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    Alright, so basically the intermediate secondary carbocation is formed in preference to the alternative primary because it is more stable. Carbocations are planar about the positive C atom and the Br ion has equal chance of attacking from above or below creating equal amounts of the two enantiomers.
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    Optical isomerism + it's importance in drug action.

    - Drugs often contain a chiral C atom.·

    -The cost of separating the two enantiomers is high and therefore the drug is usually prescribed as a racemic mixture.

    - However, the two enantiomers can have unequal therapeutic effects on the body bc sometimes one enantiomer is harmful and the other beneficial.
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    Compounds containing the carbonyl group – Aldehydes + Ketones –Topic 5.

    Okay so Aldehydes can be oxidised into Carboxylic acids, whereas Ketones cannot.

    For example:

    CH3CH2CHO (propanal) + [O] -----------> CH3CH2COOH(propanoic acid)

    Reagent: K2Cr2O7,H2SO4
    Conditions: reflux.

    ~


    Alright, so I'm just going to copy the next bit of info off my other thread bc it's the same stuff but we still need to know it for this unit:


    Distinguishing between aldehydes and ketones

    Right, so there are basically 3 tests which can be used to distinguish between an aldehyde and a ketone.


    The first test is K2CR2O7, H2SO4 (orange solution)

    Observation after adding to aldehyde: Green solution.
    Observation after adding to ketone: No reaction.



    The second test is Fehling's solution (blue solution)

    Observation after adding to aldehyde: Brick red precipitate.
    Observation after adding to ketone: No reaction.



    The third + final test is Tollen's reagent (colourless solution)

    Observation after adding to aldehyde: Silver mirror.
    Observation after adding to ketone: No reaction.

    ~

    In all three reactions, the aldehyde is oxidised to a carboxylic acid on warming.

    E.g. CH3CH2CHO + [O] ------------------> CH3CH2COOH
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    Hazards of using HCN and/or KCN + precautions that should be taken when handling.

    Both are highly poisonous/toxic and exposure to only small quantities can lead to rapid death.

    -HCN is a gas at room temperature – fume cupboard

    - KCN is a soluble solid – ingestion leads to rapid death - wear gloves
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    Alright so there are basically two types of nucleophillic addition reactions that we need to know:

    With Cyanide (HCN/KCN)or with sodiumtetrahydroborate.(NaBH4)

    Either of these reagents can react with an aldehyde or a ketone.

    So, the first example I'm going to do is with HCN reacting with an aldehyde, specifically- propanal.

    I'll draw the mechanism for it below:
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    Nucleophilic addition reaction mechanism between an ALDEHYDE and HCN.

    The organic product produced is 2-hydroxybutanenitrile.

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    Okay, so now we're going to do HCN again but this time with a ketone, specifically - Butanone.

    Mechanism below:
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    Nucleophilic addition reaction mechanism between a KETONE and HCN.

    The organic product produced is 2-hydroxy-2-methylbutanenitrile.

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    Use the mechanism above to explain why a racemic mixture is formed in this reaction?

    - The product of the reaction has a chiral C atom and therefore exists in two isomeric forms·

    - The planar C=O group allows attack of a nucleophile from above or below with equal probability·

    - This leads to formation of equal amounts of the two enantiomeric products which consequently together have no optical activity
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    Okay, so now we're going to move onto the second type of nucleophillic addition and that is with NaBH4.

    Aldehydes are reduced to primary alcohols + Ketones are reduced to secondary alcohols using NaBH4 as a reducing agent.

    The example I'm going to do first is NaBH4 reacting with an aldehyde, specifically - ethanal.

    Reaction mechanism below:
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    Nucleophilic addition reaction mechanism between an ALDEHYDE and NaBH4.

    The organic product produced is ethanol. (primary alcohol)

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    ..
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    Okay, so now we're going to do NaBH4 again but this time with a ketone, specifically - Propanone.

    Mechanism below:
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    (Original post by EnterNamehereplz)
    Are these two things even that important?
    yes, it's important bc it's on the specification. - Mentioned in sections 3.4.4 and 3.4.5

    If you don't deem it as so, then just ignore it.

    Please can you stop posting in this thread until I've finished! - I'd really appreciate it!!!!!!
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    Okay.

    Nucleophilic addition reaction mechanism between a KETONE and NaBH4.

    The organic product produced is propan-2-ol. (secondary alcohol)

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    Alright, so just a small point that the product has no chiral C atom and is therefore not optically active
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    Compounds containing the carbonyl group – Carboxylic acids + esters –Topic 5.

    Okay so carboxylic acids are weak acids but will liberate CO2 from carbonates. Here is an example of the dissociation of ethanoic acid:

    CH3COOH -----------> CH3COO¯ + H+

    - The equilibrium is over to the LHS

    - And it is only slightly dissociated – therefore weak acid

    ~


    And here is an equation for the example reaction between ethanoic acid and solid sodium carbonate:

    2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

    How can the above reaction be used to distinguish between a carboxylic acid from an alcohol or ester?

    Well, carboxylic acids produce effervescence on addition of solid sodium carbonate whereas alcohols and esters do not.
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    Esterification

    Okay, so you can produce an ester by reacting an alcohol with a carboxylic acid.

    Conditions: Heat, concentrated H2SO4

    An example equation for the esterification reaction between propanoic acid and butan-2-ol to produce 2-butylpropanoate:

    CH3CH2COOH + CH3CH(OH)CH2CH3 → CH3CH2COOC(CH3)HCH2CH3 + H2O


    Characteristic smell of some esters.

    - Fruity, sweet.


    Common uses of esters.

    - Solvents.

    - Flavourings.

    - Perfumes.

    - Plasticisers.
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    Hydrolysis of esters.

    So, esters can be hydrolysed and here is an example of the reaction between 1-propylethanoate and sodium hydroxide.

    CH3COOCH2CH2CH3 + NaOH -------------> CH3COONa (sodium ethanoate)+ CH3CH2CH2OH (Propan-1-ol)

    ~

    Alright so, vegetable oils and animal fats are esters of propane-1,2,3-triol (glycerol). I'll draw the general structure of vegetable oils + animal fats below:
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    WHERE:

    R1, R2 and R3 are long hydrocarbon chains.

    And remember that:

    - Oils are usually unsaturated.

    - Fats are saturated.

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