Grignard Reaction Lab Report
The purpose of this experiment was to synthesize triphenylmethanol from a Grignard reagent. The Grignard reaction technique was used in this synthesis but due to the fact that it is such a strong nucleophile and base, it was important to prevent water from interfering with the Grignard reaction. Purity of the product was determined by measuring the melting point.
Reagent Table:
Structure Name Molecular formula
Molar mass
Density
Melting point
Boiling Point
Diethyl ether C4H10O 74.12 g mol− 0.7134 g/cm3, liquid -116.3 °C, 157 K, -177 °F 34.6 °C, 308 K, 94 °F
Bromobenzene C6H5Br 157.01 g mol−1 1.495 g/cm³, liquid -30.8 °C (242.35 K) 156 °C (429.15 K)
Phenylmagnesium bromide C6H5MgBr 181.31 g/mol 1.14 …show more content…
This is where you can find the following instruction for this experiment. In the pre-lab notebook the experiment is explained in full details which will specify that there were no changes made to the experiment.
Calculations:
Theoretical Yields:
1.094g benzophenone * (1 mol benzophenone/ 182.22 g benzophenone) = 0.006003732 mol benzophenone
0.006003732 mol benzophenone * (1 mol triphenylmethanol/1 mol benzophenone) * (260.33 g triphenylmethanol/ 1 mol triphenylmethanol) = 1.562951552 g triphenylmethanol
0.681 g triphenylmethanol/ 1.562 g triphenylmethanol = 0.435
Percent yield = 43.5 %
Product Theoretical
Yield Actual
Yield %
Actual Yield Actual
m.p Literature
m.p
Triphenylmethanol 1.562g 0.423g 43.5% 156-160 162 …show more content…
The melting point range for the product was determined to be 156-160°C, and the literature melting point is 162°C. The product contains some impurities; one of the impurities contributing to the difference of melting point from the literature melting point might have been biphenyl. This by-product is formed as a result of radical pairing of the Grignard reagent with unreacted bromobenzene. To decrease the formation of the biphenyl, the bromobenzene was added slowly to maintain a low concentration. Before starting this experiment we were explicably told to have all glassware was dried to insure no water. However water could have still gotten into the reaction and this would react with the Grignard reagent, causing a reduction of the phenyl magnesium bromide to the hydrocarbon benzene. This would contaminate our product, consequently lowering our melting point. To avoid this contaminate, the glassware used was dried and the apparatus was closed with calcium chloride and a cotton ball. During the experiment we also had to avoid some of the Grignard reagent reacting with carbon dioxide which may have gotten into the reaction apparatus and interfered with the purity of our product. Another possible reason for low product was several transfers of product to different flasks, and it’s likely that some of the product remained in the flask even after proper rinsing of the
Reagent Table:
Structure Name Molecular formula
Molar mass
Density
Melting point
Boiling Point
Diethyl ether C4H10O 74.12 g mol− 0.7134 g/cm3, liquid -116.3 °C, 157 K, -177 °F 34.6 °C, 308 K, 94 °F
Bromobenzene C6H5Br 157.01 g mol−1 1.495 g/cm³, liquid -30.8 °C (242.35 K) 156 °C (429.15 K)
Phenylmagnesium bromide C6H5MgBr 181.31 g/mol 1.14 …show more content…
This is where you can find the following instruction for this experiment. In the pre-lab notebook the experiment is explained in full details which will specify that there were no changes made to the experiment.
Calculations:
Theoretical Yields:
1.094g benzophenone * (1 mol benzophenone/ 182.22 g benzophenone) = 0.006003732 mol benzophenone
0.006003732 mol benzophenone * (1 mol triphenylmethanol/1 mol benzophenone) * (260.33 g triphenylmethanol/ 1 mol triphenylmethanol) = 1.562951552 g triphenylmethanol
0.681 g triphenylmethanol/ 1.562 g triphenylmethanol = 0.435
Percent yield = 43.5 %
Product Theoretical
Yield Actual
Yield %
Actual Yield Actual
m.p Literature
m.p
Triphenylmethanol 1.562g 0.423g 43.5% 156-160 162 …show more content…
The melting point range for the product was determined to be 156-160°C, and the literature melting point is 162°C. The product contains some impurities; one of the impurities contributing to the difference of melting point from the literature melting point might have been biphenyl. This by-product is formed as a result of radical pairing of the Grignard reagent with unreacted bromobenzene. To decrease the formation of the biphenyl, the bromobenzene was added slowly to maintain a low concentration. Before starting this experiment we were explicably told to have all glassware was dried to insure no water. However water could have still gotten into the reaction and this would react with the Grignard reagent, causing a reduction of the phenyl magnesium bromide to the hydrocarbon benzene. This would contaminate our product, consequently lowering our melting point. To avoid this contaminate, the glassware used was dried and the apparatus was closed with calcium chloride and a cotton ball. During the experiment we also had to avoid some of the Grignard reagent reacting with carbon dioxide which may have gotten into the reaction apparatus and interfered with the purity of our product. Another possible reason for low product was several transfers of product to different flasks, and it’s likely that some of the product remained in the flask even after proper rinsing of the