111davey1
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Hi,
in this question would it be ok to have the esterification of both the phenol group and the alcohol group giving a structure with three benzene rings?
Thanks
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Pigster
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To form an ester, you need a carboxylic acid group: of which there is only one. That can esterify with an OH group of which there are two. The MS allowed either one to form. One COOH group cannot form two ester groups simultaneously.

You perhaps also should know that phenol groups don't easily esterify; needing something like RCOCl to make it happen.
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111davey1
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(Original post by Pigster)
To form an ester, you need a carboxylic acid group: of which there is only one. That can esterify with an OH group of which there are two. The MS allowed either one to form. One COOH group cannot form two ester groups simultaneously.

You perhaps also should know that phenol groups don't easily esterify; needing something like RCOCl to make it happen.
Thanks,
So how do you know that there isnt more than 1 molecule with the COOH group available?
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111davey1
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So if the compound C had another CH2OH group would you esterify that or not?
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Pigster
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Compound A is oxidised. The CHO group -> COOH, the phenol group won't oxidise.

Compound A is then reduced. The CHO group -> CH2OH, the phenol group won't oxidise.

The COOH group on the oxidised version of A can react with either OH group on C (but essentially won't react with the phenol group, but the MS allowed it).

The only other reaction that could take place would be the polymerisation of the oxidised version of A (but that involves esterification through a phenol group, which I might have mentioned is unlikely).

Adding another CH2OH to A just gives the one COOH group on the oxidised version of A another possible target.
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111davey1
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(Original post by Pigster)
Compound A is oxidised. The CHO group -> COOH, the phenol group won't oxidise.

Compound A is then reduced. The CHO group -> CH2OH, the phenol group won't oxidise.

The COOH group on the oxidised version of A can react with either OH group on C (but essentially won't react with the phenol group, but the MS allowed it).

The only other reaction that could take place would be the polymerisation of the oxidised version of A (but that involves esterification through a phenol group, which I might have mentioned is unlikely).

Adding another CH2OH to A just gives the one COOH group on the oxidised version of A another possible target.
Thanks, i understand that there is one COOH group on that molecule but if you had two of them molecules would there not be two COOH groups available to oxidise either of the Oh groups (as they allowed the esterification of the phenol group)... which could potentially lead to a molecule with 3 benzene rings (two ester groups) or do you have to treat it as just one molecule available .. or is it just not possible to have one ester group of the alcohol group and one on the phenol group even if there were two molecules available
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Pigster
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If one molecule started off with two CHO groups and was completely oxidised, it would form two COOH groups and could then form two ester linkages to C and the resulting molecule would have three benzene rings.

You were correct all along. If only you'd have explained yourself better at the beginning
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111davey1
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Sorry i have not explained this well at all. Basically what I cant understand is why the molecule with two OH groups does not produce a molecule with three benzene rings ( two ester groups) given a reaction with the COOH molecule they gave in the question.

The way i am thinking is 1 molecule of the one with two OH groups it reacted with 2 molecules of the one with the (one) COOH group and what will happen is that the two COOH groups (one from each molecule) which are available (because there are two molecules) will join onto the two OH groups in the molecule (one on the phenol and one on the CH2OH group)

Does this just not happen or does the flow diagram show that there is only one molecule with a COOH group available.
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Pigster
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Aha, you mean one benzene ring with two alcohol groups which react with separate molecules each with a COOH group to form a molecule with three benzene rings.

That'd work.
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111davey1
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(Original post by Pigster)
Aha, you mean one benzene ring with two alcohol groups which react with separate molecules each with a COOH group to form a molecule with three benzene rings.

That'd work.
Yes thats it . is there a reason why this would not be accepted?
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Pigster
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(Original post by 111davey1)
Yes thats it . is there a reason why this would not be accepted?
Quite simply it is because compound A cannot be converted into a molecule with two COOH groups.

The phenol group cannot be oxidised.
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111davey1
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(Original post by Pigster)
Quite simply it is because compound A cannot be converted into a molecule with two COOH groups.

The phenol group cannot be oxidised.
Thanks,
But this doesnt make sense to me because that molecule is reacting with a molecule with 2 OH groups so surely if a bunch of them molecules were together you would find some where both oh groups on that molecule had been esterified by compound A. , on the same molecule leading to a compound with three benzene rings.

Is it that it is implying that one molecule of A is reacting with one of C?
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Pigster
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To quote me earlier:

(Original post by Pigster)
Aha, you mean one benzene ring with two alcohol groups which react with separate molecules each with a COOH group to form a molecule with three benzene rings.

That'd work.
Two oxidised versions of A, each having a COOH group could, in theory, react with one molecule of compound C (which has two OH groups) forming a molecule with three benzene rings.

As I (almost) said earlier, that'd work.

Except in this case it wouldn't as phenol groups don't like esterifying. The old OCR A spec didn't worry about that, but now that we've got acyl chlorides, they do: 6.1.3(f) additional guidance: "esterification of phenol, which is not readily esterified by carboxylic acids"
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MexicanKeith
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(Original post by 111davey1)
Thanks,
But this doesnt make sense to me because that molecule is reacting with a molecule with 2 OH groups so surely if a bunch of them molecules were together you would find some where both oh groups on that molecule had been esterified by compound A. , on the same molecule leading to a compound with three benzene rings.

Is it that it is implying that one molecule of A is reacting with one of C?
Given that the mark scheme says to allow esterification of the phenol oxygen, you should be absolutely fine if you suggested both esterifications.

In reality the phenol oxygen lone pairs are able to delocalise around the aromatic ring and so this esterification would be very slow compared to esterification of the alcohol group!

edit:seems like from what pigster has said, these days Phenol esterification is not kosher (quite rightly) but at least now you know
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