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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Studyinghard on June 05, 2010, 12:04:14 pm

Title: VCAA 2008
Post by: Studyinghard on June 05, 2010, 12:04:14 pm: In the vac exam question 4 part c.

http://www.vcaa.vic.edu.au/vce/studies/chemistry/exams/2008/2008chem1-web.pdf

exam link there ^^

Isn't this question a big ambiguous because the H NMR shows that there is a chemical shift at around 2.3 and when you go to your data booklet that shows that there is an ester link in the molecule.

But the molecular formula states that there is only one Oxygen in the molecule.

So like totally confused.
Title: Re: VCAA 2008
Post by: happyhappyland on June 05, 2010, 12:09:08 pm: Databook for hnmr is meant to be vague. dont take it too seriously
Title: Re: VCAA 2008
Post by: Studyinghard on June 05, 2010, 12:18:44 pm: but arent you meant to use all the information they give you ?
Title: Re: VCAA 2008
Post by: stonecold on June 05, 2010, 12:20:14 pm: Don't even worry about the chemical shift. It should be the last thing you use to determine molecule structure. First worry about the number of environments, peak height and then peak splitting if you are given high res.
Title: Re: VCAA 2008
Post by: m@tty on June 05, 2010, 01:43:28 pm: If there is a peak down around $\delta=11-12 ppm$ then automatically think carboxylic acid. (I think I remember seeing delta used to represent chemical shift...) Other than this, wait till last, as stonecold said.
Title: Re: VCAA 2008
Post by: stonecold on June 05, 2010, 02:33:21 pm: Yeah, matty is right. If there is a peak at 11.5 then you know it is a carboxilic acid. :)

Other than that, don't really bother with chemical shift unless you get desperate. I doubt it will even help that much...