Question

With reference to the carbonyl group which statement(s) is/are correct? a) Carbonyl Carbon is electrophilic b) Carbonyl Carbon is nucleophilic c) Carbonyl Oxygen is electrophilic d) Carbonyl Oxygen is nucleophilic

• A. a, d
• B. b, c
• C. b only
• D. c only

Hint:

The C=O bond in a carbonyl group is polar due to oxygen being more electronegative than carbon.
Carbonyl Carbon (C$^{\delta+}$): Electron-deficient, acts as an electrophile (site of nucleophilic attack).
Carbonyl Oxygen (O$^{\delta-}$): Electron-rich (has lone pairs), acts as a nucleophile or Lewis base (can be protonated or coordinate to Lewis acids).
Electrophile: Electron seeker (positive or partially positive center).
Nucleophile: Electron donor (negative or partially negative center with lone pairs or $\pi$ electrons).

Answer 1

The Correct Option is A

The carbonyl group consists of a carbon atom double-bonded to an oxygen atom (C=O). Oxygen is more electronegative than carbon. This leads to a polarization of the C=O double bond: \begin{itemize} \item The oxygen atom carries a partial negative charge ($\delta-$). \item The carbon atom carries a partial positive charge ($\delta+$). \end{itemize} C$^{\delta+}$=O$^{\delta-}$ Let's analyze the statements based on this polarity: a) Carbonyl Carbon is electrophilic An electrophile ("electron-loving") is an atom, ion, or molecule that is electron-deficient and seeks electrons. The carbonyl carbon has a partial positive charge ($\delta+$) due to the electronegative oxygen pulling electron density away from it. This makes the carbonyl carbon electron-deficient and thus electrophilic. It is susceptible to attack by nucleophiles. This statement is correct. b) Carbonyl Carbon is nucleophilic A nucleophile ("nucleus-loving") is an atom, ion, or molecule that is electron-rich and donates an electron pair to form a bond with an electrophile. The carbonyl carbon is electron-deficient ($\delta+$), not electron-rich. Therefore, it is not nucleophilic. This statement is incorrect. c) Carbonyl Oxygen is electrophilic The carbonyl oxygen has a partial negative charge ($\delta-$) due to its higher electronegativity. It is electron-rich, not electron-deficient. Therefore, it is not electrophilic. This statement is incorrect. d) Carbonyl Oxygen is nucleophilic The carbonyl oxygen is electron-rich ($\delta-$) and typically has lone pairs of electrons (two lone pairs in a standard C=O group). These lone pairs can be donated to an electrophile (e.g., a proton H$^+$ in acid catalysis, or a Lewis acid). Thus, the carbonyl oxygen can act as a nucleophile or a Lewis base. This statement is correct. So, the correct statements are (a) and (d). This corresponds to option (a). \[ \boxed{\text{a, d}} \]