You *know* you're a chemistry nerd when... (1 Viewer)

[Jumbo Cactuar]

You know you are a chem nerd when ...

... you get an second year organic chem assignment and on the first night you are already writing to the lecturer-in-charge telling them how the assignment is flawed. The again maybe I am crazy. hmmm... where the hell has my C13 NMR nitrile singlet gone? Give it back you bastards!

 

[The_highwayman]

When u openly discuss electrophoresis on the bus on a friday afternoon before u discuss the imminent weekend.

 

[Casmira]

you think this is bad? i spent a few hours talking to people about my chemistry trial exam

 

[Dreamerish*~]

Not necessarily chemistry, but discussing the causes of seizures and the causes, symptoms and treatment of viral and bacterial meningitis during recess.

 

[The_highwayman]

when u chortle at the physics nerds who wouldn't know how to design a valid prac if their meaningless lives depended on it. (ok that isnt really chemistry nerd stuff but i do it anyway! try it some day!)

 

[Arvin Sloane]

You post in this thread?

 

[nit]

Originally posted by nit, 5th August 2005, 08:21 PM
when you post in a chemistry nerd thread

^It's been done before

Edit: Jumbo - a.) what would you say the 1H spectrum of o-hydroxyacetophenone looked like; b.) what would you say would give you a higher Rf value in 85:15 Hexane:Ethyl acetate solvent in a TLC analysis - o-hydroxyacetophenone or o-benzoyloxyacetophenone?

 

[Emma-Jayde]

when u chortle at the physics nerds who wouldn't know how to design a valid prac if their meaningless lives depended on it. (ok that isnt really chemistry nerd stuff but i do it anyway! try it some day!)

HEY!!!!!!!

 

[The_highwayman]

Hey what?! that's just the way it is. I assume u are one of them. Please, accept my sympathy.

 

[Emma-Jayde]

Hey!! to assuming that physics nerds wouldn't know how to design a valid prac.
We so can!!

 

[Jumbo Cactuar]

^It's been done before

Edit: Jumbo - a.) what would you say the 1H spectrum of o-hydroxyacetophenone looked like; b.) what would you say would give you a higher Rf value in 85:15 Hexane:Ethyl acetate solvent in a TLC analysis - o-hydroxyacetophenone or o-benzoyloxyacetophenone?

a:
http://www.aist.go.jp/RIODB/SDBS/cg...pe=disp3&imgdir=hsp&fname=HSP01163&sdbsno=724

b:
Whichever has a higher affinity for the stationary phase.

Hexane and ethyl acetate are both relatively insoluble in water. O-hydroxyacetophenone has the ability to hydrogen bond whereas o-benzoyloxyacetophenone is a fat bastard molecule. So assuming the TLC was carried out with some forethough and the stationary phase is polar, the o-hydroxyacetophenone has a better affinity for the stationary phase.

So o-hydroxyacetophenone should have a longer retention time.

PS: You may or may not know that the ortho (o) position notation of benzene disubstitution is equivelant to the 2 notation used in the spectra.

 

[The_highwayman]

Hey!! to assuming that physics nerds wouldn't know how to design a valid prac.
We so can!!

Denial

10chars

 

[nit]

^^We were given a spectrum for part a.) - I just wanted your thoughts on how the aromatic protons would get split up - I speculated on some resonance downshifting the protons ortho and para to the acetyl group and upshifting those ortho and para to the hydroxy, but yeh.

For b.) I reasoned the same way, but in fact it was the o-hydroxyacetophenone that rose higher, suggesting a better affinity for the mobile phase, which confused me - then again, both molecules are fairly large, so the ability to act as an H-bond donor for 1 H atom is not going to be that significant - I speculated on the acidic ability of phenol derivatives, with affinity for the slightly basic ethyl acetate, but neither is a strong enough acid/base for that too be meaningful.

 

[Jumbo Cactuar]

You'd get the most constructive peak dispersion if your disubstitued benzene had the two electron withdrawing groups in the meta position. As they are ortho you get a mess, since their affect is competing.

 

[nit]

the -OH group isn't technically completely electron-withdrawing though - there are inductive donation effects competing with that. So if you draw the resonance forms out, you can delocalise a negative charge at the ortho and para positions, which would suggest a downshifting in the spectrum.

 

[Jumbo Cactuar]

And with regard to the peaks themselves;

If you could analyse each peak individually you would have 4 aromatic peaks each intergrating for 1, two of which are doublets and two of which are singlets. Also the downfield peak of CH3 integrating for 3 and the OH integrating for 1, both singlets. The aromatic hydrogens interfere with each other when there are 'on top of each other', so only a skilled and experienced nmr analyst would recognise the mess you have...

With regards to my last post if you want to see the effect of cooperative disubstitution use the organic database and search o-nitroaniline, since the nitro is e. withdrawing and the amine is e. donating. The peaks there are very nice indeed!

 

[The_highwayman]

Ok University people! This is still a HSC forum! so if ur gunna discuss uni work: run away!

But then again..i suppose u were somewhat still on topic...

 

[Shell]

You know your a chemistry nerd when

you find yourself doing soil analysis of samples found on the floor

 

[Shell]

then you pretend your a CSI, and start deducing who murdered who... when no murder took place

 

[king_of_boredom]

you know you're a chem nerd when you hope all the ozone stays in the stratosphere and not in the troposphere!