Introduction: Organic Functions - Nomenclature of Esters
The Relevance of the Topic
Esters constitute an important class of organic compounds due to their extensive presence in nature and a variety of commercial products. They are responsible for the fragrance of many flowers and fruits and are also found in fats and oils. Moreover, they have diverse applications, from the perfume industry to the manufacture of polymers.
Mastering the nomenclature of esters is a crucial step for further understanding of organic reactions, syntheses, and mechanisms involving such compounds. Standardized nomenclature allows for clear and unequivocal communication among scientists worldwide. Therefore, correctly naming these compounds is more than an academic exercise; it is an essential component for advancements in organic chemistry.
Contextualization
The chemistry discipline in the third year of high school should enable students to understand the fundamental principles of organic chemistry, providing a solid foundation for further studies at more advanced levels, and also for practical life.
The nomenclature of esters fits within the study of organic functions, a series of compounds that exhibit similar chemical behavior. The correct identification and naming of these compounds form the basis for the accurate description of chemical reactions and biological processes. At this stage of the discipline, students should already have prior knowledge of the structure and properties of the main organic functions, now adding a deeper understanding of esters.
With a firm grasp of ester nomenclature, students will be prepared to tackle more complex topics such as the synthesis and reactions of esters, as well as the study of other organic functions. Moreover, this knowledge is applicable in various areas such as medicine, the food industry, pharmaceuticals, among others.
Theoretical Development
Components
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Ester structure: Esters are compounds characterized by having an ester group -COOR, where R is an alkyl or aryl group. Structurally, esters are derived from the reaction of a carboxylic acid with an alcohol, resulting in an ester molecule and a water molecule.
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Ester substituents: In the -COOR structure, R can be an alkyl or aryl group. This substituent is determinant for the properties of the ester, including its aroma. Common examples include methyl (R = CH3), ethyl (R = CH2CH3), and phenyl (R = C6H5).
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Originating acid: The carboxylic acid that originates the ester is also a crucial component in the nomenclature. This acid is named first in the ester nomenclature (e.g., ethanoic acid).
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IUPAC nomenclature: The IUPAC (International Union of Pure and Applied Chemistry) nomenclature of an ester uses the ending "oate" instead of "ic" from the originating acid. For the substituent, the name of the radical followed by the name of the originating acid is used. Example: methyl ethanoate.
Key Terms
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Ester: functional group characterized by the presence of the -COOR group in its structure, where R is an alkyl or aryl group.
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Alkyl group: substituent formed by saturated carbon chains.
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Aryl group: substituent formed by aromatic rings, such as the benzene ring.
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Carboxylic acid: compound characterized by the presence of the -COOH group in its structure. It is the basis for the formation of esters.
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IUPAC nomenclature: system of nomenclature for organic compounds established by the International Union of Pure and Applied Chemistry.
Examples and Cases
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Methyl methanoate: This ester is formed by the reaction of methanoic acid (formic acid) with methanol. In IUPAC nomenclature, the name of the acid is modified to methanoate, and the name of the alcohol is kept as methyl.
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Methyl ethanoate: This ester is formed by the reaction of ethanoic acid (acetic acid) with methanol. In IUPAC nomenclature, the name of the acid is modified to ethanoate, and the name of the alcohol is kept as methyl.
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Ethyl ethanoate: This ester is formed by the reaction of ethanoic acid (acetic acid) with ethanol. In IUPAC nomenclature, the name of the acid is modified to ethanoate, and the name of the alcohol is kept as ethyl. This ester is commonly known as ethyl acetate.
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Methyl benzoate: This ester is formed by the reaction of benzoic acid with methanol. In IUPAC nomenclature, the name of the acid is modified to benzoate, and the name of the alcohol is kept as methyl. This ester is commonly used as a solvent in the chemical industry.
Detailed Summary
Relevant Points:
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Definition of esters: Esters are a class of organic compounds characterized by the functional group -COOR, where R is an alkyl or aryl group. They are derived from the reaction of a carboxylic acid with an alcohol.
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Nomenclature of esters: In IUPAC nomenclature, the name of the ester is formed by combining the name of the alcohol and the acid that gave rise to it. The name of the acid is modified, changing the ending "ic" to "oate", and is preceded by the name of the alkyl or aryl group.
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Properties of esters: The properties of esters, including the aroma, are determined by the alkyl or aryl group (R) present in the ester structure.
Conclusions:
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Importance of Nomenclature: Proper nomenclature is essential for accurate communication in organic chemistry. The ability to correctly name esters helps to identify the acid and the alcohol that gave rise to it, as well as their physicochemical properties.
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Applications of esters: Esters have a wide range of applications, including the perfume industry, polymer manufacturing, and are also components of fats and oils. Therefore, mastery of nomenclature is also crucial for the use and recognition of these compounds in various contexts.
Suggested Exercises:
- Identify and name the ester formed by the reaction of propanoic acid with ethanol according to IUPAC nomenclature.
R.: Ethyl propanoate.
- Write the chemical reaction for the formation of ethyl benzoate and name the reagents used.
R.: Benzoic acid + ethanol -> Ethyl benzoate + water
- Give the IUPAC name of the ester formed from the reaction of butanoic acid with methanol.
R.: Methyl butanoate.
