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    Aromatic chemistry – Delocalisation stability –Topic 6.

    The delocalisation confers energetic stability on the molecule.

    The estimation of the enthalpy change when the Kekule structure reacts with hydrogen(hydrogenation) to form cyclohexane is -120kJ


    If you assume that the three double bonds in the Kekule structure behave independently on each other, the enthalpy change of hydrogenation would be three times the value for cyclohexane, therefore:

    -120 x 3 = -360kJ

    Benzene, however, only releases 208kJ of energy.

    So, the difference between these two values. I.E. The delocalisation energy is 152kJ

    Benzene must be energetically more stable than the Kekule structure by 152kJ
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    Aromatic chemistry – Electrophillic substitution –Topic 6.

    Alright, so firstly I'll just draw the general mechanism for substitution of an electophile, E+.
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    Aromatic chemistry – Nitration –Topic 6.

    Nitration reaction.

    Reagents: Concentrated HNO3 and Concentrated H2SO4.

    Conditions: Warm to 50C, but not above to minimise further substitution.

    Mechanism name: Electrophillic substitution.

    Name of reactive inorganic species: Nitronium ion.

    Equation for the generation of the nitronium ion : HNO3 + 2H2SO4 --------> NO2+ + 2HSO4- + H3O+


    Alright, I'm going to draw out the mechanism for this below:
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    good luck and thanks for these!
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    The importance of nitration with examples:

    - Manufacture of explosives. E.g: TNT, trinitrotoluene.

    - Formation of aromatic amines by reduction and aromatic amines are useful for making dyes,drugs and polymers.
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    Aromatic chemistry – Friedel-Crafts acylation –Topic 6.

    Friedel-Crafts acylation reaction.

    Reagents: Acyl chloride or acid anhydride and AlCl3

    Conditions: Warm, anhydrous,(to prevent the AlCl3 from reacting with water since it's a nucleophile) and AlCl3

    Mechanism name: Electrophillic substitution.

    Name of reactive inorganic species: Acylium ion.

    1st equation for the generation of the acylium ion : RCOCl + AlCl3 --------> R- C+=O (Acylium ion) + AlCl4-

    2nd equation for the generation of the acylium ion : (RCO)2O + AlCl3 --------> R- C+=O (Acylium ion) + RCOOAlCl3-

    Okay, mechanism for this is below:
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    How the catalyst in this reaction changes and is then regenerated.

    AlCl3 (Catalyst) + Cl ------> AlCl4

    AlCl4 + H+ ------> AlCl3 (Regenerated) + HCl
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    Amines – Base properties(Bronsted-Lowry) –Topic 7.

    Explanation for differences in base strength ammonia, primary aliphatic and primary aromatic amines(in terms of the availability of a lone pair on the N atom.)


    Primary aliphatic amine > Ammonia > Aromatic amine.

    In a primary aliphatic amine, through the inductive effect from the alkyl group the lone pair of electrons on the N atom is more available for donation to a proton than the lone pair on the N atom of ammonia. In an aromatic amine, the lone pair of electrons on the N atom is least available for donation because it is delocalised in to the benzene ring.
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    This thread is awesome but don't forget to get some sleep
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    Amines – Nucleophillic properties –Topic 7.

    Okay, so amines.

    Primary amines = 1 alkyl group. For example: Methylamine.

    Secondary amines = 2 alkyl groups. For example: Dimethylamine OR ethylmethylamine.

    Tertiary amines = 3 alkyl groups. For example: Trimethylamine.

    ~

    Okay, I'm going to give examples of primary, secondary + tertiary amines below by drawing the structures that I've named above so you know what they look like.
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    Here is a PRIMARY AMINE. - Methylamine.

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    Here are SECONDARY AMINES - dimethylamine on the left, ethylmethylamine on the right.

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    Finally here is a TERTIARY AMINE. - Trimethylamine.

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    Production of amines from the reaction between ammonia/amines with haloalkanes.

    The mechanism name is nucleophillic substitution.

    I'm going to use bromoethane as an example.

    So, below I'll draw the mechanism for bromoethane + :NH3 which will produce a primary amine, specifically- ethylamine.
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    NUCLEOPHILLIC SUBSTITUTION MECHANISM between BROMOETHANE and NH3 to produce A PRIMARY AMINE.

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    In case I haven't said this yet GOOD LUCK ON YOUR EXAM!! :jumphug: :hugs: :lovehug:

    And listen to AngryRedhead? :puppyeyes:
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    Alright, so basically what happens now is a further substitution takes place.

    The primary amine that has just been produced from the first reaction reacts with the bromoethane.

    This means that the ethylamine that we have just made reacts with the bromoethane.

    So below, I'll draw the mechanism for bromoethane and ethylamine which will produce, this time a secondary amine.
 
 
 
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