Aldehydes, Ketones and Carboxylic Acids — Class 12 Chemistry Notes

Aldehydes, Ketones and Carboxylic Acids · Class 12 Chemistry · 9 topics.

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Topics covered in Aldehydes, Ketones and Carboxylic Acids

  1. 1.Introduction of Aldehydes, Ketones and Carboxylic Acids

    Short Answer

    Aldehydes, Ketones, and Carboxylic Acids are organic compounds that are found in many everyday substances. Aldehydes and Ketones are known for their sweet, sometimes pungent smells, and are used in perfumes and flavorings. Carboxylic Acids are found in vinegar (acetic acid) and citrus fruits (citric acid), and play a significant role in food and medicine.

    • Use in Real Life: In food flavorings, perfumes, pharmaceuticals, and as solvents.
    • Careers: Chemistry, food science, pharmaceuticals, and environmental science.

    Long Answer

    Introduction

    Organic chemistry is a fascinating branch of chemistry that involves the study of carbon-containing compounds. Within this realm, Aldehydes, Ketones, and Carboxylic Acids stand out due to their widespread use and significance in both daily life and various industrial applications.

    Aldehydes and Ketones

    1. Structure: Aldehydes have a carbonyl group (C=O) at the end of the carbon chain, while Ketones have the carbonyl group within the chain.
    2. Sources and Uses:
      • Aldehydes are commonly found in fragrances and flavors. For example, vanillin, the primary component of vanilla bean extract, is an aldehyde.
      • Ketones are used in solvents and in the production of plastics and textiles. Acetone, a well-known ketone, is used as a solvent in nail polish remover.
    3. Real-life Example: Formaldehyde is used in preserving biological specimens, while acetone is widely used as a solvent in industries and laboratories.

    Carboxylic Acids

    1. Structure: They contain a carboxyl group (-COOH), which is a combination of a carbonyl group and a hydroxyl group (-OH).
    2. Sources and Uses:
      • Vinegar contains acetic acid, a simple carboxylic acid.
      • Citric acid, found in citrus fruits, is used in food preservation and as a flavoring agent.
    3. Real-life Example: Aspirin, a pain reliever, contains salicylic acid, which is a type of carboxylic acid.

    Applications and Careers

    • Food Science: Understanding the chemistry of these compounds helps in the creation of flavors and preservatives.
    • Pharmaceuticals: Many drugs are designed based on the functional groups present in these compounds.
    • Environmental Science: Analyzing and breaking down pollutants often involve understanding these organic compounds.

    In summary, Aldehydes, Ketones, and Carboxylic Acids are integral to various products and processes that impact our daily lives and the environment. Their study opens pathways to careers in research, environmental science, pharmaceuticals, and much more.

  2. 2.Nomenclature and Structure of Carbonyl Group

    Short Answer

    Nomenclature of Aldehydes and Ketones:

    • Common Names: Derived from the sources or properties of the compounds, such as formaldehyde, known for preserving biological specimens.
    • IUPAC Names: Aldehydes are named by replacing the -e in the alkane name with -al (ethane becomes ethanol), and ketones with -one (propane becomes propanone).

    Structure of the Carbonyl Group: A carbon atom double-bonded to an oxygen atom (C=O), crucial in both aldehydes and ketones, differentiating by placement in the molecule.

    Reaction Examples:

    • Aldehydes: Oxidation of ethanol produces ethanal (an aldehyde).
    • Ketones: Oxidation of secondary alcohols leads to ketones, e.g., oxidation of propan-2-ol produces propanone.

    Long Answer

    Nomenclature of Aldehydes and Ketones

    1. Common Names:
      • Based on traditional sources or characteristics. Formaldehyde, used in preservatives, and acetone, known for its solvent properties, are examples.
    2. IUPAC Names:
      • Aldehydes: The IUPAC system names aldehydes by changing the alkane's ending to -al. Methane becomes methanal, ethane to ethanal.
      • Ketones: Named by changing the ending to -one. Propane becomes propanone, butane to butanone.

