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Does anyone know how to complete dialkylation of diethyl malonate...
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Does anyone know how to complete dialkylation of diethyl malonate...
you can carry out the reaction in the presence of a large excess of sodium hydride in tetrahydrofuran at 0 ° C. then add three equivalent of bromoethane and refluxing.
you can carry out the reaction in the presence of a large excess of sodium hydride in tetrahydrofuran at 0 ° C. then add three equivalent of bromoethane and refluxing.
Sridhara, "In the past, the formation of the enolate anion required using a strong base such as sodium ethoxide (made by reacting sodium metal with ethanol) to remove a proton alpha to the carbonyl group. There are several problems with this method: 1) the handling of highly reactive sodium metal; 2) the necessity of preparing absolutely anhydrous ethanol; 3) the large amount of E2 elimination of the alkyl halide. While carbonate anion is not a very strong base in aqueous medium (pKa=8.5), in an organic medium it is basic enough to remove a proton from an active methylene compound. A cyclic polyether or a tetraalkylammonium salts will allow dissolution of carbonates in organic solvents. A liquid-solid two phase system using anhydrous K2CO3 or Na2CO3 has the added advantage of absorbing the water formed in the reaction, thus minimizing ester hydrolysis. Since diethylmalonate has two acidic a hydrogens, it can be dialkylated (a minor product of this reaction) by reaction with two equivalents of an alkyl halide." See
Sridhara, "In the past, the formation of the enolate anion required using a strong base such as sodium ethoxide (made by reacting sodium metal with ethanol) to remove a proton alpha to the carbonyl group. There are several problems with this method: 1) the handling of highly reactive sodium metal; 2) the necessity of preparing absolutely anhydrous ethanol; 3) the large amount of E2 elimination of the alkyl halide. While carbonate anion is not a very strong base in aqueous medium (pKa=8.5), in an organic medium it is basic enough to remove a proton from an active methylene compound. A cyclic polyether or a tetraalkylammonium salts will allow dissolution of carbonates in organic solvents. A liquid-solid two phase system using anhydrous K2CO3 or Na2CO3 has the added advantage of absorbing the water formed in the reaction, thus minimizing ester hydrolysis. Since diethylmalonate has two acidic a hydrogens, it can be dialkylated (a minor product of this reaction) by reaction with two equivalents of an alkyl halide." See
Sridhara, You wrote "Does anyone know how to complete dialkylation of diethyl malonate using potassium carbonate as a base?" and the answer is to use PTC such as tetraalkyl ammonium salts ! Good luck
Sridhara, You wrote "Does anyone know how to complete dialkylation of diethyl malonate using potassium carbonate as a base?" and the answer is to use PTC such as tetraalkyl ammonium salts ! Good luck
Try this one: 10 - 15 mL dioxane, 1 g diethyl malonate, 1 g potassium carbonate (sesquihydrate = 1.5 aq is better), 2.5 eq alkylating agent and 100 mg cetrimide as S-L PTC. Stirring at 30 - 40 °C. GC or TLC control (detection by anisidine agent).
Try this one: 10 - 15 mL dioxane, 1 g diethyl malonate, 1 g potassium carbonate (sesquihydrate = 1.5 aq is better), 2.5 eq alkylating agent and 100 mg cetrimide as S-L PTC. Stirring at 30 - 40 °C. GC or TLC control (detection by anisidine agent).
you can carry out the reaction in the presence of a large excess of sodium hydride in tetrahydrofuran at 0 ° C. then add three equivalent of bromoethane and refluxing.
you can carry out the reaction in the presence of a large excess of sodium hydride in tetrahydrofuran at 0 ° C. then add three equivalent of bromoethane and refluxing.
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Sridhara,
"In the past, the formation of the enolate anion required using a strong base such as sodium ethoxide (made by reacting sodium metal with ethanol) to remove a proton alpha to the carbonyl group. There are several problems with this method: 1) the handling of highly reactive sodium metal; 2) the necessity of preparing absolutely anhydrous ethanol; 3) the large amount of E2 elimination of the alkyl halide. While carbonate anion is not a very strong base in aqueous medium (pKa=8.5), in an organic medium it is basic enough to remove a proton from an active methylene compound. A cyclic polyether or a tetraalkylammonium salts will allow dissolution of carbonates in organic solvents. A liquid-solid two phase system using anhydrous K2CO3 or Na2CO3 has the added advantage of absorbing the water formed in the reaction, thus minimizing ester hydrolysis. Since diethylmalonate has two acidic a hydrogens, it can be dialkylated (a minor product of this reaction) by reaction with two equivalents of an alkyl halide." See
---http://courses.chem.psu.edu/chem36/Experiments/Exp13.pdf
Good luck
Sridhara,
"In the past, the formation of the enolate anion required using a strong base such as sodium ethoxide (made by reacting sodium metal with ethanol) to remove a proton alpha to the carbonyl group. There are several problems with this method: 1) the handling of highly reactive sodium metal; 2) the necessity of preparing absolutely anhydrous ethanol; 3) the large amount of E2 elimination of the alkyl halide. While carbonate anion is not a very strong base in aqueous medium (pKa=8.5), in an organic medium it is basic enough to remove a proton from an active methylene compound. A cyclic polyether or a tetraalkylammonium salts will allow dissolution of carbonates in organic solvents. A liquid-solid two phase system using anhydrous K2CO3 or Na2CO3 has the added advantage of absorbing the water formed in the reaction, thus minimizing ester hydrolysis. Since diethylmalonate has two acidic a hydrogens, it can be dialkylated (a minor product of this reaction) by reaction with two equivalents of an alkyl halide." See
---http://courses.chem.psu.edu/chem36/Experiments/Exp13.pdf
Good luck
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Dilakylation of diethyl malonate is possible with excess of sodium ethoxide in absolute ethanol & alkyl halide under refluxing condition
Dilakylation of diethyl malonate is possible with excess of sodium ethoxide in absolute ethanol & alkyl halide under refluxing condition
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Sridhara,
You wrote
"Does anyone know how to complete dialkylation of diethyl malonate using potassium carbonate as a base?"
and the answer is to use PTC such as tetraalkyl ammonium salts !
Good luck
Sridhara,
You wrote
"Does anyone know how to complete dialkylation of diethyl malonate using potassium carbonate as a base?"
and the answer is to use PTC such as tetraalkyl ammonium salts !
Good luck
More
VOTE
Try this one: 10 - 15 mL dioxane, 1 g diethyl malonate, 1 g potassium carbonate (sesquihydrate = 1.5 aq is better), 2.5 eq alkylating agent and 100 mg cetrimide as S-L PTC. Stirring at 30 - 40 °C. GC or TLC control (detection by anisidine agent).
Try this one: 10 - 15 mL dioxane, 1 g diethyl malonate, 1 g potassium carbonate (sesquihydrate = 1.5 aq is better), 2.5 eq alkylating agent and 100 mg cetrimide as S-L PTC. Stirring at 30 - 40 °C. GC or TLC control (detection by anisidine agent).
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you can see the following bibliography. That can help you.
you can see the following bibliography. That can help you.
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What about while using NaOH?
What about while using NaOH?
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Pavel Pazdera, is there a way to prepare the potassium sesquihydrate easily in the lab ?
Pavel Pazdera, is there a way to prepare the potassium sesquihydrate easily in the lab ?
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you can see the following bibliography. That can help you.
you can see the following bibliography. That can help you.
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