Identify the electrophile and the nucleophile in each of the following reaction steps. Then draw curved arrows to illustrate the bond-making and ­bond-breaking processes.
a.

Verified step by step guidance

1. Step 1: Analyze the reactants. The molecule H₃CC≡CH with the positively charged iodine (I⁺) is the electrophile because it has an electron-deficient iodine atom. The negatively charged iodide ion (I⁻) is the nucleophile because it has a lone pair of electrons and is electron-rich.
2. Step 2: Identify the interaction between the electrophile and nucleophile. The nucleophile (I⁻) will attack the electrophile (I⁺) to form a new bond.
3. Step 3: Draw the curved arrow to represent the bond-making process. The curved arrow should start from the lone pair of electrons on the nucleophile (I⁻) and point toward the positively charged iodine atom (I⁺) in the electrophile.
4. Step 4: Illustrate the bond-breaking process. The bond between the positively charged iodine atom (I⁺) and the carbon atom in the electrophile will break, transferring the electrons to the carbon atom. Draw a curved arrow starting from the bond and pointing toward the carbon atom.
5. Step 5: Confirm the product structure. The final product will show the iodine atom (I⁻) bonded to the carbon atom, and the triple bond remains intact. Ensure the lone pairs on iodine are correctly represented in the product structure.

Key Concepts

Electrophiles

Electrophiles are species that accept electron pairs from nucleophiles during chemical reactions. They are typically positively charged or neutral molecules with an electron-deficient atom, making them attractive to electron-rich species. In the provided reaction, the positively charged carbon in the alkene acts as the electrophile, seeking electrons to form new bonds.

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. In the reaction shown, the negatively charged species (likely a carbanion or similar) acts as the nucleophile, attacking the electrophilic carbon to form a new bond.

Curved Arrows in Mechanisms

Curved arrows are used in organic chemistry to illustrate the movement of electron pairs during bond-making and bond-breaking processes. The tail of the arrow indicates the electron source (where the electrons are coming from), while the head points to the electron destination (where the electrons are going). In the reaction, curved arrows will show how the nucleophile donates electrons to the electrophile and how bonds are formed or broken.