Search results
Results from the WOW.Com Content Network
A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium CH + 3, methanium CH + 5, acylium ions RCO +, and vinyl C ...
Stabilization is ranked the order, -F < -Cl < -CH 3 < -CH=CH 2. All substituents impart stability except for fluorine which destabilized the vinyl cation by 7 kcal/mole. This phenomenon can be explained by comparing a-fluorine substituent effects on vinyl and ethyl cations. In ethyl cations, fluorine stabilizes the carbocation.
The stability of alkyl-substituted carbocations follows the order 3° > 2° > 1° > methyl. This trend can be inferred by the hydride ion affinity values (231, 246, 273, and 312 kcal/mol for (CH 3 ) 3 C + , (CH 3 ) 2 CH + , CH 3 CH + 2 , and CH + 3 ). [ 9 ]
The chemical basis for Markovnikov's Rule is the formation of the most stable carbocation during the addition process. Adding the hydrogen ion to one carbon atom in the alkene creates a positive charge on the other carbon, forming a carbocation intermediate.
The 2-Norbornyl cation is one of the best characterized carbonium ion. It is the prototype for non-classical ions. As indicated first by low-temperature NMR spectroscopy and confirmed by X-ray crystallography, [1] it has a symmetric structure with an RCH 2 + group bonded to an alkene group, stabilized by a bicyclic structure.
Hammond's postulate is useful for understanding the relationship between the rate of a reaction and the stability of the products. While the rate of a reaction depends just on the activation energy (often represented in organic chemistry as ΔG ‡ “delta G double dagger”), the final ratios of products in chemical equilibrium depends only ...
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
The driving force for this rearrangement step is believed to be the relative stability of the resultant oxonium ion. Although the initial carbocation is already tertiary, the oxygen can stabilize the positive charge much more favorably due to the complete octet configuration at all centers.