To deduce the structure of a compound using the data from an electron impact mass spectrum, we need to analyze the M/z values (mass-to-charge ratio) and the relative intensities of the peaks.
Here's how you can approach it:
1. Identify the base peak: The base peak is the peak with the highest relative intensity. In this case, the M/z 64 peak has a relative intensity of 100, so it is the base peak.
2. Look for fragment peaks: Fragment peaks are created when the compound undergoes fragmentation during the electron impact. Fragments are formed by breaking bonds within the molecule. Start by looking for peaks that are lower than the base peak but higher than the noise level. Peaks that are one or two units higher in M/z than the base peak are often due to the loss of a methyl (CH3) or methylene (CH2) group.
In this case, we can observe peaks with M/z values of 66 and 49. The M/z 66 peak can be explained by the presence of a methyl group (CH3+) as it is only two mass units higher than the base peak (64). The M/z 49 peak indicates the loss of a methyl group (CH3) from the original molecule.
3. Analyze the remaining peaks: After identifying the fragment peaks, we can focus on the remaining peaks for clues about the compound's functional groups. In this case, we have M/z peaks of 29, 28, and 27.
The M/z 29 peak indicates a molecular ion peak (M+) which suggests the presence of a fragment with a mass of 29. This mass corresponds to the methyl cation (CH3+). Therefore, the presence of a methyl group can be confirmed.
The M/z 28 peak has a relatively high intensity and may correspond to the loss of one hydrogen atom (H) from the original molecule. This suggests the presence of a hydrogen atom attached to another fragment.
The M/z 27 peak can be explained by the loss of a hydrogen atom (H) from the M/z 28 fragment. This suggests the presence of a hydrogen attached to another fragment, which further suggests the presence of a functional group containing a hydrogen atom.
Based on the identified peaks and their relative intensities, we can deduce the possible structure:
- Methyl group (CH3)
- Fragment with molecular weight 28, possibly containing a hydrogen atom
- Fragment with molecular weight 27, possibly containing a functional group with a hydrogen atom attached
Taking into account all the available information, a possible structure for the compound could be:
CH3 - (Fragment with M/z 28) - (Functional group with M/z 27)