Expt. 14.1 A The Grignard Synthesis of Triphenylmethanol

1. Expt. 14.1 A The Grignard Synthesis of Triphenylmethanol

2. Bonjour, Monsieur Grignard One of the most useful synthetic reactions ever developed Victor Grignard French chemist (1871-1935) 1912 Nobel Prize

3. The Grignard Reaction RX + Mg ? RMgX (the Grignard reagent) “R” has substantial carbanion character Able to form new carbon-carbon bonds The Grignard reaction is very versatile “R” can be 1o, 2o, or 3o alkyl, cycloalkyl, alkenyl, or aryl A common synthetic pathway to various alcohols and carboxylic acids

4. The Grignard Reaction RMgX + formaldehye ? 1o alcohols RMgX + aldehydes ? 2o alcohols RMgX + ketones ? 3o alcohols RMgX + esters ? 3o alcohols RMgX + CO2 ? carboxylic acids

5. Reaction Step 1: Preparation of Grignard Reagent

6. Reaction Step 3: Hydrolysis to form the alcohol

7. Competing Reactions

8. Pre-lab Preparation – week 1 Read/Review Experiment 14.1 – Background and Part A Technique G – Reflux Technique F – Recrystallization Carey Ch 14 Prepare notebook (see Syllabus examples) Header information Purpose Procedural reference (title, authors, edition, pages) Table of reagents & products For each reactant, solvent, and product (triphenylmethanol and biphenyl only) include structure, molecular weight, melting or boiling point as appropriate, density or concentration and hazards.

9. Pre-lab Preparation – week 1 Prepare notebook (continued) Chemical reaction Formation of triphenylmethanol only Limiting reagent and theoretical yield Use quantities in the lab text Procedures Two-column format You may include the procedures for both weeks or just week one. During this first week, we will get through the addition of the 3M HCl.

10. Tips for week one No need to polish the Mg Be sure to set up the Claisen adapter as in the diagram on page 354. The condenser has to go on the side arm!! Syringes Be sure the needles are on tight Properly dispose of needles and syringes Remove the CaCl2 from the drying tube at the end of the day; else it becomes a solid mass. Regular trash can OK.

11. More Week One Tips Drawing the bromobenzene/ether solution into the syringe Since the ether is very volatile, you must equilibrate the syringe and the ether solution With the cap OFF the conical vial, pull a small amount into the syringe and expel back into the vial. Repeat at least two more times; each time increasing the amount of ether pulled into the syringe When adding the ether solution to the Mg, start by adding ~ 1 mL.

12. Pre-lab Preparation – week 2 Construct a flowchart for the isolation, and purification of triphenylmethanol Template will be provided in lab this week; fill in the parts that are missing. Due at the start of class on Week 2 This entire procedure will be a good test of your lab skills. You will need to come prepared and work efficiently.