Lab Report 7, Grignard Reaction, Triphenyl Methanol Synthesis

Lab Report #7

Vishal Dasari

TA Adrienne Pesce

Grignard Synthesis: Preparation of Triphenylmethanol

Introduction: Main Reaction and Mechanism:

Included in PreLabs Included in PreLabs

Table of Reactants: Included in Prelabs Limiting Reagents: Included in Prelabs

Table of Products: Included in Prelabs

Yield Data:

Part 1: Esterification: Methyl Benzoate

• Benzoic Acid (122.12g/mol) = 5.63g = 0.046mol

• Methanol volume = 12ml

• Sulfuric Acid = 1.5ml

• Theoretical Methyl Benzoate mass (136.15g/mol) = 0.046mol = 6.28g

• Product Methyl Benzoate mass = 3.16g

o % Yield = (experimental yield/theoretical yield)*100 = 50.32%

• Recovered Benzoic Acid mass = 0.07g

o Melt Temp = 122.1oC-122.3oC

Part 2: Grignard Synthesis: Phenylmagnesium Bromide; Triphenylmethanol

• Magnesium mass = 0.5g (preweighed) = 0.021mol mixed with 2ml anhydrous ether

• Bromobenzene volume = 2ml = 0.019mol

• Methyl Benzoate volume = 1.2ml = 0.010mol mixed with 5ml anhydrous ether

• Crude Triphenylmethanol product = yellow crystals

• Pure Triphenylmethanol (260.33g/mol) product (white crystals) = 0.89g = 0.00342mol

o % Yield = (Experimental yield/theoretical yield)*100 = (0.89/2.6)*100 = 34.23%

o Melt Temp = 160.9oC-161.3oC

Synopsis and Notes on Experimental Procedure:

Part 1: Esterification: Methyl Benzoate

- 5.63g benzoic acid and 12ml methanol are mixed in a 50ml Rb flask. 1.5ml conc sulfuric acid is added and the mixture is put through reflux for 45 minutes. The mixture is washed with 20ml water and 20ml dichloromethane, the latter of which is also used to wash out the reaction flask. The dichloromethane layer is washed again with 20ml water and then with 20ml 5% sodium bicarbonate solution.

- When aqueous layer is basic, the layers are separated. Organic layer is washed with 20ml brine to make it less cloudy, then it is dried over sodium sulfate. Clear organic layer is rotavapped and the product is put through simple distillation. This slightly cloudy...