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 →
React... 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
Draw the displayed formula of compound J.
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Answer
The displayed formula for compound J is:
H H H
| | |
H--C--C--C--Br
| | |
H H H
This represents 1-bromopropane.
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 ammonia (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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Answer
First, calculate moles of CH3CH2CH2Br using its molar mass (Molar mass = 123 g/mol):
extMolesofCH3CH2CH2Br=123extg/mol25.2 g≈0.205extmol
Given the reaction is 1:1, moles of CH3CH2CH2NH2 produced = 0.205 mol.
The theoretical mass of CH3CH2CH2NH2 (Molar mass = 75 g/mol):
extTheoreticalmass=0.205extmol×75extg/mol≈15.375extg
Actual mass considering 75.0% yield:
extActualmass=15.375extg×0.75=11.53125extg
Thus, the answer rounded to 3 significant figures is 11.5 g.
Step 4
Draw the skeletal formula of the compound.
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Answer
The skeletal formula for the compound with molecular formula C3H9N is:
H H
| |
H--C--C--N-H
| |
H H
This represents a tertiary amine.
Step 5
Identify the functional group in the compound including its classification.
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Answer
The functional group is an amine classified as a tertiary amine.
Step 6
Identify the reagent and conditions used in Reaction 3.
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The reagent used in Reaction 3 is sodium hydroxide (NaOH), and the conditions are aqueous and reflux.
Step 7
Name and outline a mechanism for Reaction 3.
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The mechanism for Reaction 3 is (Base) Elimination.
Sodium hydroxide acts as a base, abstracting a beta-hydrogen.
This leads to the formation of a double bond with the elimination of bromide, resulting in an alkene.
