ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: shea43 on June 06, 2010, 10:13:05 pm
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Ok, so I've been doing my practice exams and I keep making mistakes on the number of hydrogen environments. I really only have trouble with the ones like esters and stuff like that. Is the number of H environments influenced by what is next to the carbon?
e.g. if there is two CH2 groups next to each other then an O then another CH2 group would this be one H environment or two?
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/thread hijack
NMR question.
One of the isomers of C3H6I2 has the semi structural formula CH2I - CH2 - CH2I. Its H NMR spectrum would consist of
a) two triplets
b) two singlets
c) three triplets
d) a triplet and a five line pattern.
For a easier read of the question go to page 59 of your checkpoints. item 12.
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D!!
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deffz D!
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Why cant it be B. 2 hydrogen enviornments
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/thread hijack
NMR question.
One of the isomers of C3H6I2 has the semi structural formula CH2I - CH2 - CH2I. Its H NMR spectrum would consist of
a) two triplets
b) two singlets
c) three triplets
d) a triplet and a five line pattern.
For a easier read of the question go to page 59 of your checkpoints. item 12.
the "five line pattern" is due to the central CH2 group being influenced by 4 protons in the same environment. because of this, the n+1 rule is applicable and as there are four protons influencing this
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Why cant it be B. 2 hydrogen enviornments
well that is a good point - it can.
unless the question specifies high res or low res spectra then this question is fail
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^^ thank you. thats what I was waiting for :P.
It didnt specify High or low resolution. Its not the first time Ive seen this. Stupid checkpoints =@
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because they want the high res in these types of questions...
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because they want the high res in these types of questions...
no i still think this question is a massive fail - too ambiguous and could be interpreted differently
you can't just say "coz they want it in these questions"
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And 'singlet' in my opinion is in reference to a high res. spectrum.
Low res refers to peaks, and not '...ets'. These are specific to high res and peak splitting, so the answer is D. I wouldn't expect any leniency if this came up on VCAA.
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And 'singlet' in my opinion is in reference to a high res. spectrum.
Low res refers to peaks, and not '...ets'. These are specific to high res and peak splitting, so the answer is D. I wouldn't expect any leniency if this came up on VCAA.
VCAA wont have this kind of ambiguity
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when all the options talk of x peaks on a spectrum, u can safely assume its low-res. however when its got singlets,triplets etc as the options, its gotta be high res.
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Even though this is true, I expect VCAA would specify high resolution.
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when all the options talk of x peaks on a spectrum, u can safely assume its low-res. however when its got singlets,triplets etc as the options, its gotta be high res.
Still a big ambiguous because singlets are still peaks and vice versa. However now I shall just go with this theory that the terms "ets" refers to High res.
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There is nothing wrong with the question. Answer is D. Clear cut. I could see VCAA putting something like this on the exam. It would be a good question to separate those who have who have a good understanding of Low Res and High Res NMR from the rest.
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Totally agree.
No ambiguity at all. How could you possibly have 5 lines ANYWAY if it were low-res!?!