Benzonitrile

Definition

Benzonitrile is an aromatic nitrile compound with the chemical formula C6H5CN. It is a colorless, flammable liquid with a distinctive almond-like odor. Benzonitrile is an important organic compound that is relevant in the context of spectroscopy of carboxylic acids and nitriles, as well as the basicity of arylamines.

5 Must Know Facts For Your Next Test

1. Benzonitrile exhibits a characteristic infrared (IR) absorption band around 2230 cm$^{-1}$ due to the stretching vibration of the nitrile group (-C≡N).
2. The $^{13}$C NMR spectrum of benzonitrile shows a signal around 118 ppm for the carbon atom of the nitrile group.
3. The basicity of benzonitrile is relatively low compared to aliphatic nitriles due to the electron-withdrawing effect of the aromatic ring.
4. Benzonitrile can be synthesized by the dehydration of benzamide or the reaction of benzene with cyanogen chloride.
5. Benzonitrile is used as a precursor in the synthesis of various pharmaceutical and agrochemical compounds.

Review Questions

• Explain the characteristic IR absorption band of benzonitrile and how it can be used for identification.
  • The nitrile group (-C≡N) in benzonitrile exhibits a characteristic IR absorption band around 2230 cm$^{-1}$. This strong and distinctive absorption band can be used as a diagnostic tool for the identification of benzonitrile and other nitrile-containing compounds. The position and intensity of this IR band provide valuable information about the presence and nature of the nitrile functional group in the molecule, which is crucial for the spectroscopic analysis of carboxylic acids and nitriles.
• Discuss the basicity of benzonitrile and how it compares to aliphatic nitriles.
  • The basicity of benzonitrile is relatively low compared to aliphatic nitriles due to the electron-withdrawing effect of the aromatic ring. The aromatic ring in benzonitrile delocalizes the electrons, reducing the electron density on the nitrogen atom of the nitrile group. This decreases the ability of the nitrogen to accept protons, resulting in a lower basicity for benzonitrile compared to aliphatic nitriles. The reduced basicity of benzonitrile is an important consideration in the context of the basicity of arylamines, as the presence of the aromatic ring can influence the acid-base properties of the compound.
• Analyze the synthetic routes and applications of benzonitrile, and explain how its chemical properties relate to its uses.
  • Benzonitrile can be synthesized through the dehydration of benzamide or the reaction of benzene with cyanogen chloride. These synthetic routes highlight the reactivity of the nitrile group and its ability to undergo various transformations. The chemical properties of benzonitrile, such as its characteristic IR absorption, $^{13}$C NMR signal, and relatively low basicity, make it a valuable precursor in the synthesis of various pharmaceutical and agrochemical compounds. These applications demonstrate the importance of understanding the spectroscopic and acid-base properties of benzonitrile, as they directly influence its reactivity and utility in organic synthesis and the development of functional materials.

Related terms

Nitrile: A nitrile is a functional group that contains a carbon-nitrogen triple bond (-C≡N). Nitriles are commonly used in organic synthesis and as solvents.

Arylamine: An arylamine is an organic compound containing an amino group (-NH2) attached directly to an aromatic ring, such as benzene.

Carboxylic Acid: A carboxylic acid is an organic compound that contains a carboxyl group (-COOH), which consists of a carbonyl group (-C=O) and a hydroxyl group (-OH).