Slide 1: Aldehydes, Ketones & Carboxylic Acids

  • Aldehydes, ketones, and carboxylic acids are important organic compounds.
  • They are characterized by the presence of carbonyl group (C=O).
  • The position of carbonyl group and the presence of other functional groups determine their properties and reactivity.
  • In this lecture, we will focus on the concept-based problems and reaction sequence of toluenes.

Slide 2: Definition of Aldehydes

  • Aldehydes are organic compounds that contain a carbonyl group (-C=O) at the terminal carbon of a carbon chain.
  • The general formula for aldehydes is R-CHO, where R represents an alkyl or aryl group.
  • Aldehydes are named by replacing the “-e” of the alkane name with “-al”.
  • Example: Methanal (formaldehyde), Ethanal (acetaldehyde), Propanal (propionaldehyde)

Slide 3: Properties of Aldehydes

  • Aldehydes have a lower boiling point compared to alcohols of similar molecular weight.
  • They exhibit a characteristic fruity or nutty odor.
  • Aldehydes can undergo oxidation to form carboxylic acids.
  • They react with nucleophiles to undergo addition reactions.
  • Aldehydes are generally more reactive than ketones due to the presence of a hydrogen atom attached to the carbonyl carbon.

Slide 4: Definition of Ketones

  • Ketones are organic compounds that contain a carbonyl group (-C=O) bonded to two carbon atoms within the carbon chain.
  • The general formula for ketones is R-CO-R’, where R and R’ represent alkyl or aryl groups.
  • Ketones are named by replacing the “-e” of the alkane name with “-one”.
  • Example: Propanone (acetone), Butanone (methyl ethyl ketone), Hexan-2-one

Slide 5: Properties of Ketones

  • Ketones have higher boiling points compared to alkanes and alkenes of similar molecular weight.
  • They have lower boiling points compared to alcohols and carboxylic acids of similar molecular weight.
  • Ketones do not undergo oxidation like aldehydes.
  • They react with nucleophiles to undergo addition reactions.
  • Ketones are less reactive than aldehydes due to the absence of a hydrogen atom attached to the carbonyl carbon.

Slide 6: Definition of Carboxylic Acids

  • Carboxylic acids are organic compounds that contain a carboxyl group (-COOH) bonded to a carbon atom within the carbon chain.
  • The general formula for carboxylic acids is R-COOH, where R represents an alkyl or aryl group.
  • Carboxylic acids are named by replacing the “-e” of the alkane name with “-oic acid”.
  • Example: Methanoic acid (formic acid), Ethan(o)ic acid (acetic acid), Butan(o)ic acid

Slide 7: Properties of Carboxylic Acids

  • Carboxylic acids have higher boiling points compared to aldehydes, ketones, and alcohols of similar molecular weight.
  • They exhibit a sour taste and are responsible for the sourness of citrus fruits and vinegar.
  • Carboxylic acids readily donate a proton (H+) due to the presence of the carboxyl group.
  • They undergo reduction to form primary alcohols.
  • Carboxylic acids can form esters through the reaction with alcohols.

Slide 8: Reaction Sequence of Toluene to Benzyl Alcohol

  1. Toluene combines with ozone to form benzaldehyde.
  1. Benzaldehyde is further reduced by sodium borohydride to benzyl alcohol.
  1. Benzyl alcohol can be oxidized to benzoic acid by using oxidizing agents such as potassium permanganate.
  1. The reaction sequence can be represented as: Toluene → Benzaldehyde → Benzyl Alcohol → Benzoic Acid.

Slide 9: Concept-Based Problems - Aldehydes

  1. Name the following compound: CH3-CH2-CH2-CHO
    • The compound is named as butanal.
  1. Write the IUPAC name for the compound: CH3-CH(COOH)-CH2-CH2-CHO
    • The IUPAC name is 4-oxohexanoic acid.
  1. Draw the structure for formaldehyde.
    • H-C=O
  1. Identify the functional group present in the compound: CH3-CH=CH-CO-CH3
    • The functional group is a ketone.

Slide 10: Concept-Based Problems - Ketones

  1. Name the following compound: CH3-CO-CH2-CH2-CH3
    • The compound is named as pentan-2-one.
  1. Write the IUPAC name for the compound: CH3-CO-CH2-CH(COCH3)-CH3
    • The IUPAC name is heptan-3-one.
  1. Draw the structure for acetone.
    • CH3-CO-CH3
  1. Identify the functional group present in the compound: CH3-CH2-CO-CH2-CH3
    • The functional group is a ketone.

