Analytical Techniques
62 questions· page 1 of 7
Calculate the relative abundance, , of the peak at using the information from Table 5.1.
The mass spectrum of also shows peaks at and .
Suggest the molecular formulae of these fragments.
Absorption A is shown in Fig. 5.1.
Absorption B is shown in Fig. 5.2.
Complete Table 5.3 using the information given in Fig. 5.1, Fig. 5.2 and Table 5.2.
Table 5.3
| absorption | bond | functional group containing the bond |
|---|---|---|
| A | ||
| B |
Use the information in (a) and (b)(i) to draw the structure of in the box in Fig. 5.3.
Deduce the number of carbon atoms present in a molecule of Z using Fig. 5.1. Show your working.
There are also peaks at and .
Suggest the formulae of these fragments. Deduce the name of Z.
..............................................................................................................................
..............................................................................................................................
name of Z ...........................................................................................................................
A student monitors the progress of reaction 2 using infrared spectroscopy.
Use Table 5.1 to suggest why it is difficult to distinguish between N and 5-hydroxyhexanoic acid using infrared spectroscopy.
Table 5.1
| bond | functional group containing the bond | characteristic infrared absorption range (in wavenumbers)/ |
|---|---|---|
| C–O | hydroxy, ester | 1040–1300 |
| C=C | aromatic compound, alkene | 1500–1680 |
| C=O | amide carbonyl, carboxyl ester | 1640–1690 1670–1740 1710–1750 |
| C≡N | nitrile | 2200–2250 |
| C–H | alkane | 2850–3100 |
| N–H | amine, amide | 3300–3500 |
| O–H | carboxyl hydroxy | 2500–3000 3200–3650 |
Unknown lactone Q is analysed using mass spectrometry.
Table 5.2 shows information from the mass spectrum.
Table 5.2
| peak | abundance | |
|---|---|---|
| 72 | 95.5 | |
| 73 | 3.15 |
Use these data to deduce the structure of Q.
Show your working.
A student monitors the progress of reaction 2 using infrared spectroscopy.
Use Table 5.1 to suggest why it is difficult to distinguish between N and 5-hydroxyhexanoic acid using infrared spectroscopy.
Table 5.1
| bond | functional group containing the bond | characteristic infrared absorption range (in wavenumbers) / |
|---|---|---|
| hydroxy, ester | 1040–1300 | |
| aromatic compound, alkene | 1500–1680 | |
| amide carbonyl, carboxyl ester | 1640–1690 1670–1740 1710–1750 | |
| nitrile | 2200–2250 | |
| alkane | 2850–3100 | |
| amine, amide | 3300–3500 | |
| carboxyl hydroxy | 2500–3000 3200–3650 |
Unknown lactone Q is analysed using mass spectrometry.
Table 5.2 shows information from the mass spectrum.
Table 5.2
| peak | abundance | |
|---|---|---|
| 72 | 95.5 | |
| 73 | 3.15 |
Use these data to deduce the structure of Q.
Show your working.
Deduce the molecular formula of Z. Explain your answer by referring to the molecular ion peak in Fig. 6.1 and the empirical formula of Z.
Use Fig. 6.1 to suggest the formulae of the fragments with peaks at 45 and at 71.
45: ................................................................................................................................
71: ................................................................................................................................
Use Fig. 6.1 to deduce the number of carbon atoms in a molecule of R.
Show your working.
number of carbon atoms = ..............................
Compound U contains a chiral centre and has the same molecular formula as compound P, .
• Compound U readily decolourises a sample of bromine water.
• Compound U does not show cis-trans isomerism.
• When compound U is heated under reflux in the presence of excess acidified potassium dichromate(VI), the organic product gives the infra-red spectrum shown.
Use the information given to suggest a structure for compound U.
Explain your answer.
Use the data from Table 4.2 to show that U contains 7 carbon atoms.
Show your working.
Table 4.2
| peak | relative abundance |
|---|---|
| 7.2 | |
| 0.55 |
Fig. 4.2 shows the infrared spectrum of U.
Table 4.3 shows characteristic infrared absorption ranges.
Table 4.3
| bond | functional groups containing the bond | characteristic infrared absorption range (in wavenumbers) / |
|---|---|---|
| C–O | hydroxy, ester | 1040–1300 |
| C=C | aromatic compound, alkene | 1500–1680 |
| C=O | amide carbonyl, carboxyl ester | 1640–1690 1670–1740 1710–1750 |
| CN | nitrile | 2200–2250 |
| C–H | alkane | 2850–2950 |
| N–H | amine, amide | 3300–3500 |
| O–H | carboxyl hydroxy | 2500–3000 3200–3650 |
Use Fig. 4.2 and Table 4.3 to identify the functional group present in U.
Explain your answer fully.
functional group: .................................................................................................................
explanation: ........................................................................................................................
The infra-red spectrum shown corresponds to one of P, Q or R.
Deduce which of the compounds, P, Q or R, produces this spectrum. Explain your reasoning.
In your answer, identify any relevant absorptions in the infra-red spectrum and the bonds that correspond to these absorptions in the region above .