    Structure of the Carbonyl Group

    • Characterized by a carbon atom double-bonded to an oxygen atom (C=O). This polar group makes aldehydes and ketones highly reactive.
    • In Aldehydes: The carbonyl group is at the end of the carbon chain.
    • In Ketones: The carbonyl group is within the carbon chain, flanked by carbon atoms.

    Reaction Examples

    1. Aldehydes:

      • Oxidation of Ethanol to Ethanal: 32+[]→3+2CH3​CH2​OH+[O]→CH3​CHO+H2​O Ethanol is oxidized to produce ethanal (an aldehyde) and water.

    2. Ketones:

      • Oxidation of Propan-2-ol to Propanone: 33+[]→33+2CH3​CH(OH)CH3​+[O]→CH3​COCH3​+H2​O Secondary alcohol (propan-2-ol) is oxidized to produce propanone (a ketone) and water.

    Real-Life Application and Careers

    • Chemical Industry: Aldehydes and ketones are used in synthesizing plastics, pharmaceuticals, and fragrances.
    • Environmental Science: Understanding the reaction mechanisms helps in the degradation of pollutants.
    • Research and Development: Developing new materials and medicinal compounds involves detailed knowledge of organic reactions involving carbonyl groups.

    In summary, the nomenclature, structure, and reactivity of the carbonyl group are fundamental in organic chemistry, with extensive applications across various fields. Understanding these concepts is crucial for careers in the chemical industry, environmental science, and research.

  3. 3.Common and IUPAC Names of Some Aldehydes and Ketones.

    Chart: Common and IUPAC Names of Some Aldehydes and Ketones

    Compound TypeCommon NameIUPAC NameStructural Formulaहिंदी में यौगिक का प्रकारसामान्य नामIUPAC नामसंरचनात्मक सूत्र
    AldehydeFormaldehydeMethanalHCHOएल्डिहाइडफॉर्मलडिहाइडमेथनलHCHO
    AldehydeAcetaldehydeEthanalCH₃CHOएल्डिहाइडएसीटाल्डिहाइडइथनलCH₃CHO
    AldehydePropionaldehydePropanalCH₃CH₂CHOएल्डिहाइडप्रोपिओनाल्डिहाइडप्रोपनलCH₃CH₂CHO
    KetoneAcetonePropanoneCH₃COCH₃कीटोनएसीटोनप्रोपेनोनCH₃COCH₃
    KetoneMethyl ethyl ketoneButanoneCH₃COCH₂CH₃कीटोनमिथाइल एथिल कीटोनब्यूटेनोनCH₃COCH₂CH₃

    This chart lists some common aldehydes and ketones along with their common names, IUPAC names, and structural formulas. Understanding these names and structures is a fundamental part of organic chemistry, which is crucial for various applications in industries, including pharmaceuticals, manufacturing, and environmental sciences.

  4. 4.Preparation of Aldehydes and Ketones

    Preparation of Aldehydes and Ketones

    Aldehydes and ketones are versatile compounds in organic chemistry with a wide range of applications in industries such as pharmaceuticals, perfumery, and plastics. Their preparation involves various methods, including the oxidation of alcohols, dehydrogenation of alcohols, and from hydrocarbons. Here's a detailed explanation, including reaction examples.

    1. By Oxidation of Alcohols

    • Aldehydes: Primary alcohols can be oxidized to aldehydes using agents like PCC (Pyridinium chlorochromate) in dichloromethane.

      Example: 32→PCCDichloromethane3+2CH3​CH2​OHDichloromethanePCC​CH3​CHO+H2​O (Ethanol is oxidized to ethanal)

    • Ketones: Secondary alcohols are oxidized to ketones using oxidizing agents like KMnO₄, CrO₃, or Jones reagent.

