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Topic: Organic solvents and solutes  (Read 7156 times)

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Offline FishFace

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Organic solvents and solutes
« on: September 15, 2011, 12:30:25 PM »
Hi, I'm having trouble with some reactions of organic compounds in organic solvents and would really appreciate some help...
I need to know what is produced when benzoic acid is dissolved in ether, all I found online to help me was that ether is a Bronstead base, so my line of thinking is this:

C6H5COOH + (C2H5)2O --->  C9H10O2 + C2H5OH

This seems correct to me but I wanted to make sure. Now the next question is ethylamine and ether, so following the same theory as I used before with ether accepting the hydrogen, I get this:

CH3CH2NH2 + (C2H5)2O --->  CH3CH2NHCH2CH3 + C2H5OH

However what confuses me for this last one is that our TA gave us a hint, saying that "there is no chemical change in ether". I'm wondering if ethylamine doesn't actually dissolve in ether because ethylamine is polar and ether isn't polar enough to have a reaction? That doesn't really make sense to me though because then it would be the same case for the first question..

Thanks so much for helping!

Offline opsomath

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Re: Organic solvents and solutes
« Reply #1 on: September 15, 2011, 01:40:43 PM »
Okay, I'm afraid you are way overthinking these. You are basically showing an ethyl group moving from one molecule to another, which can't happen in these compounds. The bond between the ethyl group and the oxygen is too strong.

The short answer is that no chemical change occurs when either of those compounds are dissolved in ether.  Neither one is a strong enough acid to protonate ether.

How exactly is the question phrased?

Offline FishFace

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Re: Organic solvents and solutes
« Reply #2 on: September 15, 2011, 01:50:41 PM »
Okay, I'm afraid you are way overthinking these. You are basically showing an ethyl group moving from one molecule to another, which can't happen in these compounds. The bond between the ethyl group and the oxygen is too strong.

The short answer is that no chemical change occurs when either of those compounds are dissolved in ether.  Neither one is a strong enough acid to protonate ether.

How exactly is the question phrased?

Thanks for the help. I could definitely see how no reaction could occur, it just seemed like something must be occurring based on the question. These are how the questions are stated.

1. Draw the structure of a benzoic acid molecule when it is dissolved in ether.
2. Draw the structure of an ethylamine molecule when it is dissolved in ether.

So basically you're saying neither compound dissolves in ether and they just remain as is?

Offline opsomath

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Re: Organic solvents and solutes
« Reply #3 on: September 15, 2011, 01:55:10 PM »
Okay, that is odd...are you studying intermolecular forces? Do they want you to draw the hydrogen bond between the O-H and N-H protons and the oxygen of the ether?

Offline FishFace

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Re: Organic solvents and solutes
« Reply #4 on: September 15, 2011, 02:09:41 PM »
This was a lab on solubility actually. There are other questions asking the structure of a benzoic acid molecule dissolved in 5% NaOH and an ethyl amine molecule dissolved in 5% NaOH, but those were fairly straight forward to do. I don't think they want us to show the bonds in the molecule or anything.. Maybe I'll have to try contacting them.. it just makes no sense to me

Offline opsomath

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Re: Organic solvents and solutes
« Reply #5 on: September 15, 2011, 02:11:18 PM »
Oh, I understand now. Yes, just draw the structures in ether as is. They just want you to understand that neither compound is ionized in ether, but one is ionized and one is not in aqueous NaOH.

Offline FishFace

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Re: Organic solvents and solutes
« Reply #6 on: September 15, 2011, 02:17:06 PM »
Ah okay, thanks so so much for your help

Offline FishFace

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Re: Organic solvents and solutes
« Reply #7 on: September 15, 2011, 04:55:36 PM »
Sorry, I realized I have one more question.. When you mix benzoic acid and 5% NaOH together, does this create sodium benzoate and water or is benzoic acid ionized and the Na+ is separate? I keep seeing such a reaction written both ways, but I was under the impression it because  sodium salt with water.
Thanks again in advance!

Offline opsomath

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Re: Organic solvents and solutes
« Reply #8 on: September 15, 2011, 05:23:22 PM »
Rephrase the question; when a sodium salt dissolves in water, is it ionized with the ions separated from each other?

Offline FishFace

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Re: Organic solvents and solutes
« Reply #9 on: September 15, 2011, 05:31:00 PM »
Well when something is ionized it means the compound becomes an ion, right? So as sodium benzoate isn't an ion.. what should happen is that benzoic acid would become an ion with a negative charge and Na+ would become an ion floating around in the h2o as well?

E: Sorry, not sure if you were trying to understand what I said, but that's the question yeah.. I keep seeing it written both ways online
« Last Edit: September 15, 2011, 05:44:13 PM by FishFace »

Offline YellowLemon

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Re: Organic solvents and solutes
« Reply #10 on: September 16, 2011, 06:26:56 AM »
Well when something is ionized it means the compound becomes an ion, right? So as sodium benzoate isn't an ion.. what should happen is that benzoic acid would become an ion with a negative charge and Na+ would become an ion floating around in the h2o as well?

E: Sorry, not sure if you were trying to understand what I said, but that's the question yeah.. I keep seeing it written both ways online

The hydroxide group will deprotonate the benzoic acid and form water. The Benzoate anions negative charge on the oxygens will be stabilized by the sodium-ions positive charge. Keep in mind that the 2 oxygens on the Benzoate ion is equivalent and the ion is thereby stabilized by resonance.

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