Question

Hello, in the image attached below, why cant we form a gringard in the presence of the OH?

HO NaCN HO H30+ НО, CI H2O heat OH 2-Chloroethanol 2-Cyanoethanol 3-Hydroxypropanoic acid The presence of the hydroxyl group in 2-chloroethanol precludes the preparation of a Grignard reagent from this material, and so any attempt at the preparation of 3-hydroxypropanoic acid via the Grignard reagent of 2-chloroethanol is certain to fail.

Answer 1

Grignard reagent has the alkyl group with negative polarity , which acts as a strong nucleophile as well a strong base also.

Thus if the substrate has an acidic proton like -OH, -NH2 , -COOH or with water the Grignard reagent undergoes acid-base reaction rather than nucleophilic substitution/addition.

If the -OH is within the same species it destoys itself and no further Grignard reaction takesplace.

Mg Br ₃ CHz öreg Bre R-H PR 3 е-ни FTN t + R Me Br tig W rad u Mgom proce is the ether NOT Hon Mg ca.