A2 Does Phenol make a Salt

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Audiology-Med
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#1
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#1
This is one thing which is making me confused as some say it does and others say it doesn't.

So in C6H5OH in excess Na would it make C6H5O-Na+.

I have uploaded my exam paper for two questions from F324 june 2014 which I got wrong, according to my tutor a OH on a Benzene ring can't make a salt unless theres more than one OH.

Why would my answers be wrong.
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Audiology-Med
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#2
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#2
What would be the right answers to these question uploaded as I got both wrong and dont know how to get to the right answer. Does the OH in phenol make a salt or a ester linkage.
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Ruxy
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#3
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#3
(Original post by haseebi82)
What would be the right answers to these question uploaded as I got both wrong and dont know how to get to the right answer. Does the OH in phenol make a salt or a ester linkage.
I think it makes a salt I don't know about the second question though (my worst topic are polymers and repeat units so ... Sorry)


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username1410894
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#4
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(Original post by haseebi82)
This is one thing which is making me confused as some say it does and others say it doesn't.

So in C6H5OH in excess Na would it make C6H5O-Na+.

I have uploaded my exam paper for two questions from F324 june 2014 which I got wrong, according to my tutor a OH on a Benzene ring can't make a salt unless theres more than one OH.

Why would my answers be wrong.
I believe only the OH group on the phenol will lose a hydrogen ion and become replaced with a Na ion from the NaOH. This is because of the lone pair of electrons on the oxygen, whereas the COOH carboxylic group does not have a lone pair of electrons therefore there is no reaction with that functional group. So you were marked incorrect as you modified the carboxylic group and because the markschemes are harsh you lost the mark.
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Mr_Cupcakes
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#5
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#5
Actually carboxylic acids are weak acids, they dissociate in water so naturally undergo Acid + Base --> Salt + water. As long as the NaOH is in excess it will form a carboxylate salt. Phenol is also a weak acid and will also react with Naoh to give sodium phenoxide, which has the group O-Na+ as you've put, I don't think you got it wrong.

Edit: I know I've worded this really badly but what I'm trying to say is both the phenol group and the carboxyl group will react giving the O-Na+ and COO-Na+ as you've put. Let me know if this makes sense or not, If it doesn't I'll try and explain it better.
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username1445490
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#6
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#6
The problem is that you put a covalent bond between the O and the Na as in O-Na+ This is incorrect as it is ionic. Also your O-Na+ is just floating and not connected to the ring. I know you did this because you scribbled out something else but it has to connect so you should have redrawn it all.
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username1445490
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#7
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#7
The repeat unit is not correct it should be

-COCH2CH2-O-CO-C6H4-O-
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username1445490
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#8
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See my answer to this in the other thread.
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Mr_Cupcakes
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#9
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(Original post by Madasahatter)
The problem is that you put a covalent bond between the O and the Na as in O-Na+ This is incorrect as it is ionic. Also your O-Na+ is just floating and not connected to the ring. I know you did this because you scribbled out something else but it has to connect so you should have redrawn it all.
Looks like a negative charge to me, look at the position of it.
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#10
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(Original post by Mr_Cupcakes)
Looks like a negative charge to me, look at the position of it.
No. I am an examiner and this will have been taken as a covalent bond. Aside from that the fact it is not attached means it is wrong anyway.
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Audiology-Med
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#11
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#11
(Original post by Madasahatter)
No. I am an examiner and this will have been taken as a covalent bond. Aside from that the fact it is not attached means it is wrong anyway.
yeah after looking at it , I thought I wouldn't get the mark because it wasn't attached and it was meant to be a negative charge, i need to make sure i make it more clearer next time, thanks for your help.
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Pigster
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#12
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#12
Next time, cross out the entire answer and start again.
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username1445490
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#13
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#13
(Original post by Pigster)
Next time, cross out the entire answer and start again.
Sound advice. The other common error is change a number by writing over the top of another one. Always a recipe for losing a mark.
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tab_awesome
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#14
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#14
(Original post by haseebi82)
This is one thing which is making me confused as some say it does and others say it doesn't.

So in C6H5OH in excess Na would it make C6H5O-Na+.

I have uploaded my exam paper for two questions from F324 june 2014 which I got wrong, according to my tutor a OH on a Benzene ring can't make a salt unless theres more than one OH.

Why would my answers be wrong.



Hey could you please post the rest of the pictures of your test paper.

Thanks
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