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Why is methanol chosen as the solvent for recrystallization? What would happen if the student uses dichloromethane instead? The reaction is Electrophilic Aromatic Substitution: Friedel-Crafts Alkylation.

Why is methanol chosen as the solvent for recrystallization? What would happen if the student uses dichloromethane instead? The reaction is Electrophilic Aromatic Substitution: Friedel-Crafts Alkylation.

Chemistry: The Molecular Science
Chemistry: The Molecular Science
5th Edition
ISBN:9781285199047
Author:John W. Moore, Conrad L. Stanitski
Publisher:John W. Moore, Conrad L. Stanitski
Chapter13: The Chemistry Of Solutes And Solutions
Section: Chapter Questions
Problem 83QRT
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  1. Why is methanol chosen as the solvent for recrystallization? What would happen if the student uses dichloromethane instead?

The reaction is Electrophilic Aromatic Substitution: Friedel-Crafts Alkylation. More info attached

In this experiment, the tert.-butyl cation is produced by the reaction of tert. butanol and concentrated sulfuric acid. A tert.-butyl cation will be used and since no carbocation rearrangement can occur, any method can be used to produce this cation. Just remember that while anhydrous AlCl3 is often used for Friedel-Craft reactions, this class of EAS simply requires a carbocation, regardless of how it is generated. In the current experiment, a different electrophile (the tert.-butyl cation) is used to alkylate 1,4-dimethoxybenzene. This is a Friedel-Crafts Alkylation reaction. LOCH3 (H;C);C. LOCH3 (CH3);COH CH;COOH/H,SO4 H3CO H3CO `C(CH3)3 The primary difference between Friedel-Crafts EAS reactions and other EAS reactions (i.e., nitration, halogenation, etc.) is that in a Friedel-Crafts reaction (alkylation or acylation), the electrophile is a carbon atom (i.e., in this experiment it is a tert.-butyl carbocation). In many cases, the Friedel-Crafts electrophile is generated using a chlorine-containing molecule (i.e., an acyl [acid] chloride or an alkyl chloride) and an appropriate Lewis acid (i.e., AIC13, BF3) catalyst
Transcribed Image Text:In this experiment, the tert.-butyl cation is produced by the reaction of tert. butanol and concentrated sulfuric acid. A tert.-butyl cation will be used and since no carbocation rearrangement can occur, any method can be used to produce this cation. Just remember that while anhydrous AlCl3 is often used for Friedel-Craft reactions, this class of EAS simply requires a carbocation, regardless of how it is generated. In the current experiment, a different electrophile (the tert.-butyl cation) is used to alkylate 1,4-dimethoxybenzene. This is a Friedel-Crafts Alkylation reaction. LOCH3 (H;C);C. LOCH3 (CH3);COH CH;COOH/H,SO4 H3CO H3CO `C(CH3)3 The primary difference between Friedel-Crafts EAS reactions and other EAS reactions (i.e., nitration, halogenation, etc.) is that in a Friedel-Crafts reaction (alkylation or acylation), the electrophile is a carbon atom (i.e., in this experiment it is a tert.-butyl carbocation). In many cases, the Friedel-Crafts electrophile is generated using a chlorine-containing molecule (i.e., an acyl [acid] chloride or an alkyl chloride) and an appropriate Lewis acid (i.e., AIC13, BF3) catalyst
Recrystallize the dried product using hot methanol. Add enough methanol to dissolve the product. You do not want to add too much methanol, but if you do, you can always evaporate some of it away. To facilitate your re-crystallization, do the following: Add some methanol (i.e., 10-15 mL) Place the beaker containing solid and methanol onto a heating plate. Turn on the heating plate and continue to heat your beaker until all the solid has dissolved. If the methanol is boiling, and all the solid has not dissolved add more methanol (in 2-mL quantities) until the boiling mixture is free of solid material. When all the solid has dissolved in the boiling methanol, add about 5 mL more methanol. Remove the beaker and contents from the heating plate, and let it cool at room temperature. When your beaker has cooled to room temperature, place the beaker into an ice bucket for an additional 10 min (do not place your beaker in the ice bucker until it has cooled to room temperature). Your sample should be a free-flowing slurry, meaning that there is enough liquid to keep the solid moving around. If you do not produce a lot of crystals, you might try evaporating some of the solvents by heating the mixture to the boiling point of methanol (64 °C). Remove the beaker and let it sit again at room temperature until crystals form. To collect your solid material, you will do a vacuum filtration. When you add your filter paper to the Büchner Funnel, do not wet it with water, you must keep it dry. You can use a little bit of methanol to add to the filter before adding your solid, but do not use water. Wash your beaker with a little methanol, to attempt to add as much of your solid as possible to the funnel. Let the vacuum continue to draw air over your sample, letting it dry by evaporating all the methanol (about 15 min). After this 15-min period of drying your sample, you can use the crystalline material directly in a melt temp.
Transcribed Image Text:Recrystallize the dried product using hot methanol. Add enough methanol to dissolve the product. You do not want to add too much methanol, but if you do, you can always evaporate some of it away. To facilitate your re-crystallization, do the following: Add some methanol (i.e., 10-15 mL) Place the beaker containing solid and methanol onto a heating plate. Turn on the heating plate and continue to heat your beaker until all the solid has dissolved. If the methanol is boiling, and all the solid has not dissolved add more methanol (in 2-mL quantities) until the boiling mixture is free of solid material. When all the solid has dissolved in the boiling methanol, add about 5 mL more methanol. Remove the beaker and contents from the heating plate, and let it cool at room temperature. When your beaker has cooled to room temperature, place the beaker into an ice bucket for an additional 10 min (do not place your beaker in the ice bucker until it has cooled to room temperature). Your sample should be a free-flowing slurry, meaning that there is enough liquid to keep the solid moving around. If you do not produce a lot of crystals, you might try evaporating some of the solvents by heating the mixture to the boiling point of methanol (64 °C). Remove the beaker and let it sit again at room temperature until crystals form. To collect your solid material, you will do a vacuum filtration. When you add your filter paper to the Büchner Funnel, do not wet it with water, you must keep it dry. You can use a little bit of methanol to add to the filter before adding your solid, but do not use water. Wash your beaker with a little methanol, to attempt to add as much of your solid as possible to the funnel. Let the vacuum continue to draw air over your sample, letting it dry by evaporating all the methanol (about 15 min). After this 15-min period of drying your sample, you can use the crystalline material directly in a melt temp.
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