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Organic Chemistry
Table of Contents
Unit 21 Overview: Carboxylic Acid Derivatives: Acyl Substitution
21.1 Naming Carboxylic Acid Derivatives
21.2 Nucleophilic Acyl Substitution Reactions
21.3 Reactions of Carboxylic Acids
21.4 Chemistry of Acid Halides
21.5 Chemistry of Acid Anhydrides
21.6 Chemistry of Esters
21.7 Chemistry of Amides
21.8 Chemistry of Thioesters and Acyl Phosphates: Biological Carboxylic Acid Derivatives
21.9 Polyamides and Polyesters: Step-Growth Polymers
21.10 Spectroscopy of Carboxylic Acid Derivatives

Carboxylic acid derivatives are key players in organic chemistry. They all share a carbonyl group bonded to another atom or group, making them versatile and important in many reactions.

Naming these compounds follows specific rules based on their structure. From acid halides to acyl phosphates, each type has its own naming convention. Recognizing their structural features is crucial for proper identification and understanding their reactivity.

Naming and Identifying Carboxylic Acid Derivatives

Introduction to Carboxylic Acid Derivatives

Carboxylic acid derivatives are a class of organic compounds that contain functional groups derived from carboxylic acids. These compounds share a common structural feature: the carbonyl group (C=O) bonded to another atom or group. Understanding the nomenclature and structural features of these derivatives is crucial for proper identification and naming.

IUPAC nomenclature for acid derivatives

  • Acid halides named by replacing the -ic acid suffix with -yl halide specifying the halogen (chloride, bromide, iodide) (acetyl chloride)
  • Anhydrides named by replacing the -ic acid suffix with -ic anhydride, naming both acyl groups in alphabetical order if unsymmetrical (acetic anhydride)
  • Esters named by replacing the -ic acid suffix with -ate, naming the alkyl group attached to oxygen first followed by the carboxylate anion (ethyl acetate)
  • Amides named by replacing the -ic acid suffix with -amide, naming substituents as N-alkyl or N,N-dialkyl (acetamide)
  • Thioesters named by replacing the -ic acid suffix with -thioate, naming the alkyl group attached to sulfur first followed by the carboxylate anion (ethyl thioacetate)
  • Acyl phosphates named by replacing the -ic acid suffix with -yl phosphate (acetyl phosphate)

Structural features of acid derivatives

  • Acid halides contain a halogen atom (Cl, Br, I) bonded to the acyl carbon with general formula R-COX (X = Cl, Br, I)
  • Anhydrides formed by condensation of two carboxylic acid molecules eliminating water, contain two acyl groups bonded to a central oxygen atom with general formula R-CO-O-CO-R'
  • Esters contain an alkoxy group (-OR') bonded to the acyl carbon with general formula R-COOR'
  • Amides contain a nitrogen atom bonded to the acyl carbon, may be unsubstituted (R-CONH2) or substituted with one or two alkyl groups (R-CONHR', R-CONR'R'')
  • Thioesters contain a sulfur atom bonded to the acyl carbon with an alkyl group attached to sulfur, general formula R-COSR'
  • Acyl phosphates contain a phosphate group bonded to the acyl carbon with general formula R-CO-O-PO(OH)2

Structures from IUPAC names

  1. Identify the parent chain and any substituents based on the IUPAC name

  2. Determine the functional group (acid halide, anhydride, ester, amide, thioester, acyl phosphate) based on the suffix and other structural information provided

  3. Draw the parent chain and attach the appropriate functional group

    • For acid halides, attach the halogen to the acyl carbon
    • For anhydrides, draw two acyl groups bonded to a central oxygen atom
    • For esters, attach the alkoxy group to the acyl carbon
    • For amides, attach the nitrogen atom (with any specified substituents) to the acyl carbon
    • For thioesters, attach the alkylthio group to the acyl carbon
    • For acyl phosphates, attach the phosphate group to the acyl carbon

  4. Add any specified substituents to the parent chain or functional group as indicated by the IUPAC name

    • Follow IUPAC naming rules for proper placement and numbering of substituents

Key Terms to Review (35)

