Rank trans-stilbene, benzoic acid, and fluorenone by polarity (least polar to mo
ID: 488633 • Letter: R
Question
Rank trans-stilbene, benzoic acid, and fluorenone by polarity (least polar to most polar). Provide an explanation for your proposed ranking. Hexane, ethyl acetate and acetone will be used as solvents for the first TLC experiment. Which of these solvents is considered polar? Which is considered non-polar? Which can hydrogen bond? What is the relative order of polarity (ranking in terms of least to most)? If the polarity of the eluent solvent is increase will the Re values for compounds on the TLC plate increase or decrease? Please explain your choice. Caffeine is quite Polar. In an initial experiment, caffeine had a Revalue of 0. (Stuck on the baseline). What would you do to get caffeine to move of the baseline?Explanation / Answer
(1)
trans-stilbene<fluorenone<benzoic acid
trans-stilbene can be classified as nonpolar, 9-fluorenone asmoderately polar, and benzoic acid as polar
Trans-stilbene was determined to be nonpolar because of its structure. It has verylittle to none of a dipole moment because carbon and hydrogen have basically the same electronegativity values.
9- fluorenone was determined to bemoderately polar also because of its structure due to the fact it has an electronegative oxygen and also because ittended to be soluble in moderately polar solvents.
benzoic acid was determined to be polar because of its structure containing a hydroxyl group and also being soluble in very polar solvents such as ethanol and water
(2)
Hexane-non polar
ethyl acetate -moderately polar
Acetone-polar
The polarity of the solvents going from nonpolar to most polar was hexane, ethyl aceetate and acetone.
(3)
As polarity increase R value also increase.
A greater Rf value corresponds with a higher eluting ability. In the general trend was that nonpolar solvents, such as hexane, had a lower eluting ability, compared to more polar solvents, such as acetone, which had ahigher eluting ability and greater Rf values.
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