Match list I (reactants which react with Grignard reagent, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{MgBr}\) ) with list II (products obtained in the reaction) and select the correct answer. List I 1\. Ethanol 2\. Ethylene chlorohydrin 3\. Acetaldehyde 4\. Ethylene oxide List II (1) butan-1-ol (2) butan-2-ol The correct matching is: 1 2 3 4 (a) (1) \(\quad\) (2) \(\quad(-)\) (b) (1) (2) (1) (-) (c) \((-)\) (1) (2) (1) (d) (1) \(\quad(-)\) (2) (2)

Organometallic compounds are chemical species that feature bonds between carbon and a metal. They are central to many synthetic reactions due to their high reactivity, particularly with polar bonds. In the case of the Grignard reagents, such as \( C_2H_5MgBr \), the organic moiety \( (C_2H_5)^- \) functions as a nucleophile, meaning it can donate a pair of electrons, and is thus highly reactive towards electrophilic centers, like those found in carbonyl compounds.

One essential aspect of organometallics like the Grignard reagents is their sensitivity to water and other protic substances, such as alcohols. Even the acidic hydrogen of alcohols can lead the organometallic compound to degrade, yielding a hydrocarbon instead of participating in the intended transformation. This is precisely what occurs when a Grignard reagent is exposed to ethanol; the reaction stops at ethane, making it an unproductive route for synthetic purposes.

The versatility of organometallics in creating new carbon-carbon bonds is what makes them indispensable in modern synthetic organic chemistry.

Carbonyl group reactions are pivotal in organic chemistry and are characterized by the reactivity of the carbon double bonded to an oxygen (\( C=O \) group). This carbon is electrophilic, which means it seeks out electrons and thus, is an attractive target for nucleophilic attack. Grignard reagents, when encountered with a carbonyl compound such as acetaldehyde, will attack the electrophilic carbonyl carbon, forming an alkoxide intermediate.

The mechanism unfolds as the nucleophilic carbon from the Grignard reagent forms a new carbon-carbon bond with the carbonyl carbon. After the addition of water during the work-up (hydrolysis), the alkoxide intermediate is protonated to produce a secondary alcohol. In our exercise, the acetaldehyde, a two-carbon aldehyde, reacts with ethyl magnesium bromide to ultimately form butan-2-ol upon hydrolysis, showing how a simple carbonyl compound can be built into a more complex alcohol through a Grignard addition.

Epoxides, or oxiranes, are three-membered cyclic ethers that are considerably strained due to their ring size. This strain makes them highly reactive, particularly towards ring-opening reactions. Grignard reagents are effective nucleophiles for initiating epoxide ring opening due to their ability to attack the less sterically hindered carbon atom of the epoxide.

In the presence of the Grignard reagent, the epoxide's strained ring is cleaved, and a new carbon-carbon bond is formed. This reaction proceeds with the formation of a new alkoxide, which, upon subsequent hydrolysis, yields an alcohol. For example, ethylene oxide reacts with ethyl magnesium bromide to generate a chain-extended alcohol, specifically butan-1-ol, once water is added to the reaction. This transformation highlights the utility of Grignard compounds in opening small rings like epoxides to create larger organic molecules with functional alcohol groups.