      Example: 33→KMnO433+2CH3​CH(OH)CH3​KMnO4​​CH3​COCH3​+H2​O (Propan-2-ol is oxidized to propanone)

    2. By Dehydrogenation of Alcohols

    • Both aldehydes and ketones can be prepared by the dehydrogenation of alcohols, where hydrogen is removed from the alcohol molecule. This is often done using a catalyst like copper at high temperature.

      Example for Aldehyde: 32→copperΔ3+2CH3​CH2​OHΔcopper​CH3​CHO+H2​ (Ethanol is dehydrogenated to ethanal)

      Example for Ketone: 33→copperΔ33+2CH3​CH(OH)CH3​Δcopper​CH3​COCH3​+H2​ (Propan-2-ol is dehydrogenated to propanone)

    3. From Hydrocarbons

    • Aldehydes and Ketones: Hydrocarbons can be converted into aldehydes and ketones through controlled oxidation reactions. For aldehydes, this method is more specific for the preparation from aromatic hydrocarbons.

      Example for Aldehyde from Hydrocarbon: 66→OxidationCOCl2/AlCl365C6​H6​COCl2​/AlCl3​Oxidation​C6​H5​CHO (Benzene is converted to benzaldehyde)

      Example for Ketone from Hydrocarbon: 66+→HClAlCl3653C6​H6​+COAlCl3​HCl​C6​H5​COCH3​ (Benzene reacts with carbon monoxide in the presence of AlCl₃ to form acetophenone)

    Preparation of Aldehydes

    1. From Acyl Chloride (Acid Chloride)

    Acyl chlorides react with dialkyl cadmium, generated from a Grignard reagent, to give aldehydes.

    Example: 3+2→3+CH3​COCl+R2​Cd→CH3​CHO+RCdCl (Acetyl chloride reacts with dialkyl cadmium to give ethanal)

    2. From Nitriles and Esters

    • Reduction of nitriles using DIBAL-H (Diisobutylaluminium hydride) or esters can yield aldehydes.

      Example from Nitrile: +2[]→DIBAL-HRCN+2[H]DIBAL-H​RCHO (A nitrile is reduced to an aldehyde)

    3. From Hydrocarbons

    • Ozonolysis of alkenes followed by reductive workup can also produce aldehydes.

      Example: =2+3→+22RCH=CH2​+O3​​RCHO+H2​O2​ (An alkene undergoes ozonolysis to form an aldehyde)

    Preparation of Ketones

    1. From Acyl Chlorides

    • Friedel-Crafts acylation of aromatic rings with acyl chlorides in the presence of a Lewis acid catalyst (e.g., AlCl₃) forms ketones.

      Example: 66+3→AlCl3653C6​H6​+CH3​COClAlCl3​​C6​H5​COCH3​ (Benzene reacts with acetyl chloride to give acetophenone)

    2. From Nitriles

    • Nitriles can be converted to ketones through a process involving Grignard reagents followed by hydrolysis.

      Example: +′→′=RCN+R′MgBr→RR′C=O (A nitrile reacts with a Grignard reagent to form a ketone)

    3. From Benzene or Substituted Benzenes

    • Alkylation of benzene followed by oxidation can yield ketones.

      Example: 66+3→AlCl3Friedel-Crafts Alkylation653→O2Oxidation653C6​H6​+CH3​ClFriedel-Crafts AlkylationAlCl3​​C6​H5​CH3​OxidationO2​​C6​H5​COCH3​ (Benzene is first alkylated to form toluene, which is then oxidized to form acetophenone)

    These methods highlight the versatility of organic synthesis, allowing for the preparation of a wide range of aldehyde and ketone compounds from simple precursors. Each method has its specific applications and is chosen based on the desired product and starting materials.

