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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Problem of the Week Archive => Topic started by: Borek on April 08, 2013, 11:03:32 AM

Title: Problem of the week - 08/04/2013
Post by: Borek on April 08, 2013, 11:03:32 AM
Have you ever wondered where the term „vinyl” came from? Turns out it has its source in the Latin vinum, meaning wine. In 1809 von Vogel discovered a compound which could decompose producing either diethyl ether or ethene (and another product, identical in both cases). As synthesis started with one of the wine components, Gmelin suggested to name the gaseous product of the decomposition Vine or Vinegas, and later – in 1854 – Kolbe proposed the name „vinyl” for the monovalent radical C2H3– of this gas, thus we have vinyl alcohol, vinyl chloride, polivinyl chloride (PVC), and so on.

Suggest the identity of von Vogel's compound knowing that it contains 25.42% of sulfur and its solutions have low pH.
Title: Re: Problem of the week - 08/04/2013
Post by: Big-Daddy on April 09, 2013, 04:34:25 PM
Could it be that von Vogel's compound is (C2H5)2SO4? But this is only 20.8% sulphur, and because of the SO42- the pH may not be low ... but it fits all other needs, having the 2 ethyl groups which your decomposition products call for. Your extra product is probably H2SO4, though I can't get the equation to balance for diethyl ether. SO anyway this is surely not the right answer but anyway I feel I've given my first Problem of the Week a decent attempt :) If there are any more hints please let me know!
Title: Re: Problem of the week - 08/04/2013
Post by: DrCMS on April 10, 2013, 04:27:11 AM
Nearly there but instead think about one molecule of "vinic" alcohol reacting with one molecule of sulphuric acid.
Title: Re: Problem of the week - 08/04/2013
Post by: delta609 on April 12, 2013, 03:04:44 PM
C2H5HSO4  because sulfuric acid is a diprotic acid it steps down to a monoprotic acid before it completely dissociates.
Title: Re: Problem of the week - 08/04/2013
Post by: Big-Daddy on April 12, 2013, 04:20:08 PM
Quote from: DrCMS on April 10, 2013, 04:27:11 AM
Nearly there but instead think about one molecule of "vinic" alcohol reacting with one molecule of sulphuric acid.

What is "vinic" alcohol? C2H3OH?
Title: Re: Problem of the week - 08/04/2013
Post by: DrCMS on April 12, 2013, 04:27:15 PM
Quote from: Big-Daddy on April 12, 2013, 04:20:08 PM
What is "vinic" alcohol? C2H3OH?

No its ethanol see http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/107.%20Vinyl.pdf
Title: Re: Problem of the week - 08/04/2013
Post by: delta609 on April 12, 2013, 04:34:35 PM
Quote from: delta609 on April 12, 2013, 03:04:44 PM
C2H5HSO4  because sulfuric acid is a diprotic acid it steps down to a monoprotic acid before it completely dissociates.

Is this not correct?  The percentage is spot on, and in solution it would have a low pH due to the dissociation of the H bonded to the sulfate group.
Title: Re: Problem of the week - 08/04/2013
Post by: DrCMS on April 12, 2013, 04:39:31 PM
Yes C2H5HSO4 is the correct answer see the link I posted above.
Title: Re: Problem of the week - 08/04/2013
Post by: delta609 on April 12, 2013, 04:50:56 PM
Oh okay.  Sorry about that.
Title: Re: Problem of the week - 08/04/2013
Post by: Borek on April 12, 2013, 05:38:10 PM
Hard to deny Jensen's JCE column was a source of the problem :)