NMR Environments

[shea43]

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?

[Studyinghard]

/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.

[happyhappyland]

D!!

[stonecold]

deffz D!

[Studyinghard]

Why cant it be B. 2 hydrogen enviornments

[olly_s15]

/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

[olly_s15]

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

[Studyinghard]

^^ thank you. thats what I was waiting for .

It didnt specify High or low resolution. Its not the first time Ive seen this. Stupid checkpoints =@

[stonecold]

because they want the high res in these types of questions...

[olly_s15]

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"

[stonecold]

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.

[olly_s15]

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

[superflya]

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.

[m@tty]

Even though this is true, I expect VCAA would specify high resolution.

[Studyinghard]

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.