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Experiment 12 Discussion
Discussion assignment for experiment 12
Course
Organic Chemistry Lab II (CHEM201401)
46 Documents
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University
Boston College
Academic year: 2022/2023
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Experiment 12 Discussion
Course: Organic Chemistry Lab II (CHEM201401)
46 Documents
Students shared 46 documents in this course
University: Boston College
Was this document helpful?
The objective of this experiment was to synthesize triphenylmethanol via a Grignard
reagent. Bromobenzene was first reacted with magnesium metal to form phenylmagnesium
bromide, which is the Grignard reagent used to form new carbon-carbon bonds. After this part of
the reaction was completed, the solution had turned brown. This corresponds to the formation of
phenylmagnesium bromide as the appearance of this compound is amber to brown in liquid
form. The phenylmagnesium bromide was then reacted with methyl benzoate resulting in a
solution that first became dark reddish-purple in color, then became a pinkish-orangish-light
brown, and finally settled on light brown. Also, heat was generated during the reaction. In this
part of the experiment, the phenylmagnesium bromide acted as a nucleophile and attacked the
methyl benzoate to form a new carbon-carbon bond. This reaction is exothermic which
corresponds to the heat that was generated. The color change corresponds to the formation of
triphenyl methoxide magnesium bromide, the magnesium alkoxide intermediate. Finally, this
intermediate was hydrolyzed, and the solution became yellow and produced white crystals upon
purification. This corresponds to the formation and isolation of triphenylmethanol.
I recovered 2.749 grams of triphenylmethanol, which is less than the theoretical yield of
9.622 grams. The calculated percent yield was 28.57%. This low yield could have been the result
of side-reactions occurring, like between phenylmagnesium bromide and bromobenzene to
produce biphenyl, or it could have been the result of some of the reagents not fully reacting. The
experimental melting range of triphenylmethanol was 160.7–163.3°C. This is very close to the
given melting range, which is 160–163°C. This suggests that the product was highly purified and
there was minimal impurity still present.
