Each of these compounds can react as an electrophile. In each case, use curved arrows to show how the electrophile would react with the strong nucleophile sodium ethoxide, Na^{+ −}OCH₂CH₃.
a.
b. NH₄⁺

Verified step by step guidance

1. Identify the electrophilic center in each compound. For compound (a), the carbonyl carbon is electrophilic due to the polarization of the C=O bond. For compound (b), the nitrogen atom in NH4+ is electrophilic due to its positive charge.
2. Consider the nucleophile, sodium ethoxide (Na+ −OCH2CH3). The ethoxide ion (−OCH2CH3) is a strong nucleophile due to the presence of a negatively charged oxygen atom.
3. For compound (a), draw a curved arrow from the lone pair on the oxygen atom of the ethoxide ion to the electrophilic carbonyl carbon. This represents the nucleophilic attack on the carbonyl carbon.
4. For compound (b), draw a curved arrow from the lone pair on the oxygen atom of the ethoxide ion to the nitrogen atom in NH4+. This represents the nucleophilic attack on the positively charged nitrogen.
5. After the nucleophilic attack, consider the possible rearrangements or changes in bonding. For compound (a), the carbonyl oxygen may become negatively charged, and for compound (b), the nitrogen may lose a proton, resulting in NH3.

Key Concepts

Electrophiles

Electrophiles are species that accept electron pairs from nucleophiles during chemical reactions. They are typically positively charged or have a partial positive charge, making them attractive to electron-rich species. In the context of organic reactions, understanding the nature of electrophiles is crucial for predicting reaction pathways and mechanisms.

Nucleophiles

Nucleophiles are electron-rich species that donate an electron pair to electrophiles in a chemical reaction. They can be negatively charged ions or neutral molecules with lone pairs of electrons. Recognizing the strength and reactivity of nucleophiles, such as sodium ethoxide in this case, is essential for understanding how they interact with electrophiles.

Curved Arrows in Mechanisms

Curved arrows are used in organic chemistry to illustrate the movement of electron pairs during chemical reactions. The tail of the arrow indicates the source of the electrons, while the head points to the destination. Mastery of using curved arrows is vital for accurately depicting reaction mechanisms and understanding how reactants transform into products.