Nomenclature of Aldehydes and Ketones

• Aldehydes are named by replacing the -e of the corresponding alkane with -aldehyde
• Ketones are named by replacing the -e of the corresponding alkane with -one Examples:
• Ethanal (CH3CHO) is an aldehyde
• Propanone (CH3COCH3) is a ketone

Physical Properties of Aldehydes and Ketones

• Aldehydes and ketones have higher boiling points than alkanes and ethers due to the presence of dipole-dipole interactions
• The boiling points generally increase with the increase in molecular weight
• Aldehydes and ketones are polar compounds and can form hydrogen bonds with water Examples:
• Acetone (CH3COCH3) has a boiling point of 56.2°C
• Formaldehyde (CH2O) has a boiling point of -19°C

Chemical Reactions of Aldehydes

1. Oxidation:
   • Aldehydes can be oxidized to carboxylic acids using strong oxidizing agents like potassium permanganate (KMnO4)
   • The aldehyde is converted into a carboxylic acid by gaining oxygen and losing hydrogen Example:
   • Oxidation of ethanol (CH3CH2OH) gives acetic acid (CH3COOH)

2. Reduction:
   • Aldehydes can be reduced to primary alcohols using reducing agents like lithium aluminum hydride (LiAlH4)
   • The aldehyde is converted into an alcohol by gaining hydrogen Example:
   • Reduction of formaldehyde (CH2O) gives methanol (CH3OH)

Chemical Reactions of Ketones

1. Nucleophilic Addition:
   • Ketones undergo nucleophilic addition reactions where a nucleophile adds to the carbonyl group, forming a new bond
   • The oxygen of the carbonyl group is relatively electron deficient and attracts nucleophiles Example:
   • Addition of alcohol to acetone (CH3COCH3) forms a hemiacetal

2. Oxidation:
   • Ketones are generally resistant to oxidation and do not easily undergo oxidation reactions
   • However, some ketones can be oxidized to form carboxylic acids using strong oxidizing agents Example:
   • Oxidation of secondary alcohol, cyclohexanone, forms cyclohexanone carboxylic acid

Chemical Reactions of Carboxylic Acids

1. Esterification:
   • Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters
   • The carboxylic acid loses a water molecule and the alcohol adds to the carbonyl group, forming a new bond Example:
   • Reaction between acetic acid (CH3COOH) and methanol (CH3OH) forms methyl acetate

2. Decarboxylation:
   • Carboxylic acids can undergo decarboxylation reactions to form carbon dioxide and the corresponding hydrocarbon
   • This reaction is often catalyzed by heat or strong acids Example:
   • Decarboxylation of acetic acid (CH3COOH) forms methane (CH4)

Tests for Aldehydes and Ketones

1. Tollens’ Test:
   • Aldehydes react with Tollens’ reagent (ammoniacal silver nitrate) to form a silver mirror
   • Ketones do not react with Tollens’ reagent Example:
   • Formaldehyde (CH2O) gives a silver mirror when treated with Tollens’ reagent

2. Fehling’s Test:
   • Aldehydes react with Fehling’s solution (a mixture of copper sulfate and sodium hydroxide) to form a red precipitate of copper(I) oxide
   • Ketones do not react with Fehling’s solution Example:
   • Glucose (an aldehyde) gives a red precipitate when treated with Fehling’s solution

Nucleophilic Addition Reactions of Aldehydes and Ketones

1. Addition of Alcohol:
   • Aldehydes and ketones react with alcohol in the presence of an acid catalyst to form hemiacetals and acetals
   • The alcohol adds to the carbonyl group, forming a new bond, and water is eliminated Example:
   • Addition of methanol to formaldehyde forms methoxymethanol

2. Addition of Ammonia and Primary Amines:
   • Aldehydes and ketones react with ammonia and primary amines to form imines and enamines
   • The nitrogen of the ammonia or amine replaces the oxygen of the carbonyl group, forming a new bond Example:
   • Reaction between formaldehyde and ammonia forms methylimine

Condensation Reactions of Aldehydes and Ketones

1. Aldol Condensation:
   • Two molecules of an aldehyde or ketone react to form a beta-hydroxy aldehyde or ketone in the presence of a base
   • The carbonyl group of one molecule adds to the alpha carbon of another molecule, forming a new bond Example:
   • Condensation of two molecules of formaldehyde forms ethylene glycol

2. Cannizzaro Reaction:
   • Aldehydes with no alpha hydrogen atoms undergo self-cannizzaro reaction, forming a carboxylic acid and alcohol
   • This reaction is facilitated by a strong base Example:
   • Formaldehyde undergoes self-cannizzaro reaction to form formic acid and methanol

