Alcohol, Aldehydes, Ketones, Carboxylic Acid, Esters, Amines and Amides

Alcohols and Phenols

• Alcohols: One or more hydrogen atoms in an alkane are replaced by an -OH group, connected to an sp³ hybridized carbon atom.
• Phenols: -OH group attached to a carbon atom within a benzene ring.
• Classification of Alcohols (based on the number of carbon atoms bonded to the carbon bearing the hydroxyl group):
  • Primary (1°): Hydroxyl-bearing carbon attached to one other carbon atom.
  • Secondary (2°): Hydroxyl-bearing carbon attached to two other carbon atoms.
  • Tertiary (3°): Hydroxyl-bearing carbon attached to three other carbon atoms.
• Phenols are more acidic than alcohols.

Physical Properties

• Alcohols: Non-polar (alkane-like) chain and a polar hydroxyl group.
  • Short-chain alcohols are miscible in water.
  • Miscibility decreases as the number of carbon atoms increases, but the boiling point increases.
• Phenols: Hydroxyl group attached to a benzene ring.
  • More acidic than alcohols.
  • Can form stronger hydrogen bonds, influencing boiling points and solubility.
• Alcohols have higher boiling points than alkanes of the same chain length due to hydrogen bonding.
• Polyhydroxy alcohols have higher boiling points than monohydroxy alcohols due to increased hydrogen bonding.

Classification of Alcohols (According to Location)

• Primary (1°) Alcohols
• Secondary (2°) Alcohols
• Tertiary (3°) Alcohols

Classification of Alcohols (According to the Number of -OH Groups)

• Diols: Alcohols with two hydroxyl groups.
• Triols: Alcohols with three hydroxyl groups.
• Concentrated phenol solutions are highly toxic and can cause severe burns.

Oxidation of Alcohols

• Products depend on the type of alcohol and the oxidizing agent used.
• Mild oxidizing agents (e.g., PCC) selectively oxidize primary alcohols to aldehydes.
• Strong oxidizing agents (e.g., $KMnO<em>4$, $K</em>2Cr<em>2O</em>7$) are commonly used in laboratory settings.
  • Primary alcohols oxidize to aldehydes, then to carboxylic acids (if conditions allow).
  • Secondary alcohols oxidize to ketones (e.g., isopropanol to acetone).
  • Tertiary alcohols do not undergo oxidation under normal conditions due to the absence of a hydrogen atom on the carbon bearing the -OH group.
• Phenols have different reactivity due to the aromatic ring.
  • More acidic than alcohols.
  • Undergo electrophilic aromatic substitution reactions.

Bordwell-Wellman Test

• Solution contains potassium dichromate dissolved in sulfuric acid.
• Orange-yellow solution due to the presence of the $Cr<em>2O</em>7^{-2}$ ion.
• During oxidation, the oxidation state of chromium is reduced from +6 to +3, forming $Cr^{+3}$.
• Color changes to blue-green or greenish, indicating the presence of primary or secondary alcohols.

Chromic Acid Test

• Primary alcohols are oxidized to carboxylic acids.
• Secondary alcohols are oxidized to ketones.
• Tertiary alcohols do not undergo oxidation.

Miscibility Test

• $KMnO<em>4$: Initially purple, produces a brown precipitate of $MnO</em>2$ when reduced.
• $K<em>2Cr</em>2O<em>7$ in acidic medium (H2SO4) changes from orange to green or blue-green as $Cr</em>2O_7^{-2}$ ions are reduced to $Cr^{+3}$ ions.
• Phenols can also be oxidized using chromic acid and potassium dichromate, yielding different products compared to alcohols.

Lucas Test

• Reagent: Zinc chloride in concentrated HCl (freshly prepared).
  • Tertiary alcohols react immediately (solution heats up, insoluble chloride forms two layers or a cloudy dispersion).
  • Secondary alcohols become cloudy in 5 to 10 minutes (use a hot water bath if needed).
  • Primary alcohols show no reaction within a reasonable timeframe.

Iodoform Test

• Detects carbonyl compounds with the structure R-CO-CH3 or alcohols with the structure R-CH(OH)-CH3.
• Iodine and a base react to produce a yellow precipitate of iodoform ($CHI_3$), which has a distinct yellow color and a medicinal odor.
  • The iodine oxidizes the carbonyl compound or alcohol.
  • The base deprotonates the intermediate to form iodoform.
  • The presence of the yellow precipitate confirms the presence of the specific carbonyl or alcohol structure.

Ferric Chloride Test

• Phenols react with ferric ions to form highly colored coordination complexes (blue-violet).
• Alcohols do not form highly colored complexes.
• Add a few drops of ferric chloride solution to the test substance. A blue-violet coloration indicates the presence of phenols.

