Glossary

20.5 Preparing Carboxylic Acids

2 min read•may 7, 2024

are essential organic compounds with diverse synthesis methods. From to alcohols and , these versatile molecules can be created through various chemical transformations. Understanding these pathways is crucial for grasping the broader scope of organic reactions.

offer another route to carboxylic acids, showcasing the importance of carbon-carbon bond formation. These synthesis methods highlight the interconnectedness of functional groups and demonstrate how different starting materials can lead to the same product through carefully chosen reaction conditions.

Synthesis of Carboxylic Acids

Carboxylic acids from alkyl halides

Top images from around the web for Carboxylic acids from alkyl halides

  • 21.5. Hydrolysis of nitriles | Organic Chemistry II View original

    Is this image relevant?

  • 22.1: Introduction - Chemistry LibreTexts View original

    Is this image relevant?

  • 21.5. Hydrolysis of nitriles | Organic Chemistry II View original

    Is this image relevant?

1 of 3

Top images from around the web for Carboxylic acids from alkyl halides

  • 21.5. Hydrolysis of nitriles | Organic Chemistry II View original

    Is this image relevant?

  • 22.1: Introduction - Chemistry LibreTexts View original

    Is this image relevant?

  • 21.5. Hydrolysis of nitriles | Organic Chemistry II View original

    Is this image relevant?

1 of 3
  • Convert alkyl halides to carboxylic acids using a two-step process
    • reaction with cyanide ion (CN−CN^-) forms a intermediate (R-C≡N)
      • React alkyl halide with (NaCN) or (KCN)
      • R−X+CN−→R−C≡NR-X + CN^- \rightarrow R-C\equiv N
    • Hydrolyze the nitrile under acidic or basic conditions to yield the carboxylic acid (R-COOH)
      • Acidic : Heat nitrile with aqueous HCl or H2SO4
        • R−C≡N+H2O+H+→R−COOH+NH4+R-C\equiv N + H2O + H^+ \rightarrow R-COOH + NH4^+
      • Basic hydrolysis: Heat nitrile with aqueous NaOH or KOH, then acidify
        • R−C≡N+2H2O+OH−→R−COO−+NH3R-C\equiv N + 2H2O + OH^- \rightarrow R-COO^- + NH3
        • R−COO−+H+→R−COOHR-COO^- + H^+ \rightarrow R-COOH

Oxidation of alcohols and aldehydes

  • Oxidize to carboxylic acids using strong (KMnO4, H2CrO4, Na2Cr2O7)
    • Two-step : Primary alcohol → aldehyde → carboxylic acid
      • R−CH2OH→R−CHO→R−COOHR-CH2OH \rightarrow R-CHO \rightarrow R-COOH
  • Directly oxidize aldehydes to carboxylic acids using milder oxidizing agents
    • (Ag(NH3)2OH), (Cu2+ in alkaline solution), (Cu2+ in alkaline citrate solution)
      • R−CHO→R−COOHR-CHO \rightarrow R-COOH
  • Aldehydes and other can be oxidized to carboxylic acids

Carboxylic acids from Grignard reagents

  • React Grignard reagents (R-MgX) with (CO2) to form
    • CO2 acts as an electrophile and undergoes with the Grignard reagent
    • R−MgX+CO2→R−COOMgXR-MgX + CO2 \rightarrow R-COOMgX
  • Protonate the carboxylate salt with a strong acid (HCl) to yield the carboxylic acid
    • R−COOMgX+H+→R−COOH+Mg2++X−R-COOMgX + H^+ \rightarrow R-COOH + Mg^{2+} + X^-
  • Useful for preparing carboxylic acids with specific R groups determined by the Grignard reagent

Additional Reactions and Properties

  • Carboxylic acids can undergo reactions, forming derivatives such as esters and amides
  • of carboxylic acids can produce aldehydes or primary alcohols
  • Carboxylic acids participate in , acting as proton donors in aqueous solutions

Key Terms to Review (29)

