OCR Salters Chemistry F335 12th June 2013 Exam revision thread

Harantony explained it really well a few pages back:

There was a question in the 2012 Jan paper about heating a dicarboxylic acid (fumaric acid). The acid loses water on heating to form compound X. In the question it asks you to draw the structural formula for compound X. Apparently the two carboxyl groups in the dicarboxylic acid react with each other on heating with the elimination of a water molecule. Is this reaction in the syllabus or is something we are supposed to be able to guess in the exam?

Please don't remind me, I'm doing F334 as well which I haven't even started revising for as I have 4 other exams before it!

Here the peak on the left represents the two protons between the oxygens but this peak is larger then the one on the right which represents 6 protons

Is it the height of the peak which represents the amount of protons in the environment or the area underneath ?

(the compound is diethoxymethane http://www.chemicalbook.com/ChemicalProductProperty_EN_CB4128049.htm)

Ouch dude... Just gotta put your head down I guess; at least by next Wednesday it'll be all over



Yes it's the height of the peak which represents the ratio/amount of protons. So the ratio of 6 should represent 6 protons in the CH₂ environment. It's quite a confusing question as its diethoxymethane, so you'll have to watch out for the CH₂-O environment.

That's a horrible nmr question regardless!

well I just asked my teacher and he stressed that it's the cumulative area under the peak (and its splitting) and as it's a singlet on the left it is in the end a lower area then the triplet on the right

They are interchangeable. The relative areas of the peaks is proportional to the number of protons in that proton type.

i think you just had to be able to put it together as if you drew out the molecule without water you could see an o with no attachment which doesn't normally occur in non salt long chain molecules so the joining to make a cyclo chain should seem the reasonable solution

well I just asked my teacher and he stressed that it's the cumulative area under the peak (and its splitting) and as it's a singlet on the left it is in the end a lower area then the triplet on the right

Not entirely sure if it's on the syllabus but the dehydration of two carboxylic acids forms an acid anhydride

Hi, I have the January 2013 paper, but I don't have the mark scheme :/
Could someone post on here please, be really grateful

Hi, I have the January 2013 paper, but I don't have the mark scheme :/
Could someone post on here please, be really grateful

Not entirely sure if it's on the syllabus but the dehydration of two carboxylic acids forms an acid anhydride

Do you know if the acid anhydride formed in this way is always cyclic?

Here it is.

Hi can you post the paper?

Hi,

On page 50 of the A2 official revision guide, it says that increasing the total pressure may change the rate of reaction. Why will it not always change the rate?

Thanks!