[toadesque]

So I have the NMR (I think H-NMR??) of my unknown. Looks like this:





So how do I read this to explain how I know that my compound is 1-pentyne?

[toadesque]

Peak Data

      Hz         ppm     Int.

    202.50   2.262     78
    201.69   2.253     99
    200.13   2.235    105
    198.94   2.222    125
    195.75   2.186    180
    194.81   2.176    270
    192.88   2.154    181
    192.19   2.146    375
    188.94   2.110    132
    187.94   2.099    145
    186.00   2.077    208
    185.56   2.072    230
    175.69   1.962    378
    173.19   1.934    443
    170.44   1.904    246
    157.31   1.757     45
    156.81   1.751     42
    151.56   1.693     33
    150.75   1.684     75
    149.38   1.668    139
    148.56   1.659     42
    145.00   1.620     38
    143.31   1.601    127
    142.63   1.593    236
    141.56   1.581    158
    137.00   1.530     75
    136.38   1.523    120
    135.81   1.517    166
    134.75   1.505    211
    129.63   1.448     66
    128.38   1.434    158
    122.19   1.365     43
    121.50   1.357     49
     96.81   1.081    264
     95.88   1.071    443
     95.19   1.063    285
     89.25   0.997   1000
     88.44   0.988    432
     82.63   0.923    161
     81.56   0.911    261
     80.25   0.897    128

[Grundalizer]

Man I hate when I forget stuff I knew well at one time.

The number of peaks represents the number of unique hydrogens attached to adjacent carbons.

Look at that HUGE single peak at 1, that means that there is a carbon with only ONE hydrogen attached to it, which then means that in order to make up the other 3 bonds, there HAS to be a tripple bond.  The reason there has to be a tripple bond and not 3 single carbon-carbon bonds is because the single peak is so massive.  If the single peak were smaller, you would know there would be more hydrogens on adjacent carbons.

So look at 1 ppm, single MASSIVE peak, but also two smaller peaks, meaning another carbon with 2 unique hydrogens.  So our peaks at 1 ppm is the spectrum for the carbon in between the ones labeled A and B.

Now we have a boatload of stuff happening at 1.5 ppm and 2 ppm.

Looking at 1.5 ppm, there is what looks like a multiplet, which I would attriubute to the carbon labbeled "C" because there are 5 adjacent hydrogens.

The peaks going on at around 2ppm look like either a doublet or triplet, a doublet would nicely explain the "D" carbon, as its adjacent to 2 hydrogens.

Frankly, I'm at a bit of a loss for peaks for every single carbon.  On our practice NMR sheets we are given the molecular formula, but not the structure.  So I don't see how its possible to look at the spectrum and say, oh, there are 5 carbons.  We also usually get nicely circled groups of peaks which say, "doublet, triplet, quadruplet, etc

[Grundalizer]

So In short, the number of peaks localized at one section means, if you take one carbon, and count the hydrogens off of adjacent carbons, they add up to the number of peaks.  I can't tell how many peaks are in those spectrum groups though, because sometimes they look like doublets or triplets or multiplets.

I suggest googling, "How to read an H-NMR" or also youtubing how to

http://academics.keene.edu/rblatchly/OrgoCommon/hand/Spectroscopy/nmr/ReadNMR.pdf

http://www.wfu.edu/~ylwong/chem/nmr/h1/

[toadesque]

Thanks for the detailed response.

Actually we weren't given the structure or the molecular formula. We were simply given the NMR spectra and we have to analyze it to figure out what the unknown compound was. The problem is that I did all the NMR stuff in Organic I and I'm at the end of Organic II now so I completely forgot how to do this, and I was never any good at it anyway.

But yeah thanks for helping out!