Understanding Benzoic Acid Mass Spectrum Fragmentation
Benzoic acid has the chemical formula $\text{C}_7\text{H}_6\text{O}_2$. Its molecular weight is approximately 122 amu.
In mass spectrometry, molecules are ionized and fragment. The base peak represents the most abundant fragment ion, indicating high stability.
Identifying the Base Peak Fragment
A common fragmentation pathway for benzoic acid involves the loss of the entire carboxyl group ($\cdot\text{COOH}$) from the molecular ion ($M^+$).
- Molecular ion mass: approx. 122 amu.
- Mass of $\cdot\text{COOH}$: approx. 45 amu.
- Fragment mass ($M - \cdot\text{COOH}$): $122 - 45 = 77$ amu.
This fragmentation yields the phenyl cation ($\text{C}_6\text{H}_5^+$), which is a stable aromatic ion.
Conclusion on Base Peak m/z
Due to the stability of the phenyl cation ($\text{C}_6\text{H}_5^+$), the fragment with $m/z = 77$ is typically the most abundant ion in the mass spectrum of benzoic acid, making it the base peak (100% relative abundance).
Therefore, the $m/z$ value for the base peak is 77.
Important Questions from Organic Structure Stability
The total number of tautomers for the following molecule (including the structure provided below) is ____________
The reactants P and Q in the following reaction are
- The Diels-Alder adduct from the reaction between cyclopentadiene and benzyne is
The major product from the following reaction is
The order of resonance energy for the following molecules is