Acid-Base Reactions: Acid-base reactions are chemical processes in which an acid and a base interact to form a new product. These reactions involve the transfer of protons (H+ ions) from the acid to the base, resulting in the formation of a salt and water.
Acylation: Acylation is a chemical reaction in which an acyl group (such as an acetyl or benzoyl group) is introduced into a molecule, typically by the reaction of a carboxylic acid or its derivative with another compound. This process is central to the preparation of carboxylic acids, nucleophilic acyl substitution reactions, the chemistry of thioesters and acyl phosphates, and the reactions of amines.
Aldehydes: Aldehydes are a class of organic compounds characterized by the presence of a carbonyl group (C=O) with a hydrogen atom attached to the carbon. They are important intermediates in many chemical reactions and have a wide range of applications in various industries, from pharmaceuticals to fragrances.
Alkyl Halides: Alkyl halides are organic compounds that consist of an alkyl group (a hydrocarbon chain) bonded to a halogen atom (fluorine, chlorine, bromine, or iodine). They are widely used in organic synthesis and have various applications in chemistry and biology.
Benedict's Solution: Benedict's solution is a reagent used to test for the presence of reducing sugars, such as glucose, fructose, and lactose. It is commonly used in the context of preparing carboxylic acids, as the oxidation of these sugars can lead to the formation of carboxylic acids.
Carbon Dioxide: Carbon dioxide (CO2) is a colorless, odorless gas that is a byproduct of cellular respiration and a crucial component of the carbon cycle. It is an important molecule in the context of both preparing carboxylic acids and the citric acid cycle, which are essential processes in organic chemistry and cellular metabolism.
Carbonyl Compounds: Carbonyl compounds are a class of organic compounds that contain a carbon-oxygen double bond (C=O), known as the carbonyl group. This functional group is found in a variety of important molecules, including aldehydes, ketones, carboxylic acids, esters, and amides, which are all integral to many organic chemistry topics and reactions.
Carboxylate Salts: Carboxylate salts are ionic compounds formed when a carboxylic acid reacts with a base, resulting in the replacement of the acidic hydrogen with a metal cation. These salts are important in the context of preparing carboxylic acids, as they can be used as intermediates in various synthetic reactions.
Carboxylation: Carboxylation is a chemical reaction that introduces a carboxyl group (-COOH) into an organic compound, often catalyzed by enzymes in biological processes. This reaction is fundamental in synthesizing carboxylic acids from substrates that may not initially contain a carboxyl group.
Carboxylic Acids: Carboxylic acids are a class of organic compounds containing a carboxyl functional group (-COOH) attached to an alkyl or aryl group. They are characterized by their acidic properties and play a crucial role in various chemical reactions and biological processes.
Carboxylic acids, RCO2H: Carboxylic acids are organic compounds characterized by the presence of a carboxyl group (-COOH), where "R" represents an alkyl or aryl group attached to the carbon atom of the carboxyl group. They are known for being acidic due to the ability of the hydroxyl (OH) part of the carboxyl group to release a proton (H+).
Chromic Acid: Chromic acid, also known as chromium(VI) oxide, is a strong oxidizing agent commonly used in organic chemistry. It is a bright orange-red crystalline compound with the chemical formula CrO3, which can be used to oxidize various organic compounds.
Fehling's Solution: Fehling's solution is a reagent used to test for the presence of aldehydes and reducing sugars. It is a copper-based solution that undergoes a color change and precipitate formation when reacted with these compounds, indicating a positive test result.
Grignard Reagents: Grignard reagents are a class of highly reactive organometallic compounds that are widely used in organic synthesis. They are formed by the reaction of an alkyl or aryl halide with magnesium metal and play a crucial role in various organic transformations.
Hydrolysis: Hydrolysis is a chemical reaction in which a compound is cleaved into smaller molecules by the addition of water. This process involves the breaking of chemical bonds through the insertion of water molecules, often resulting in the formation of new functional groups or the decomposition of larger molecules.
Nitrile: A nitrile is a functional group consisting of a carbon-nitrogen triple bond (C≡N). Nitriles are important in organic chemistry, with applications in the synthesis of various compounds and as precursors to other functional groups.
