A student separated a 2-g mixture of fluorene, 2-naphthoic acid, and diphenylamine (shown below) dissolved in 25 mL of the organic solvent diethyl ether.The separation experiment was performed according to the following steps:Step 1The mixture solution was partitioned by pouring it into a separatory funnel containing 10 mL water, and the organic layer was extracted with 10 mL 1 M NaOH(aq).Step 2The aqueous layer was transferred to Flask A, and concentrated HCl(aq) was added dropwise to the flask until pH paper indicated that the solution was acidic. Flask A was then placed in ice water to induce precipitate formation.Step 3The organic layer was extracted with 10 mL 3 M HCl(aq). The resulting aqueous layer was then transferred to Flask B and 8 M NaOH was added dropwise to Flask B until pH paper indicated that the solution was basic. Flask B was then placed in ice water, to maximize precipitate formation.Step 4The precipitates in flasks A and B were collected separately by vacuum filtration, rinsed with distilled water, and dried in an oven.Step 5The organic layer was transferred into Flask C and dried by adding anhydrous MgSO4 to remove any residual water present. The organic solvent was separated from the MgSO4 in Flask C by gravity filtration, and the solvent was evaporated, yielding white crystals.Step 6The purity of the three isolated compounds was analyzed by thin-layer chromatography (TLC) on silica plates. A sample of the mixture was spotted on the TLC plate as a reference in addition to the isolated compound. Question 42Why does fluorene remain in the organic layer during the extraction with 3 M HCl(aq)?Fluorene cannot accept H+ from HCl(aq).Fluorene is hydrophilic and remains in the nonpolar layer.Fluorene is hydrophobic and remains in the nonpolar layer.A.I onlyB.II onlyC.III onlyD.I and III only
Question
A student separated a 2-g mixture of fluorene, 2-naphthoic acid, and diphenylamine (shown below) dissolved in 25 mL of the organic solvent diethyl ether.The separation experiment was performed according to the following steps:Step 1The mixture solution was partitioned by pouring it into a separatory funnel containing 10 mL water, and the organic layer was extracted with 10 mL 1 M NaOH(aq).Step 2The aqueous layer was transferred to Flask A, and concentrated HCl(aq) was added dropwise to the flask until pH paper indicated that the solution was acidic. Flask A was then placed in ice water to induce precipitate formation.Step 3The organic layer was extracted with 10 mL 3 M HCl(aq). The resulting aqueous layer was then transferred to Flask B and 8 M NaOH was added dropwise to Flask B until pH paper indicated that the solution was basic. Flask B was then placed in ice water, to maximize precipitate formation.Step 4The precipitates in flasks A and B were collected separately by vacuum filtration, rinsed with distilled water, and dried in an oven.Step 5The organic layer was transferred into Flask C and dried by adding anhydrous MgSO4 to remove any residual water present. The organic solvent was separated from the MgSO4 in Flask C by gravity filtration, and the solvent was evaporated, yielding white crystals.Step 6The purity of the three isolated compounds was analyzed by thin-layer chromatography (TLC) on silica plates. A sample of the mixture was spotted on the TLC plate as a reference in addition to the isolated compound. Question 42Why does fluorene remain in the organic layer during the extraction with 3 M HCl(aq)?Fluorene cannot accept H+ from HCl(aq).Fluorene is hydrophilic and remains in the nonpolar layer.Fluorene is hydrophobic and remains in the nonpolar layer.A.I onlyB.II onlyC.III onlyD.I and III only
Solution
The correct answer is D. I and III only.
Fluorene remains in the organic layer during the extraction with 3 M HCl(aq) because it cannot accept H+ from HCl(aq) and it is hydrophobic, meaning it prefers to stay in the nonpolar layer.
Fluorene is a nonpolar compound and does not have any functional groups that can form an ion by reacting with HCl. Therefore, it does not dissolve in the aqueous layer but remains in the organic layer. This is statement I.
Statement II is incorrect because fluorene is not hydrophilic. Hydrophilic substances are attracted to water and can form hydrogen bonds with water, but fluorene cannot do this.
Statement III is correct because fluorene is hydrophobic. Hydrophobic substances are repelled by water and prefer to stay in nonpolar environments, such as the organic layer in this case.
Similar Questions
Step 1The mixture solution was partitioned by pouring it into a separatory funnel containing 10 mL water, and the organic layer was extracted with 10 mL 1 M NaOH(aq).Step 2The aqueous layer was transferred to Flask A, and concentrated HCl(aq) was added dropwise to the flask until pH paper indicated that the solution was acidic. Flask A was then placed in ice water to induce precipitate formation.Step 3The organic layer was extracted with 10 mL 3 M HCl(aq). The resulting aqueous layer was then transferred to Flask B and 8 M NaOH was added dropwise to Flask B until pH paper indicated that the solution was basic. Flask B was then placed in ice water, to maximize precipitate formation.Step 4The precipitates in flasks A and B were collected separately by vacuum filtration, rinsed with distilled water, and dried in an oven.Step 5The organic layer was transferred into Flask C and dried by adding anhydrous MgSO4 to remove any residual water present. The organic solvent was separated from the MgSO4 in Flask C by gravity filtration, and the solvent was evaporated, yielding white crystals.Step 6The purity of the three isolated compounds was analyzed by thin-layer chromatography (TLC) on silica plates. A sample of the mixture was spotted on the TLC plate as a reference in addition to the isolated compound. Question 41In which of the following steps is 2-naphthoic acid separated from the mixture?A.Step 1B.Step 3C.Step 4D.Step 5
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a method of separating and analyzing mixtures of chemicals according to solubility
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