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![Page 1: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/1.jpg)
Tutorial
Spectroscopy & Chromatography
1. Consider the following reaction scheme:
C6H6 + CH3COCl C6H5COCH3 + HCl A
C6H5COCH3 C6H5CH(OH)CH3
B
(a) Give the reagents and conditions needed for step 1 and step 2
(i) Step 1 Aluminium chloride / AlCl3 / iron (III) chloride / FeCl3
(1)
(ii) Step 2 LiAlH4
Dry ether(2)
(b) The IR spectrum for compounds A and B are shown below and the data of the spectrum is given in table 1.
Bond Assigment Wavenumber / cm-1
C - H AlkanesAlkenes, arenes
2850 – 29503000 - 3100
Benzene ring Arenes 1450 - 1650C = O Aldehydes, ketones, esters,
carboxylic acids1680 - 1750
O – H FreeHydrogen bonded in alcohols or phenolsHydrogen bonded in carboxylic acids
3580 – 36703230 – 3550
2500 - 3300
Step 1
Step 2
![Page 2: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/2.jpg)
![Page 3: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/3.jpg)
(i) Using suitable data from Table 1, give evidence from the spectra which shows that compound A has been reduced. You will need to comment on both spectra.
A spectrum shows bond due to C=O at 1680 – 1700 cm-1 (1)B spectrum shows bond due to OH at 3230 – 3550 cm-1 (1)A has no OH or no bond at 3230 – 3550 cm-1 (1)
(ii) Compound B is chiral. The IR spectra of the two optical isomers of B are identical. Suggest why this is so.
IR spectra due to bonds present (1)Same bonds / functional groups in both isomers (1)
2. An alcohol, C3H8O was analyzed by low resolution NMR spectroscopy. The spectrum is given below.
![Page 4: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/4.jpg)
The chemical shift of some hydrogen nuclei are given in the following table (where R represents an alkyl group)
group δ / ppm group δ / ppm
CH3-R 0.8 – 1.2 R - OH 1.0 – 6.02.0
R – CH2 - R 1.1 – 1.5 R – CH2 - OH 3.3 – 4.0
CH – R3 1.5 R2 – CH -OH 3.2 – 4.1
Show that the alcohol must be propan-2-ol
3 types of H ratio 6:1:1 or some correct reference to height peaks (1)This related to structure of propan-2-ol in shift data (1)
![Page 5: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/5.jpg)
3. Compounds A and B shown below are used as intermediates in the manufacture of ibuprofen.
(i) Suggest how infra-red spectroscopy could be used to identify an impurity in a sample of ibuprofen which is known to be one of these compounds. A table of infrared absorbencies is given below.
Bond Assigment Wavenumber / cm-1
C - H AlkanesAlkenes, arenes
2850 – 29503000 - 3100
Benzene ring Arenes 1450 - 1650C = O Aldehydes, ketones, esters,
carboxylic acids1680 - 1750
O – H FreeHydrogen bonded in alcohols or phenolsHydrogen bonded in carboxylic acids
3580 – 36703230 – 3550
2500 - 3300
A spectrum will include absorbance at 1700 cm-1 but not 3600 cm-1
B will include 3600 cm-1
Identification of groups to note (1)Link to peaks in spectrum (1)How to distinguish (1)
(3)
4. The two organic compounds of C and D contain the elements carbon, hydrogen and oxygen only. Compound C were found to give yellow precipitate with 2, 4-dinitrophenylhydrazine and red precipitate with Fehling solution. Compound D produced
![Page 6: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/6.jpg)
a pleasant smell when reacted with ethanol and concentrated sulphuric acid. Mass spectrum of compounds C and D are given below.
State m/e and suggest a full structural formula for both compounds.
Compound C
m/e = 44 CH3 – CHO
Compound D
m/e = 74 CH3 – CH2-COOH
Mass Spectrum of compound C
![Page 7: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/7.jpg)
Mass Spectrum of compound D
![Page 8: Tutorial - WordPress.com€¦ · Web viewSpectroscopy & Chromatography. Consider the following reaction scheme: C6H6 + CH3COCl C6H5COCH3 + HCl. A. C6H5COCH3 C6H5CH(OH)CH3. B. Give](https://reader033.vdocument.in/reader033/viewer/2022043016/5f39487625851125e65ac0aa/html5/thumbnails/8.jpg)