Experiment 7 - Grignard Synthesis

Parth Patel Mark Fegley

4/5/2011 Experiment #7

Grignard Synthesis: Preparation of Triphenylmethanol

Reference: Experimental Organic Chemistry: A Miniscale and Microscale Approach, 5th ed.

By Gilbert and Martin, Sections 19.2-19.3, 20.1-20.2

Lab Manual Pages 63-70

Pre-Labs for Days 1 and 2

See attached copies of laboratory notebook submissions.

Yield Data: Theoretical and Observed

A. Fischer Esterification of Benzoic Acid to Methyl Benzoate

Esterification |

Mass Used – Benzoic Acid (L.R.) | 5.03 g |

Moles Used – Benzoic Acid | 0.04094 mol |

Moles Expected – Methyl Benzoate | 0.04094 mol |

Mass Expected – Methyl Benzoate | 5.574 g |

Mass Observed – Methyl Benzoate | 3.29 g |

Percent Yield – Methyl Benzoate | 59.0% |

B. Grignard Addition of Phenylmagnesium Bromide to form Triphenylmethanol

Grignard Addition |

Mass Used – Methyl Benzoate | 1.32 g |

Moles Used – Methyl Benzoate | 0.010 mol |

Moles Expected – Triphenylmethanol | 0.010 mol |

Mass Expected – Triphenylmethanol | 2.603 g |

Mass Observed – Triphenylmethanol | 1.05 g |

Percent Yield – Triphenylmethanol | 40.3% |

Experimental Notes and Observations

A. Fischer Esterification of Benzoic Acid to Methyl Benzoate [3-22-2011]

* Obtained 50 mL round bottom flask. Added 5.03 g benzoic acid, 12.5 mL methanol, and large magnetic stirbar. Pipetted 1.5 mL of concentrated H2SO4 into the flask.

* Set up reflux apparatus. Heated with thermowell at 70 V, with stirring, for 45 minutes.

* Transferred to cold water bath to cool reaction flask.

* Meanwhile, set up separatory funnel, and added 20 mL H2O.

* Washed reaction flask by adding 20 mL CH2Cl2, and added entire mixture to the water in the separatory funnel.

* Extracted lower (organic) layer into Erlenmeyer flask. Discarded the remaining aqueous layer.

* Reinserted organic layer into the sep funnel. Added another 20 mL...