[vikingsfan345]

I really need some help determining the identity of an unknown compound from these spectra.  I need to get it done by tomorrow at noon and I'm completely stuck.  I understand the basics of interpreting spectra, but I'm having a hard time getting much from the mass spec.  I pretty much understand the C and H nmrs, but I'm not sure how to interpret the splitting for the proton at approximately 1.75 ppm.  The thing that really gets me is that the molecular weight is listed as 196.0641, but there only appear to be 5 distinct carbons and no large atoms such as bromine.  This must mean that there are multiple carbons for most of the nmr peaks.  Anyways, I could really use some major hints, or the answer if you explain your reasoning.  Any help is greatly appreciated.  By the way, as stated, the molecular weight was given as 196.0641 amu.

[vikingsfan345]

What I have determined so far is this:

There is a carbonyl present due to the ir peak at 1736 cm-1.  Also, a C-O single bond is likely present due to the peak at 1203 cm-1.  There are four unique protons (a singlet, two triplets, and one that I'm not sure of).  The integration heights are as follows: 1.1 cm, 0.7 cm, 0.7 cm, 1.4 cm, respectively.  Thus, the ratio of protons is: 3:2:2:4.  From the 13C NMR, there are 5 unique carbon atoms (I'm assuming the peak at ~78 ppm is the solvent), a quaternary, methyl, and three methylene, respectively.  The quaternary carbon is likely attached to an oxygen as part of a carbonyl due to its high shift.  I'm having a hard time determining anything from the mass spec.

[MOTOBALL]

I do not seen any mass spectrum----in lieu of me interpreting that, please refer to my posts of  Nov. 23, 24 and Oct. 18, 21, 22 of last year (and even further back if you care to).

This topic of MS unknowns comes up regularly, and there IS a systematic way of approaching it.

[Babcock_Hall]

I count six carbons.  What is your explanation for the presence of peaks at both 194 and 196 m/z in the mass spectrum?

[kriggy]

I count six carbons.  What is your explanation for the presence of peaks at both 194 and 196 m/z in the mass spectrum?

This   
From the intensity of the peak with highest m/z and m+1/z you can calculate amount of carbons in molecule. Every type of molecule - ie . aliphatic/aromatic has some characteristic peaks in EI-MS. Maybe look into your notes and check if some of them are present

[Rihards]

I suppose the unknown compound is 5-bromo-pentanoic acid methyl ester.
Mass spcetra gives very usefull information, like:
1) m/z = 194 and m/z = 196 shows that molecule in molecular ion contains 1x bromine atom;
2) 194 - 163 = 31 (loss of methoxy radical) which refers to cation with m/z = 163 (see in add fig.);
3) 194 - 135 = 59 (loss of carboxy methyl radical) which refers to cation with m/z = 135
4) Other mass refers to the cations without bromine (in add fig.)
IR and 1H NMR spectra just approves some significant elements of the unknown molecule, for example, C=O group, R1-CH2-CH2-CH2-CH2-R2 pattern, and so on.

I hope I'm right!
Have a nice day!

[Babcock_Hall]

Rihards, The general philosophy here is to try to get the OP to work out the solution himself or herself, and we provide the hints and corrections.