Carboxylic acid derivatives: Carboxylic acid derivatives are compounds that feature a functional group derived from the substitution of the hydroxyl (-OH) group in carboxylic acids with other atoms or groups of atoms. They retain the carbonyl (C=O) group but differ in the atom or group attached to the acyl moiety.
Acid halides: Acid halides are a type of carboxylic acid derivative where the hydroxyl group (OH) of the carboxylic acid is replaced by a halogen (e.g., chlorine, bromine). They are highly reactive compounds that participate in nucleophilic acyl substitution reactions.
Acyl phosphates: Acyl phosphates are high-energy carboxylic acid derivatives where the acyl group is bonded to a phosphate group. They are key intermediates in nucleophilic acyl substitution reactions, facilitating the transfer of the acyl group due to their high reactivity.
Acid anhydrides: Acid anhydrides are organic compounds formed by the removal of water between two carboxylic acid molecules. They play a significant role in nucleophilic acyl substitution reactions, where they act as electrophiles ready to react with nucleophiles.
Functional Groups: Functional groups are specific arrangements of atoms within a molecule that determine the chemical reactivity and physical properties of that molecule. These groups play a crucial role in understanding and predicting the behavior of organic compounds.
Substituents: Substituents are atoms or functional groups that replace hydrogen atoms in a molecule's structure. They are an essential concept in organic chemistry, as they play a crucial role in determining the properties, reactivity, and naming of various organic compounds.
Nomenclature: Nomenclature refers to the systematic naming and classification of chemical compounds based on established rules and conventions. It is a crucial aspect of organic chemistry, as it provides a standardized way to identify and communicate the structures of various compounds.
-amide: The -amide functional group is a key structural feature found in various organic compounds, particularly carboxylic acid derivatives. It consists of a carbonyl carbon (C=O) bonded to a nitrogen atom, forming a characteristic amide linkage. This functional group plays a crucial role in the classification and naming of carboxylic acid derivatives, as well as in the understanding of their chemical properties and reactivity.
Ethyl Acetate: Ethyl acetate is a versatile organic compound that serves as a common solvent, a flavoring agent, and an important intermediate in various chemical reactions. It is the ester formed by the reaction between acetic acid and ethanol, and its diverse applications make it a crucial compound in both laboratory and industrial settings.
Acetamide: Acetamide is an organic compound with the formula CH3CONH2. It is a simple amide derived from acetic acid and ammonia, and is the simplest member of the amide functional group. Acetamide is an important compound in organic chemistry and is relevant to the topics of functional groups, the chemistry of nitriles, and the naming of carboxylic acid derivatives.
Parent Chain: The parent chain is the longest continuous carbon chain in a molecule, which serves as the basis for naming organic compounds. This key term is central to the systematic nomenclature used across various classes of organic compounds, including alkanes, alkenes, aromatic compounds, alcohols, phenols, and carboxylic acid derivatives.
Esters: Esters are a class of organic compounds formed by the reaction between a carboxylic acid and an alcohol, resulting in the replacement of the hydroxyl group (-OH) of the acid with an alkoxy group (-OR). Esters are ubiquitous in nature and play a crucial role in various chemical processes and applications.
Amides: Amides are a class of organic compounds that contain a carbonyl group (C=O) bonded to a nitrogen atom. They are derived from carboxylic acids and can be considered the result of replacing the hydroxyl group (-OH) of a carboxylic acid with an amino group (-NH2). Amides are important functional groups in many organic molecules, including proteins, and play a crucial role in various chemical reactions and processes.
Carboxylic Acid Derivatives: Carboxylic acid derivatives are a class of organic compounds that are structurally related to carboxylic acids, but have a different functional group attached to the carbonyl carbon. These derivatives include esters, acyl halides, anhydrides, and amides, and they play crucial roles in various chemical reactions and biological processes.
Acetyl Chloride: Acetyl chloride is an organic compound with the chemical formula CH3COCl. It is a colorless, volatile liquid that is commonly used as a reagent in organic synthesis reactions, particularly in the formation of carboxylic acid derivatives.
-ic Anhydride: An -ic anhydride is a type of carboxylic acid derivative that is formed by the removal of a water molecule between two carboxylic acid groups. These compounds are important in the context of naming and understanding carboxylic acid derivatives.
Ethyl Thioacetate: Ethyl thioacetate is a carboxylic acid derivative that features a sulfur atom in place of the oxygen atom found in the more common ethyl acetate. This structural difference gives ethyl thioacetate unique chemical properties and reactivity compared to its oxygen-containing counterpart.
