-CN

Definition

-CN, also known as the cyano group, is a functional group consisting of a carbon atom triple-bonded to a nitrogen atom. It is commonly encountered in the context of nucleophilic aromatic substitution reactions, where it can serve as a leaving group or a directing group, influencing the reactivity and regioselectivity of the substitution process.

5 Must Know Facts For Your Next Test

1. The -CN group is a strong electron-withdrawing group, which makes the aromatic ring more susceptible to nucleophilic attack.
2. When -CN is present as a leaving group, it can be readily displaced by a nucleophile, facilitating the substitution reaction.
3. As a directing group, -CN can direct the incoming nucleophile to the ortho or para position relative to its own position on the aromatic ring.
4. The reactivity of the -CN group in nucleophilic aromatic substitution is influenced by the nature of the other substituents on the aromatic ring.
5. The presence of other electron-withdrawing groups, such as nitro (-NO₂) or halogen (-X) groups, can further enhance the reactivity of the -CN group in these reactions.

Review Questions

• Explain how the -CN group can influence the reactivity of an aromatic ring in nucleophilic aromatic substitution reactions.
  • The -CN group is a strong electron-withdrawing functional group, which increases the electrophilicity of the aromatic ring. This makes the ring more susceptible to nucleophilic attack, facilitating the nucleophilic aromatic substitution process. Additionally, the -CN group can serve as a leaving group, allowing it to be readily displaced by a nucleophile during the substitution reaction.
• Describe the role of the -CN group as a directing group in nucleophilic aromatic substitution reactions.
  • The -CN group can act as a directing group in nucleophilic aromatic substitution reactions, influencing the regioselectivity of the substitution. Specifically, the -CN group can direct the incoming nucleophile to the ortho or para position relative to its own position on the aromatic ring. This is due to the electron-withdrawing nature of the -CN group, which stabilizes the intermediate formed during the substitution process at these specific positions on the ring.
• Analyze how the presence of other electron-withdrawing groups on the aromatic ring can affect the reactivity of the -CN group in nucleophilic aromatic substitution reactions.
  • The reactivity of the -CN group in nucleophilic aromatic substitution reactions can be further enhanced by the presence of other electron-withdrawing groups on the aromatic ring, such as nitro (-NO₂) or halogen (-X) groups. These additional electron-withdrawing substituents increase the overall electrophilicity of the aromatic ring, making it even more susceptible to nucleophilic attack. This synergistic effect between the -CN group and other electron-withdrawing groups can significantly improve the reactivity and efficiency of the nucleophilic aromatic substitution process.

Related terms

Nucleophilic Aromatic Substitution: A type of aromatic substitution reaction where a nucleophile replaces a leaving group on an aromatic ring, typically in the presence of an activating group such as -CN.

Leaving Group: A functional group or atom that is displaced during a substitution reaction, allowing a new group to be introduced in its place.

Directing Group: A functional group that influences the regioselectivity of an aromatic substitution reaction, directing the incoming group to a specific position on the ring.