ORG CHEM

• α-Carbon


  Carbon atom adjacent to the carbonyl carbon
• Carbonyl carbon


  • Electrophilic in nature
  • Susceptible to attack by nucleophiles
• Oxygen atom in carbonyl

  • Nucleophilic in nature
  • Attacked by electrophiles
• Hydrogen atom at α-carbon

  • Acidic in nature
  • Prone to attack by electrophiles
• Aldehydes are more reactive than ketones
• Nucleophilic addition reaction


  General reaction of addition of nucleophiles on the carbonyl group
• Nucleophilic addition mechanism under basic conditions


  1. Nucleophile attacks carbonyl group to form tetrahedral intermediate

  2. Protonation from solvent (H2O or alcohol)
• Nucleophilic addition mechanism under acidic conditions

  1. Protonation of carbonyl oxygen

  2. Nucleophile attacks carbonyl carbon
• Electrophile


  Reagent that is deficient in electrons and attacks the negative part of a molecule
• Nucleophile


  Reactant that gives an electron pair to form a covalent bond, usually charged negatively or neutral with lone pair
• Formation of cyanohydrins


  1. Carbonyl compounds react with hydrogen cyanide

  2. Proton (electrophile) adds to oxygen

  3. Cyanide ion (nucleophile) adds to carbon
• Formation of acetals and ketals

  1. Aldehydes/ketones react with alcohols in acid catalyst

  2. Initial formation of hemiacetal

  3. Further transformation to acetal/ketal
• Formation of alcohols from Grignard reagents

  1. Grignard reagent (RMgX) reacts with aldehydes/ketones

  2. Gives primary/secondary/tertiary alcohols
• Reaction with ammonia and derivatives

  1. Aldehydes/ketones react with ammonia/primary amines

  2. Gives imines (C=N compounds)
• Oxidation of aldehydes


  1. Aldehydes can be oxidized to carboxylic acids

  2. Using oxidizing agents like chromic acid, permanganate, silver oxide

  3. Tollen's test uses silver ions to detect aldehydes
• Oxidation of aldehydes by Fehling's solution

  1. Aldehydes reduce Cu2+ ions in alkaline medium

  2. Gives brick red precipitate of Cu2O
• Alkenes


  Hydrocarbons that contain at least one double bond between two adjacent carbon atoms
• Preparation of alkenes from alkynes

  1. Reduction of alkynes with hydrogen in the presence of palladized charcoal

  2. Alkyne to alkene conversion results in cis geometry

  3. Reduction of alkynes with sodium in liquid ammonia results in trans geometry
• Preparation of alkenes from alkynes

  • CH≡CH + H2 → CH2=CH2 (Ethene)
  • CH3C≡CH + H2 → CH3CH=CH2 (Propene)
• Preparation of alkenes from alkyl halides

  1. Heating alkyl halides with alcoholic potash

  2. Dehydrohalogenation (removal of a single molecule of halogen acid)
• Preparation of alkenes from vicinal dihalides

  1. Reaction with zinc metal

  2. Dehalogenation (loss of halogen molecules)
• Preparation of alkenes from alcohols

  1. Reaction with concentrated sulphuric acid

  2. Acidic dehydration (removal of a water molecule)
• Preparation of alkenes from alcohols

  • CH3CH2OH → CH2=CH2 + H2O (Ethene)