Identify the base peak and the molecular peak of the following mass spectrum. What is the molar mass of the substance?
$\frac{m}{z}=57\; \Rightarrow $ Base peak $\frac{m}{z}=128\; \Rightarrow $ Molecular peak $ M=128 \frac{g}{mol}$
It is assumed that this is an alkane. Find an argument in favor of this hypothesis!
With $C_nH_{2n+2}=128\Rightarrow n=9$ This is probably an alkane.
By examining the spectrum we see that there is missing a fragment that should be there for a linear alkane. Which one?
The fragment $\frac{m}{z}=85$ of $CH_3(CH_2)_4CH_2^+$
It would therefore not be a linear alkane, nor a branched alkane with a straight chain of 6 carbon atoms. Give possible condensed structural formulas!
The base peak $\frac{m}{z}=57$ has 4 carbon atoms $C$ : $C_4H_9^+$ Since the break is preferably near a branch, which of the above possibilities can you exclude?
We can exclude a) b) and d)
What can you say?
This is likely to be c) or e)