Add about 15 mL of the 1 M Grignard reagent phenylmagnesium bromide in tetrahydrofuran THF to your beaker containing the dry ice. There should be obvious signs of mixing which includes gas bubbling from the dry ice when the Grignard reagent is added. This gas is carbon dioxide, but your Grignard reagent will be reacting with the dry ice in the beaker.
After you have added the phenylmagnesium bromide, let the beaker sit at room temperature until all the dry ice has sublimed and the frozen solid has melted. The Grignard reaction product should appear as a viscous glassy mass with a brownish color. You will need to hydrolyze the Grignard adduct by slowly adding about 10 mL of 3 M HCl with stirring you can use a glass stirring rod or simply swirl the contents of the beaker by hand.
After the addition of your HCl, monitor the pH to make certain that the pH is about 1 using pHydroin paper. At this low pH, all of the benzoic acid should be protonated. Continue to mix the contents of your beaker using a glass stirring rod or by swirling its contents.
Since THF is mostly soluble in water, you can enhance its evaporation by letting the contents of the beaker sit in the hood at room temperature until the next lab period.
Solid benzoic acid will be apparent even while some THF is present. Letting your sample sit until the next lab period will leave the benzoic acid suspended in the aqueous layer. Even if some or all of the water evaporates, this will not affect your ultimate yield or product. Your triphenylmethanol product should be be free of THF and diethyl ether after sitting until this second lab period.
Add about 25 mL of 1. Transfer the contents of your Erlenmeyer flask to your Separatory funnel remembering to always use a funnel when pouring through ground glass openings. Add about 20 mL of diethyl ether it does not need to be anhydrous diethyl ether from this point forward, but it is okay and up to mL of 1.
Swirl the flask well to promote hydrolysis the acid converts the alkoxide ion into an alcohol of the addition product. Pour the wash liquid from your flask into the Separatory funnel. You may use up to 10 mL of diethyl ether to remove any remaining crystals. Shake the Separatory funnel vigorously for up to 5 minutes and let the two phases separate if all solids have not dissolved add a little more diethyl ether. Remove and discard the lower aqueous layer, which does not contain your triphenylmethanol, since it is more dense than the ether phase.
If in doubt, simple add a little distilled water, and see which phase gets larger, which would then be the aqueous phase. After removal of the aqueous phase, add about 10 mL of the 1. Note: It is important to note that quantities of the wash liquids is not critical, and it is usually sufficient to use about one-third to one-half of the volume of the ether for each wash with the aqueous solutions.
To effect drying of the ether solution removal of any dissolved water in the ether , decant the ether layer from the Separatory funnel into an mL Erlenmeyer flask.
Add about 2 g of anhydrous Na 2 SO 4 and swirl the flask from time to time. If it appears that the sodium sulfate crystals are clumping together, add a little more anhydrous salt until what you add remains free flowing no clumping. After about min remove the Na 2 SO 4 solids by gravity filtration no vacuum; use regular funnel with folded larger filter paper into a new flask.
Rinse the flask and any drying agent into the filter with a small amount of diethyl ether. Add 15 mL of ligroin o C ligroin; ligroin is an organic solvent sometimes referred to as pertroleum ether, but it is not an ether chemically and concentrate the diethyl ether-liqroin solution using a heating plate in the hood, to vent the ether.
Because diethyl ether has a low boiling point 35 o C , it will preferentially be removed compared to the ligroin. Continue to slowly evaporate the ethers until crystals of triphenylcarbinol another name for triphenylmethanol just begin to form. Remove the flask from the heating hot plate and let the flask cool slowly to room temperature.
Crystals should be apparent. After reaching room temperature with the flask sitting on the bench top, you can then place the flask in an ice bath, but only after the flask has reached room temperature. Let the flask sit on ice until no more crystals form min. Perform a vacuum filtration and collect your crystals. After collecting most of your crystals, you can wash the remainder into the funnel using ligroin not water. Concentration of the mother liquor the filtrate may yield a second crop of crystals, but this is not necessary.
If you desire to increase your yield, simply take the filtrate and evaporate more of the ligroin until you start to see crystals again. Cool to room temperature, place on ice, and filter again. Combine crystals from the second crystallization if you do it with the first batch of crystals. Store the crystals in the drying oven until the next lab period. To purify your collected benzoic acid from your first day, add about 10 mL of diethyl ether and after swirling to mix and dissolve the acid, simply transfer all of your material into a Separatory funnel.
You can wash your container with a little diethyl ether which should dissolve any remaining benzoic acid crystals. Shake your funnel and let the two phases separate. Both liquid phases should be clear.
Remove the lower aqueous phase, which will be discarded as a precaution, keep all material until you are sure you have the correct phase with your benzoic acid in it. If two phases are not readily apparent, or if phases are not clear, you should add a little more diethyl ether and maybe a little HCl.
After the aqueous phase has been removed, wash the top ether phase, which contains dissolved benzoic acid, with about 10 mL 1 M NaOH, which will convert the benzoic acid into the benzoate ion, which in turn will partition into the lower aqueous basic phase. Pungente , William P. Next generation macrocyclic and acyclic cationic lipids for gene transfer: Synthesis and in vitro evaluation.
Mass spectral and NMR studies of some cinnolines. Journal of Heterocyclic Chemistry , 5 5 , Pair your accounts. Your Mendeley pairing has expired. Please reconnect. This website uses cookies to improve your user experience.
By continuing to use the site, you are accepting our use of cookies. Note disposable dram vials need not be washed, but should be rinsed with acetone. Just prior to your experiment carefully remove dry glassware from the oven, assemble and immediately cap it with a septum. If the rubber septum in your kit has been punctured multiple times obtain a replacement septum from your GSI. The hard side of the septum is the solvent resistant Teflon side and should be place downward.
Stopper the disposable dram vials with corks. Allow all glassware to cool to room temperature before proceeding with the experiment. Keep the vessel capped throughout the course of the experiment unless you need to add something to it. Experiment 7 is a two week experiment. At the end of the first session be sure to re-clean and replace your glassware in the oven so as to ensure that it is dry for the second session.
With careful planning each group member should be able to carry out 2 complete Grignard experiments. Obtain 3 mL of anhydrous diethyl ether from your GSI in one of the oven dried dram vials. Weigh magnesium powder 50 mg, 2 mmol and add it to your reaction vessel.
Using a 1. In a separate oven dried vial, add bromobenzene mg, 2. Replace the septum, making sure to release pressure as necessary using a needle to vent as necessary. The solution should turn cloudy and start to boil, indicating that the reaction has started.
To prevent the ether from boiling away, wrap a damp paper towel around neck of the Claisen adapter. It is important to control the addition of bromobenzene to avoid the rapid evolution of heat. After boiling slows, add a magnetic stir bar to the reaction tube and stir. The reaction is complete when none of the magnesium remains. If the level of the ether has decreased, add more. In order prevent decomposition of the Grignard reagent it will be used immediately in the solution that it is in; there is no isolation or purification of the phenylmagnesium bromide.
In an oven dried vial, dissolve benzophenone mg, 2 mmol in 1 mL of anhydrous ether. With a dry 1 mL syringe, slowly add the solution to the reaction vessel containing the Grignard reagent, thus maintaining a gentle reflux.
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