2-iodopentane was passed through a mass spectrometer. The
most abundant fragment ion gave a peak with m/z = 183.
Draw the displayed formula of this fragment ion. Include its charge.
Show WORKING OUT for determining the abundent fragment ion.
To determine the most abundant fragment ion of 2-iodopentane (C5H11I), we need to consider the possible fragmentation patterns and the resulting ions.
1. Start by examining the molecular formula of 2-iodopentane: C5H11I.
2. Look for possible fragmentation sites. In this case, the iodine (I) atom is a common source of fragmentation.
3. The most common fragmentation that occurs in these cases is the loss of a neutral iodine atom, resulting in a positively charged fragment ion.
C5H11I → C5H11+ + I-
4. Calculate the mass-to-charge ratio (m/z) of the fragment ion using the formula:
m/z = molar mass of fragment ion / charge
Given that the m/z of the fragment ion is 183, we can set up the equation:
183 = molar mass of the fragment ion / 1 (assuming a single positive charge)
Rearranging the equation, we find that the molar mass of the fragment ion is 183 Da.
5. Using the molecular formula of the fragment ion (C5H11+), we can calculate its molar mass:
C5H11+: (12.01 x 5) + (1.01 x 11) = 69.15 Da
6. Since the calculated molar mass of the fragment ion (69.15 Da) is significantly less than the measured m/z (183), we can determine that the fragment ion in question is a molecular ion containing additional atoms beyond C5H11+.
7. To determine the composition of the fragment ion, we need to calculate the difference in mass between the measured m/z and the known mass of C5H11+ (69.15 Da).
183 - 69.15 = 113.85 Da
8. The difference (113.85 Da) represents the additional mass within the fragment ion when compared to C5H11+. To identify this additional mass, we can calculate the molecular formula for this extra mass difference.
9. Due to the complexity of this calculation, it is best to use a molecular formula calculator. By providing 113.85 Da as the extra mass, the calculator will suggest possible molecular formulas.
Based on calculations, the molecular formula with a mass of 113.85 Da is C4H8O2. Therefore, the displayed formula of the fragment ion is C5H11O2 with a single positive charge.