Tomato paste contains lycopene and -carotene. A student designed a column chroma
ID: 1027526 • Letter: T
Question
Tomato paste contains lycopene and -carotene. A student designed a column chromatography experiment in which he used alumina for stationary phase. He started by eluting the first band with hexanes and then switched to a mixture of 10% acetone in hexanes. Perform a literature search and determine which was the first band and which was the second one. Give the structure of both compounds and explain your answer. (4 points). 2. 3. Why were you not able to separate as many bands as you did in TLC even though you used the same mobile phase composition? (2 points) 4. A student wanted to separate compounds A, B and C by column chromatography. Before deciding on a mobile phase, he ran TLC in the three solvent systems he was considering for this experiment, solvent 1, solvent 2 and solvent 2 (shown below). (10 points) Based on the TLC results what can you conclude regarding the polarity of compounds A, B and C? What can you conclude regarding the polarity of the mobile phases solventl, 2 and 3? Explain a. b. c. Which of the solvents would you choose to successfully separate the three solids? d. If you only wanted to separate solid A, which solvent would you use?Explanation / Answer
2 Lycopene and b-carotene both are hydrocarbane and but in b-carotene 11 double bond are present while in lycopene 13 double bond are there. More the Double bond more polar compound. Lycopene is attracted to alumina more strongly then b-carotene. So crotene band move faster in column than lycopene bond.
3 In TLC solvent system run against gravity which slow down the movement of mobile phase so we can separate as many bandwhile in column chromatography which run with the gravity due to which mobile phase speed up the movement of mobile phase result in merging of bands.
4 a) A is non-polar B is intermediate while C is polar compound
b) In Solvent 1, mobile phase is very polar solvent. in solvent 2 in non-polar solvent while solvent 3 intermediate solvent system
c) For column chromatography, First use of solvent 1 to get pure compond A then change the polarity of system by solvent 3 now we will get pure compond B and finally solvent 1 to get pure compond C.
d) Solvent 2