Recognition of cyclic, acyclic, exocyclic, and spiro acetals via structurally diagnostic ion/molecule reactions with the (CH3)2N-C(+)=O acylium ion.
Reactions of the model acylium ion (CH3)2N-C(+)=O with acyclic, exocyclic, and spiro acetals of the general formula R(1)O-CR(3)R(4)-OR(2) were systematically evaluated via pentaquadrupole mass spectrometry. Characteristic intrinsic reactivities were observed for each of these classes of acetals. The two most common reactions observed were hydride and alkoxy anion [R(1)O(-) and R(2)O(-)] abstraction. Other specific reactions were also observed: (a) a secondary polar [4(+) + 2] cycloaddition for acetals bearing alpha,beta-unsaturated R(3) or R(4) substituents and (b) OH(-) abstraction for exocyclic and spiro acetals. These structurally diagnostic reactions, in conjunction with others observed previously for cyclic acetals, are shown to reveal the class of the acetal molecule and its ring type and substituents and to permit their recognition and distinction from other classes of isomeric molecules.
Benassi
Mario
M
ThoMSon Mass Spectrometry Laboratory, State University of Campinas, Campinas-SP, Brazil 13083-970.
Moraes
Luiz Alberto B
LA
Cabrini
Liliane G
LG
Dias
Luiz Carlos
LC
Aguilar
Andrea M
AM
Romeiro
Gilberto A
GA
Eberlin
Livia S
LS
Eberlin
Marcos N
MN