Further organic chemistry

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  • Further organic cemistry
    • Isomerism
      • Structural
      • E/Z (only possible with a double bond
      • Optical
        • Mirror images (non-superimposable)
        • Always two enantiomers
          • A mixture of equal volumes gives a racemate
        • Used to work out reaction mechanisms
          • SN1 will give a racemate, as the nucleophile can attack from either side
          • SN2 will give only one enantiomer, as the nucleophile can only join to one side.
    • Aldehydes and Ketones
      • Don't H bond with themselves, but do with water
      • Hydrogen cyanide will react by nucleophilic addition with carbonyls
        • HCN dissociates and the CN- attacks the slightly positive C in C=O
        • Forms a hydroxynitrile (racemic mixture shows C=O is planar and can be attacked from either side)
      • Brady's reagent (2,4 DNPH in methanol and conc H2SO4) forms a bright orange precipitate with an ald or ket
        • The precipitate (a dreivative of the carbonyl) is purified by recrystalisation and the melting point compared to the data book
      • Tollens form a silver mirror (from a colourless solution) with ald, not ket
      • Fehling's goes from blue to brick red with alds, not kets
      • Reflux an aldehyde with an oxidising agent eg potassium dichromate, and a carboxylic acid will form (orage to green)
        • Heat a primary alcohol with an oxidising agent to form an acid
      • Reduce an ald or ket to an alcohol with LiAlH4 (nucleophilic addition)
      • If it has a methyl carbonyl group, it will from a yellow precipitate when heated with iodine (CHI3) and smell like antiseptic
    • Carboxylic acids
      • Heat a primary alcohol with an oxidising agent to form an acid
      • Reflux a nitrile (C triple bond N) with dilute HCl (hydrolysis)
      • React with alkalis and carbonates to form salts and water
      • Can be reduced by LiAlH4 in dry diethyl ether to an alcohol
      • Mix with PCl5 to form an acyl chloride
      • Add alcohol to form an ester (in the presence of an acid catalyst eg conc H2SO4)
        • Reversible reaction, so product is distilled off at 80' and added to sodium carbonate. The top layer is then separated
    • Esters
      • Name the alcohol section first and the acid section second, but draw it the opposite way.
      • Reflux with dilute acid to form the alcohol and acid (rev, hydrolysis)
      • Reflux with a dilute alkali to get a carboxylate ion and alcohol (rev, hydrolysis)
        • Used to make soap (heat a fat or oil with conc NaOH, then ad NaCl. The soap will crust on the surface)
      • React with alcohols to make new esters (replace the alcohol section)
        • Used to make margarine to avoid hydrogenation, and in making biodeisel from vegetable oils.
      • Carboxylic acid + a diol make a polyester, water is eliminated
        • Used in carpets, clothes fizzy drink bottles. Strong and flexible
    • Acyl chlorides
      • React vigorously with water to form a carboxylic acid
      • React vigorously with alcohol to form an ester
      • Reacts violently with ammonia to form an amide (Cl is replaced with NH2)
      • Reacts violently with amines to form an n-substituted amide( Cl is replaces with NH2CH3)


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