Raffles Institution H3 Chem Tutorial 5B Combined Spectra Tutorial Questions.pdf

© Raffles Institution 1 Raffles Institution Year 6 H3 Chemistry 2025 Tutorial 5B: Structural Elucidation using Mass Spectrometry, IR Spectroscopy and NMR Spectroscopy Use the following table to work out and tabulate your data for the questions in the tutorial. NMR spectrum δ/ppm Integration Splitting Deductions IR spectrum Wavenumber (cm−1) Deductions Mass spectrum m/e Species responsible / Deductions

© Raffles Institution 2 Self-Check Question (refer to IVY for solutions to self-check questions) Q1 Interpret the following spectra and use them to suggest a structure for compounds A and B. (a) Spectra for compound A 43 88

© Raffles Institution 3 (b) Spectra for compound B 43 137

© Raffles Institution 4 Practice Questions Q2 43 93

© Raffles Institution 5 Q3 Interpret the following spectra and use them to suggest a structure for compounds 1 and 2. (a) Spectra for compound 1 77 106 121 M+ 2H 3H 1H 2H 3H

© Raffles Institution 6 (b) Spectra for compound 2 41 43 57 121 136 3.2 3.3 1.0 1.05 2H 1H 1.9 1.85 1.95 6H

© Raffles Institution 7 Q4 A compound X was isolated as a minor constituent in an extract from garden cress. Its spectra are shown below. Interpret the spectra given and suggest a structural formula for X showing reasoning. 5 2

© Raffles Institution 8 Q5 [N12/4(b)] Compound H is a useful intermediate for the synthesis of drugs. Apart from carbon, hydrogen and oxygen atoms, the molecule H contains at least two halogen atoms, which may be chlorine or bromine of a mixture of both. The major peaks in its mass spectrum are listed in the table below The NMR spectrum of H is shown below. Relative number of protons responsible for each NMR signal may be inferred from the integration trace shown on the spectrum. (i) Use the mass spectrum to determine the num ber of atoms of each halogen contained in the molecule of H. (ii) Analyse the NMR spectrum to suggest the likel y environments of the protons in the molecule of H, and the number of protons in each environment. (iii) Apart from the molecular ion peaks, identify wh ich of the peaks in the mass spectrum arise from fragments that contain bromine or chlorine atoms, and suggest which halogen they contain. (iv) Suggest the molecular formulae of the fragm ents responsible for the peaks in the mass spectrum. (v) Use the information you have derived from the two spectra to suggest a structure for H