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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    (Original post by marioman)
    This is not examinable because it is not in the specification. Not everything in the textbook can be asked in the exam.
    I think people are more skeptic after F321 strayed from the spec a little.



    Oxidation of oxygen as +2 in F2O caught people out in F321 2016
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    (Original post by Rust Cohle)
    I think people are more skeptic after F321 strayed from the spec a little.



    Oxidation of oxygen as +2 in F2O caught people out in F321 2016
    examiners be like i wanna make ppl unlucky
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    (Original post by itsConnor_)
    thanks phew
    AQA unit 4 june 2014
    I just checked. The MS is just a simpler version of what OCR asks for - but you would still get the marks. AQA mechanism doesn't show the heterolytic fission of H-CN (where delta H+ electron pair transfers to CN-). Instead its a H+ ion which is a more basic demonstration of the mechanism.

    For the optical isomer, AQA scheme emits the 3D bond angle lines. More basic
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    (Original post by shanaj)
    omg im such an idiot i did all the past papers in an hour lmao thanks
    i swear that 15 mins has been the difference in me getting a U grade or an A grade in the recent past papers (pre 2012 papers are 1 hr though)
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    Question on Proton Nmr. Ive realised on more than one past paper where the peak for a hydrogen bonded to a carbon attatched to a benzene cHc6h5 which has a narrow range of 2.2-2.4 has a peak higher at around 2.8. This makes it very confusing to identify as you can mistake the peak for a HC-C=O. How do you correctly identify this peak? Do you just assume it might have a higher chemical shift than given on the data sheet. Example of this on June 2012 RPA paper Q5b
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    1b help please
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    (Original post by Cal 1)
    Ahh yes they are! My bad haha
    What is it? It's not in my book?
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    (Original post by Rust Cohle)
    I think people are more skeptic after F321 strayed from the spec a little.

    <snip>
    Oxidation of oxygen as +2 in F2O caught people out in F321 2016
    I can't look at the question again because ChemistryALevel has deleted his answers, but from what I remember the all the information needed was given in the question.
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    (Original post by tcameron)
    1b help please
    Would it be the middle one?

    Ps what paper is this?


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    the middle one.
    make it an aldehyde and then the chiral centre is the carbon with the methyl group attactched

    if they are carbonyl groups it means the only points that can be chiral centres are the ones with methyl groups. the first one doesnt have a methy group and the last one has two on one carbon so its not a chiral centre.
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    (Original post by tcameron)
    1b help please
    (Original post by Saywhatyoumean)
    Would it be the middle one?

    Ps what paper is this?


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    Yeah it's the middle. Not the second as when it's ketone its bonded to two CH3 groups. Not the first as that is bonded to two H groups when ketone.
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    (Original post by tictac198)
    Question on Proton Nmr. Ive realised on more than one past paper where the peak for a hydrogen bonded to a carbon attatched to a benzene cHc6h5 which has a narrow range of 2.2-2.4 has a peak higher at around 2.8. This makes it very confusing to identify as you can mistake the peak for a HC-C=O. How do you correctly identify this peak? Do you just assume it might have a higher chemical shift than given on the data sheet. Example of this on June 2012 RPA paper Q5b
    Yes - as it says on the data sheet, the ranges are only typical values. As for identifying the peak, you generally have to work out the peaks that you know first. For example the cluster of splitting at 7.2 ppm is obviously caused by the protons on a benzene ring. The relative area for this peak is 5, so you know that the benzene ring has 5 protons. Now you can look at the singlet. This is in the right range for a C-H attached to a benzene ring, but if this was the environment then the relative peak area of 3 combined with the singlet means that this would be the end of the molecule and the entire structure would just be a CH3 attached to a benzene ring. This doesn't fit the information given in the question (an ester with mr = 164) so you now know to assign this peak to HC-C=O instead.

    Hopefully this explanation is at least some help - although the best way to get good at NMR is to solve past questions!
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    (Original post by Saywhatyoumean)
    Would it be the middle one?

    Ps what paper is this?


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    old spec - jan 09
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    (Original post by tictac198)
    Question on Proton Nmr. Ive realised on more than one past paper where the peak for a hydrogen bonded to a carbon attatched to a benzene cHc6h5 which has a narrow range of 2.2-2.4 has a peak higher at around 2.8. This makes it very confusing to identify as you can mistake the peak for a HC-C=O. How do you correctly identify this peak? Do you just assume it might have a higher chemical shift than given on the data sheet. Example of this on June 2012 RPA paper Q5b
    I understand where you're coming from. Having looked at it, it's still possible to correctly ID the peak.

    Since we have C6H5 the 2.2 peak can't be C6H5CH3 as it would leave no space for the ester bond. Meaning the ester link will be in between the C6H5 and CH3.
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    this is a really basic question but in there's 4 carbon environments for this ketone, but i can only identify 3... would the 3rd carbon count as 2 environments (c=o and c-c)? EDIT: never mind, read the mark scheme wrong haha. you can tell I'm fasting.
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    does anybody wanna skype revise?
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    For isoelectric points (pH at which amino acid exists as a zwitterion, the dipolar ionic form of an amino acid in which there is no overall charge as both charges present in NH3+ and COO-):

    The more NH2 groups there are on the R group, the higher the isoelectric point
    The more COOH groups there are on the R group, the lower the isoelectric point
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    I don't know what else I can do to revise, done all the pp, learned all the reactions, I really hope a proton NMR long answer question comes up and also the problems with optical isomers and how to separate them question
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    If you're going from an aldehyde to a carboxylic acid do you still have to reflux it with acidified potassium dichromate?
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    there might be a zwitterion question for an amino acid with multiple groups of amine and carboxyl groups. followed by a question with low, high pH conditions for the amino acid.
 
 
 
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