Formaldehyde reacts with which one of the following to give primary alcohols?
Correct answer: C. Grignard's reagant
- A. Fehling's reagent
- B. Benedict's reagent
- C. Grignard's reagant
- D. Millon's reagant
Explanation
Formaldehyde (HCHO) can react with Grignard reagents (RMgX, where R is an alkyl or aryl group and X is a halogen) to form primary alcohols through a nucleophilic addition reaction. Here's the general reaction scheme: Formation of Grignard Reagent: RMgX + Mg → R-Mg-X Nucleophilic Addition of Grignard Reagent to Formaldehyde: R-Mg-X + HCHO → R-CH(OH)-R The Grignard reagent acts as a nucleophile, attacking the electrophilic carbon of formaldehyde, which is the carbonyl group (C=O). The reaction results in the formation of an intermediate alkoxide compound. Subsequently, protonation occurs to give the primary alcohol. C2H5MgBr + HCHO → C2H5-CH(OH)-H In this case, the product is ethyl alcohol (C2H5OH), which is a primary alcohol. The Grignard reagent adds to the carbonyl carbon of formaldehyde, resulting in the formation of the alcohol moiety.
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About Alcohols and Phenols
Alcohols are classified as primary, secondary or tertiary and studied through their hydrogen bonding, acidity, oxidation and reactions with active metals, acids and halogenating agents. Phenols require separate treatment because the hydroxyl group is attached to an aromatic ring, making their acidity and electrophilic substitution different from ordinary alcohols.
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