Electrophilic Addition Reactions of Aldehydes and Ketones

1. Addition of Hydrogen Cyanide:
   • Aldehydes and ketones react with hydrogen cyanide to form cyanohydrins
   • The cyanide ion adds to the carbonyl group, forming a new bond Example:
   • Addition of hydrogen cyanide to ethanal forms cyanohydrin

2. Addition of Grignard Reagents:
   • Aldehydes and ketones react with Grignard reagents to form alcohols
   • The carbon of the carbonyl group adds to the carbon of the Grignard reagent, forming a new bond Example:
   • Addition of phenylmagnesium bromide to propanone forms 1-phenyl-2-propanol

Nucleophilic Addition Reactions of Aldehydes and Ketones

• Addition of Grignard Reagents:
  • Aldehydes and ketones react with Grignard reagents to form alcohols
  • The carbon of the carbonyl group adds to the carbon of the Grignard reagent, forming a new bond Example:
  • Addition of phenylmagnesium bromide to propanone forms 1-phenyl-2-propanol
• Addition of Hydrazine and Derivatives:
  • Aldehydes and ketones react with hydrazine (N2H4) or its derivatives to form hydrazones
  • The nitrogen of the hydrazine or derivative adds to the carbonyl group, forming a new bond Example:
  • Reaction between formaldehyde and phenylhydrazine forms phenylhydrazone
• Addition of Sodium Bisulfite:
  • Aldehydes and some ketones react with sodium bisulfite (NaHSO3) to form bisulfite addition products
  • The bisulfite ion adds to the carbonyl group, forming a new bond Example:
  • Reaction between formaldehyde and sodium bisulfite forms a crystalline addition product

Condensation Reactions of Aldehydes and Ketones

• Aldol Condensation:
  • Two molecules of an aldehyde or ketone react to form a beta-hydroxy aldehyde or ketone in the presence of a base
  • The carbonyl group of one molecule adds to the alpha carbon of another molecule, forming a new bond Example:
  • Condensation of two molecules of formaldehyde forms ethylene glycol
• Claisen Condensation:
  • Two molecules of an ester or a ketone react in the presence of a strong base to form a beta-keto ester or a beta-diketone
  • The carbonyl group of one molecule adds to the alpha carbon of another molecule, forming a new bond Example:
  • Condensation of ethyl ethanoate and ethyl propanoate forms ethyl 3-oxobutanoate
• Dieckmann Condensation:
  • The intramolecular ester condensation of a diester forms a cyclic beta-keto ester
  • The carbonyl group of one ester adds to the alpha carbon of the other ester within the same molecule Example:
  • Condensation of diethyl malonate forms 5,5-diethyl-1,3-cyclopentanedione

Reactions of Carboxylic Acids

• Decarboxylation:
  • Carboxylic acids can undergo decarboxylation reactions to form carbon dioxide and the corresponding hydrocarbon
  • This reaction is often catalyzed by heat or strong acids Example:
  • Decarboxylation of acetic acid (CH3COOH) forms methane (CH4)
• Reduction:
  • Carboxylic acids can be reduced to primary alcohols using reducing agents like lithium aluminum hydride (LiAlH4) or hydrogen gas with catalysts
  • The carboxylic acid group is converted to an alcohol group by gaining hydrogen Example:
  • Reduction of acetic acid (CH3COOH) gives ethanol (CH3CH2OH)
• Esterification:
  • Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters
  • The carboxylic acid loses a water molecule and the alcohol adds to the carboxyl group, forming a new bond Example:
  • Reaction between acetic acid (CH3COOH) and ethanol (CH3CH2OH) forms ethyl acetate

Physical Properties of Carboxylic Acids

• Carboxylic acids are polar compounds and can form hydrogen bonds with water
• They have higher boiling points compared to alcohols and ethers of similar molecular weight due to the presence of hydrogen bonding
• The boiling points generally increase with the increase in molecular weight
• Carboxylic acids up to four carbon atoms are soluble in water, but solubility decreases with increasing molecular weight Example:
• Acetic acid (CH3COOH) has a boiling point of 118.1°C
• Butanoic acid (CH3CH2CH2COOH) has a boiling point of 163.7°C

Nomenclature of Carboxylic Acids

• Carboxylic acids are named by replacing the -e of the corresponding alkane with -oic acid
• The carboxyl carbon is assigned the lowest possible number
• For carboxylic acids with other functional groups, the carboxyl group is considered the primary functional group and receives the lowest possible number Examples:
• Methanoic acid (HCOOH) is the simplest carboxylic acid
• Ethanoic acid (CH3COOH) is commonly known as acetic acid

Tests for Carboxylic Acids

• Sodium Bicarbonate Test:
  • Carboxylic acids react with sodium bicarbonate (NaHCO3) to produce carbon dioxide gas
  • The evolution of gas is observed as effervescence Example:
  • Reaction between acetic acid and sodium bicarbonate produces carbon dioxide gas bubbles
• Litmus Test:
  • Carboxylic acids turn blue litmus paper red, indicating their acidic nature
  • They are capable of donating a proton to the litmus, which acts as a weak acid Example:
  • Diphenylmethanoic acid turns blue litmus paper red

