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
The isomers that would react include Q, R, S, and T. The expected observation is that the orange solution turns green due to the reduction of Cr(VI) to Cr(III).
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
The only isomer that would react with Tollens' reagent is T. The expected observation is the formation of a silver mirror.
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
The isomers that would react with ethanolic acid are Q and R. A simple way to detect this is by observing the formation of a sweet smelling liquid.
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
The mixture is poured into sodium hydrogen carbonate solution to neutralize any unreacted acid and to observe the formation of carbon dioxide gas, indicating a 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
The type of structural isomerism shown by isomers P, Q, R, and S is positional 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 S and R can be distinguished by their IR spectra peaks. Isomer S will have an O-H alcohol peak around 3230-3550 cm⁻¹, while isomer T will have a peak for C=O near 1730 cm⁻¹. Additionally, S is unique as it will show fingerprint regions below 1500 cm⁻¹, which can be compared to a database or known spectra for identification.
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
Mass spectrometry using electrospray ionisation is not suitable as all the isomers will have the same molecular ion peak due to having the same molecular formula.
