Predict the values of m/z and the most abudent fragments you would observe in the mass spectrum of di-n-propyl ether?
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To predict the values of m/z (mass-to-charge ratio) and the most abundant fragments in the mass spectrum of di-n-propyl ether, we need to consider the molecular structure and possible fragmentation patterns.
Di-n-propyl ether, with the chemical formula C6H14O, consists of a hydrocarbon chain with two propyl groups (CH3CH2CH2) attached to an oxygen atom (O).
In the mass spectrum, di-n-propyl ether could undergo several common fragmentation pathways, such as alpha-cleavage, beta-cleavage, and McLafferty rearrangement. Let's explore the possible fragments and their m/z values:
1. Molecular Ion (M+): The molecular ion represents the intact di-n-propyl ether molecule. Its m/z value is equal to the molecular weight of the compound. In this case, it would be the sum of the atomic masses of carbon (C), hydrogen (H), and oxygen (O):
Molecular Ion (M+): C6H14O = 6(12.011) + 14(1.008) + 16(15.999) = 102.182
2. Alpha-Cleavage: Alpha-cleavage occurs by breaking the bond adjacent to the oxygen atom. This fragmentation produces a propyl cation (CH3CH2CH2+) and an alkyl radical (CH3CH2CH2-O•). The m/z value of the propyl cation would be:
Propyl Cation (CH3CH2CH2+): 3(12.011) + 7(1.008) = 59.112
3. Beta-Cleavage: Beta-cleavage occurs by breaking the bond between the two carbon atoms in the propyl group. This fragmentation results in an alkyl cation (CH3CH2CH2•+) and an alkyl radical (CH3CH2-OCH2CH2•). The m/z value of the alkyl cation would be:
Alkyl Cation (CH3CH2CH2•+): 3(12.011) + 8(1.008) = 43.097
4. McLafferty Rearrangement: The McLafferty rearrangement involves the loss of a neutral fragment from the parent molecule. In di-n-propyl ether, this can occur by cleaving the carbon-oxygen bond adjacent to one of the propyl groups, resulting in a propyl cation (CH3CH2CH2+) and an acyloxy radical (CH3-O•CH2CH2CH2-). The m/z value of the propyl cation would be the same as mentioned in Point 2.
Based on these fragmentation pathways, the predicted values of m/z and the most abundant fragments observed in the mass spectrum of di-n-propyl ether are as follows:
Molecular Ion (M+): m/z 102.182
Propyl Cation (alpha-cleavage): m/z 59.112
Alkyl Cation (beta-cleavage): m/z 43.097
These values represent the peaks corresponding to the most abundant fragments in the mass spectrum of di-n-propyl ether.