Answer :
Final answer:
A feasible Grignard reagent must not contain functional groups with acidic hydrogens or electrophilic entities, preventing successful preparation from halo alcohol due to incompatibility with the C-Mg bond of the Grignard reagent.
Explanation:
Not all functional groups are compatible with Grignard reagents. A Grignard reagent cannot be prepared from halo alcohol or other substrates containing functional groups with acidic hydrogens. This limitation is due to the strong base nature of Grignard reagents; they will deprotonate acidic hydrogens present in groups like alcohols (ROH), carboxylic acids (RCO₂H), thiols (RSH), and terminal alkynes (RC≡CH), among others, instead of performing the intended nucleophilic addition to a carbonyl. For example, attempting to prepare a Grignard reagent in the presence of an alcohol group will not be successful, as the Grignard reagent will react with the alcohol before it can attack a carbonyl, leading to the formation of a hydrocarbon instead of the desired organometallic compound.
Therefore, a feasible Grignard reagent is one that is not only devoid of acidic hydrogens but is also free from electrophilic functional groups that could react with the organometallic compound itself, such as carbonyl groups, C=N, nitriles, N=O, and S=O. This principle is crucial for predicting reactivity patterns in organic synthesis and for preparing alcohols from Grignard reagents through effective ascension in a homologous series.
