● The degree of unsaturation or index of hydrogen defi ciency (IHD) can be used to determine from
a molecular formula the number of rings or multiple bonds in a molecule.
● Mass spectrometry (MS), proton nuclear magnetic resonance spectroscopy (1H NMR), and infrared
spectroscopy (IR) are techniques that can be used to help identify and to determine the structure
of compounds.
Guidance
● The electromagnetic spectrum (EMS) is given in the data booklet in section 3. The regions employed
for each technique should be understood.
● The operating principles are not required for any of these methods.

● Determination of the IHD from a molecular formula.
● Deduction of information about the structural features of a compound from percentage
composition data, MS, 1H NMR, or IR.
Guidance
● The data booklet contains characteristic ranges for IR absorptions (section 26), 1H NMR data (section
27), specifi c MS fragments (section 28), and the formula to determine IHD. For 1H NMR, only the
ability to deduce the number of different hydrogen (proton) environments and the relative numbers
of hydrogen atoms in each environment is required. Integration traces should be covered but splitting
patterns are not required.

● Structural identifi cation of compounds involves several different analytical techniques, including
IR, 1H NMR, and MS.
● In a high-resolution 1H NMR spectrum, single peaks present in low resolution can split into further
clusters of peaks.
● The structural technique of single crystal X-ray crystallography can be used to identify the bond
lengths and bond angles of crystalline compounds.
Guidance
● The operating principles are not required for any of these methods.
● High resolution 1H NMR should be covered.
● The precise details of single crystal X-ray crystallography need not be known in detail, but students
should be aware of the existence of this structural technique in the wider context of structural
identifi cation of both inorganic and organic compounds.

● Explanation of the use of tetramethylsilane (TMS) as the reference standard.
● Deduction of the structure of a compound given information from a range of analytical
characterization techniques (X-ray crystallography, IR, 1H NMR, and MS).
Guidance
Students should be able to interpret the following from 1H NMR spectra: number of peaks, area under
each peak, chemical shift, and splitting patterns. Treatment of spin–spin coupling constants will not be
assessed but students should be familiar with singlets, doublets, triplets, and quartets.

Task: 
1. Go through the slides and complete the tasks set. (use the link if the embedded slides do not load)
2. Complete a full analysis of the IR and NMR spectra of Ibuprofen and explain your analysis using flipgrid 

Task: 

1. Access the IR and NMR spectra 
2. Choose to analyse sample A or B
3. Analyse the spectra and determine if students have in fact synthesized Aspirin 
4. Explain why you think students have or have not synthesised Aspirin , using your knowledge of spectroscopy and scientific reasoning
5. Record your explanation using Flipgrid