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Double transacetalization of diacylium ions
Author(s) -
Sparrapan Regina,
Mendes Maria Anita,
Eberlin Marcos N.
Publication year - 2000
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(200002)35:2<189::aid-jms929>3.0.co;2-i
Subject(s) - chemistry , ion , ionic bonding , delocalized electron , double bond , acetal , dissociation (chemistry) , reactivity (psychology) , stereochemistry , medicinal chemistry , polymer chemistry , organic chemistry , medicine , alternative medicine , pathology
A novel gas‐phase reaction of diacylium ions of the OCX + CO type (X = N, CH) is reported: double transacetalization with cyclic acetals or ketals. The reaction is exothermic and highly efficient, and forms members of a new class of highly charged‐delocalized ions: cyclic ionic diketals. Pentaquadrupole double‐ and triple‐stage mass spectrometric (MS 2 and MS 3 ) experiments reveal the high double transacetalization reactivity of OCN + CO and OCCH + CO, whereas the synthesis of differently substituted cyclic ionic diketals is performed in MS 3 experiments via sequential mono‐ and double transacetalization of OCN + CO and OCCH + CO with different acetals. With cyclic acetals, the acylium‐thioacylium ion OCN + CS reacts promptly and selectively by mono‐transacetalization at its acylium site, but the free thiacylium site of its cyclic ionic ketal is nearly unreactive by double transacetalization. Therefore, only the acylium site of OCN + CS can be efficiently protected by transacetalization. Low‐energy MS 3 collision‐induced dissociation of the cyclic ionic diketals of OCN + CO and OCCH + CO sequentially frees each of the protected acylium site to form the mono‐derivatized ion, and then the fully deprotected diacylium ion. Copyright © 2000 John Wiley & Sons, Ltd.