2,3-Dimethyl-2-butyl cation

Degenerate 1,2-hydride shifts as in 2,3-dimethyl-2-butyl cation [10] take place with low barriers, ca 3-4 kcal mol". The 1,3-hydride shift in 2,4-dimethyl-2-pentyl cation [11] also takes place through a nonlinear transition state (TS) and with a higher barrier = 8.5 kcal mol" (Brouwer and van... 

The isotopic perturbation method was first developed using H-nmr spectroscopy and deuterium as the perturbing isotope. The isomerization of 3-deuterio-2,3-dimethyl-2-butyl cation (Saunders et al., 1971), 2,3,3-trimethyl-2-butyl cation and cyclopentyl cation (Saunders and Vogel, 1971a) and methyl interchange in 2,3-dimethyl-2-butyl cation [10] (Saunders and Vogel, 1971b) were studied. 

Electrostatic potential map for 2,3-dimethyl-3-hydroxy-2-butyl cation show most positively-charged regions (in blue) and less positively-charged regions (in red). 

Obtain energies for the carbocation intermediates for the case of R = CH3 (2,3-dimethyl-3-hydroxy-2-butyl cation and 3,3-dimethyl-2-hydroxy-2-butyl cation). Is the... 

Methyl vinyl ketone (entry 3) and the tert-butyl cation (entry 4) are also reactive toward complex 3. The naphthalenium complexes resulting from the addition of these electrophiles will add the conjugate base of dimethyl malonate (generated in situ from a combination of dimethyl malonate (DMM) and diisopropylethylamine (DIEA)) to complete the tandem additions. Oxidation of the resulting complexes yields cis-l,4-dihydronaphthalenes. The entire sequence of complexation, tandem addition, and demetalation employed for all entries in Table 4 can be performed using bench-top conditions (i.e., a non-inert atmosphere). 

CF3COOH, PhSH, 20°, 1 h, 100% yield.18 Thiophenol is used to scavenge the liberated r-butyl cations, thus preventing alkylation of methionine or tryptophan. Other scavengers such as anisole, thioanisole, thiocresol, cre-sol, and dimethyl sulfide have also been used.19... 

In view of these results, it is surprising that no rearrangement occurs during the aluminium chloride-catalyzed reaction of terf-butyl chloride with ethylene [97]. The intermediacy of a primary carbocation can, therefore, be ruled out and the selective formation of 18 may be rationalized by assuming the intermediacy of a bridged cation (tert-butyl-bridged ethylene). Alternatively, the attack of the /er/-butyl cation at ethylene may be nucleophilically assisted by the AIC14 ion because of the low stability of the 3,3-dimethyl-l-butyl cation (Scheme 22) [98],... 

When propylene is in the feed, it will react with t-C4Hg to form dimethyl pentyl cations this reaction is very similar to Reaction G shown in Table II. In addition, propylene reacts with sulfuric acid to form sec-propyl sulfates similar to Reaction 1-1. Goldsby (21,22) has described the production of sec-propyl sulfates In some cases, d1-sec-propyl sulfate Is formed. These propyl sulfates are more thermally stable than butyl sulfates. 

The resulting propylene will then react primarily with t-butyl cations and heavier cations forming dimethyl pentyl and still heavier cations. 

Rapid 1,2-fluorine shifts have been shown by Olah and Bollinger (1967) to be responsible for the equivalence of the four methyl groups in 2-fluoro-2,3-dimethyl-3-butyl cation. 

The ions [315] are long-lived compared with other p-aryl-substituted carbonium ions such as 2,3-dimethyl-3-aryl-2-butyl cations [93] and [95] and are therefore suitable for observation of intramolecular donor-acceptor com-plexation between an aromatic donor at C and a carbocation centre. Borodkin et al. (1973) studied the UV-spectra of ions [315 X = CH3, H, Cl, F or CF3] and found charge-transfer bands as a result of the donor-acceptor interaction. There is a linear relationship between the frequency of these... 

Use SpartanView to examine electrostatic potential maps of trifluoroacetic acid, 3-chloropropene, ter -butyl cation, and protonated dimethyl ether. Assuming that the most positive atom is also the most electrophilic, identify the most electrophilic atom in each molecule. (Identity the most electrophilic carbon atom in 3-chloropropene.)... 

Due to the ease of dealkylation of r-alkylbenzenes, such as t-butylbenzene, some interesting applications of this process in both the syndietic and mechanistic areas have resulted. The intermediacy of the r-butyl cation was hinted to account for the observed products. Thus, Knight et al obtained excellent yields of pivalic acid by dealkylating r-butylbenzene and 1,3-dimethyl-S-t-butylbenzene in the presence of carbon monoxide and BFs-HaO as the catalyst (equation 120). They also found that H3PO4, H2SO4 and MeSOsH were ineffective for the dealkylation-carbonylation of t-butylbenzene. 

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