The following compounds undergo McLafferty rearrangement in the mass spectrometer. Predict the masses of the resulting charged fragments.

(a) pentanal (b) 3-methylhexan-2-one (c) 4-methylhexan-2-one

(a. The mechanism of McLafferty rearrangement of pentanal can be shown by the transfer of hydrogen from the gamma position $\text{(}\gamma \text{- H)}$to the carbonyl functional group via a cyclic transition state which is followed by the homolytic cleavage of $\alpha -Cand\beta -C$ . This results in the formation of a neutral alkene and an enol radical cation. The peak of enol radical cation is observed at$\frac{\text{m}}{\text{z}} \text{=} \text{44}$ .

(b). The mechanism of McLafferty rearrangement of $\text{3}-\text{methylhexan}-\text{2}-\text{one}$can be shown by the transfer of hydrogen from the gamma position $\text{(}\gamma \text{- H)}$to the carbonyl functional group via a cyclic transition state which is followed by the homolytic cleavage of role="math" localid="1664864445832" $\alpha -Cand\beta -C$ .This results in the formation of a neutral alkene and an enol radical cation. The peak of enol radical cation is observed at $\frac{\text{m}}{\text{z}} \text{=} 72$.

(c). The mechanism of McLafferty rearrangement of $4-\text{methylhexan}-\text{2}-\text{one}$ can be shown by the transfer of hydrogen from the gamma position$\text{(}\gamma \text{- H)}$ to the carbonyl functional group via a cyclic transition state which is followed by the homolytic cleavage of role="math" localid="1664864328002" $\alpha -Cand\beta -C$.This results in the formation of a neutral alkene and an enol radical cation. The peak of enol radical cation is observed at$\frac{\text{m}}{\text{z}} \text{=} 58$ .