Aldehydes and Ketones

• Aldehydes: General formula RCHO (R can be aliphatic or aromatic).
• Ketones: General formula R-CO-R' (R and R' represent aliphatic or aromatic groups).
• Carbonyl group (C=O) is highly reactive.
• Aldehydes have at least one hydrogen atom directly bonded to the carbonyl carbon, while ketones have two organic groups.

Carboxylic Acids and Esters

• Carboxylic acids: Defined by the carboxyl group (HO-C=O), which combines the carbonyl group (C=O) with the hydroxyl group (-OH).
• Esters: Derived from carboxylic acids, replace the hydroxyl group (-OH) with an alkoxy group (-OR).
• Carbonyl carbon is polar (slight positive charge on carbon, slight negative charge on oxygen).
• Carboxylic acids are weak acids that ionize slightly in water.
• Aldehydes and ketones have higher boiling points than amines, esters, ethers, and hydrocarbons due to dipole-dipole interactions but lower than alcohols due to the lack of intermolecular hydrogen bonding.
• Lower aldehydes and ketones are miscible with water due to hydrogen bonding.
• Lower aldehydes emit strong, pungent odors that become more fragrant with increasing molecular size.
• Low Molecular Weight Carboxylic Acids are HIGHLY SOLUBLE IN WATER, more so than alcohols, ethers, aldehydes, and ketones, due to stronger hydrogen bonding.
• Larger Carboxylic Acids are INSOLUBLE IN WATER unless converted to a salt, which significantly increases their solubility.
• Esters are known for their pleasant odors and are used as fragrances and flavorings.

Properties of Carboxylic Acids and Esters

• Direct bonding of hydroxyl and carbonyl groups causes each to influence the properties of the other.
• A key distinction in carboxylic acids is the hydrogen atom attached to the oxygen, which allows for the formation of hydrogen bonds between molecules.
• The functional group of an ester is the ester group (-COOR), consisting of a carbonyl group (C=O) bonded to an alkyl or aryl group (R) via an oxygen atom.
• Esters exhibit a variety of physical properties influenced by molecular size, functional groups, and intermolecular forces.

Solubility

• All aldehydes and ketones are relatively soluble in organic solvents (benzene, ether, methanol, chloroform).
• Their solubility decreases as the alkyl chain length increases.
• Many naturally occurring aldehydes and ketones are used in perfumery and the food industry.

Chemical Properties of Aldehydes and Ketones

• Aldehydes are easily oxidized due to the presence of a hydrogen atom bonded to the carbonyl group.
• Ketones are highly resistant to oxidation (can only be oxidized by powerful oxidizing agents capable of breaking carbon-carbon bonds).

Oxidation Reactions

• Aldehyde Oxidation: $(aldehyde) RCHO + (O) \rightarrow RCOOH (carboxylic acid)$
• Ketone Oxidation: $(ketone) RCOR’ + strong oxidizing agent \rightarrow No visible reaction$

Tollen’s Test

• Distinctive qualitative test for aldehydes.
• Silver ion (in the form of the complex ion $Ag(NH<em>3)</em>2^+$) oxidizes aldehydes to corresponding carboxylic acids and is reduced to metallic silver (silver mirror test).
• Ketones do not typically react with Tollen’s reagent.

Fehling’s Test

• Specifically used for detecting aliphatic aldehydes.
• Reagent: Deep-blue, alkaline solution that contains a complex cupric ion.
• Aliphatic aldehyde reacts with Fehling's solution, cupric ion is reduced to cuprous oxide, which precipitates as an orange-to-brick-red solid.

Fehling's Test Reaction

• $RCHO + Cu^{+2} + NaOH \rightarrow RCOO^-Na^+ + Cu_2O (BRICK-RED PRECIPITATE)$

Properties of Esters

• Typically liquids at room temperature, but smaller esters can be volatile, and larger esters may be waxy solids.
• Soluble in organic solvents (alcohols, ethers, chloroform) but have limited solubility in water.
• Smaller esters tend to have lower boiling and melting points and lower densities than water.
• Aromatic aldehydes are insensitive to Fehling's solution due to additional resonance stabilization.

2,4-Dinitrophenylhydrazine (DNP) Test

• Most aldehydes and ketones react readily, forming bright yellow or orange 2,4-dinitrophenylhydrazones.
• Hydrazones have distinct melting points and can be used to confirm the presence of these functional groups.
• Yellow precipitates indicate non-conjugated ketones or aldehydes, whereas red-orange precipitates indicate conjugated systems.

Schiff’s Test

• Fuchsin (roseaniline hydrochloride) is a red-pink triphenylmethane dye.
• When Schiff’s reagent is added to an aldehyde, it forms a magenta-red color.
• A color change from pink or colorless to violet-purple/magenta-red indicates the presence of an aldehyde functional group.
• Fehling's test is also used to quantitatively measure