You are told to analyze the purity of your product with TLC. Which of the – [Free] B96
You are told to analyze the purity of your product with TLC. Which of the following TLC plates would indicate a pure product? Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer, a A TLC plate where the product lane has one spot with an Rf value that exactly matches that of the starting material. A TLC plate where the product lane has one spot which has a lower Rf value than the starting material. C A TLC plate where the product lane has two spots, one with a higher Rf value than the starting material and one with a lower Rf value. d ATLC plate where the product lane has one spot which has a higher Rf than the starting material.
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Question on TLC Analysis
Question:
You are told to analyze the purity of your product with TLC. Which of the following TLC plates would indicate a pure product?
Correct Answer: d) A TLC plate where the product lane has one spot which has a higher Rf than the starting material.
When judging the purity of a compound using Thin Layer Chromatography (TLC), you ideally want to observe a single spot in the product’s lane. This indicates the presence of a single compound and hence purity.
Moreover, this spot should not match the position of the starting material. If the reaction has occurred and the product is a new compound, its Rf value should be different. In many reactions, the product becomes less polar than the starting material, allowing it to travel further on the TLC plate, giving a higher Rf.
Here’s a breakdown of the options:
- Option (a): The spot matches the Rf of the starting material — this may suggest that no reaction has occurred, and the compound is unreacted starting material.
- Option (b): One spot is seen, lower Rf — it might be the product, but lower Rf implies more polarity. This depends on the expected polarity trend of the product vs. reactant.
- Option (c): Two spots — this clearly shows the presence of multiple compounds, indicating impurity.
- Option (d): One spot with a higher Rf than the starting material — this is ideal. It suggests the formation of a new, pure product that is less polar and hence travels further on the TLC plate.
Hence, option (d) is the best indicator of a pure compound.