Spring 2018 Chem. 234--3petio Prelab: Synthesis of Triphenylmethane Dyes Date La

Question

Spring 2018 Chem. 234--3petio Prelab: Synthesis of Triphenylmethane Dyes Date Lab Section_ Name Mohrig et al. p. 203-209 and the modifications handout on Canvas lassware and solvent for the Grignard reaction to make the Provide the unwanted reaction (show the structures) that for th 1. It is important that the dyes are completely dry. would occur if water is introduced into the reaction when making the Grignard reagent. Which dye did you make? Based on the theoretical amounts you will use in this experiment determine the ratio of equivalents of 4-bromo-N,N diemethylaminobenzene to ester used to form the dye you will make. Show al 2. work. 3. Diethyl ether is often used as solvent for Grignard reactions but in this experiment you use THF as your solvent. Draw the structure of THF and explain why it is used in this experiment instead of diethyl ether. ester is added to your Grignard solution?

Explanation / Answer

1. water react irreversibly with Grignard reagent, the molecular mass of water is so low that a little goes a long way, and ineptly dried solvent or glassware will seriously reduce your yield. The reaction of a Grignard with water:

RMgX+H2ORH+MgX(OH).

This is very facile, and will occur even with atmospheric moisture.

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