Expt. 14.1 A

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• Expt. 14.1 A
• The Grignard Synthesis of Triphenylmethanol

Chem 334
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Bonjour, Monsieur Grignard

• One of the most useful synthetic reactions ever
  developed
• Victor Grignard
• French chemist (1871-1935)
• 1912 Nobel Prize

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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

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The Grignard Reaction

• RMgX formaldehye ? 1o alcohols
• RMgX aldehydes ? 2o alcohols
• RMgX ketones ? 3o alcohols
• RMgX esters ? 3o alcohols
• RMgX CO2 ? carboxylic acids

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Reaction

• Step 1 Preparation of Grignard Reagent

Step 2 Reaction of Grignard Reagent with the
ketone
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Reaction

• Step 3 Hydrolysis to form the alcohol

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Competing Reactions
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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.

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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.

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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.

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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.

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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.