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

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ranz
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Original post by lai812matthew
no, but they might come up in the exam


CN to COOH? amine to carboxylic acid ?


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Original post by ranz
ImageUploadedByStudent Room1465816923.829333.jpg
this compound contains one O only and its an aldehyde yet theres a peak at 3-4 ppm?


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Part b of that question states that the peak at 3.7 ppm would normally be expected at 2.7 ppm. So you look up 2.7 ppm which is for the benzene-CH proton.
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ranz
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Original post by KB_97
Part b of that question states that the peak at 3.7 ppm would normally be expected at 2.7 ppm. So you look up 2.7 ppm which is for the benzene-CH proton.


ahh i seee, ive been so confused about that sentence. so when they say that they dont mean for every single peak just for the ome they mentioned?


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Original post by ranz
CN to COOH? amine to carboxylic acid ?


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Nitrile into a carboxylic acid
Original post by AqsaMx
This specification point 'Describe and explain the increased use of esters of fatty acids as biodiesel'

What does it want us to know?


I assume it wants you to know about transesterification and Why it's useful. Like it had better atom economy and it uses methanol that comes from plants/renewable sources
Original post by AqsaMx
'Explain the term retention time, and interpret gas chromatograms in terms of retention times and the approximate proportions of the components of a mixture'

What does the second part mean, about the approximate proportions?



The time between the injection of a sample and its emergence from the column
Original post by RetroSpectro
Does anyone know if our spec covers that fact that from CN to COOH is a hydrolysis reaction?


It's not on our spec but they might throw it in with some explanation in a question
Original post by ReTakingF324/5
Lol I mixed them up too. I thought the 2.7 was the first one.

Just a Question. does the most left one have any splitting pattern? I couldn't figure it out. I left it at the end and filled it out and got it right but those ****ing jaggy ass lines are hard to read.


Original post by ForeverDay
Yep, it's that question and the one on the very left. 😀 I would've put it as 3 separate peaks not as one multiplet so I was a bit confused.


Yeah, I got confused about that one when I was doing it, but my teacher said not to worry about the splitting of any benzene peaks, apparently it's higher level than A level.

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Original post by ranz
ahh i seee, ive been so confused about that sentence. so when they say that they dont mean for every single peak just for the ome they mentioned?


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Yup
What is the exact range for benzene-CH in proton nmr. Because I've seen questions with chemical shifts that represent it but don't match up to the range on the data sheet
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ranz
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Original post by KB_97
Yup


ok just to make sure lol so i understand, all peaks are in their correct position. but that one peak at 3.7 ppm?


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Original post by KB_97
What is the exact range for benzene-CH in proton nmr. Because I've seen questions with chemical shifts that represent it but don't match up to the range on the data sheet


According to the data sheet, around 6.5 -7.9 ppm.
Just like the oxygen shields splitting of the proton (in OH)

does the nitrogen do the same for NH?
Why will more than one nitro group be substituted onto the benzene ring if the temperature rises above 50 degrees?
TMS = the reference peak which other peaks are compared to
D20 just removes the OH and NH peaks because they undergo proton exchange
CdCl3 just prevents a peak from showing on the nmr
TMS is used as a standard for the chemical shift measurements - it has 12 hydrogens in one environment so produces one peak at 0ppm.
Cdcl3 and D2O are deuterated solvents so the D is basically an isotope of H that is H2 as opposed to H1. NMR only produces peaks when there is an odd number of nucleons, so the D of the deuterated solvent exchanges with the H of OH/NH2 (labile protons) so the peaks for the OH and NH groups no longer show up. You can compare the spectras with and without D2O to see where the peaks for OH/NH2 are.
Original post by RetroSpectro
Nitrile into a carboxylic acid


Do we need to know this..?
Original post by AqsaMx
Do we need to know this..?


No
Snapchat-3626287179591686856.jpg why does N02 have to be in that position (highlighter one) and not the one i drew in pen
Original post by PensAndPaper
Snapchat-3626287179591686856.jpg why does N02 have to be in that position (highlighter one) and not the one i drew in pen


You have to nitrate the correct carbon so you get the correct product at the end of the series of reactions

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