This question is about the structural isomers shown - AQA - A-Level Chemistry - Question 3 - 2020 - Paper 2
Question 3
This question is about the structural isomers shown.
Identify the isomer(s) that would react when warmed with acidified potassium dichromate(VI).
State the expecte... show full transcript
Worked Solution & Example Answer:This question is about the structural isomers shown - AQA - A-Level Chemistry - Question 3 - 2020 - Paper 2
Step 1
Identify the isomer(s) that would react when warmed with acidified potassium dichromate(VI).
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Isomer(s): Q, R, S, T
Expected observation: The solution turns green, indicating the reduction of dichromate.
Step 2
Identify the isomer(s) that would react with Tollens' reagent.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Isomer(s): T
Expected observation: A silver mirror forms on the surface of the container.
Step 3
Identify the isomer(s) that would react with ethanolic acid.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Isomer(s): P, R, S
Suggestion: To detect the reaction, test for the formation of an ester by observing the sweet smell that develops.
Step 4
Give a reason why the mixture is poured into sodium hydrogen carbonate solution.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Reason: The mixture is neutralized and any unreacted acid is neutralized, preventing further reaction.
Step 5
State the type of structural isomerism shown by isomers P, Q, R and S.
97%
117 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Position isomerism.
Step 6
Describe fully how infrared spectra can be used to distinguish between isomers S, R and T.
97%
121 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Isomers R, S & T will have unique absorption peaks in the infrared region. For example, S will show a broad OH stretch peak around 3230-3550 cm^-1. The C=O peak for T will occur around 1680-1750 cm^-1. Comparing spectra can help identify distinct functional groups.
Step 7
State why mass spectrometry using electrospray ionisation is not a suitable method to distinguish between the isomers.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
All have the same molecular ion (M+) peak, thus providing no differentiation between the isomers.
