Synthesis of Triphenylmethanol

Topics: Magnesium, Diethyl ether, Grignard reaction Pages: 9 (2645 words) Published: April 14, 2012
This report presents the synthesis of triphenylmethanol from magnesium, bromobenzene, and benzophenone. A reflux apparatus was used to carry out most of the experiment. A great deal of color changes were noted throughout this process.

Triphenylmethanol was successfully synthesized, as can be verified by the IR that was obtained. The melting point was found to be 98.30°C- 146.2°C and the percent yield of triphenylmethanol was calculated to be 61.2%. Introduction

One of the most useful reactions to organic chemists, are those which can form carbon-carbon bonds. The Grignard reaction is one method by which to so.
Discovered by Victor Grignard, who received the Nobel Prize for his discovery in 1912, “the Grignard reaction involves the nucleophilic addition of an organomagnesium complex to a carbonyl carbon, followed by acid work-up” (Lab Manual, 69). Through carefully deciding which carbonyl compound to use, it is possible, using the Grignard reaction, to synthesize a primary, secondary, or tertiary alcohol.

The reaction is first started by forming a “Grignard reagent,” also known as an organomagnesium compound (Vollhardt, 305). This reagent is easily formed by reacting a haloalkane with a metal (either lithium or magnesium) suspended in diethyl ether or tetrahydrofuran (THF) (Vollhardt, 304).

“Grignard reagents are rarely isolated,” after formation, they are usually used immediately in the desired reaction (Vollhardt, 305). Since Grignard reagents are sensitive to both air and moisture, “they must be prepared and handled under rigorously air- and water-free conditions” (Vollhardt, 305). Once formed, the reagent will act similar to a Lewis acid, and attach to molecules which are Lewis basic, or will be solvated by the unshared pairs of electrons on the solvent (diethyl ether or THF).

The Grignard reagent will also act as a strong base and strong nucleophile. The reagent will react with protons which are more acidic than those on alkenes and alkanes; for this reason, the reagent will react readily with things such as water, alcohols, and amines to form an alkane.

After formation of the Grignard reagent, a carbonyl-containing compound can then be added to the solution. Upon its addition, a magnesium alkoxide will be produced. After the production of the magnesium alkoxide, the final step of the Grignard reaction is hydrolysis. Hydrolysis performed by a mineral acid, will produce the final alcohol.

A generalized Grignard reaction scheme can be viewed below.

Reagent Table

Name/ StructureMolecular Weight (g/mol)Amount Used
(g, mL, or mol)ConcentrationDensity (g/mL)Melting Point (°C)Boiling Point (°C)Safety Note Magnesium

24.31 g/mol1.50g1.74 g/mL651.0°C1100°CMay be irritating to skin, eyes, and mucous membranes; reaction with water yields flammable gas Iodine Crystal

253.81 g/mol4.93 g/mL113.7°C184.4°CHarmful if swallowed or inhaled Anhydrous Ethyl Ether

74.12 g/mol205.0mL0.713 g/mL-116.3°C34.60°CCauses skin irritation, and irritation to respiratory tract and mucous membranes Bromobenzene

157.02 g/mol5.30mL1.50 g/mL-30.60°C156.2°CHazardous in case of eye contact, skin contact, ingestion, or inhalation Benzophenone

182.22 g/mol

9.18g1.11 g/mL49.00°C305.4°CHazardous in case of skin contact, eye contact, ingestion, or inhalation Name/ StructureMolecular Weight (g/mol)Amount Used
(g, mL, or mol)ConcentrationDensity (g/mL)Melting Point (°C)Boiling Point (°C)Safety Note Sulfuric Acid

98.08 g/mol4.50mL1.84 g/mL-35.00°C to 10.36°C270.0°C to 340.0°CCan cause eye damage, burns, and respiratory irritation at high concentrations Methanol

32.04 g/mol200.0mL0.792 g/mL-97.8°C64.5°CToxic to eyes; repeated exposure may produce general deterioration of health Triphenylmethanol

260.34 g/mol8.03g1.20 g/mL160.0°C to 163.0°C360.0°CMay be harmful is swallowed, inhaled, or absorbed...

References: Huston, Ericka, Ryan Weiss, Nicole Kennedy, and George Bandik. Chem 0340: Organic Chemistry II
Laboratory Manual. Plymouth: Hayden-McNeil Publishing, 2012. 69. Print.
Vollhardt, Peter, and Neil Schore. Organic Chemistry: Structure and Function. 6th. New York: W.H.
Freeman and Company, 2011. 304-305. Print.
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