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
NH3
CH3CH2CH2NH2
Reaction 3
C3H8
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Worked Solution & Example Answer:Figure 1 shows some compounds made from a halogenoalkane - AQA - A-Level Chemistry - Question 1 - 2017 - Paper 2
Step 1
Draw the displayed formula of compound J.
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Answer
The displayed formula of compound J is:
H H H
| | |
H - C - C - C - Br
| | |
H H H
Step 2
Name the mechanism for Reaction 2 and give an essential condition used to ensure that CH3CH2CH2NH2 is the major product.
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Answer
The mechanism for Reaction 2 is nucleophilic substitution. An essential condition to ensure that CH3CH2CH2NH2 is the major product is to use excess NH3.
Step 3
Calculate the mass, in grams, of CH3CH2CH2NH2 produced from 25.2 g of CH3CH2CH2Br in Reaction 2 assuming a 75.0% yield.
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To find the mass of CH3CH2CH2NH2 produced, first calculate the moles of CH3CH2CH2Br:
Calculate moles of CH3CH2CH2Br:
Molar mass of CH3CH2CH2Br = 25.2 g / 205 g/mol = 0.1229 mol
Calculate expected mass of CH3CH2CH2NH2:
Molar ratio = 1:1, so 0.1229 mol of NH2 produced.
Molar mass of CH3CH2CH2NH2 = 3(14) + 7(1) = 44 g/mol
Mass = 0.1229 mol * 44 g/mol = 5.4136 g
Calculate final mass accounting for yield:
Final mass = 5.4136 g * 0.75 = 4.0602 g
Therefore, the mass of CH3CH2CH2NH2 produced is 4.06 g to three significant figures.
Step 4
Draw the skeletal formula of the compound.
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Answer
The skeletal formula for the compound with molecular formula C3H7N is:
H H
| |
H - C - C - C - N
| |
H H
Step 5
Identify the functional group in the compound including its classification.
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Answer
The functional group in the compound is the amine group, classified as a primary amine since it is bonded to one alkyl group.
Step 6
Identify the reagent and conditions used in Reaction 3.
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The reagent used in Reaction 3 is NaOH in ethanol. Conditions include heating under reflux.
Step 7
Name and outline a mechanism for Reaction 3.
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Answer
The mechanism for Reaction 3 is base elimination. The mechanism involves:
A base abstracts a proton from the β-carbon.
The leaving group (Br) departs, forming a double bond between the α and β carbons, producing an alkene.
