Organic Functions: Nitrile and Isonitrile

Relevance of the Topic

Organic Functions Nitrile and Isonitrile are essential components in the study of Organic Chemistry. They are part of a group of compounds that play a significant role in the pharmaceutical industry, being found in medications, pesticides, and even explosives.

By learning about nitriles and isonitriles, you will be acquiring the ability to recognize and identify these organic functions in a variety of compounds. This will broaden your understanding of the properties and uses of these compounds, including understanding their impacts on health, the environment, and technological applications. Therefore, this topic is fundamental to deepen your knowledge in Organic Chemistry.

Contextualization

Nitriles and isonitriles are two of the many organic functions you will encounter during the study of Organic Chemistry in high school. They are closely related to other concepts, such as the nomenclature of organic compounds and organic syntheses.

When studied together with other organic functions, nitriles and isonitriles provide a more complete view of the diversity of structures, properties, and reactivities of organic compounds. They offer an example of compounds that have different physical and chemical properties, despite sharing the same molecular formula.

This content is located in the "Organic Functions" section of the Chemistry curriculum in high school. Understanding nitriles and isonitriles will be useful to advance in more complex topics, such as addition and substitution reactions in organic compounds, and to develop a solid foundation for further studies in Chemistry at university or technical courses.

Theoretical Development

Components

• Nitriles: Also known as cyanides, nitriles are organic compounds characterized by the presence of the CN group (cyanide) attached to a saturated carbon. The official nomenclature of nitriles is obtained by replacing the terminal "o" of the corresponding carboxylic acid with "nitrile". For example, HCN (hydrocyanic acid) is the source of cyanide in chemical reactions. Its general structure is R-C≡N.

• Isonitriles: Isonitriles are organic compounds characterized by the presence of the NC group (isonitrile) attached to a saturated carbon. The official nomenclature of isonitriles is obtained by replacing the terminal "o" of the corresponding carboxylic acid with "isonitrile". For example, the structure of isonitrile ethanoate is CH3-NC-CH3. Its general structure is R-N≡C.

• Nitriles and Isonitriles in Nature: Nitriles and isonitriles can be found in natural products, such as in some plant species. Cyanide, a nitrile, is naturally produced by some plants as a defense mechanism against herbivores.

• Reactivity of Nitriles and Isonitriles: Nitriles generally react through a nucleophilic addition mechanism, while isonitriles typically react through a 1,3-dipolar reaction mechanism. The reaction with acid provides the alkylated analog and the reaction with alcohol results in the corresponding oxime.

Key Terms

• Organic Function: Term used to describe a category of chemical compounds with similar chemical properties due to the presence of one or more functional groups.

• Cyanide Group (CN): It is a functional group found in nitriles and related compounds. It consists of a carbon atom triple-bonded to a nitrogen atom.

• Isocyanide Group (NC): It is a functional group found in isonitriles and related compounds. It consists of a nitrogen atom triple-bonded to a carbon atom.

• Reaction Mechanism: Detailed description of the individual steps through which a chemical reaction occurs. In Organic Chemistry, the reaction mechanism describes the route from the reactants to the products, including the interaction between chemical bonds.

Examples and Cases

• Nitriles in the Pharmaceutical Industry: Nitriles are widely used in the synthesis of medications. For example, nitroglycerin, a powerful vasodilator used to treat angina pectoris, is prepared from the reaction of nitric acid with glycerol (an alcohol) in the presence of sulfuric acid.

• Isonitriles in Organic Syntheses: Isonitriles have a unique reactivity in the formation of transition metal complexes, making them useful in the synthesis of organic compounds. For example, the Pinner Reaction uses an isonitrile to transform a carboxylic acid into an ester. This is an example of an acylation reaction.

• Cyanide, a Nitrile in Toxicology: Cyanide is a highly toxic compound. Its toxicity mechanism is due to the inhibition of cellular respiration in the presence of high concentrations, leading to oxygen deficiency in tissues. This property is commonly exploited in applications such as pesticides and poisons.

• Nitriles and Isonitriles in Space Expeditions: Nitriles and isonitriles can be used as fuels in rocket engines, as they have high energy density. This property is essential for propulsion needs in space expeditions.

Detailed Summary

Relevant Points

• Composition of Nitriles and Isonitriles: Nitriles are organic compounds that contain the CN group (cyanide) attached to a saturated carbon, while isonitriles have the NC group (isonitrile) attached to a saturated carbon. The general structure of a nitrile is R-C≡N and that of an isonitrile is R-N≡C, with "R" representing a carbon chain or a functional group.

• Nomenclature and Derivatives: The systematic nomenclature of nitriles derives from the name of the corresponding carboxylic acid, replacing the final "o" with "nitrile". In the case of isonitriles, the final "o" is replaced with "isonitrile". For example, the nitrile derived from ethanoic acid is called propanonitrile and the corresponding isonitrile is called ethanoate of isonitrile.

• Reactivity of Nitriles and Isonitriles: Nitriles react through nucleophilic addition, while isonitriles mainly react through 1,3-dipolar reaction. Nitriles easily undergo hydrolysis and can be converted into amides or carboxylic acids. Isonitriles are highly reactive and have been used in various syntheses of complex organic compounds.

• Properties and Use of Nitriles and Isonitriles: Nitriles and isonitriles have diverse applications in the pharmaceutical industry, coordination chemistry, and technological applications such as rocket fuels. The toxicity of cyanide, a nitrile, is well known, but other nitriles and isonitriles do not have the same degree of toxicity.

Conclusions

• Versatility of Applications: Nitriles and isonitriles are highly versatile compounds, with a wide range of applications in different sectors, from the manufacture of medications and chemicals to the rocket industry.

• Differentiated Reactivity: Nitriles and isonitriles have distinct reaction mechanisms and, therefore, exhibit different reactivities and chemical properties. This difference is crucial in determining their reaction products and uses.

• Global Understanding: The study of nitriles and isonitriles allows for a deeper understanding of organic functions and molecular structures, contributing to a more comprehensive understanding of Organic Chemistry.

Suggested Exercises

1. Identify the Functions: Given the compound CH3CN, identify the organic function present and give the official name according to systematic nomenclature.

2. Reactivity of Nitriles and Isonitriles: Write the chemical equation that represents the reaction of propanonitrile with water.

3. Technological Applications: Explain how isonitriles can be used as fuels in rocket engines.