CHEM 269 Lecture 7: Nucleophilic displacement - Formation of an ether by an SN2 reaction

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lemonplatypus384

30 Jun 2016

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Document Summary

Nucleophilic displacement - formation of an ether by an sn2 reaction. Purpose: to investigate the williamson-ether synthesis by using nucleophilic displacement on 2-naphthol to yield an ether, butyl naphthyl ether (an sn2 reaction). Then to determine the best solvent system of hexane and ethyl acetate to separate 2-naphthol and prepared ether product using a thin layer chromatography (tlc) analysis. The purity was then confirmed through taking a melting point of the product. To a 5ml round-bottomed flask (rbf) was added naoh (0. 064g), 2-naphthol (0. 204g), boiling stones (3), and absolute ethanol (3 ml) then an air condenser was attached. The mixture was then heated until it gently boiled, and allowed to reflux until all solids dissolved in the rbf flask. The mixture was then refluxed for another 25 minutes, and the solution was cooled for 3 minutes. After this time, the mixture had a light green color.

Related Questions

% yield question

20.34 mL diethyl malonate, 50mL sodium ethoxide, 14.38mL n-butyl bromide made 9.11g diethyl n-butylmalonate

% yield question

To a 250 mL round-bottomed flask were added 35 mL of absolute ethanol and 50 mL (0.134 mol) of NaOEt solution and stirred. The flask was then fitted with a reflux condenser and a dropping funnel via claisen adapter and a drying tube was attached. Diethyl malonate (20.34 mL, 0.134 mol) was added portion-wise over 15 min through dropping funnel. Then to the clear solution was added n-butyl bromide (14.38 mL, 0.134 mol) dropwise. The reaction mixture was refluxed for 10 min and then cooled. The solution was then mixed with 200 mL of cold water and aqueous layer was extracted four times with 50 mL portion of ethyl ether. Combined organic layer was dried over MgSO₄, filtered, and ether was evaporated over steam bath. Remaining solution was transferred into a pre-weighed round-bottomed flask and simple distillation (temp <90 ËC) was performed to remove excess ether and ethanol. The product diethyl n-butylmalonate (amount) was obtained as pale orange liquid in ____% yield.

Please consider the preperation of benzoic acid: a Grignard Reaction.

Bromobenzene and diethyl ether is used in the formation of Grignard reagent. Note: procedure is listed below for reference

QUESTION:

Procedure:

* add 1.2g of magnesium and 3 crystals of iodine to RB flask and immediately assemble the dry water condenser and drying tube containing cotton and anhydrous calcium chloride to RB flask

*then add 5.2 mL bromobenzene to 5 mL of diethyl ether to seperatory funnel and turn on condenser

* add about one third of ether-bromobenzene mixture down the condenser into the RB flask by momentarily removing drying tube. Place the drying tube back as quickly as possible.

* now add 30 mL of ether to the bromobenzene-ether mixture remaining in the seperatory funnel

*to initiate reaciton, place hands under flask and gently swril

* once the reaction maintains reflux, remove hands and set the flask down on a cork ring

*maintain the vigorousness of the reaciton by continuously adding 3.5 mL portions of diluted bromobenzene-ether mixture every 30 seconds

* make sure all of the bromobenzene-ether mixture has been added

* now obtain some dry ice, CO₂ (s) and transfer 50 mL of this to the reaciton mixture inside the flask

*when all the dry ice has been added, add 80 mL of 6M HCl (aq) to flask

* finally, add 100mL of solvent grade diethyl ether (not anhydrous) and carefully stir

* transfer mixture to a 250mL seperatory funnel, allow layers to seperate and discard the lower aqueous layer

*now add 20 mL of 6 M NaOH (aq) and add 100mL of deionized water to seperatory funnel containing the ether solution

* drain the lower aqueous layer into a large beaker and slowly acidify using concentrated 12M HCl (aq). Stir the mixture and add HCl (aq) until pH is about 1-2 pH units.

*cool solution in ice-water bath and collect precipitate of benzoic acid

Please consider the preperation of benzoic acid: a Grignard Reaction.

Bromobenzene and diethyl ether is used in the formation of Grignard reagent.

PLEASE READ PROCEDURE TO HELP ANSWER THE QUESTION:

Procedure(question is in the pic below):