L4 alcohols and phenol 2022

ALCOHOLS, PHENOLS, & ETHERS

  • Hydroxy group: -OH functional group.

  • Alcohols: Contains an -OH group attached to an aliphatic carbon (R-OH).

  • Phenols: -OH group is attached to a benzene ring.

  • Ethers: Functional group is R-O-R’. General formula is R-O-R'.

NAMING ALCOHOLS

  1. Identify the longest chain where the -OH group is attached; modify the hydrocarbon name by dropping the final -e and replace it with -ol.

  2. Number the longest chain to assign the lowest number to the carbon with the -OH group.

  3. Example: For 3-hexanol, structure CH3—CH2—CH2—CH—CH2—CH3 is numbered as:

    • Position: 6 5 4 3 2 1

    • Group: OH located at 3.

  4. Locate and name any other substituents on the longest chain.

  5. Combine the names and positions of substituents with the -OH and the longest chain for the final name.

    • Alcohols with two -OH groups are called diols and those with three are triols (IUPAC names use -diol and -triol).

    • Example structure for 2,4-dimethyl-3-hexanol: CH3—CH2—CH—CH—CH—CH3.

NAMING PHENOLS

  • Substituted phenols are named as derivatives of phenol itself.

    • Examples:

      • Phenol: OH

      • 4-bromophenol: Br

      • 2,4,6-tribromophenol: Br

CLASSIFICATION OF ALCOHOLS

Types of Alcohols:

  • Primary: R-CH2-OH (e.g., 1-propanol/p-ropyl alcohol)

  • Secondary: R-CH-OH-R' (e.g., 2-propanol/isopropyl alcohol)

  • Tertiary: R-C(OH)-R' (e.g., 2-methyl-2-propanol/t-butyl alcohol)

PHYSICAL PROPERTIES OF ALCOHOLS

  • The -OH group is polar, enabling hydrogen bonding.

  • Low molecular weight alcohols are highly soluble in water due to hydrogen bonding.

  • Larger alkanes increase hydrophobicity, leading to decreased solubility in water.

    • Example with 1-heptanol: hydrophilic part (water-loving) vs hydrophobic part (water-hating).

  • Boiling points are influenced by hydrogen bonds among alcohol molecules, leading to relatively high boiling points.

    • Example: Hydrogen bonding in pure ethanol.

ALCOHOL REACTIONS

  • Dehydration Reaction: The removal of water from an alcohol at 180°C producing an alkene.

  • Dehydration at 140°C can yield an ether.

  • Oxidation Reactions:

    • Primary alcohols oxidize to aldehydes, then to carboxylic acids.

    • Secondary alcohols oxidize to ketones.

    • Tertiary alcohols do not undergo oxidation.

IMPORTANT ALCOHOLS

  • Methanol (wood alcohol, CH3OH):

    • Solvent and industrial material; highly toxic.

  • Ethanol (ethyl alcohol, CH3CH2OH):

    • Produced from ethylene or fermentation; used as solvent, fuel, and in beverages; moderately toxic.

  • 2-Propanol (isopropyl alcohol): Main component of rubbing alcohol.

  • Glycerol (1,2,3-propanetriol): Used in foods and personal care for moisture.

  • Cholesterol: In cell membranes, high levels correlate with heart disease.

  • Antifreezes: e.g., 1,2-ethanediol (ethylene glycol).

USES OF PHENOLS

  • Phenol in dilute solutions is a disinfectant.

  • Derivatives used as disinfectants and antioxidants in food.

NAMING ETHERS

  • IUPAC Naming: Name the smaller R group as an alkoxy group and attach it to the parent chain.

  • Common Naming: Alphabetically name the groups attached to oxygen and add "ether."

    • Example: sec-butyl ethyl ether.

PROPERTIES OF ETHERS

  • Less polar than alcohols; more soluble in water than alkanes but less than alcohols.

  • Low boiling/melting points due to absence of hydrogen bonds between ether molecules; highly flammable.

POLYFUNCTIONAL COMPOUNDS

  • Defined as compounds with two or more functional groups; the functional groups determine the chemical properties of the compounds.

REDOX REACTIONS

  • Reduction: Gain of electrons; decrease in oxidation number.

  • Oxidation: Loss of electrons; increase in oxidation number.