  5. 5.The Physical Properties of Aldehydes and Ketones

    Short Answer

    Aldehydes and Ketones share similar physical properties due to the presence of the carbonyl group (C=O). They are generally colorless liquids or solids with distinctive odors. Both are soluble in organic solvents but have varying solubility in water, with lower members being more soluble. Their boiling points are higher than hydrocarbons but lower than alcohols of similar molecular weight.

    Long Answer

    Physical Properties of Aldehydes and Ketones

    1. State and Odor: Most aldehydes and ketones are colorless liquids at room temperature, with the exception of some higher molecular weight compounds which are solids. Many have strong, often pleasant odors and are used in perfumery and flavorings (e.g., vanillin, the primary component of vanilla bean extract).

    2. Solubility: Aldehydes and ketones have a polar carbonyl group, making them soluble in organic solvents like ether, alcohol, and chloroform. The solubility in water decreases with increasing carbon chain length; smaller molecules (up to 4 carbons) are quite soluble in water due to their ability to form hydrogen bonds with water molecules.

    3. Boiling Point: The boiling points of aldehydes and ketones are higher than those of ether and hydrocarbons of similar molecular weight because of the polar nature of the carbonyl group which allows for dipole-dipole interactions. However, they are generally lower than those of alcohols, as aldehydes and ketones cannot form hydrogen bonds with each other as effectively as alcohols can.


    4. Density: Aldehydes and ketones typically have densities slightly less than that of water. For example, acetone (a ketone) has a density of 0.786 g/cm³ at 25°C.

    5. Reactivity: The carbonyl group makes aldehydes and ketones highly reactive. They undergo various chemical reactions, including nucleophilic addition, making them important in synthetic chemistry.

    Applications and Implications

    • Industrial Use: Due to their distinct odors, aldehydes and ketones are widely used in the fragrance and flavor industries. Acetone, a ketone, is a common solvent in the paint and plastics industries.
    • Solubility Characteristics: Their solubility properties make them useful as solvents in various chemical reactions and processes.
    • Environmental Impact: The volatility of lower molecular weight aldehydes and ketones, such as formaldehyde and acetone, poses risks as pollutants and requires careful handling and regulation.

    Understanding the physical properties of aldehydes and ketones is crucial for their application in industrial processes, their role in environmental science, and their handling in laboratories.

  6. 6.Nomenclature and Structure of Carboxyl Group

    Short Answer

    The carboxyl group is a functional group in organic chemistry consisting of a carbon atom double-bonded to an oxygen atom (C=O) and single-bonded to a hydroxyl group (OH). It is denoted by -COOH. This group is found in carboxylic acids and gives them their acidic properties.

    Long Answer

    The carboxyl group (-COOH) plays a crucial role in organic chemistry, particularly in the chemistry of life. The structure consists of a carbon atom that forms two bonds: a double bond with an oxygen atom and a single bond with a hydroxyl group (OH). This unique arrangement is what makes the carboxyl group acidic. When in an aqueous solution, the hydrogen atom in the hydroxyl part can dissociate as a proton (H+), leaving behind a negatively charged carboxylate ion (COO-).

    Real-life example:
    Vinegar, which contains acetic acid, is a common household item that features the carboxyl group. The sour taste of vinegar is due to the acetic acid's carboxyl group.

    Activity to understand:
    To visualize the carboxyl group, you can draw a carbon atom (C) and attach it to an oxygen atom with a double bond (O=). Then, draw a single bond from the carbon to an OH group. This simple drawing represents the carboxyl group structure.

    Application in real life and career/industry:
    The carboxyl group is fundamental in the food industry for flavoring and preservatives, in pharmaceuticals for developing drugs, and in biochemistry for understanding and manipulating biological processes. Career paths include biochemistry, pharmaceuticals, and food science.

  7. 7.Methods of Preparation of Carboxylic Acids

    What are Carboxylic Acids?

    • Carboxylic acids are organic compounds containing the carboxyl functional group (-COOH).
    • They are weakly acidic.
    • Examples: Acetic acid (vinegar), formic acid (ant stings), benzoic acid (food preservative).