Slide 11: Concept-Based Problems - Aldehydes

  • Identify the functional group present in the compound: CH3CH2CH2COCH3
    • The functional group is an aldehyde.
  • Write the IUPAC name for the compound: CH3CH2CHO
    • The IUPAC name is propanal.
  • Draw the structure for pentanal.
    • CH3CH2CH2CH2CHO
  • Name the following compound: HCOCH2CH3
    • The compound is named as ethanal.
  • Predict the product obtained when butanal reacts with hydrogen cyanide (HCN).
    • The product is a cyanohydrin: CH3CH2CH2CHO + HCN → CH3CH2CH(OH)CN

Slide 12: Concept-Based Problems - Ketones

  • Identify the functional group present in the compound: CH3COCH2CH2CH2CH3
    • The functional group is a ketone.
  • Write the IUPAC name for the compound: CH3COCH2COCH3
    • The IUPAC name is pentan-2,3-dione.
  • Draw the structure for butanone.
    • CH3COCH2CH2CH3
  • Name the following compound: CH3COCH(CH3)COCH3
    • The compound is named as 3-methylpentan-2-one.
  • Predict the product obtained when pentan-3-one reacts with sodium ethoxide (CH3CH2O-Na+).
    • The product is an aldol condensation product: CH3COCH2CH2COCH3 + CH3CH2O-Na+ → CH3COCH2CH(OH)CH2CH3

Slide 13: Concept-Based Problems - Carboxylic Acids

  • Identify the functional group present in the compound: CH3CH2COOH
    • The functional group is a carboxylic acid.
  • Write the IUPAC name for the compound: CH3CH2CH2COOH
    • The IUPAC name is butanoic acid.
  • Draw the structure for methanoic acid.
    • HCOOH
  • Name the following compound: CH3COOCH2CH2CH3
    • The compound is named as ethyl propanoate.
  • Predict the product obtained when propanoic acid reacts with methanol (CH3OH).
    • The product is an ester: CH3CH2COOH + CH3OH → CH3CH2COOCH3 + H2O

Slide 14: Oxidation of Aldehydes

  • Aldehydes can be oxidized to carboxylic acids using oxidizing agents such as potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7).
    • Example: CH3CHO + [O] → CH3COOH
  • Tollens’ reagent, also known as silver mirror test, can be used to differentiate between aldehydes and ketones.
    • Tollens’ reagent is a solution of silver nitrate (AgNO3) in ammonia (NH3).
    • Aldehydes are oxidized by Tollens’ reagent to form a silver mirror on the inner surface of the test tube.
    • Ketones do not react with Tollens’ reagent.
  • Fehling’s solution can also be used to test for the presence of aldehydes.
    • Fehling’s solution contains copper(II) sulfate (CuSO4) and sodium potassium tartrate (NaKC4H4O6).
    • Aldehydes are oxidized by Fehling’s solution to form a brick red precipitate of copper(I) oxide (Cu2O).

Slide 15: Nucleophilic Addition Reactions - Aldehydes and Ketones

  • Aldehydes and ketones undergo nucleophilic addition reactions.
    • The carbonyl carbon of aldehydes and ketones is electrophilic and can be attacked by nucleophiles.
  • Nucleophiles such as hydroxide ions (OH-), cyanide ions (CN-), and grignard reagents (RMgX) can react with aldehydes and ketones to form alcohols.
    • Example: CH3COCH3 + OH- → CH3COCH2OH
  • Aldehydes and ketones can also react with hydrazine (NH2NH2) to form hydrazones.
    • Example: CH3CHO + NH2NH2 → CH3CH(NH-NH2)O
  • Ketones containing an α-hydrogen atom can undergo an aldol condensation reaction to form β-hydroxyaldehyde or β-hydroxyketone.
    • The reaction involves the nucleophilic addition of the enolate ion formed by the α-hydrogen elimination and subsequent dehydration.
    • Example: CH3COCH2CH3 + OH- → CH3CH(OH)CH2CH3

Slide 16: Oxidation of Primary Alcohols to Carboxylic Acids

  • Primary alcohols can be oxidized to carboxylic acids using strong oxidizing agents such as potassium dichromate (K2Cr2O7) or potassium permanganate (KMnO4).
    • Example: CH3CH2CH2OH + [O] → CH3CH2COOH
  • Secondary alcohols cannot be oxidized to carboxylic acids, as they lack an H atom attached to the carbon bearing the -OH group.
    • Example: CH3CH(OH)CH3 + [O] will not produce a carboxylic acid.
  • Tertiary alcohols are resistant to oxidation and do not undergo oxidation reactions.
    • Example: (CH3)3COH + [O] will not produce a carboxylic acid.
  • The oxidation reactions of alcohols involve the loss of hydrogen and gain of oxygen.

Slide 17: Esterification

  • Esterification is the reaction between a carboxylic acid and an alcohol to form an ester.
    • The reaction is catalyzed by an acid (such as sulfuric acid or hydrochloric acid).
  • Esterification can be represented as: RCOOH + R’OH → RCOOR’ + H2O
    • R and R’ represent alkyl or aryl groups.
  • Esterification reactions are reversible, and the equilibrium can be shifted towards ester formation by using excess alcohol or removing water from the reaction mixture.
  • Esters are commonly used as fragrances and flavors, as well as solvents in various industries.

