The IR spectra of ethane-1,2-diol, C2H6O2, and ethanedioic acid dihydrate,C2H2O4.2H2O, are shown in spectrum C and D. Use Section 26 of the Data Booklet to answer this question.
Spectrum CSpectrum D
Which spectrum belongs to each molecule? Justify your answer.
Methyl cinnamate, C10H10O2, is a white crystalline solid used in the perfume industry. A sample of methyl cinnamate was analysed by 1H NMR spectroscopy.
A simplified spectrum is shown below.
i)
Name the compound responsible for the peak at a chemical shift of 0 ppm. State its purpose.
ii)
Identify the proton environment that causes the peak at a chemical shift of 3.8 ppm by circling it on the structure of methyl cinnamate shown. Justify your answer.
This question is about the use of 1H NMR spectroscopy to distinguish between isomers of C6H12O2.
Draw the two esters with formula C6H12O2 that each have only two peaks, both singlets, in their 1HNMR spectra. The relative peak areas are 3:1 for both esters.
The high resolution 1H NMR spectrum of another isomer of C6H12O2 is shown below.
The integration values for the peaks in the 1H NMR spectrum of this isomer, are given below.
Chemical shift, δ/ppm
3.8
3.5
2.6
2.2
1.2
Integration value
0.6
0.6
0.6
0.9
0.9
Splitting pattern
triplet
quartet
triplet
singlet
triplet
i)
Deduce the simplest ratio of the relative numbers of protons in each environment in the isomer.
ii)
Use Section 27from the Data Booklet and the information given to deduce the part of the isomer that causes the signal at δ= 3.5 and the part of the structure at the isomer that causes the signal at δ=1.2.
Explain why the splitting patterns of these peaks are produced.
Question 3d
Marks: 2
d)
Four isomers of C6H12O2 are shown below.
Which isomer matches the 1H NMR spectrum below? Justify your choice.
Using Sections 26 & 27 of the Data Booklet and other sources, state three pieces of different spectroscopic evidence that would give structural information to identify benzene.
An isomer with the molecular formula C5H10O2 was analysed by infrared spectroscopy, to confirm it was a carboxylic acid.
i)
Give the wavenumbers of two characteristic absorptions for a carboxylic acid. Indicate the bond responsible for each absorption. Suggest why one of the absorptions is broad.
ii)
The 1H NMR spectrum of this isomercontains only two peaks with the integration ratio 9:1. Using this information from the spectra, deduce the structure of the isomer.
This question is about two aldehydes, 2-aminopropanal and 3-aminopropanal.
Explain how 1H NMR spectra can be used to distinguish between these two aldehydes. You need to reference the splitting patterns and integration pattern in your answer.
Spectrum D
