Inductive destabilization groups

At all levels of theory, the N-acetyl group of N-acetyl-N-arylnitrenium ions is rotated out of the plane of the aromatic ring, although to different extents." The N-acetyl group destabilizes the ion by ca. 20 kcal/mol relative to an N-methyl substituent in comparison with the neutral amide and amine precursors. This destabilization was attributed by Ford and Herman to loss of resonance in the amide precursor on going to the nitrenium ion, not to inductive destabilization of the ion by the acyl group. 

The greatly diminished stabilization of the silylenium compared to the carbenium structure by it substituents is connected with the known low effectiveness of 2p-3p (it) conjugation. Calculations were made on the =Si+ cation substituted with a phosphorus group with the hope of showing a superior 3p-3p (tt) conjugation of P—Si+ moiety (26,28). A smaller inductive destabilization by phosphorus than by electronegative substituents of the second period (N, O) was also expected. However, all... 

Bulky groups such as methoxymethyl (which is also inductively destabilizing to a cation) resulted in mixtures of the two regioisomeric products from cyclization at the substituted and unsubstituted position. When the a substituent R is an aryl group such as p-tolyl, despite its cation-stabilizing properties, the regio- and stereocontrol of the reaction is lost due to its bulk thus three isomers 67,68, and 69, of the tricyclic product were isolated. While the first step of the cyclization process, the H abstraction, has been... 

Trifluoromcthyl hypofluorite exhibits a similar stereochemical behaviour to acetyl hypofluorite in its reactions with stilbene123, cytosine, and uracil124. The tendency towards ath addition has been attributed to the inductive destabilization of a vicinal carbocation which is not mitigated by cyclic fluoronium ion formation. This short-lived carbocation induces ion pairing and neighboring group participation123. 

Attack at the meta position leads to a more stable intermediate than attack at either the ortho or the para position and so meta substitution predominates Even the inter mediate corresponding to meta attack however is very unstable and is formed with dif ficulty The trifluoromethyl group is only one bond farther removed from the positive charge here than it is m the ortho and para intermediates and so still exerts a significant although somewhat diminished destabilizing inductive effect... 

The basic piSTa values, which have to be considered as equilibrium values, including those of anhydrous and hydrated species, reveal a destabilizing inductive effect of the 6- and 7-methyl group towards 3,4-hydrate formation, as do also the 2-methylamino and 2-dimethylamino groups for additional steric reasons. If the cation of 2-aminopteridine did not add water its value would be about 1.6, arrived at by substracting from the piSTa 2.6 of the essentially anhydrous 2-amino-4,7-dimethylpteridine cation 0.3 for the 7- and 0.7 for the 4-methyl group. The difference between the observed value of 4.29 and the... 

Electronegative, nonconjugating groups (which interact with an incipient carbocation only by an inductive or field effect) discourage attack at C. This is due to destabilization of transition state (49) by the juxtaposition of positive charge. 

The temperature at which elimination of thiophenol occurs depends on the substituents on the sulfur-bearing carbon. Thioke-tals react rapidly at 25°. In some cases the elimination of thiophenol from the less reactive thioacetals may also be performed at 25°. However, in the present case the combined inductive effects of the vinyl and methoxy groups evidently destabilize the incipient car-bonium ion and necessitate a higher temperature for the reaction. 

In the structure on the left, the charge is somewhat stabilized by the inductive effects of the neighboring chlorine atoms. In contrast, the structure on the right is destabilized by the presence of methyl groups. Therefore, the structure on the left is more stable. 

Are there any inductive effects (electronegative atoms or alkyl groups) that stabilize or destabilize any of the conjugate bases ... 

Induction The negative charge on the left is destabilized by an electron-donating alkyl group. The one on the right is not destabilized in this way. 

The reactions and compound presented in this chapter support the notion that the formation of o-QMs from the parent phenols is a quite complex process. In the case of the oxidation by Ag20 but also likely in other oxidations, a zwitterionic intermediate is involved that can be stabilized intermolecularly, for example, by electrostatic interaction with other suitable zwitterions, or intramolecularly by neighboring groups or inductive/mesomeric effects. By stabilizing the zwitterionic intermediate and destabilizing the o-QM, the energetic gap between these two intermediates is lowered and... 

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