Methylenimmonium ion and the role of resonance and inductive stabilization in carbonium ions

1973 ◽  
Vol 95 (2) ◽  
pp. 458-463 ◽  
Author(s):  
Peter A. Kollman ◽  
William F. Trager ◽  
Steve. Rothenberg ◽  
James E. Williams
Keyword(s):  
Carbonium Ions

A MNDO study of planar thioacyl-substituted carbocations

1992 ◽  
Vol 70 (1) ◽  
pp. 111-115 ◽  
Author(s):  
Jack Leon Ginsburg ◽  
Richard Francis Langler ◽  
Raj Kumar Raheja ◽  
Laura Precedo
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Mndo Method ◽  
Saturation Effect ◽  
Semiempirical Calculations ◽  
Isodesmic Reactions ◽  
Electron Population ◽  
Resonance Saturation ◽  
Carbonium Ions

Relative gas phase stabilities of pairs of planar regioisomeric thioacyl-substituted carbocations have been calculated using the MNDO method. These systems are stabilized by good π donors. The role of S π-electron population as a gauge of substituent effects is examined. Similar results were obtained using isodesmic reactions to gauge substituent effects. Results of this and earlier studies are consistent with the resonance saturation effect. Keywords: semiempirical calculations, carbonium ions.

scholarly journals The Role of Carbonium Ions in Color Reception

1965 ◽  
Vol 48 (5) ◽  
pp. 753-760 ◽  
Author(s):  
Paul E. Blatz
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Benzene Solution ◽  
Fundamental Property ◽  
Conjugated Systems ◽  
Carbonium Ion ◽  
Carbonium Ions ◽  
Ion Treatment ◽  
Good Agreement

It is a fundamental property of conjugated systems to accept a proton or Lewis acid and form a stable carbonium ion. Polyenes that are protonated or add Lewis acids in this manner undergo substantial red shifts. For example, vitamin A1 acetate absorbs at 350 mµ in neutral and at 650 mµ in acidic benzene solution. The fundamental basis for absorption of polyene systems was described in detail in quantum mechanical terms. Applying the carbonium ion treatment to the visual chromophores retinal1 and retinal2 gives a very satisfactory explanation why these polyenes can be made to absorb in the visual region. Furthermore, by proper placement of the Lewis acid several absorption maxima can be gained from the carbonium ions which result. This treatment can be applied to explain experimental results. Individual cones from the frog are now known to absorb at 455, 537, and 625 mµ. If the value for the green cone (537 mµ) is used to calculate the Vo value in Kuhn's equation, the other two wave lengths may then be calculated. The calculated values are 460 and 600 mµ; this is in good agreement with the results from experiment.

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