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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Pandora on September 17, 2018, 07:48:15 AM

Title: Titration of Isomeres
Post by: Pandora on September 17, 2018, 07:48:15 AM
Hello everyone,

I am not to experienced with titrations, so I hoped I could get a tip regarding the subject.
I want to titrate a substance, which is an isomere to another substance, which the titration is usable for.
It is regarding the formula C4H9NO3 (Threonine and L-homoserine)

Would this give the same result when titrating??

Thanks for the replies,
Title: Re: Titration of Isomeres
Post by: sjb on September 17, 2018, 08:08:45 AM
How do these compounds differ and how are they the same?
Title: Re: Titration of Isomeres
Post by: Pandora on September 17, 2018, 08:13:07 AM
They both have a double bond O linked to an OH, and a NH2 group. But I am unsure whether the CH3 group, which is located at another position (see images), can alter the titration performed. I have the idea that the L-homoserin is more unstable, causing titration to have a lower endpoint.  But I am unsure of this.
Title: Re: Titration of Isomeres
Post by: sjb on September 17, 2018, 08:37:13 AM
Much would depend on the actual titration you're doing.

Consider e.g. titrating hexan-1-ol and hexan-2-ol against dichromate for instance, or hex-1-ene and hex-2-ene against bromine.
Title: Re: Titration of Isomeres
Post by: Pandora on September 17, 2018, 09:37:53 AM
I am thinking about a formic acid/acetic acid solution with perchloric titration.

The downside is I can't titrate, because I don't have a lab availaible. So I'm trying to find out the theory behind it.
Title: Re: Titration of Isomeres
Post by: sjb on September 17, 2018, 09:42:01 AM
OK, so what particularly are you measuring with that titration?
Title: Re: Titration of Isomeres
Post by: Pandora on September 17, 2018, 09:51:39 AM
To check an assay value, if it complies with the amount prescribed by the supplier. 

I am measuring the L-Homoserine, and found a technique of Threonine which I think could work.
Title: Re: Titration of Isomeres
Post by: Arkcon on September 17, 2018, 10:12:55 AM
Hi there, Pandora:, we like to help, here on the Chemical Forums, but our rules specify that you have to show your work, based on your knowledge.  I think its worthwhile, for me to mention, that this response, from you:

To check an assay value, if it complies with the amount prescribed by the supplier. 

doesn't actually answer the question that was asked of your here:

OK, so what particularly are you measuring with that titration?

Also this statement here:
Quote
I am measuring the L-Homoserine, and found a technique of Threonine which I think could work.

Just restates your original problem, in a different way.

Now, when you say:

I am thinking about a formic acid/acetic acid solution with perchloric titration.

What reaction occurs, that leads to the tirtation endpoint?  Does your analyate have the same functional groups?  Does it have some extra ones that also react?
Title: Re: Titration of Isomeres
Post by: Pandora on September 17, 2018, 10:31:09 AM
My apologies, I was not aware of the rules. And my knowledge of titration is an absolute minimum.

From the molecules shown in my original post I would think that only the NH2 groups would respond and no other analytes would, however due to my lack of knowledge in this subject I cant assure this.

Since there is a small difference between the two analystes I have mentioned before, I am not certain whether free electrons near the double bonds could affect this..
Title: Re: Titration of Isomeres
Post by: Arkcon on September 17, 2018, 03:09:49 PM
OK.  Here's a reference to perchloric acid titration of amino acids: http://www.jbc.org/content/125/1/259.citation  It starts off by telling you what the reaction is.