Organic Chemistry Laboratory I (CHEM 244) Uploaded by. x�b```���@�(?�3� EY8X�թ���T T�i��ҷ�W��:�\ f�``6�(.�[email protected]�e�"��,:�/�8�������`�x�i�>�eɄ]��������#Ƹ��j7�$W��@lv�Ao �ħ �{"} Only handle with gloves in a well-ventilated area (e.g., hood). 0000001218 00000 n With a glass stirring rod, crush some of the magnesium to expose fresh surface. Confirm the presence of an alcohol group from the product and the lack of a carbonyl from the aldehyde. Into a 10 mL Erlenmeyer flask, prepare a solution of 0.72 mL (0.58 grams or 10.0 mmol) propanal (58.1 g/mol) and 3 mL of anhydrous ether. To this, you then slowly added a solution of 2.4 g benzophenone in anhydrous ether. Since we will. Unreacted magnesium should also be slowly consumed. Which of the following anhydrous solvents would be NOT appropriate for a Grignard reaction because they would react with the Grignard reagent to form an alkane? Predict the 1 H-NMR spectrum for triphenylmethanol. In an oven dried vial, dissolve benzophenone (364 mg, 2 mmol) in 1 mL of anhydrous ether. The contents in the temporary waste container should then be transferred into an appropriately labeled waste container making sure to note compounds present and amounts thereof on the waste container. Academic year. After all the aldehyde solution has been added, gently heat to a rolling boil (i.e., reflux) the entire mixture for 15 min. Do not use in the presence of open flames or sparks. Cool the reaction flask containing the Grignard reagent to room temperature (NOTE:  do not disconnect the flask from the condenser). 0000002136 00000 n 0000000896 00000 n Weight and Melting Point Determination of Triphenylmethanol Inspect your product and if it appears to be dry, weigh it and calculate the percent yield. The limiting reagent in a Grignard reaction is usually the substance to which you add the Grignard reagent, but you have to confirm this by calculation. For synthetic organic chemistry, many important reagents are organometallic compounds derived from metals in family IA (Li, Na, K) and IIA (Mg). Warm the flask gently, with a heating mantle. 3-octanol is one of the alarm pheromones isolated from the fungus-growing ant, the myrmicine ant. When the reaction is occurring properly, the liquid will continue to boil without external heat being applied. In an oven dried vial, dissolve benzophenone (364 mg, 2 mmol) in 1 mL of anhydrous ether. > EXAMPLE Assume that, in a preparation of triphenylmethanol, you prepared phenylmagnesium bromide by reacting 2.1 mL of bromobenzene (density 1.50 g/mL) with 0.50 g of magnesium in anhydrous ether. NOTE:  a small amount of magnesium may not have reacted. Calculate the mass of 1.5 mmoles of benzophenone (MW = 182.220 mg/mmole) to the nearest mg. Record the calculation. 0000002554 00000 n Any material remaining in the reaction flask may be hydrolyzed by pouring the aqueous acid/ether mixture back in and swirling. The most famous of these are the organomagnesium halides (named "Grignard reagents" after Victor Grignard). There is little restriction on the structure of the alkyl group although the rate of formation decreases as one changes from primary halides to tertiary halides. %%EOF Weigh your dried product to determine theoretical, actual, and percent yields. Obtain the IR spectrum of your crude/purified product. Since the reagent is available, proceed directly to doing Parts A & B. 0000003074 00000 n The carbon bound to the magnesium of a Grignard reagent acts as what kind of species? [7]  Image produced and provided by T. B. Cavitt. (Ex. 30650 views 0000008310 00000 n In a tared sample bottle, collect the distilled and purified 3-octanol (boiling point:  170-176°C). 0000003118 00000 n 0000003948 00000 n Initiate stirring and water flow through the condenser. How do you determine how much of the excess reactant is left over? The procedure for synthesis is included here in order to show you the complete way of making the chemical. Thus, the R group will serve as a nucleophile (Nu–) and will preferentially react with electron deficient centers such as the carbon in carbon dioxide and the carbon of the ketone (Figure 4) to form a new carbon-carbon bond. Grignard Synthesis of Triphenylmethanol and Benzoic Acid Lexa Marchese Chem 316 3/5/16 Objectives To form an alcohol from an appropriate akyl halides and carbonyl compounds Obtain a mass of triphenylmethanol Find how pure our alcohol was by finding a melting point Obtain the percent yield of triphenylmethanol Theory Some precautions must be taken in the preparations and reactions of Grignard reagents. Primary alcohols are formed by reaction with formaldehyde (one carbon elongation), secondary alcohols by reaction with aldehydes, and tertiary alcohols by reaction with ketones. trailer Learners will be able to perform and describe the following regarding Grignard reactions: Organometallic compounds are compounds, which contain direct metal-carbon bonds. aldehyde or ketone). Rinse the benzophenone vial with a small amount of anhydrous ether and add this to the reaction tube also. Bromides are often used as a compromise between reactivity and cost. Course. 0 They are readily prepared according to Figure 1. Visual indication of a properly initiated Grignard reagent is evidenced by appearance of turbidity (i.e., cloudiness), and spontaneous refluxing (i.e., boiling). An apparatus suitable for preparation of the Grignard reagent is illustrated below (Figure 8). INSTRUCTOR OPTION:  At this point transfer the mixture to an Erlenmeyer flask, stopper it with a. Add anhydrous magnesium sulfate to complete the drying process. Since benzophenone has the fewest moles, it is the limiting reactant. endstream endobj 17 0 obj <> endobj 18 0 obj <> endobj 19 0 obj <>/ColorSpace<>/Font<>/ProcSet[/PDF/Text/ImageC/ImageI]/ExtGState<>>> endobj 20 0 obj <> endobj 21 0 obj <> endobj 22 0 obj <> endobj 23 0 obj [/ICCBased 39 0 R] endobj 24 0 obj [/Indexed 23 0 R 55 40 0 R] endobj 25 0 obj [/Indexed 23 0 R 10 42 0 R] endobj 26 0 obj <> endobj 27 0 obj <> endobj 28 0 obj <> endobj 29 0 obj <> endobj 30 0 obj <>stream The ice should completely melt during this process. Note molar amounts used in the experiment and the stoichiometry of the reactions to determine the limiting reagent. The triphenylmethanol reaction was a bit more tricky and only 24.7% was recovered, though what was recovered was seemingly very pure. H���Ko�0���. After all the ether has been removed (i.e., no more liquid distills at low heat), increase the heat to distill the product, 3-octanol. Into a 10 mL round-bottomed flask, place 0.26 grams (10.7 mmol) of magnesium (24.3 g/mol) turnings, one small crystal of iodine, and the stir bar, and complete the apparatus assembly that has been dried in an oven (Figure 8, Videos 1 & 2). aldehyde or ketone). Even though the bond is a covalent bond, it is highly polarized so that the carbon has significant carbanion character (Figure 3). Experiment The Preparation of Benzoic Acid Studyclix. 2. %PDF-1.4 %���� From the mixture in the Erlenmeyer flask, draw off the lower aqueous acid layer and discard. 10 mL round-bottomed flask and arrange for. The reaction apparatus is setup as follows (all items mustbe clean and dry): 1.