Chemical Reactions of Carboxylic Acids

• Decarboxylation:
  • Carboxylic acids can undergo decarboxylation reactions to form carbon dioxide and the corresponding hydrocarbon
  • This reaction is often catalyzed by heat or strong acids Example:
  • Decarboxylation of acetic acid (CH3COOH) forms methane (CH4)
• Esterification:
  • Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters
  • The carboxylic acid loses a water molecule and the alcohol adds to the carboxyl group, forming a new bond Example:
  • Reaction between acetic acid (CH3COOH) and ethanol (CH3CH2OH) forms ethyl acetate
• Reduction:
  • Carboxylic acids can be reduced to primary alcohols using reducing agents like lithium aluminum hydride (LiAlH4) or hydrogen gas with catalysts
  • The carboxylic acid group is converted to an alcohol group by gaining hydrogen Example:
  • Reduction of acetic acid (CH3COOH) gives ethanol (CH3CH2OH)

Reactions of Carboxylic Acids

• Oxidation:
  • Carboxylic acids can be oxidized to form carbon dioxide and water using strong oxidizing agents like potassium permanganate (KMnO4)
  • The carboxylic acid gains oxygen and loses hydrogen during the oxidation process Example:
  • Oxidation of ethanoic acid (CH3COOH) forms carbon dioxide and water
• Esterification:
  • Carboxylic acids react with alcohols in the presence of an acid catalyst to form esters
  • The carboxylic acid loses a water molecule and the alcohol adds to the carboxyl group, forming a new bond Example:
  • Reaction between acetic acid (CH3COOH) and ethanol (CH3CH2OH) forms ethyl acetate
• Nucleophilic Substitution:
  • Carboxylic acids can undergo nucleophilic substitution reactions, where a nucleophile replaces the leaving group on the carboxyl carbon
  • The nucleophile forms a new bond with the carboxyl carbon, resulting in the formation of a new compound Example:
  • Reaction between acetic acid and ammonia forms acetamide

Derivatives of Carboxylic Acids: Acid Chlorides

• Acid Chlorides:
  • Acid chlorides are derivatives of carboxylic acids where the -OH group is replaced by a -Cl group
  • They are highly reactive compounds and are often used as intermediates in organic synthesis Example:
  • Ethanoic acid (CH3COOH) can be converted to ethanoyl chloride (CH3COCl)
• Reactions of Acid Chlorides:
  • Acid chlorides react with nucleophiles like alcohols and amines to form esters and amides, respectively
  • The -Cl group is replaced by -OR or -NR2 groups, forming new compounds Example:
  • Ethanoyl chloride (CH3COCl) reacts with methanol (CH3OH) to form methyl ethanoate (CH3COOCH3)

Derivatives of Carboxylic Acids: Esters

• Esters:
  • Esters are derivatives of carboxylic acids where the -OH group is replaced by an -OR group
  • They have pleasant odors and are often used in perfumes and flavorings Example:
  • Ethanoic acid (CH3COOH) can be converted to ethyl acetate (CH3COOCH2CH3)
• Reactions of Esters:
  • Esters can undergo hydrolysis reactions in the presence of acids or bases to form carboxylic acids and alcohols
  • The ester bond is cleaved, and the -OR group is replaced by -OH and -R groups Example:
  • Hydrolysis of methyl ethanoate (CH3COOCH3) in the presence of an acid or base forms methanol (CH3OH) and ethanoic acid (CH3COOH)

Aldehydes, Ketones & Carboxylic Acids

• Example: Addition of Alcohol

  • Aldehydes and ketones react with alcohols in the presence of an acid catalyst to form hemiacetals and acetals
  • The alcohol adds to the carbonyl group, forming a new bond, and water is eliminated

  Reaction:
  CH3CHO + CH3OH ⟶ CH3CH(OMe) + H2O (Ethanal) (Methanol) (Ethyl Methoxide)

• Example: Addition of Ammonia and Primary Amines

  • Aldehydes and ketones react with ammonia and primary amines to form imines and enamines
  • The nitrogen of the ammonia or amine replaces the oxygen of the carbonyl group, forming a new bond

  Reaction: CH3CHO + NH3 ⟶ CH3CH=NH + H2O (Ethanal) (Ammonia) (Methylamine)

• Example: Addition of Sodium Bisulfite

  • Aldehydes and some ketones react with sodium bisulfite to form bisulfite addition products
  • The bisulfite ion adds to the carbonyl group, forming a new bond

  Reaction: CH3CHO + NaHSO3 ⟶ CH3CH(OH)SO3Na (Ethanal) (Sodium bisulfite) (S