.01 = 59.1 g/mol.
The theoretical yield = 0.162 moles x 59.1 g/mol ≈ 9.58 g.
Considering a yield of 75.0%:
- Actual yield = 0.75 x 9.58 g ≈ 7.19 g.
Thus, the mass of CH3CH2CH2NH2 produced is 7.19 g, rounded to three significant figures.
Step 4
Step 5
Step 6
Step 7
Name and outline a mechanism for Reaction 3.
Answer
The mechanism for Reaction 3 is known as Elimination (specifically Base-induced elimination).
In this mechanism, the hydroxide ion (OH-) acts as a base, abstracting a proton (H+) adjacent to the carbon halide. This creates a double bond, resulting in the formation of an alkene and the loss of the halide ion (Br-).
The mechanism can be summarized as follow:
- Formation of the alkoxide ion as OH- deprotonates the substrate leading to the formation of a double bond.
- Simultaneous loss of the leaving group (Br-) creates the alkene product.