question about IR, HNMR and CNMR

[ddsshin]

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hi, I was wondering how should we study for this section. Do we have know how to identify the whole compound using both IR and HNMR (ex: identify structure of isomer C4H8O2) ????
Do you guys ever see those spectrum graph in the test????

 

[peyman2002]

close but I wouldnt think they would ask u to indentify hard ones like what u mentioned, make sure u know IR numbers for C=O and stuff

 

[klutzy1987]

Know the major IR numbers (ketone, alcohol, amine, aldehyde) and NMR numbers (aromatics, carboxy,methyl). Im not sure if I am missing any but just know the major ones.

 

[SnowDog]

You should know the major functional groups that show up on IR.
For CMNR know how to count how many different C's there are.
For HNMR know which H's correspond to splitting patterns on the spectra.

 

[Seenary]

yes know how to do this, i got 2 CNMR on the same test and screwed up both

 

[klutzy1987]

You should know the major functional groups that show up on IR.
For CMNR know how to count how many different C's there are.
For HNMR know which H's correspond to splitting patterns on the spectra.

This too especially the splitting patterns and symmetry and identical Hydrogens.

 

[Broncos85]

You should know the major functional groups that show up on IR. Know the difference between the OH group at 3300 and an NH (or NH2) group at 3300. Know that a carbonyl group shows up at 1720, a C=C at 1650 and a C triple at 2220 but if theres a terminal H on the triple bond theres a spike at 3300

For CMNR: know how to count different C's and pay attention to symmetry because if the carbons are symmetrical then they are the same .

For HNMR: Be able to recognize that how H's are different and beware of symmetry. Also know how to recognize a compound based on it's deshielded H's via the HNMR graph, which H's would be most downfield (ones next to electronegative atom), and how H's split each other. For example if there was a CH2 group connected to an O and a CH3 group. The CH2 group is split by the CH3 group (wont be by the oO) and will show three spikes known as a quartet and would be more downfield than the CH3 group that would be a triplet (3 spikes).