how do you guys prepare for NMR, IR, and lab technique for ochem section.

[wkawk2416]

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yeah, recently i heard, theres quite a few question on NMR, IR, and also some odd lab techniques in organic chemistry section. How do you guys prepare for those?

 

[drgreen]

For IR just know a bunch of the main functional groups

carbonyl: 2700
Alcohol: 3000 (fat)

Look at this table for some main functional groups alkenes alkynes alkanes, amines nothing more than that, http://en.wikipedia.org/wiki/Infrared_spectroscopy_correlation_table

For HNMR Destroyer's pretty good, but you can read wikipedia:
http://en.wikipedia.org/wiki/HNMR
Read through it, but focus on the Spin Spin coupling.

 

[jdent]

IR just know important specs. NMR- know how to interpret a carbon and a Hydrogen graph. Also understand the basic details behind it, aint to difficult- take out a text book and read up on it.

 

[klutzy1987]

For IR just know a bunch of the main functional groups

carbonyl: 2700
Alcohol: 3000 (fat)

Isnt a cabonyl at 1700 not 2700??

 

[DentalDeac]

yeah carbonyl is 1700-1750

 

[wkawk2416]

thanks, but yeah carbonyl is around 1700. also when a compound is meso compound, a hydrogen does not split and gives a singlet. is that right?

 

[klutzy1987]

Also if someting has no dipole and is nonpolar it will not have any IR.

 

[Jammanisback]

Isn't an alcohol at 3300

 

[ddsjc2014]

Typical OH band is ~3300 with broad band
Caboxylic Acid OH shows little less region around 2500 - 3000cm-1
NH band also shows at ~3300 region but with spike + broad band.
Carbonyl shows ~1700 - 1750 region.
In NMR major thing to distinguish is that whether they are equivalent or not. And just memorize the numerical value of various C-H bonds...
C13 NMR basically same thing.
Aldehyde around 165-200
Alkene 100-150
Aromatic C 115-150
C-O 55-90
alkyne 75-95
C-Cl or C-Br 30-65
Alkane 0-32
and know the shielding and deshielding effect.
deshiedling atom will make the connected or adjacent atom to be located at the lower field than where it supposed to be show spike.

 

[gentile1225]

i would definitely say practice some first, but you really just need to know some basics. For example,
* Functional group spikes, C=O, NH2, NH, OH, i dont think they will test much of bonding for alkenes and alkynes but good to probably
* Splitting patterns; singlets, doublets, triplets, quartets, multiplets, downfield and upfield signal differentiation; triplet of quartets is an ethyl group
* Presence of a dipole; no diple, no signal
*Symmetry; more symmetrical less signals

Hope this helps.