Performing mass spectrometry on analytes with this property can form unstable tropylium ions. For 10 points each:
[10m] Name this property possessed by acidic compounds used as the matrix in MALDI, such as sinapinic acid. Molecules with this property generate diatropic currents in NMR due to proton deshielding.
ANSWER: aromaticity [prompt on cyclic or rings]
[10e] Aromatic intermediates may form when compounds with this functional group undergo a McLafferty rearrangement during fragmentation. These functional groups are characterized by a carbon-oxygen double bond.
ANSWER: carbonyls [accept ketones or aldehydes]
[10h] The McLafferty rearrangement of carbonyls often competes with this type of fragmentation that breaks the neighboring carbon-carbon bond of the carbonyl to form a neutral radical and an acyl cation.
ANSWER: alpha-cleavage
<Munir Siddiqui, Chemistry>