Questions: (2 points each) 1) A mixture of mixture of 1:1 Petroleum Ether- benza
ID: 706617 • Letter: Q
Question
Questions: (2 points each) 1) A mixture of mixture of 1:1 Petroleum Ether- benzalde hyd e, benzoic acid, to Ethyl Acetate as the components in the sample (fastest to slowest). solvent. Predict the sequence of relative Ryvalues for the three componenetroleum Ether-Etvlgact an toluene is spotted on a silica gel TLC plate and developed in a 2) What would happen to the Ry concentration of the Petroleum Ether in the solvent mixture? values of the compounds in question 1 if you were to increase the relative 3) Which compound will elute first when a mixture of chlorobenzene and 1,4-dichlorobenzene is loaded on a silica gel column and hexane is used as the eluent? 14Explanation / Answer
ANS:
1)
In the TLC system nonpolar compounds comes to top of the TLC and the polar compounds are at the bottom of the TLC plate. If the compound is of more polar, The spot is more bottom of the plate.
In the given compounds Benzoic acid is more polar than Benzaldehyde. Benzaldehyde is polar than Toluene.
Hence Benzoic acid is bottom, Benzaldehyde comes some of the above to the Benzoic acid and Toluene comes above to the Benzaldehyde.
2)
Petroleum ether is the nonpolar solvent than the ethyl acetate, If we Increase the concentration of the petroleum ether nonpolarity increases in the solvent system, Hence the Rf value decreases.
3)
Generally the Nonpolar compounds first elutes than polar compounds from the column.
Chlorobenzene is the Nonpolar than 1,4-di Chlorobenzene. Hence Chlorobenzene elutes first.
Note:
Cl is the electronegativity atom. If the electronegativity of the molecule increases, The polarity of the molecule also increases.
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