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OCR F324-June 2013 Chemistry

Reply 2260

thers

5

Original post by mrmccarl

when you reduce a carboxlic acid, do you get 2 alcohol groups as a result?

Reduction of carboxylic acid is not on the spec. Only carbonyl compounds (ketones and aldehydes).

Reply 2261

otrivine

OP

14

Original post by thers

Correct. My turn.

1) Which patient should not have MRI scan

2) State the difference between proton and carbon-13 spectrums

3) Suggest which spectrum is more accurate in determining a compound

Reply 2262

kevloui

I'm liking the look of this!

Reply 2263

Onkar-M

Original post by mrmccarl

when you reduce a carboxlic acid, do you get 2 alcohol groups as a result?

no- just one!

Reply 2264

George_

2

Although I don't do this exam board, I enjoy Chemistry and plan on studying it next year! If you have any questions, I'll be happy to try and answer them! PM me or just quote me.

Reply 2265

thers

5

Original post by otrivine

1) Which patient should not have MRI scan

2) State the difference between proton and carbon-13 spectrums

3) Suggest which spectrum is more accurate in determining a compound

1) Those with artificial pacemakers/metal implants

2) Proton NMR shows splitting patterns to determine number of adjacent protons. C-13 does not

3) Proton NMR because of above.

What is the difference between structural isomers and stereoisomers?
What is meant by E/Z isomerism?
What is meant by cis-trans isomerism?

Reply 2266

mrmccarl

Original post by thers

Reduction of carboxylic acid is not on the spec. Only carbonyl compounds (ketones and aldehydes).

im sure there was a question in the past papers that we had to reduce a carboxylic acid?

Reply 2267

Raafae

Original post by JimmyA*

It's because it can undergo further substitution, page 38 of the text book :smile:

Thanks!

Reply 2268

NilabKebab

3

Original post by thers

Correct. My turn.

Hello, I don't quite understand question 4c in Jan 2012 paper, for the ester the structure was C(CH3)3CH2COOCH2CH3 (check mark scheme) but I got C(CH3)3COOCH2CH2CH3 (Ive attached the molecule I got).

Why is my structure wrong?

Attachment not found

Reply 2269

mrmccarl

Original post by thers

1) Those with artificial pacemakers/metal implants

2) Proton NMR shows splitting patterns to determine number of adjacent protons. C-13 does not

3) Proton NMR because of above.

What is the difference between structural isomers and stereoisomers?
What is meant by E/Z isomerism?
What is meant by cis-trans isomerism?

why should patients with pacemakers not undergo MRI?

Reply 2270

thers

5

Original post by mrmccarl

im sure there was a question in the past papers that we had to reduce a carboxylic acid?

That was Jan 12. You could have completed the whole question without knowledge of reduction of carboxylic acid. From synthesis 2, you worked backwards to determine how this happens. Then in synthesis 3, you had to use this knowledge to reduce the next carboxylic acid.

Reply 2271

2013leaver

5

Original post by thers

Reduction of carboxylic acid is not on the spec. Only carbonyl compounds (ketones and aldehydes).

it came up on jan 2012

Reply 2272

tatters

No - you get an aldehyde

Reply 2273

otrivine

OP

14

Original post by thers

1) Those with artificial pacemakers/metal implants

2) Proton NMR shows splitting patterns to determine number of adjacent protons. C-13 does not

3) Proton NMR because of above.

What is the difference between structural isomers and stereoisomers?
What is meant by E/Z isomerism?
What is meant by cis-trans isomerism?

correct!

1) structural isomer is where the compound has the same molecular formula but with different arrangements of atom, stereoisomers are compounds with the same structural formula but with different arragnements of atom in space

2/3) E/Z isomerisim (cis/trans) occurs when a carbon is attached to 2 different atoms or groups of atom and because of the restricted rotation of the c=c bond. Also, the cis isomerisim is where the hydrogen atoms are on the same side and the trans isomer is where the hydrogen atoms are on opposite sides to/of each other.

Reply 2274

Raafae

Can someone help me with the conditions for the formation of an azo dye.
In my notes for January I wrote down "alkaline conditions" after looking at all the mark schemes.
But when I looked at the mark scheme for January 2013 it specifically says "hot aqueous NaOH" :s-smilie:

Why does OCR change their mark shceme and what should I write in the exam tomorrow?

Reply 2275

hussaincute

can somebody plz explain nmr question on jan 2013 paper?

Reply 2276

tatters

Someone please help! I thought that at the isoelectric point if you have an NH2 on the R group that gets protonated as well, but on the mark scheme for June 2012 I just did it says only accept one NH2 group protonated?!

Reply 2277

Sarangtaec

Original post by tatters

Someone please help! I thought that at the isoelectric point if you have an NH2 on the R group that gets protonated as well, but on the mark scheme for June 2012 I just did it says only accept one NH2 group protonated?!

No! Just remember that the isoelectric point is when a ZWITTERION exists meaning there is NO NET OVERALL CHARGE so only one NH2 is protonated, if 2 were protonated then the overall charge would be -1

Reply 2278

thers

5

Original post by Raafae

Can someone help me with the conditions for the formation of an azo dye.
In my notes for January I wrote down "alkaline conditions" after looking at all the mark schemes.
But when I looked at the mark scheme for January 2013 it specifically says "hot aqueous NaOH" :s-smilie:

Why does OCR change their mark shceme and what should I write in the exam tomorrow?