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    (Original post by annie79)
    Thanks a lot, so..in CH3Cl if it asks which atoms the permanent dipole is between, they'd most probably give the electronegativity values in a table or something so you'd know whether it is hydrogen or carbon that is the delta positive atom, right?
    Chlorine is definitely delta negative in CH3Cl and it is always the safest to go for the atom which is directly attached to the very electronegative atom so carbon is safe to go

    C-H bond, although not much, is polar. Which is why methane is a greenhouse gas.


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    When cracking dodecane, why does a 'Labelled ceramic fibre / any sort of wool' need to be soaked in dodecane? Why cant the dodecane be cracked on its own?
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    (Original post by annie79)
    When cracking dodecane, why does a 'Labelled ceramic fibre / any sort of wool' need to be soaked in dodecane? Why cant the dodecane be cracked on its own?
    Well the tube has to be somewhat horizontal to prevent the catalyst falling down and dip into dodecane
    And if it's horizontal and dodecane is left as a liquid and not soaked into anything it would spread out in the tube if you know what I mean



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    (Original post by annie79)
    oh also! my teacher told m '+ aq' in a reaction just means adding water, but in the reaction CuSO4.5H2O(s) + aq--> CuSO4(aq), one of the questions is:

    'List three possible reasons for this which do not relate to the quality of theapparatus or chemicals used or possible mistakes in carrying out the procedure.'

    two of the marking points are:

    • approximation in (specific) heatcapacity of solution
    • Density of solution is taken asthe same as water

    the word 'solution' therefore implies +aq means solution...NOT water..right?

    However in the previous question it asks how to carry out the reaction to calculate the enthalpy change, and here you have to mention to measure out a known volume of WATER... which totally contradicts the question above..
    As water is added copper sulfate starts to become solution so that is what's meant by solution


    aq just means water indeed

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    (Original post by annie79)
    thank you thank you thank youuuuuu!!! Im learning so much in one evening, this is great XD
    Hahaha np :top:

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    when bromine water (Br-OH) is added to an alkene, is it the Br or OH that is the nucleophile in the mechanism for the reaction?
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    (Original post by annie79)
    when bromine water (Br-OH) is added to an alkene, is it the Br or OH that is the nucleophile in the mechanism for the reaction?
    When bromine water is added to alkene electrophilic addition occurs so it is electrophile. You're prob confusing with sodium hydroxide and halogenoalkane thing


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    (Original post by C0balt)
    When bromine water is added to alkene electrophilic addition occurs so it is electrophile. You're prob confusing with sodium hydroxide and halogenoalkane thing


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    But the OH- donates a pair of electrons to the carbocation..so itsnt the OH- classed as a nucleophile?
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    (Original post by annie79)
    But the OH- donates a pair of electrons to the carbocation..so itsnt the OH- classed as a nucleophile?
    Hm yeah true
    It is a weird question asking for nucleophile in electrophilic addition though :hmmm:

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    (Original post by annie79)
    when bromine water (Br-OH) is added to an alkene, is it the Br or OH that is the nucleophile in the mechanism for the reaction?
    Bromine water is just Br2, there's no hydroxide group
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    (Original post by Joshthemathmo)
    Bromine water is just Br2, there's no hydroxide group
    No Br2 is different, with bromine water you form a bromoalcohol
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    (Original post by Joshthemathmo)
    Bromine water is just Br2, there's no hydroxide group
    Br2+H2O->BrOH+HBr

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    (Original post by frozo123)
    No Br2 is different, with bromine water you form a bromoalcohol
    Never heard of that, but sounds cool
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    (Original post by Joshthemathmo)
    Never heard of that, but sounds cool
    It's basically because the :OH group reacts preferentially to the :Br.
    You must have heard of the term bromoalcohol? It's surely on your syllabus? It's just the general name for a halogenoalkane (in this case a bromoalkane with OH groups attached)
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    (Original post by annie79)
    when bromine water (Br-OH) is added to an alkene, is it the Br or OH that is the nucleophile in the mechanism for the reaction?
    (Original post by C0balt)
    When bromine water is added to alkene electrophilic addition occurs so it is electrophile. You're prob confusing with sodium hydroxide and halogenoalkane thing


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    (Original post by annie79)
    But the OH- donates a pair of electrons to the carbocation..so itsnt the OH- classed as a nucleophile?
    (Original post by C0balt)
    Hm yeah true
    It is a weird question asking for nucleophile in electrophilic addition though :hmmm:

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    (Original post by Joshthemathmo)
    Bromine water is just Br2, there's no hydroxide group
    (Original post by frozo123)
    No Br2 is different, with bromine water you form a bromoalcohol
    (Original post by C0balt)
    Br2+H2O->BrOH+HBr

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    (Original post by Joshthemathmo)
    Never heard of that, but sounds cool
    Saw you guys were a bit confused... One of the above posters are right, Br2(aq) is bromine water, Br-OH? Nope

    I've drawn the mechanism below and am pretty certain it's right, this stuff comes up in A2 too

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    (Original post by RagaZ)
    Saw you guys were a bit confused... One of the above posters are right, Br2(aq) is bromine water, Br-OH? Nope

    I've drawn the mechanism below and am pretty certain it's right, this stuff comes up in A2 too

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    Nahh mate, in bromine water, the concentration of H20 molecules is greater in proportion than Br2 molecules, hence the secondary carbocation has a greater chance reacting with the H20 than the Br-

    How you finding A2? Unit 5 is long
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    (Original post by frozo123)
    Nahh mate, in bromine water, the concentration of H20 molecules is greater in proportion than Br2 molecules, hence the secondary carbocation has a greater chance reacting with the H20 than the Br-

    How you finding A2? Unit 5 is long
    ahh right! i actually get it now,
    http://www.chemguide.co.uk/organicpr...ogenation.html (scroll down to see it explained)ok thanks my mistake

    and actually its going pretty ok, just anxious to get it over and done with tbh
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    (Original post by RagaZ)
    Saw you guys were a bit confused... One of the above posters are right, Br2(aq) is bromine water, Br-OH? Nope

    I've drawn the mechanism below and am pretty certain it's right, this stuff comes up in A2 too

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    Well I would like to believe that chemguide, other random sites out there, and my experienced teacher are right.


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    (Original post by RagaZ)
    ahh right! i actually get it now,
    http://www.chemguide.co.uk/organicpr...ogenation.html (scroll down to see it explained)ok thanks my mistake

    and actually its going pretty ok, just anxious to get it over and done with tbh
    tbh I don't even know what to expect, lets hope for the best haha
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    (Original post by gabby07)
    It's basically because the :OH group reacts preferentially to the :Br.
    You must have heard of the term bromoalcohol? It's surely on your syllabus? It's just the general name for a halogenoalkane (in this case a bromoalkane with OH groups attached)
    I've heard of the compound but i've not encountered that mechanism! I'm on AQA by the way
 
 
 
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