Negative inductive effect

The observed acidities in the gas phase are interpreted in terms of the negative induction effect of the halo substituents however, the microscopic picture of the solvent effects in addition to such induction effects of the solute have not been clarified. 

Wanzlick showed that the stability of carbenes is increased by a special substitution pattern of the disubstituted carbon atom [12-16]. Substituents in the vicinal position, which provide n-donor/a-acceptor character (Scheme 2, X), stabilize the lone pair by filling the p-orbital of the carbene carbon. The negative inductive effect reduces the electrophilicity and therefore also the reactivity of the singlet carbene. 

In the N-Bz derivatives of Gly and Gly-Gly, the planar [R3Sn(IV)] moieties are bridged by -COO groups. Because of the negative inductive effect of the Ph group, which reduces the donor ability of oxygen atoms, coordination of the amide -C = O in the latter compounds could be ruled out. 

The acidity of polynitrophenols is a direct consequence of the negative inductive effect of the nitro groups. This has implications for other polynitroarylenes as practical explosives. 

If there is a suitable electron-withdrawing substituent, hydrate formation may be favoured. Such a situation exists with trichloroacetaldehyde (chloral). Three chlorine substituents set up a powerful negative inductive effect, thereby increasing the 8- - charge on the carbonyl carbon and favouring nucleophilic attack. Hydrate formation is favoured, to the extent that chloral hydrate is a stable solid, with a history of use as a sedative. 

The cyanide groups (L" = C6H5CH2NC, L = CN) in I deactivate the aromatic ring(s) by a negative inductive effect. 

Unsaturated fluorinated compounds are fundamentally different from those of hydrocarbon chemistry. Whereas conventional alkenes are electron rich at the double bond, fluoroal-kenes suffer from a deficiency of electrons due to the negative inductive effect. Therefore, fluoroalkenes react smoothly in a very typical way with oxygen, sulfur, nitrogen and carbon nucleophiles.31 Usually, the reaction path of the addition or addition-elimination reaction goes through an intermediate carbanion. The reaction conditions decide whether the product is saturated or unsaturated and if vinylic or allylic substitution is required. Highly branched fluoroalkenes, obtained from the fluoride-initiated ionic oligomerization of tetrafluoroethene or hexafluoropropene, are different and more complex in their reactions and reactivities. 

It should be noted that, because of the strong negative induction effect of the... 

It was found that asymmetric N02 vibrations are readily subject to a change in frequency when R in the molecule R—ON02 is changed. A positive and negative induction effect of R respectively lowers and raises the frequency of vas (N02). This fact makes it possible to distinguish between primary, secondary and tertiary alkyl nitrates. 

Bromination of allylic positions cannot be achieved specifically by using elementary bromine, unless electrophilic addition to the rc-bond (Eq. 18) is unfavorable because the substituents have a high negative inductive effect. Efficiency of electrophilic addition of Br2 may also be diminished by steric effects. In addition to these secondary thermal reactions, the specificity of photochemical brominations of allylic positions using Br2 will also suffer from the competing (radical) addition of Br to the double bond (Eq. 19) [31]. 

Methylation of normacrorine with dimethyl sulfate gave a 2 1 mixture of 116 and 117. On the basis of the negative inductive effect of the quinolyl substituent on the imidazole ring, one would expect on methylation in nonbasic medium isomacrorine to be the major product. The fact that, contrary to this expectation the main product is macrorine, can be explained by assuming a shielding of the most reactive imidazole nitrogen (N") by the quinolyl substitutent. 

Scheme 39 further shows that the introduction of a phenyl group into an allylic position of isobutene causes a rate reduction of 20. The reactivity of the benzyl-substituted double bond is obviously diminished by the negative inductive effect of phenyl, and phenonium stabilization of the intermediate carbocation does not take place [148]. 

In nonconjugated dienes, the negative inductive effect of the extra double bond reduces the nucleophilicity of the other 7r-system (Fig. 8) [148], There is no evidence for anchimeric assistance by the additional double bond, as observed in certain solvolytic reactions [10,151-153]. When the two double bonds are separated by four methylene groups, they behave as isolated double bonds, and their reactivity equals that of an analogous monoene. 

Silylated ketene acetals are more reactive than silyl enol ethers (Scheme 46), and the higher reactivity of cyclopentenes compared to cyclohexenes, which has already been reported for the hydrocarbon series (Scheme 41), is also observed for this class of compounds. The negative inductive effect of oxygen, which operates at the position of electrophilic attack, makes the bisenol ether (Scheme 46, right column, bottom) 20 times less reactive than the structurally analogous monoenol ether. 

The same authors also showed that the 2-cyano-2-methyl- and 2-cyano-2-phenylsparteine derivatives crystallise in a cisoidal form, as monosalts, probably due to the reduction of the basic nature of the N-1 atom by the negative inductive effect of the cyano substituent. The protonation of the N-16 atom leads to its inversion and establishment of an intramolecular hydrogen bond, as in the case of the 2-methyl- and 2-phenylsparteine derivatives [197]. 

The negative inductive effect of the NO2 group operates significantly as far as the third carbon atom in the chain. This can be seen from S ppm data for 1 nitropropane to 1-nitropentane ... 

The chlorine exerts a negative inductive effect, and so pulls the electrons within the a bond towards itself. This in turn makes the carbon atom slightly positive. 

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