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

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I can't tell if I'm confusing myself here but how do we know which peak the protons are from in proton NMR? (The ones I circled) I don't even know how to ask this question properly but hoping someone understands me lol ImageUploadedByStudent Room1465077016.212644.jpg

ImageUploadedByStudent Room1465077016.212644.jpg

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Reply 521

alow

Original post by Saywhatyoumean

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You only circled one proton...

Reply 522

Saywhatyoumean

Original post by alow

You only circled one proton...

Yeah but I mean which peak would that proton be for the chemical shift values? The H-C-O or the H-C=O?

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Reply 523

alow

Original post by Saywhatyoumean

Yeah but I mean which peak would that proton be for the chemical shift values? The H-C-O or the H-C=O?

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What do you mean?

Reply 524

Saywhatyoumean

Original post by alow

What do you mean?

I wish I knew lol hang on let me find the question ImageUploadedByStudent Room1465078992.152548.jpg

ImageUploadedByStudent Room1465079079.845987.jpg

So when I'm drawing the spectrum, why is the CH2 singlet peak between 3.3-4.3ppm instead of ~2-3ppm?

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Reply 525

alow

Original post by Saywhatyoumean

I wish I knew lol hang on let me find the question ImageUploadedByStudent Room1465078992.152548.jpg

So when I'm drawing the spectrum, why is the CH2 singlet peak between 3.3-4.3ppm instead of ~2-3ppm?

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The CH2 is deshielded by virtue of its proximity to two electron withdrawing groups.

Reply 526

suibster

Original post by alow

The CH2 is deshielded by virtue of its proximity to two electron withdrawing groups.

surely it's because the carbon atom attached to the 2Hs is also attached to an oxygen.Therefore the corresponding chemical shift would be 3.3-4.3,which represents the HC-O proton signal.

Reply 527

alow

Original post by suibster

surely it's because the carbon atom attached to the 2Hs is also attached to an oxygen.Therefore the corresponding chemical shift would be 3.3-4.3,which represents the HC-O proton signal.

The chemical shift of an environment isn't only determined by one of the groups it is attached to...

Reply 528

alow

Original post by suibster

No it's determined by the functional group the c is attached to.

I don't think you understood what I said.

Reply 529

AqsaMx

I got 7.8g, think I did it wrong though..

Reply 530

ImNervous

Original post by AqsaMx

I got 7.8g, think I did it wrong though..

I got 7.79 but I used a really old calculater so I couldn't store the values.

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Reply 531

chuckster111

Hi, can somebody clarify how you make a diazonium ion (with a balanced equation) please?
In the textbook, pg. 39, it says you need 2HCl but I think this is incorrect?

Reply 532

Serine Soul

Original post by chuckster111

Hi, can somebody clarify how you make a diazonium ion (with a balanced equation) please?
In the textbook, pg. 39, it says you need 2HCl but I think this is incorrect?

Hey you need 1 HCl to make HNO2 and another to make the ion

Reply 533

rory58824

Original post by chuckster111

Hi, can somebody clarify how you make a diazonium ion (with a balanced equation) please?
In the textbook, pg. 39, it says you need 2HCl but I think this is incorrect?

Yes, that equation is wrong, it's only 1 HCl. If you wanted to write a full equation, its:

phenylamine + NaNO2 + 2HCl ----> diazonium ion + NaCl + 2H2O

Reply 534

chuckster111

Original post by rory58824

Yes, that equation is wrong, it's only 1 HCl. If you wanted to write a full equation, its:

phenylamine + NaNO2 + 2HCl ----> diazonium ion + NaCl + 2H2O

Ok, so if you want the overall equation, it's the above? (Wouldn't it be the diazonium salt rather than ion btw?).

And if you do it in two steps, it would be:
1. NaNO2 + HCl ----> NaCl + HNO2
2. phenylamine + HNO2 + HCl ---> diazonium salt + 2H2O

?

Reply 535

Serine Soul

Original post by chuckster111

Isn't my attachment loading? :colondollar:

Reply 536

rory58824

Original post by chuckster111

I've noticed the textbook changes between ion and salt (maybe someone who knows more could clarify this lol). Probably best to use salt, my bad.

And yep, that looks fine.

(edited 7 years ago)

Reply 537

chuckster111

Original post by Serine Soul

Isn't my attachment loading? :colondollar:

Hi, sorry I'm on my phone I didn't realise there was an attachment! :colondollar:

Thanks for that :smile:

Reply 538

KaylaB

Original post by rory58824

I've noticed the textbook changes between ion and salt (maybe someone who knows more could clarify this lol)

And yep, that looks fine.

It is a salt if another negative ion is with it, like Chlorine. It then becomes Diazonium chloride which is a salt

If it is just the first part by itself, like below, then it is a diazonium ion

Reply 539

Serine Soul

Original post by rory58824

I've noticed the textbook changes between ion and salt (maybe someone who knows more could clarify this lol)

And yep, that looks fine.

I haven't looked at the textbook for this topic (too simplified) but remember that the diazonium salt is essentially the diazonium ion with a Cl-

In synthetic routes etc on a question paper, it often says to ignore the presence of the Cl- ion next to the diazonium ion.

When writing the full reaction in itself though, I'd go for the HNO2 + HCl route and draw the salt as the product rather than just the ion