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Offline T

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Question from Olympiad
« on: July 15, 2015, 04:45:12 AM »
Hello, can someone tell me if I did something wrong in this question? The answer I have is different to the answer given.



Firstly the ethanoic acid will react with X to produce water. So I added the molar mass of ethanoic acid + molar mass of X - molar mass of water.

Only the compound D will give a sum of over 193g.

60 + 172.9 - 18 = 214.9g.

Could someone help me?

Thanks

Offline mjc123

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Re: Question from Olympiad
« Reply #1 on: July 15, 2015, 04:53:42 AM »
Are you sure the stoichiometry is 1:1? Can anything react with more than 1 mole of ethanoic acid?

Offline T

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Re: Question from Olympiad
« Reply #2 on: July 15, 2015, 07:15:11 AM »
I am not sure about that.

Thanks

Offline Dan

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Re: Question from Olympiad
« Reply #3 on: July 15, 2015, 07:49:51 AM »
I am not sure about that.

Thanks

You know that none of these compounds would give MW = 193 g/mol if condensed with acetic acid in a 1:1 ratio - the simplest explanation is that the stoichiometry is not 1:1. Go from there.
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Offline T

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Re: Question from Olympiad
« Reply #4 on: July 16, 2015, 03:50:00 AM »
I see thanks. I thought all reactions with alcohols and acids would be:

alcohol + carobxylic acid  :rarrow: ester + water

I will think about the question because I am still learning about organic pathways.

Thanks 

Offline Dan

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Re: Question from Olympiad
« Reply #5 on: July 16, 2015, 04:10:55 AM »
I see thanks. I thought all reactions with alcohols and acids would be:

alcohol + carobxylic acid  :rarrow: ester + water

I will think about the question because I am still learning about organic pathways.

Yes, alcohols (phenols in this case) react with carboxylic acid in a 1:1 ratio, but there are also other functional groups present (aromatic nitro, aniline, aryl bromide...). Could any of those other groups also react with carboxylic acids?
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Offline T

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Re: Question from Olympiad
« Reply #6 on: July 16, 2015, 06:06:14 AM »
Ok thanks, I will try and figure it out. I have been studying organic pathways recently.

Is it correct to say that if 2 organic compounds both have a OH group then the 2 OH will always form water and the extra O will join the 2 compounds?

Eg. Alcohol + carboxylic acid --> Ester + water

I have been trying to find rules to determine reactions for organic compounds. Is there a general rule for determining reactions for organic compounds? Eg. They will always produce water when possible. Or are they all very different.

Thanks, this would help me a lot.
« Last Edit: July 16, 2015, 06:16:36 AM by T »

Offline Dan

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Re: Question from Olympiad
« Reply #7 on: July 16, 2015, 11:10:00 AM »
They will always produce water when possible. Or are they all very different.

You have to be very careful generalising, because there are a lot of factors to consider. I suppose you could say that all alcohols can potentially undergo Fischer esterification. How feasible it is in practice depends on the structural details (sterics, electronics,...) and the reaction conditions. For less reactive alcohols, different reactions involving more reactive acylating agents tend to be used.

You can expect Fischer esterification of the phenols you posted to proceed though.

Fischer esterification of something like this phenol would be very difficult:

C(C)(C)(C)c1c(O)c(C(C)(C)(C))cc(N(=O)=O)c1
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Offline T

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Re: Question from Olympiad
« Reply #8 on: July 17, 2015, 04:03:51 AM »
I see, thank you very much Dan

Offline T

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Re: Question from Olympiad
« Reply #9 on: July 18, 2015, 06:55:01 PM »
So I have been thinking about it and I have some ideas:

-Since the C-H bonds are strong then they won't be the bonds that break in the reaction
-The O and the OH are where the 2 phenols will attach to in the carboxylic acid since they are both slightly negative compared to the C-H bonds which have no polarity.
-2 phenols will attach to the carboxylic acid, one of them to the OH producing water and ester. The other double bonded O will attract the NH2 and bond with the H2 producing water. And the N will double bond with the C that was double bonded to the O.

My answer is A. But the mass still doesn't add up:

Mass = 2×(16+1.008×7+14.01+12×6)-2×18+12×2+1.008×4+32
Mass = 242.164g

Thanks

Offline sjb

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Re: Question from Olympiad
« Reply #10 on: July 19, 2015, 05:25:47 AM »
What is the functionality in A with the nitrogen?

Offline T

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Re: Question from Olympiad
« Reply #11 on: July 19, 2015, 06:20:10 AM »
I am not sure what you are asking but I am presuming you mean how the nitrogen will react.

I think that

An "A" molecule will react with the OH group in ethanoic acid producing water and an ester.

Another "A" molecule will react with the double bonded O, the 2 H from the nitrogen will bond with the O producing water, and then the N will double bond with the C that the O was previously double bonded to.

Thanks

Offline Dan

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Re: Question from Olympiad
« Reply #12 on: July 19, 2015, 09:06:24 AM »
I am not sure what you are asking but I am presuming you mean how the nitrogen will react.

I think that

An "A" molecule will react with the OH group in ethanoic acid producing water and an ester.

Another "A" molecule will react with the double bonded O, the 2 H from the nitrogen will bond with the O producing water, and then the N will double bond with the C that the O was previously double bonded to.

Thanks

Really you should give systematic names or draw the products you propose, because your descriptions are confusing.

Are you suggesting that this molecule forms?

Nc1cc(ccc1)OC(C)=Nc2cc(O)ccc2

Maybe there is another way to think about this... Consider the functional groups in isolation first:

Which of the following compounds react with acetic acid? What are the products?

1. Phenol
2. Aniline
3. Nitrobenzene
4. Bromobenzene
5. Toluene
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Offline T

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Re: Question from Olympiad
« Reply #13 on: July 20, 2015, 05:40:31 AM »
Hello Dan, I tried to use the SMILES but it didn't work for some reason. But I have looked at what you typed and it should be fine now.

Which of the following compounds react with acetic acid? What are the products?

So my idea is that the O and the OH in the acetic acid will react since it is slightly negative as it draws the electrons to itself.

Phenol:
Phenol + acetic acid --> ester + water

Aniline:
CC(=O)Nc2cc(O)ccc2 + water

Nitrobenzene
CC(=O)N(=O)c1ccccc1 + water

Bromobenzene
I doubt it reacts but the best I could come up with was this:
CC(=O)c1ccccc1 + BrOH

Toluene
Not sure about this

My reactions are all based on my knowledge of organic chem, I am probably wrong. I have tried looking for sites that give you a general idea to predict organic reactions but can't find any.

Also, is the O or the OH in acetic acid more reactive? Or does it depend?

Thanks

Offline Dan

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Re: Question from Olympiad
« Reply #14 on: July 20, 2015, 06:46:08 AM »
Ok, so you know that:

1. Phenol reacts to form an ester (phenyl acetate)
2. Aniline reacts to form an amide (acetanilide)

So, if you have a molecule containing both an aniline and a phenol, what will the product be?

Note: nitrobenzene, bromobenzene and toluene will not react with acetic acid.
My research: Google Scholar and Researchgate

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