There is a systematic way to analyze MS data; try this procedure to organize the data and your thoughts.
Capital letters are only for EMPHASIS.
Step 1Perform a visual inspection of the mass spectrum.
The PRESUMED molecular ion, m/z 152, shows the presence or absence (WHICH ??) of Br, Cl and S atoms (WHY
)
The given molecular weight (MW 152 Da) is EVEN, and therefore the molecule contains an ODD or EVEN (WHICH ??) number of N atoms (odd = 1,3,5,7 OR even = 0, 2, 4, 6...etc) Google "the NITROGEN RULE in mass spectrometry". VERY, VERY important !
Check for absence/presence of "characteristic" m/z values; a "characteristic" ion is one that suggests the presence of a certain structural feature.
For instance, a (usually strong) m/z 77 is a characteristic ion (C6H5)+. ; indicates a phenyl ring. Is this in your spectrum ? Is it intense ?
Step 2Set up a table with 4 columns.
Column 1: list m/z values from highest (m/z 152) to lowest. GENERALLY, as a first pass, ignore low intensity (< 5%) m/z values.
Column 2: mass difference to next highest m/z value OR next-but-one group of ions.
Column 3: possible elemental compositions for the mass difference (e.g. 28 could be C2H4 or CO or N2).
Column 4: possible structural feature that corresponds to the elemental composition.
Step 3On a piece of paper, draw the possible structural elements that you have derived from your analysis. Try to connect them such that all of the major m/z values can be formed from the structure; be aware that sometimes, two (or more) different structures (isomers) can be constructed that will generate very similar mass spectra.
Step 4Check that the elemental composition (C, H, N, O, etc) of the assembled molecule gives MW 152.
Further, use an accurate mass calculator (available on-line) to see which of the possible C, H, N, O, etc. combinations is closest to MW 152.0125.
YOU CAN DO THIS !!!!