Proton NMREdexcel A-Level Chemistry: Flashcards

What these 13 flashcards ask

What does high-resolution 1H NMR show?
What does the chemical shift of a 1H peak tell you?
What does the area under a 1H NMR peak tell you?
What does the splitting of a peak tell you?
State the (n + 1) rule.
What are the splitting patterns for n = 0, 1, 2, 3?
What pattern does an ethyl group, CH₃CH₂–, give?
Why is the CH₃ peak in CH₃CHO a doublet?
What is the typical shift for an aldehyde CHO proton?
What is the typical shift for a carboxylic acid O–H proton?
What is the typical shift for CH₃ or CH₂ next to C=O?
Do protons in the same environment split each other?
How do you use the peak area ratio with a molecular formula?

Exam questions on Proton NMR

A student records the high-resolution 1H NMR spectrum of bromoethane, CH₃CH₂Br.
Explain why the peak caused by the CH₃ protons is a triplet.2 marks
A chemist records the high-resolution 1H NMR spectrum of ethanal, CH₃CHO. It shows two peaks, at chemical shifts (δ) of 2.2 ppm and 9.8 ppm.
Explain the splitting patterns of the two peaks in the spectrum of ethanal.2 marks
A chemist has an unlabelled ester which is either ethyl ethanoate, CH₃COOCH₂CH₃, or methyl propanoate, CH₃CH₂COOCH₃. Its high-resolution 1H NMR spectrum has three peaks: δ 1.2 (triplet, relative area 3), δ 2.0 (singlet, relative area 3) and δ 4.1 (quartet, relative area 2). Typical shift ranges (ppm): CH₃ in an alkyl chain 0.7–1.3; CH₃ or CH₂ next to C=O 2.0–2.7; CH₃ or CH₂ bonded to the oxygen of an ester 3.6–4.3.
Explain how the relative areas and the splitting patterns show that the ester contains a CH₃CH₂ group.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).