    Methods of Preparation

    1. From Primary Alcohols and Aldehydes

    • Short Answer: Primary alcohols and aldehydes are oxidized to produce carboxylic acids. Strong oxidizing agents like potassium permanganate (KMnO4) are used.

    • Long Answer:

      • Oxidation of Primary Alcohols:
        1. Primary alcohol → Aldehyde (oxidation)
        2. Aldehyde → Carboxylic acid (further oxidation)
      • Oxidation of Aldehydes: Aldehydes readily oxidize to carboxylic acids even with mild oxidizing agents.

    • Reaction example: CH3CH2OH (Ethanol) + [O] → CH3CHO (Ethanal) + [O] → CH3COOH (Ethanoic acid)

    • Real-world example: Production of vinegar (acetic acid) from ethanol in alcoholic drinks.

    • Applications: Industrial-scale production of carboxylic acids for various uses.

    2. From Alkylbenzenes

    • Short Answer: Alkylbenzenes (aromatic compounds with alkyl side chains) are oxidized using strong oxidizers to produce aromatic carboxylic acids.

    • Long Answer:

      • The entire alkyl side chain is oxidized to a carboxyl group (-COOH), regardless of its length.
      • Oxidizing agents like acidic potassium permanganate (KMnO4) or chromic acid are used.

    • Reaction Example: C6H5CH3 (Toluene) + [O] → C6H5COOH (Benzoic acid)

    • Real-world example: Benzoic acid is used as a food preservative.

    • Applications: Production of aromatic carboxylic acids for the pharmaceutical and chemical industries.

    3. From Nitriles and Amides

    • Short Answer: Nitriles and amides are hydrolyzed (react with water) in the presence of an acid or base catalyst to form carboxylic acids.

    • Long Answer:

      • Nitriles:
        1. Nitrile + Water + Acid/Base → Amide
        2. Amide + Water + Acid/Base → Carboxylic Acid
      • Amides:
        • Amide + Water + Acid/Base → Carboxylic Acid

    • Reaction Example:

      • CH3CN (Acetonitrile) + H2O + HCl → CH3CONH2 (Acetamide)
      • CH3CONH2 (Acetamide) + H2O + HCl → CH3COOH (Acetic acid)

    • Real-world example: This method has limited real-world applications due to the difficulty in obtaining nitriles and amides.

    • Applications: Laboratory-scale synthesis of carboxylic acids.

      4. From Grignard Reagents

      • Short Answer: Grignard reagents (organometallic compounds) react with carbon dioxide (CO2) to form carboxylic acids.

      • Long Answer:

        1. Grignard Reagent + CO2 → Carboxylate salt
        2. Carboxylate salt + Acid → Carboxylic Acid

      • Reaction Example:

        • CH3MgBr (Methylmagnesium bromide) + CO2 → CH3COOMgBr
        • CH3COOMgBr + HCl → CH3COOH (Acetic acid)

      • Real-world example: Laboratory synthesis of carboxylic acids, especially with more complex structures.

      • Applications: Useful for introducing new carbon chains for the synthesis of various organic molecules.

      5. From Acyl Halides and Anhydrides

      • Short Answer: Acyl halides and anhydrides undergo hydrolysis (reaction with water) to form carboxylic acids.

      • Long Answer:

        • Acyl Halides react with water to give carboxylic acids directly.
        • Anhydrides react with water, requiring more forcing conditions like heating.

      • Reaction Examples:

        • CH3COCl (Acetyl chloride) + H2O → CH3COOH (Acetic acid) + HCl
        • (CH3CO)2O (Acetic anhydride) + H2O → 2 CH3COOH (Acetic acid)

      • Real-world Example: Acyl halides are used less often due to their high reactivity and sensitivity to moisture. Anhydrides are more commonly used.

