How do you titrate Grignard reagents?

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How do you titrate Grignard reagents?

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Answer 1 · 2016-08-21T10:07:07

Simply take a known volume of the Grignard, dump it into water, and then titrate to a stoichiometric endpoint.

Explanation:

From above, we drop a solution of $R M g X$ $RMgX$ into water to give $R - H$ $R-H$ and $M g X O H$ $MgXOH$ ; an aqueous titration to a stoichometric endpoint follows with standardized $H C l (a q)$ $HCl(aq)$ .

Alternatively, there are indicators that you could dissolve up in dry ether, and titrate to an endpoint with the Grignard in ethereal solution. This is a bit more of a pfaff, but is still doable. The Grignard could even be used as the titrant; in which case we would typically use a $1$ $1$ $m L$ $mL$ syringe with $0.01 \cdot m L$ $0.01*mL$ graduations. Diphenyl acetic acid, $P h_{2} C H C O_{2} H$ $Ph_2CHCO_2H$ , in ether is used as the standard. Addition of $1$ $1$ $equiv Grignard$ $"equiv Grignard"$ gives $P h_{2} C H C O_{2}^{-} M g B r + R H$ $Ph_2CHCO_2^(-)MgBr + RH$ . The second equiv of Grignard gives $P h_{2} C^{-} C O_{2}^{-}$ $Ph_2C^(-)CO_2^-$ , which is noticeably yellow. Other such reagents exist.

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How do you titrate Grignard reagents?

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