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    Ok this is for chemists who actually want to learn and help and not just argue. So post questions and help here please.

    Also continuing the question about mechanisms needed for AS Chem- for OCR they are needed- for free radical substition, electrophilic addition and nucleophilic substitution.
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    Mechanisms for all of the above are required for AQA too. I think Edexhell has the least mechanisms in its AS course.

    My advice for learning mechanisms (it helped me learn hydroboration (degree)): keep drawing them out over and over again until you get it right evry time. Then wait a couple of hours and test yourself.
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    i dont think any mechanisms are require for edexcel
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    (Original post by lgs98jonee)
    i dont think any mechanisms are require for edexcel
    Ooh-an advantage of doing and edexcel syllabus.
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    for AQA you need to know the following mechanisms for module 3

    alkenes - electrophilic addition
    -bromine water
    -hydrogen bromide
    -sulphuric acid

    haloalkanes - nucleophilic subsistution
    -hydroxide ions
    -cyanide ions
    -ammonia

    haloalkanes - elmination
    -OH ion

    alcohols - elimination
    -H plus ion
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    ok here's a quick question from OCR Chains and Rings june 2003 paper
    first it asked you to write the equation for complete combustion of methanol but then it asks "Suggest why methanol is added to petrol"
    only a 1 mark question but i'm guessing it has something to with the equation it asked you to write just before.
    any ideas?
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    For Edexcel you need to know the following reactions by heart from organics, for all those who say it's easy:

    Alkanes: Complete and incomplete combustion, free radical substitution
    Alkenes: Electrophilic addition: Cl2, Br2, HCl, etc. and H2
    Alcahols: Oxidations, Nucleophilic substitutions, elimination, dehydration
    Haloalkanes: Nucleophilic substitutions ( i think), addition of KCN and NH4 to make nitriles and amines,

    I think that's it... but we need to know the conditions for all of them, balanced equations, products etc.
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    Mechanisms are required for Edexcel A2 Chemistry Lots of them...
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    (Original post by hihihihi)
    ok here's a quick question from OCR Chains and Rings june 2003 paper
    first it asked you to write the equation for complete combustion of methanol but then it asks "Suggest why methanol is added to petrol"
    only a 1 mark question but i'm guessing it has something to with the equation it asked you to write just before.
    any ideas?
    to stop people drinking it?
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    Oooh!

    I'm doing Edexcel Nuffield and I'm having quite a bit of dificulty understanding the entire concept of electrophilic, nucleophilic substitution, addition etc (topic 10 stuff about halogenoalkanes and also so some topic 8 stuff on alkenes) does anyone know any good websites which goes through the topic nice and slowly and clearly, because I find the student's book completly incomprehensable?

    Greatly appreciated
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    (Original post by Pegasus)
    Oooh!

    I'm doing Edexcel Nuffield and I'm having quite a bit of dificulty understanding the entire concept of electrophilic, nucleophilic substitution, addition etc (topic 10 stuff about halogenoalkanes and also so some topic 8 stuff on alkenes) does anyone know any good websites which goes through the topic nice and slowly and clearly, because I find the student's book completly incomprehensable?

    Greatly appreciated
    You dont have to understand chemistry, just know it, write out the mechnisms hundreds of times and youll get it eventually.
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    (Original post by Pegasus)
    Oooh!

    I'm doing Edexcel Nuffield and I'm having quite a bit of dificulty understanding the entire concept of electrophilic, nucleophilic substitution, addition etc (topic 10 stuff about halogenoalkanes and also so some topic 8 stuff on alkenes) does anyone know any good websites which goes through the topic nice and slowly and clearly, because I find the student's book completly incomprehensable?

    Greatly appreciated
    Electrophile - an electron loving species that accepts lone pairs. Is attracted to negative centres, such as a C=C bond (douible bond >> electron rich). That's how you get electrophilic addition of alkEnes. It's addition because nothing is being kicked out! Although the double bond was lost to bonding with the electrophile

    Nucleophile - a species that donates electon pairs - is too negative and seeks out positive centres, such as the carbon bonded to an OH group (O is electronegative and sucks the shared bonding paid away from the carbon). - the nucleophile such as NH4(+) (which has a free lone pair ready to bond) kicks out the OH and bonds with the carbon - it is substitution because the OH is kicked out.
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    Hi I am unsure of this question, as my teacher didn't have time to complete the course before study:

    2H20 + SO2 + 2[CuCl4]2- => 4H+ SO42- + 4Cl- + 2[CuCl2]-

    Identify the element being reduced in this reaction and write a half equation for the reduction of the species containing this element.
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    AS mechanisms are a complete piece of piss (for AQA anyway).
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    You need to look at the oxidation state of each element on both sides of the equation. The one that has been reduced, will, believe it or not, have a lower oxidation number. I don't have time to do the question in its entireity (I should be revising), but this should start you off.
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    say propene

    CH3CH=CH2 + HBr

    which atom goes to which?
    i read that
    CH3CHBrCH3 is Major product
    and
    CH3CH2CH2Br is Minor product
    so which one should i put in equations?
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    (Original post by etomac)
    say propene

    CH3CH=CH2 + HBr

    which atom goes to which?
    i read that
    CH3CHBrCH3 is Major product
    and
    CH3CH2CH2Br is Minor product
    so which one should i put in equations?
    The major product. Remember Markownikow!
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    so Br- goes to the one with less hydrogen while H+ goes to the one with more hydrogens attach to it?
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    (Original post by etomac)
    so Br- goes to the one with less hydrogen while H+ goes to the one with more hydrogens attach to it?
    Yes. Hydrogen goes with its friends.
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    (Original post by hornblower)
    Yes. Hydrogen goes with its friends.
    lol nice explnation

    btw wt if it is

    CH3CH2CH=CHCH2CH2CH3
 
 
 
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