      • Applications: Industrial production of carboxylic acids, particularly those needed in pure form.

      6. From Esters

      • Short Answer: Esters are hydrolyzed by acids or bases to produce carboxylic acids and alcohols.

      • Long Answer:

        • Acid hydrolysis: Ester + Water + Acid → Carboxylic acid + Alcohol
        • Base Hydrolysis (Saponification): Ester + Base → Carboxylate Salt + Alcohol (The salt is then acidified to get the carboxylic acid)

      • Reaction Example:

        • CH3COOCH2CH3 (Ethyl acetate) + H2O + H+ → CH3COOH (Acetic acid) + CH3CH2OH (Ethanol)

      • Real-world example: Production of soaps (which are carboxylate salts) from fats and oils (which are esters).

      • Applications: Breaking down complex esters in various industries, including food and cosmetics.

      Where Do We Use Carboxylic Acids?

      Carboxylic acids pop up in various aspects of our lives:

      • Industry: Production of polymers (plastics, nylon), pharmaceuticals, solvents, food additives, soaps, and detergents.
      • Food: Preservatives (benzoic acid), flavorings (citric acid, lactic acid), and in the formation of vinegar (acetic acid).
      • Biology: Important building blocks for biomolecules like fatty acids, amino acids, and proteins.

  8. 8.Physical Properties of Carboxylic Acids

    Short Answer

    • Polarity: Carboxylic acids are polar molecules due to the presence of the carboxyl group (-COOH). This makes them soluble in polar solvents like water (to an extent).
    • Hydrogen Bonding: They can form strong hydrogen bonds with each other and water molecules. This leads to higher boiling points than alcohols of similar size.
    • Smell: Smaller carboxylic acids have a strong, unpleasant smell (think of vinegar or rancid butter). Larger ones are less smelly.
    • Acidity: Carboxylic acids are weak acids, meaning they partially donate a proton (H+) in water.

    Long Answer

    1. Polarity

      • Carboxylic acids have two oxygen atoms within the carboxyl group, and oxygen is highly electronegative (it pulls electrons towards itself).
      • This creates an uneven distribution of charge within the molecule, making it polar.
      • Real-life example: Vinegar (acetic acid) mixes well with water because both substances are polar.

    2. Hydrogen Bonding

      • The carboxyl group contains both a hydrogen atom bonded to oxygen (-OH) and a double-bonded oxygen (=O).
      • This allows them to form strong hydrogen bonds. Essentially, the slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of another.
      • Real-life example: Imagine the hydrogen bonds like tiny magnets connecting carboxylic acid molecules. This is why it takes more energy (heat) to boil them compared to nonpolar molecules.

    3. Smell

      • Smaller carboxylic acids (like acetic acid in vinegar, or butyric acid in rancid butter) have strong, pungent smells.
      • As the molecules get larger, the smell becomes less intense and can even be somewhat pleasant. This is why some esters, formed from carboxylic acids and alcohols, have fruity smells used in perfumes!

    4. Acidity

      • The -OH group can donate a proton (H+), making carboxylic acids weak acids.
      • Real-life example: Citric acid is what makes lemons and oranges sour.

    Where do Carboxylic Acids Matter?

    • Food Industry: They're used as preservatives, flavorings, and acidity adjusters (think vinegar, citric acid, etc.)
    • Cosmetics & Personal Care: Some carboxylic acids are used in skincare products for their mild exfoliating properties.
    • Pharmaceuticals: Building blocks for many medicines including aspirin.
    • Polymer Industry: Used to make plastics, resins, and coatings.
    • Biological Systems: Fatty acids (long-chain carboxylic acids) are crucial components of cell membranes and energy storage in our bodies.

  9. 9.Chemical Reactions of Carboxylic Acids

    Carboxylic acids are organic compounds containing the -COOH group. This group lends them some unique chemical properties. Let's break those reactions down:

    Reactions Involving Cleavage of O–H Bond (Acidity)

    • Short Answer: Carboxylic acids are weakly acidic. They react with metals and alkalis to give salts and release hydrogen or water.

