(ii) From TLC analysis of the isomerization of dimethyl maleate which one is mor
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Question
(ii) From TLC analysis of the isomerization of dimethyl maleate which one is more polar compound, dimethyl maleate (Rf = 0.34) or dimethyl fumarate (Rf = 0.57)? How many spot(s) did you see for your final product (pure crystal) and why? (iii) If the TLC solvent was changed from 4:1 to 1:1 Hexane/Ethyl Acetate mixture, how this will affect the Rf values of your compound, ? Why? (iv) If 3.9g of dimethyl fumarate is recrystallized and 1.23g of pure dimethyl fumarate was obtained. What was the percentage recovery?Explanation / Answer
1) fumarate is less polar compound when compared to malate. Fumarate is transe isomer so dipole movement will be canceled or it will be less. In the case of malate, it is cis isomer and the dipole movement cant be zero. so it is ore polar. Even Rf indicates same. Rf more means it is more non polar and fuarate Rf is more so it is less polar than malate.
In the final product i.e. crystal only one spot we can observe because crystals obtaine for pure compounds.
2) If the solvent composition changed fro 4:1 to 1:! Hexane -EA, that means the polar componenet increased. So the more polar compound, malate will move fast along with solvent, So the Rf will increase. But fo fumarate it will be reverse. The Rf will reduce for fumarate, as the non polar solvent amount dicreased, it elute slowly
3) yield = practical yeild*100 / theoritical yield
theoritically, by isomerization, 3.9 g of fumarate should be obtained but obtained 1.23 g only.
yield = 1.23*100 / 3.9 = 31.3 %
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