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Stereochemistries of electron impact induced hydrogen abstraction reactions proceeding through 6‐membered transition states
Author(s) -
Eadon George
Publication year - 1977
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210121104
Subject(s) - chemistry , conformational isomerism , fragmentation (computing) , xanthate , hydrogen atom abstraction , electron ionization , stereochemistry , ring (chemistry) , transition state , acetaldehyde , cope rearrangement , destabilisation , medicinal chemistry , ethanol , hydrogen , molecule , organic chemistry , catalysis , ion , social psychology , psychology , computer science , ionization , operating system
The stereochemistries of nine electron‐impact induced eliminations proceeding from derivatives of the cis ‐4‐ t ‐butyl system have been determined. The predominant cis elimination observed in every case is consistent with the substantial integrity of the cyclohexyl ring prior to fragmentation, and with a cyclic transition state for hydrogen abstraction. The stereochemistries of electron impact induced eliminations from 11 derivatives of the trans ‐4‐ t ‐butylcyclohexyl system exhibit a dichotomy. The predominatn trans stereochemistry observed in six electron impact induced eliminations, and the nonstereospecific electron impact induced dehydration of trans ‐4′‐ t ‐butylcyclohexyl‐ethanol are consistent with nonconcerted elimination from a chair‐like cyclohexyl ring. Conversely, the McLafferty rearrangement of trans ‐4′‐ t ‐butyl‐cyclohexyl‐2‐propanone proceeds nonstereospecifically. trans ‐4‐ t ‐Butylcyclohexyl acetaldehyde, 2‐methyl‐3‐( trans ‐4′‐ t ‐butylcyclohexyl)‐1‐propane and trans ‐4‐ t ‐butylcyclohexyl‐ S ‐methyl xanthate exhibit predominant cis McLafferty rearrangement stereochemistry. This result may be due to fragmentation through boat‐like conformers in these compounds.