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    (Original post by otrivine)
    a quick question

    http://www.ocr.org.uk/Images/79471-q...d-analysis.pdf

    for question 2

    In stage 1 I put cl2 and AlCL3
    and the diagram i put the cl on the left side like in the diagram they put

    then step 2

    I said CONC HNO3 AND H2SO4 , 50 DEGREES

    step 3 , they put cl2 and Alcl3?? I put conc HCL and Sn ? why am I wrong
    Youre right, its just in a different order
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    The last question on June 2012 was very tough (but nice when you work it out!)
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    I have a lot still to revise, can someone tell me what are the difinite things I should know? like the most common areas that usually come up
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    (Original post by otrivine)
    Ethanoic acid has the highest boiling point as it contains OH group as well as a C=O.
    Ethanol and ethanoic acid will both have a higher boiling point because they both contain OH group and hence, can form hydrogen bond with water molecules and so more energy is needed to break the intermolecular forces. Also, ethanoic acid , the C=O is a strong bond and more energy is needed to break the poiar C=O.

    All 3 have a high boiling points, as they are straight chains which means more van der waals forces are present between molecule and more surface contact points which hence, more energy needed to break the attractive forces.

    Between all 3 there are dipole -dipole interactions present which also gives the structure strength , but not too much as they are weak intermolecular forces.
    5/5

    Ask me some questions now please.
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    (Original post by Mus1995)
    The last question on June 2012 was very tough (but nice when you work it out!)
    Personally I found the June 2011 structure the hardest to work out. Probably because they didn't give you the relative H ratio.
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    (Original post by Mus1995)
    The last question on June 2012 was very tough (but nice when you work it out!)
    That is the type of question I'd like to see on Wednesday
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    Expecting a big proton NMR question tbh.
    Only good thing is the majority of the marks are from looking at the evidence!
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    (Original post by thers)
    5/5

    Ask me some questions now please.
    of course !

    1) Name the ester CH3(CH2)2COOCH3

    2) state the ragents and conditons for the hydrolysis of the ester in the Laborartory

    3) Suggest why industries use ester
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    We might get a large C-13 question instead like on Jan 11 but longer. Those questions are like trial and error.
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    (Original post by thers)
    Personally I found the June 2011 structure the hardest to work out. Probably because they didn't give you the relative H ratio.
    I personally thought that compound was rather easy to get, although I do trial and error to get the final structure so I guess I was lucky just
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    (Original post by otrivine)
    of course !

    1) Name the ester CH3(CH2)2COOCH3

    2) state the ragents and conditons for the hydrolysis of the ester in the Laborartory

    3) Suggest why industries use ester
    1) methylpropanoate

    2) Dilute H2SO4 Reflux

    3) Fruity smell to improve quality of perfumes - for example.


    Define the term zwitterion [1]
    Define the term isoelectric point. [1]
    State the general formula for an alpha amino acid [1]
    If the R group of an amino acid contains amine groups, will the pH of the isoelectric point be greater or below pH 7? [1]
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    (Original post by otrivine)
    Hi can someone please check this, this is the Jan 2012 paper
    In a polyester, the ester linkage forms between the alcohol group and carboxyl group, not two of the same groups.
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    Wow either I'm really bad or I'm really stressed, I think it's the latter. 52/60 on June 2012. So many mistakes but there are still one or two things I don't get.

    I wasn't allowed to use hydroxyl as a functional group they wanted alcohol WTF?

    The questions are so ambiguous for 1 mark so I wrote one statement but they wanted more, again WTF?

    Just annoying. :/

    Can anyone explain 4(b) on June 2012? I'd REALLY appreciate it. How does KOH oxidise an aldehyde to an alcohol?
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    (Original post by fayled)
    In a polyester, the ester linkage forms between the alcohol group and carboxyl group, not two of the same groups.
    but you are removing water to join them
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    (Original post by thers)
    1) methylpropanoate

    2) Dilute H2SO4 Reflux

    3) Fruity smell to improve quality of perfumes - for example.


    Define the term zwitterion [1]
    Define the term isoelectric point. [1]
    State the general formula for an alpha amino acid [1]
    If the R group of an amino acid contains amine groups, will the pH of the isoelectric point be greater or below pH 7? [1]
    Seeing your question reminded me of a blind spot in my knowledge - how do you know when an isoelectric point is likely to be high or low?
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    (Original post by thers)
    1) methylpropanoate

    2) Dilute H2SO4 Reflux

    3) Fruity smell to improve quality of perfumes - for example.


    Define the term zwitterion [1]
    Define the term isoelectric point. [1]
    State the general formula for an alpha amino acid [1]
    If the R group of an amino acid contains amine groups, will the pH of the isoelectric point be greater or below pH 7? [1]

    correct

    1) zwitterion is the dipolar ionic form of an amino acid by the donation of a H+ from a carboxyl group to the amino group where both charges are present and cancel.

    2) isoelectric point is a point in pH where the zwitterion exists

    3) RCH(NH2)COOH

    4) greater 7
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    (Original post by Mus1995)
    Wow either I'm really bad or I'm really stressed, I think it's the latter. 52/60 on June 2012. So many mistakes but there are still one or two things I don't get.

    I wasn't allowed to use hydroxyl as a functional group they wanted alcohol WTF?

    The questions are so ambiguous for 1 mark so I wrote one statement but they wanted more, again WTF?

    Just annoying. :/

    Can anyone explain 4(b) on June 2012? I'd REALLY appreciate it. How does KOH oxidise an aldehyde to an alcohol?
    neucleophilic addition isn't it?
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    (Original post by Mus1995)
    Wow either I'm really bad or I'm really stressed, I think it's the latter. 52/60 on June 2012. So many mistakes but there are still one or two things I don't get.

    I wasn't allowed to use hydroxyl as a functional group they wanted alcohol WTF?

    The questions are so ambiguous for 1 mark so I wrote one statement but they wanted more, again WTF?

    Just annoying. :/

    Can anyone explain 4(b) on June 2012? I'd REALLY appreciate it. How does KOH oxidise an aldehyde to an alcohol?
    I lol'd at "I'm really bad" but gets 52/60 which is A*

    Hydroxyl refers to alcohols, phenols, carboxylic acids etc anything with an OH group. The markscheme that year wanted you to be more specific.

    4(b) OCR tell you that Benzaldehyde is both oxidized and reduced - its not on the spec. It's an application of knowledge question where they give you all the info required to answer it.
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    (Original post by Zaphod77)
    Seeing your question reminded me of a blind spot in my knowledge - how do you know when an isoelectric point is likely to be high or low?
    Zwitterion has overall neutral charge. You want the R group to contain no NH3+ so you need less H+ to stop this from happening. Solution - increase pH.
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    (Original post by thers)
    Zwitterion has overall neutral charge. You want the R group to contain no NH3+ so you need less H+ to stop this from happening. Solution - increase pH.
    Ah, I get it! Thank you
 
 
 
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