electronegative subst. in 3' on 3,4,5-pattern phens/phets?

[vecktor]

The old school short cut is to take the NMR and look at the shifts rather than messing about with math, electron withdrawing aryl groups deshield the aryl protons o p. the NMR also gives the overall addiitive and subtractive effect at a given position, something that the other methods struggle with, for example benzenesulfonyl guaiacol has an electron withdrawing group sulfonoxy as well as an electron donating group methoxy, which is stronger? what position does the compound undergo FC alkylation at and how readily? NMR tells you the answer in a few minutes.
The 1H NMR spectra for different substitutions on aryl compounds is easy to find and this is real world data including solvent effects, there is a rule, real chemists are real lazy, physical and theoretical chemists are alien physicists wrapped in chemist skins and they like math.

 

[Limpet_Chicken]

I'm royally screwed either way. No way in hell I can afford an NMR machine, and I am AWFUL at math. Severely dyscalculic, fucking blows.I've often thought that
I kinda make the world's most unlikely chemist,because I am worse than shit at math, and when it comes to algebra I've no knowledge either way.

I have to say though Vecktor, that last one liner of yours, its so true it's fucking hilarious. Of course one has to have standards, But can't beat a short cut that actually improves a process. 6-7 hours on a steam bath, producing P2NP that comes out orange in colour and soaked in red liquid? bugger that when one can just nuke it in the microwave,7 hours down to 15-20 minutes, and better nitropropenes and nitrostyrenes, quality wise, than when conventional heating is used.

 

[S.J.B.]

I'm royally screwed either way. No way in hell I can afford an NMR machine, and I am AWFUL at math. Severely dyscalculic, fucking blows.I've often thought that
I kinda make the world's most unlikely chemist,because I am worse than shit at math, and when it comes to algebra I've no knowledge either way.

Perhaps I went into too much detail. No math is needed to use the table; all one needs to know is:

a) if the "σ" value is positive, the group is electron-withdrawing, and if it's negative, it's electron-donating;

b) a bigger number means a stronger effect;

c) "σ(p)" refers to the para position while "σ(m)" refers to the meta.

No need to use the equation, as the physical chemists who came up with the values have already dealt with that! The NMR method works as well, but it's convenient to have so many substituents tabulated for easy reference.

 

[Limpet_Chicken]

Thanks, that is useful. I'll do some comparisons between highly electronegative (E.g TFM, nitro) groups and EDGs to get an idea of the scale.

NMR is definitely out. I could more than likely get someone else to run an NMR on a specific sample, but I wouldn't waste their time with something like this.

Edit-I meant the relative ED/EW characteristics of different functional groups, I definitely intend to get analysis done of the finished work before it is tasted, something more sensitive than TLC, that is.