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OCR F324-June 2013 Chemistry

guys is there any tips to stop pre-exam tension? i always seem to panic during my exams!!!

plus can we chew gum during exams?

Reply 2421

hussaincute

whenever we come across NMR questions what is the sequence for things u look e.g. which one do we need to look first splitting pattern etc. ???

Reply 2422

freetown

6

Original post by MathsNerd1

Does anyone else feel quite relaxed for this exam when they know absolutely nothing but need a top mark to get an A? For some reason there is no urgency in me today :redface:

I agree, maybe when I see the NMR tomorrow I probably wont be feeling that way anymore :P

Reply 2423

MathsNerd1

17

Original post by thers

Write an equation for the nitration of benzene
Hence calculate the atom economy for the formation of nitrobenzene. [3]

C6H6 + HNO3 (conc sulphuric acid catalyst) ---> C6H5NO2 + H20 and I'm not sure about the atom economy, would it be 50%?

Reply 2424

sals1234

1

Hey guys, can someone please explain to me why in question 5biv (feature that causes stereoisomersism in citral) we have to circle the double bond that's on the right and not the one on the left? Here's the link to the paper: http://www.ocr.org.uk/Images/58126-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thank you :smile:

Reply 2425

MathsNerd1

17

Original post by freetown

I agree, maybe when I see the NMR tomorrow I probably wont be feeling that way anymore :P

I enjoy those as they're just a puzzle :tongue:

Reply 2426

MasterYi

Original post by otrivine

No I mean, I understand i use the chemical shift to identify the type of proton environment but how would I know which side to put them like I got the correct structure but my benzene ring is in a different place

•

Okay, there isn't anything on the NMR spectra telling you where benzene goes.

•

But the peak at Delta 4 tells you where that environment goes.

•

It is a HC-O group so that means the benzene ring can not go there and has to go onto the carbon on COOH.

Reply 2427

mrmccarl

Original post by MathsNerd1

C6H6 + HNO3 (conc sulphuric acid catalyst) ---> C6H5NO2 + H20 and I'm not sure about the atom economy, would it be 50%?

all you do is the desired over all products x100. in which case the by product is water

Reply 2428

otrivine

OP

14

Original post by MasterYi

•

Okay, there isn't anything on the NMR spectra telling you where benzene goes.

•

But the peak at Delta 4 tells you where that environment goes.

•

It is a HC-O group so that means the benzene ring can not go there and has to go onto the carbon on COOH.

I see!! makes sense now, thanks

Reply 2429

Onkar-M

So TLC - adsorption, G-C = rel. solubility?

Reply 2430

thers

5

Original post by MathsNerd1

C6H6 + HNO3 (conc sulphuric acid catalyst) ---> C6H5NO2 + H20 and I'm not sure about the atom economy, would it be 50%?

Eqn is correct

atom economy = Mr desired product/Mr all products x 100

Reply 2431

mrmccarl

Original post by Onkar-M

So TLC - adsorption, G-C = rel. solubility?

Yep! TLC stationary phase is solid whereas GC stationary phase is a liquid.

Reply 2432

MathsNerd1

17

Original post by mrmccarl

all you do is the desired over all products x100. in which case the by product is water

Yeah I remember but I was taking a guess at a percentage really :tongue:

Reply 2433

MasterYi

Original post by sals1234

Hey guys, can someone please explain to me why in question 5biv (feature that causes stereoisomersism in citral) we have to circle the double bond that's on the right and not the one on the left? Here's the link to the paper: http://www.ocr.org.uk/Images/58126-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thank you :smile:

The C=C bond on the left has two of the same groups on one end, so no matter how you rotate it, it will be the same.

Geometric isomers have to have two different groups on each carbon on the C=C bond.

Reply 2434

Onkar-M

Original post by sals1234

Hey guys, can someone please explain to me why in question 5biv (feature that causes stereoisomersism in citral) we have to circle the double bond that's on the right and not the one on the left? Here's the link to the paper: http://www.ocr.org.uk/Images/58126-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thank you :smile:

Because its attached to different groups on the right!

The one on the left isn't!
:smile:

.

Reply 2435

LosMutos

Original post by MathsNerd1

Tomorrow will be fun for us :tongue:

Anyone got some questions for me? I need some practice :tongue:

Hahaha very :biggrin:

Reply 2436

MathsNerd1

17

Original post by thers

Eqn is correct

atom economy = Mr desired product/Mr all products x 100

Thanks and yeah I remember that, just thought you wanted a value instead :colondollar:

Reply 2437

Jodie_668

9

Original post by sals1234

Hey guys, can someone please explain to me why in question 5biv (feature that causes stereoisomersism in citral) we have to circle the double bond that's on the right and not the one on the left? Here's the link to the paper: http://www.ocr.org.uk/Images/58126-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Thank you :smile:

Because the carbon that is on the left on the double bond of the left (I hope that makes sense, ahaha) is bound to the same groups (bound to two CH3). For E/Z isomerism, each carbon in the C=C must be bound to two different groups. :smile:

Reply 2438

MathsNerd1

17

Original post by LosMutos

Hahaha very :biggrin:

Let's smash it! :biggrin:

Reply 2439

mrmccarl