Relating chemical shifts

[Martoman]

Just checking.

Increase in chemical shift means less magnetic field is required???

How does this make sense because the more down field the more shielded so the more you need to penetrate no? Not the other way round?

[olly_s15]

Just checking.

Increase in chemical shift means less magnetic field is required???

How does this make sense because the more down field the more shielded so the more you need to penetrate no? Not the other way round?

Chemical shift is inversely proportional to the energy required to bring to resonance. More shielded requires more energy hence smaller chemical shift.

[Martoman]

Yeah.............. consider COOH that is highly shielded yet is a HIGH chemical shift.

[olly_s15]

Yeah.............. consider COOH that is highly shielded yet is a HIGH chemical shift.

what makes you say its highly shielded?

[olly_s15]

the electronegativiyt difference between O and H?

fair point

EDIT: hold on.... COOH isn't highly shielded - the neighbouring atom, O, is more electronegative hence weaker shield around the nucleus

[kyzoo]

I just think of it like this. In TMS the protons are very shielded. So the less shielding you get, the more different the proton environment is from TMS, and the more chemical shift you get.

[Martoman]

lol i just wiki'ed it. because of electronegativity it will steal all its electrons so less shielding.

Thanks.

[olly_s15]

lol i just wiki'ed it. because of electronegativity it will steal all its electrons so less shielding.

Thanks.

yes that is precisely what i was failing to coherently say

[cindyy]

are we supposed to know this :S

[olly_s15]

are we supposed to know this :S

no, not really. don't bother it's barely examinable

[Martoman]

I just like to understand things cindyy and just realised that I didn't get this.

I now want something sadistic like: here is a chemical shift. Choosse the least and most shielded.

Also something like: define chemical shift.

[olly_s15]

I just like to understand things cindyy and just realised that I didn't get this.

I now want something sadistic like: here is a chemical shift. Choosse the least and most shielded.

Also something like: define chemical shift.

how would you define chemical shift?

[Martoman]

difference in energy needed to change spin state

[Studyinghard]

I just like to understand things cindyy and just realised that I didn't get this.

I now want something sadistic like: here is a chemical shift. Choosse the least and most shielded.

Also something like: define chemical shift.

how would you define chemical shift?

Directly proportional to shielding by the electrons which depend on electronegativity. or is it inversely proportional :S

[olly_s15]

I just like to understand things cindyy and just realised that I didn't get this.

I now want something sadistic like: here is a chemical shift. Choosse the least and most shielded.

Also something like: define chemical shift.

how would you define chemical shift?

Directly proportional to shielding by the electrons which depend on electronegativity. or is it inversely proportional :S

inversely - the more shielded, the less shift