Acetyl Phosphate: Acetyl phosphate is a high-energy intermediate compound that plays a crucial role in various metabolic pathways, particularly in the context of carboxylic acid derivatives. It serves as an important energy-rich phosphate donor and is involved in the regulation of cellular processes.
-ate: The suffix '-ate' is commonly used in the naming of carboxylic acid derivatives, such as esters, salts, and anhydrides. It indicates the presence of a specific functional group or the type of chemical reaction that has occurred.
N-alkyl: An N-alkyl group is a substituent in organic chemistry where an alkyl group is bonded to a nitrogen atom. This type of functional group is commonly found in carboxylic acid derivatives, such as those discussed in topic 21.1 Naming Carboxylic Acid Derivatives.
Acetic Anhydride: Acetic anhydride is a colorless, volatile liquid that is used as a reagent in organic synthesis, particularly in the formation of carboxylic acid derivatives. It is a key compound in various chemical reactions and processes, including those related to carboxylic acid derivatives, acid anhydrides, and DNA synthesis.
Unsubstituted: The term 'unsubstituted' refers to a compound or functional group that does not have any additional atoms or groups attached to a specific position or site. In the context of 21.1 Naming Carboxylic Acid Derivatives, it describes a carboxylic acid derivative that has not been modified by the addition of other substituents to the carbonyl carbon or the adjacent atoms.
Alkoxy Group: An alkoxy group is a functional group in organic chemistry that consists of an alkyl group bonded to an oxygen atom. It is denoted by the general formula -OR, where R represents the alkyl group. Alkoxy groups are commonly found in carboxylic acid derivatives, which are the focus of the 21.1 Naming Carboxylic Acid Derivatives topic.
-thioate: The -thioate functional group is a sulfur-containing derivative of a carboxylic acid, where the oxygen atom in the carboxyl group (-COOH) is replaced by a sulfur atom (-C(=S)O-). This structural modification results in the formation of a thiocarbonyl group, which has important implications in the reactivity and properties of carboxylic acid derivatives.
Acyl Carbon: The acyl carbon is the central carbon atom in a carboxylic acid derivative, such as an ester, amide, or acyl halide. It is the carbon atom that is double-bonded to an oxygen atom and singly-bonded to another atom or group, forming the characteristic carbonyl group of these functional groups.
IUPAC Naming Rules: IUPAC naming rules are a standardized system for naming organic compounds, developed by the International Union of Pure and Applied Chemistry (IUPAC). These rules provide a systematic approach to naming various classes of organic molecules, including carboxylic acid derivatives, which are the focus of the 21.1 topic.
Acid Halides: Acid halides, also known as acyl halides, are a class of organic compounds that contain a carbonyl group (C=O) bonded to a halogen atom (F, Cl, Br, or I). These compounds are highly reactive and serve as important intermediates in various organic reactions, particularly in the synthesis of carboxylic acid derivatives.
Acyl Phosphates: Acyl phosphates are a class of carboxylic acid derivatives that feature a phosphate group attached to the carbonyl carbon. These compounds are important intermediates in biological processes, particularly in the context of energy transfer and storage within living organisms.
-yl Phosphate: -yl phosphate is a functional group in organic chemistry that consists of a phosphate group (PO4^3-) attached to an organic molecule. This group is commonly found in various carboxylic acid derivatives and plays a crucial role in energy storage and transfer within biological systems.
Anhydrides: Anhydrides are organic compounds derived from carboxylic acids, characterized by a carbonyl-oxygen-carbonyl functional group. They play a crucial role in various reactions and transformations involving carboxylic acid derivatives, including naming, nucleophilic acyl substitution, and the chemistry of acid halides.
Thioesters: Thioesters are organic compounds that are structurally similar to esters, but with a sulfur atom replacing the oxygen atom in the carbonyl group. They are an important class of carboxylic acid derivatives that have various applications in biological processes and organic synthesis.
-yl Halide: -yl halides are organic compounds that contain a halogen atom (fluorine, chlorine, bromine, or iodine) bonded to a carbon atom that is part of an alkyl or aryl group. These compounds are important in organic chemistry, particularly in the context of carboxylic acid derivatives, as they can undergo various reactions and transformations.
N,N-dialkyl: N,N-dialkyl refers to a chemical structure where a nitrogen atom is substituted with two alkyl groups, which are hydrocarbon chains. This structural feature is commonly found in various carboxylic acid derivatives, such as amides and esters, and plays a crucial role in their nomenclature and properties.
Substituted: Substituted refers to the replacement of one or more atoms or functional groups in a molecule with different atoms or functional groups, altering the original chemical structure and properties.
Carbonyl group: A carbonyl group is a functional group characterized by a carbon atom double-bonded to an oxygen atom, represented as C=O. This group is pivotal in organic chemistry as it forms the backbone of various important classes of compounds, influencing their chemical properties and reactivity.