    • Long Answer:

      • Reaction with Metals:
        • Carboxylic acids + Metals → Salt + Hydrogen Gas
        • Example: 2CH₃COOH (Acetic Acid) + Zn (Zinc) → (CH₃COO)₂Zn (Zinc Acetate) + H₂ (Hydrogen Gas)
      • Reaction with Alkalis (Bases):
        • Carboxylic Acids + Alkali → Salt + Water
        • Example: CH₃COOH (Acetic Acid) + NaOH (Sodium Hydroxide) → CH₃COONa (Sodium Acetate) + H₂O (Water)

    • Real-Life Example: The fizz when you drop an antacid tablet (base) into vinegar (acetic acid).

    • Applications:

      • Manufacturing of soaps, detergents.
      • Food preservation (acetic acid)

    Reactions Involving Cleavage of C–OH Bond

    • Short Answer: The -OH part of the carboxylic acid can be replaced by other groups.

    • Long Answer:

      1. Formation of Anhydrides: Carboxylic acids on heating with dehydrating agents (like P₂O₅) form anhydrides.

        • Example: 2CH₃COOH (Acetic Acid) + P₂O₅ → (CH₃CO)₂O (Acetic Anhydride) + H₂O

      2. Esterification: Carboxylic acids react with alcohols in the presence of an acid catalyst forming sweet-smelling esters.

        • Example: CH₃COOH + C₂H₅OH (Ethanol) ⇌ CH₃COOC₂H₅ (Ethyl Acetate) + H₂O

      3. Reactions with PCl₅, PCl₃ and SOCl₂: These chlorinating agents replace the -OH group with a chlorine atom, forming acid chlorides.

        • Example: CH₃COOH + PCl₅ → CH₃COCl (Acetyl Chloride) + POCl₃ + HCl

      4. Reaction with ammonia: Carboxylic acids react with ammonia to form acid amides.

        • Example: CH₃COOH + NH₃ → CH₃CONH₂ (Acetamide) + H₂O

    • Real-Life Examples:

      • Esters provide fruity fragrances in perfumes and are used as flavoring agents.
      • Acid chlorides/anhydrides are important in the synthesis of polymers and other organic compounds.

    • Applications:

      • Manufacture of polymers (like polyesters).
      • Aspirin synthesis.

    Reactions Involving –COOH Group

    • Short Answer: The whole -COOH group can be removed or replaced.

    • Long Answer

      1. Reduction: Carboxylic acids can be reduced to primary alcohols using strong reducing agents like LiAlH₄.

        • Example: CH₃COOH + LiAlH₄ → CH₃CH₂OH (Ethanol) + H₂O

      2. Decarboxylation: Heating carboxylic acids with soda lime (NaOH + CaO mixture) removes the -COOH group, releasing carbon dioxide.

        • Example: CH₃COOH + NaOH + CaO → CH₄ (Methane) + Na₂CO₃

    • Applications

      • Production of alkanes from carboxylic acids.
      • Synthesis of specific alcohols

    Substitution Reactions in the Hydrocarbon Part

    • Short Answer: Atoms in the hydrocarbon part of carboxylic acids can be replaced by other atoms or groups.

    • Long Answer

      1. Halogenation (Hell-Volhard-Zelinsky reaction): Carboxylic acids react with halogens (Cl₂, Br₂) in the presence of red phosphorus to give α-halo carboxylic acids.

        • Example: CH₃COOH + Cl₂ → CH₂ClCOOH (Chloroacetic acid) + HCl

      2. Ring substitution: Aromatic carboxylic acids (like benzoic acid) can undergo electrophilic substitution reactions like nitration, halogenation etc.

    • Applications

      • Production of halogenated acids used in various chemical syntheses

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