Slide 18: Hydrolysis of Esters

  • Esters can be hydrolyzed to form carboxylic acids and alcohols.
    • The reaction is catalyzed by either an acid or a base.
  • Acid hydrolysis of esters involves the use of strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H2SO4).
    • Ester + Acid → Carboxylic Acid + Alcohol
  • Base hydrolysis of esters involves the use of strong bases, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).
    • Ester + Base → Carboxylate Salt + Alcohol
  • Hydrolysis of esters produces one molecule of carboxylic acid and one molecule of alcohol.

Slide 19: Reactions of Carboxylic Acids

  • Carboxylic acids can be reduced to primary alcohols by using reducing agents such as lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4).
    • Example: CH3COOH + 4[H] → CH3CH2OH
  • Carboxylic acids can react with alcohols in the presence of an acid catalyst to form esters through esterification reaction.
    • Example: CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O
  • Carboxylic acids undergo decarboxylation in the presence of suitable catalysts to form hydrocarbons.
    • Example: CH3COOH → CH3CO + CO2 + H2O
  • Carboxylic acids can be converted to acyl chlorides (acid chlorides) by reacting with thionyl chloride (SOCl2).
    • Example: CH3COOH + SOCl2 → CH3COC1 + SO2 + HCl

Slide 20: Summary

  • Aldehydes, ketones, and carboxylic acids are important organic compounds.
  • Aldehydes contain a carbonyl group at the terminal carbon, while ketones have a carbonyl group bonded to two carbons within the carbon chain.
  • Carboxylic acids have a carboxyl group bonded to a carbon atom within the carbon chain.
  • Aldehydes and ketones undergo nucleophilic addition reactions and can be oxidized to form carboxylic acids.
  • Primary alcohols can be oxidized to carboxylic acids, while esterification reactions form esters from carboxylic acids and alcohols.
  • Hydrolysis reactions reverse the esterification process, yielding carboxylic acids and alcohols.
  • Carboxylic acids can undergo various other reactions, such as reduction, decarboxylation, and formation of acyl chlorides.

Slide 21: Concept-Based Problems - Aldehydes

  • Identify the functional group present in the compound: CH3-CHO
    • The functional group is an aldehyde.
  • Write the IUPAC name for the compound: CH3-CH2-CHO
    • The IUPAC name is butanal.
  • Draw the structure for propanal.
    • CH3-CH2-CH=O
  • Name the following compound: CH3-CHOCH2CH3
    • The compound is named as propanal.
  • Predict the product obtained when butanal reacts with hydrogen cyanide (HCN).
    • The product is a cyanohydrin: CH3-CH2-CHO + HCN → CH3-CH2-CH(OH)CN

Slide 22: Concept-Based Problems - Ketones

  • Identify the functional group present in the compound: CH3-CO-CH2-CH3
    • The functional group is a ketone.
  • Write the IUPAC name for the compound: CH3-CO-CH2-CH2-CH3
    • The IUPAC name is pentan-2-one.
  • Draw the structure for pentanone.
    • CH3-CO-CH2-CH2-CH3
  • Name the following compound: CH3-CO-CH(CH3)-CO-CH3
    • The compound is named as 3-methylpentan-2-one.
  • Predict the product obtained when pentan-3-one reacts with sodium ethoxide (CH3CH2O-Na+).
    • The product is an aldol condensation product: CH3-CO-CH2-CH2-CO-CH3 + CH3CH2O-Na+ → CH3-CO-CH2-CH(OH)-CH2CH3

Slide 23: Concept-Based Problems - Carboxylic Acids

  • Identify the functional group present in the compound: CH3-COOH
    • The functional group is a carboxylic acid.
  • Write the IUPAC name for the compound: CH3-CH2-CH2-COOH
    • The IUPAC name is butanoic acid.
  • Draw the structure for propanoic acid.
    • CH3-CH2-COOH
  • Name the following compound: CH3-COOCH2-CH2-CH3
    • The compound is named as ethyl propanoate.
  • Predict the product obtained when propanoic acid reacts with methanol (CH3OH).
    • The product is an ester: CH3-CH2-COOH + CH3OH → CH3-CH2-COOCH3 + H2O

Slide 24: Oxidation of Aldehydes

  • Aldehydes can be oxidized to carboxylic acids using oxidizing agents such as potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7).
    • Example: CH3-CHO + [O] → CH3-COOH
  • Tollens’ reagent can be used to differentiate between aldehydes and ketones.
    • Aldehydes are oxidized by Tollens’ reagent to form a silver mirror on the inner surface of the test tube.
    • Ketones do not react with Tollens’ reagent.
  • Fehling’s solution can be used to test for the presence of aldehydes.
    • Aldehydes are oxidized by Fehling’s solution to form a