How do you titrate Grignard reagents?

1 Answer
anor277
Aug 21, 2016

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 #RMgX# into water to give #R-H# and #MgXOH#; an aqueous titration to a stoichometric endpoint follows with standardized #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# #mL# syringe with #0.01*mL# graduations. Diphenyl acetic acid, #Ph_2CHCO_2H#, in ether is used as the standard. Addition of #1# #"equiv Grignard"# gives #Ph_2CHCO_2^(-)MgBr + RH#. The second equiv of Grignard gives #Ph_2C^(-)CO_2^-#, which is noticeably yellow. Other such reagents exist.

Related questions
See all questions in Quick Introduction of Structures
Impact of this question
4597 views around the world
You can reuse this answer
Creative Commons License