Nucleophilic Addition: Nucleophilic addition is a fundamental organic reaction in which a nucleophile, a species that donates electrons, adds to an electrophilic carbon center, typically a carbonyl carbon, to form a new product. This reaction is central to understanding many important topics in organic chemistry, including functional groups, polar reactions, carbocation stability, reaction stereochemistry, and the chemistry of aldehydes, ketones, alcohols, and other carbonyl-containing compounds.
Nucleophilic addition reaction: A nucleophilic addition reaction is a chemical process where a nucleophile forms a bond with an electrophilic carbon atom of a compound, typically found in aldehydes and ketones. This reaction results in the conversion of the carbonyl group into a more complex, often larger, molecule.
Nucleophilic Substitution: Nucleophilic substitution is a fundamental organic reaction where a nucleophile (a species that donates electrons) replaces a leaving group attached to a carbon atom, resulting in the formation of a new carbon-nucleophile bond. This process is central to many organic transformations and is particularly relevant in the context of alkyl halides, alcohols, carboxylic acids, and amines.
Nucleophilic substitution reactions: Nucleophilic substitution reactions are a class of chemical reactions in organic chemistry where an electron-rich nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms to replace a leaving group. The reaction is characterized by the substitution of a nucleophile for a leaving group, which can occur via different mechanisms (SN1 or SN2).
Oxidation: Oxidation is a fundamental chemical process in which a substance loses electrons, resulting in an increase in its oxidation state. This term is central to understanding various reactions and transformations in organic chemistry, from the hydration of alkenes to the oxidation of alcohols and aldehydes.
Oxidizing Agents: Oxidizing agents, also known as oxidants, are substances that have the ability to oxidize other substances by removing electrons from them. They play a crucial role in various organic chemistry reactions, including the oxidative cleavage of alkynes, the oxidation of aromatic compounds, the oxidation of alcohols, the preparation of aldehydes and ketones, and the preparation of carboxylic acids.
Potassium Cyanide: Potassium cyanide is a highly toxic chemical compound consisting of the cyanide anion (CN-) and the potassium cation (K+). It is a white, crystalline solid that is commonly used in various industrial processes, including metal extraction and electroplating. However, potassium cyanide's toxicity makes it a dangerous substance that requires strict handling and safety protocols.
Potassium Permanganate: Potassium permanganate is a strong oxidizing agent with the chemical formula KMnO4. It is a dark purple crystalline solid that is widely used in various chemical reactions and processes due to its powerful oxidizing properties.
Primary Alcohols: Primary alcohols are organic compounds with the hydroxyl (-OH) functional group attached to the first (primary) carbon atom of an alkyl chain. These alcohols are important intermediates in various organic reactions, including the preparation of alkyl halides, the oxidation of alcohols, and the synthesis of carboxylic acids.
Reduction: Reduction is a chemical process that involves the gain of electrons by a molecule or atom, resulting in a decrease in its oxidation state. This term is particularly important in the context of various organic chemistry reactions and transformations.
Sodium Cyanide: Sodium cyanide is a highly toxic chemical compound that consists of a sodium cation and a cyanide anion. It is commonly used in various industrial processes, including gold mining and chemical synthesis, and is an important precursor in the preparation of carboxylic acids.
Sodium Dichromate: Sodium dichromate, also known as sodium bichromate, is an inorganic compound with the chemical formula Na2Cr2O7. It is a powerful oxidizing agent that has various applications in organic chemistry, particularly in the oxidation of alcohols, the preparation of aldehydes and ketones, and the preparation of carboxylic acids.
Tollens' Reagent: Tollens' reagent is a chemical solution used to test for the presence of aldehydes in organic chemistry. It is a sensitive test that can detect even small amounts of aldehydes, making it a valuable tool in the preparation and identification of carboxylic acids.
© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Back
Practice QuizGlossary
Practice QuizGlossary
Next guide