Ipso-nitration of p-t-butyltoluene. A 1,2 adduct

Fischer, Alfred; Röderer, Rolf

doi:10.1039/c3975000798b

Cited by 10 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 It is surprising that some de-tert-butylation was not observed since 20% of this occurred with p-ditert-b~t y l b e n z e n e .~~ Nitrodechlorination has rarely been observed. Some apparent nitrodebrominations may be nitrosode-bromination^.^^ p-Bromoanisole, nitrated in acetic anhydride containing urea, gave 31% of p -nitroanisole.…”

Section: Consequences Of Ipso Attackmentioning

confidence: 99%

Ipso attack in aromatic nitration

Moodie¹,

Schofield²

1976

Acc. Chem. Res.

View full text Add to dashboard Cite

Aromatic Nitration 287ate), the necessary internal return results in insignificant oxygen ~c r a m b l i n g .~~ If ion pairs formed under solvolytic conditions undergo rearrangement, attack by an added nucleophile, although rate limiting, must always suppress rearrangement20~38kv3Q since no example of skeletal rearrangement accompanying second-order substitution has ever been reported, even for the potentially favorable neopentyl case.75 These ion pairs must be "more intimate than intiand must thus behave like polarized RX molecules. This is what we believe they are, but we see no reason to call them ion pairs, for in such terms a methyl iodide molecule could be regarded as an ion pair by virtue of the C-I bond polarity.43 This would be fine in the present context since mechanistic distinction would be lost, but chemical problems cannot be solved by such semantic extensions, although we agree with the view that genuine ion pairs may possess a degree of covalent character. In fact, the postulation of ion-pair intermediates (and their formation with solvent assistance) in simple primary and secondary substrate solvolysis in reasonably nucleophilic solvents may be incorrect, and sN2 solvent attack may be the favored mode. We know of no evidence that demands intermediates in such simple solvolyses, and specifically intermediates formed without solvent or neighboring group assistance. If so, (74) A. F. Diaz, I. Lazdins, and S. Winstein, J. Am. Chern. Soc., 90, 1904 (1968). If such scrambling were detected it would still be difficult to prove that it did not occur in a mechanistic blind alley (see also ref 5). (75) Reference 1, p 742. See also G. M. Fraser and H. M. R. Hoffmann, Chem Cornrnun, 561 (1967). (76) Reference 7, p 366.there is no reason why they should intervene in nonsolvolytic substitutions with stronger nucleophiles.In summary, the "extra-intimate ion pair" is in our opinion a polarized RX molecule. The polarization arises from approach of N-, and the energy buildup needed to cross the sN2 potential barrier arises largely from solvent re~rganization~~ attendant on the merging of the original Nand RX solvation shells. We deliberately choose these words to mimic Bordwell's description of an ion-sandwich intermediate,26 noting that Bordwell himself has not been definite in postulating actual intermediacy. His results could equally well be rationalized in terms of a loose sN2 transition state (4) for his tertiary substrate and a tighter transition state (3) for the model primary system.In conclusion, the verdict which must be passed on Sneen's proposed universal unification of s N 1 and SN2 mechanisms is one which is unique to the Scottish legal system, and so I turn to the words of my forbears in stating "not proven". A more positive conclusion is not presently available, but we note that strides in this direction are being made through heavy atom isotope effect studies.45 I warmly thank Professors P. B. D. de la Mare, J. M. Harris, P. v. R. Schleyer, J. Seyden-Penne, R. A . Sneen, and J. Warkentin for ex...

show abstract

Section: Consequences Of Ipso Attackmentioning

confidence: 99%

Ipso attack in aromatic nitration

Moodie¹,

Schofield²

1976

Acc. Chem. Res.

View full text Add to dashboard Cite

show abstract

“…This technique has been developed and validated in multiple previous works [24][25][26][27][28][29]. It has been shown previously that a coupling of MD and LB is an effective and accurate way to model the colloidal [24][25][26][27] and polymer dynamics [28,29], in the systems with an interplay of hydrodynamics and molecular-level interactions. In particular, this method quantitatively reproduces the translational and rotational dynamics of spherical particles in a liquid [24,25].…”

Section: Methodsmentioning

confidence: 99%

“…The LJ bead diameter = 1 sets the unit length in simulation. The spherical solute particles are modelled by raspberrylike structures, comprising a central sphere of radius R and surface LJ beads [24][25][26][27]. All particles are coupled dissipatively to the LB background [24,28,29] by a friction force…”

Section: Methodsmentioning

confidence: 99%

Hydrodynamic lift forces on solutes in a tilted nanopillar array: A computer simulation study

2017

View full text Add to dashboard Cite

We study solute transport in a microfluidic channel, where the walls hold an array of tilted rigid nanopillars. By solving numerically the flow equations in the channel, we show that a combination of hydrodynamic effects with excluded volume interactions between the solute particles and the pillars leads to a hydrodynamic lift effect, which varies with the particle size, and depends in a strongly nonlinear fashion on the flow rate. We show that the lift force can be sufficiently strong to drive the solute accumulation or removal from the pillar region and can be switched to the opposite direction by variation of the shear rate or driving pressure. We also demonstrate that the nanopillar array can be used to selectively attract particles of certain size and enhance solute trapping at the surface.

show abstract

“…Up to now, direct proofs have been obtained that electrophilic nitration of p-alkyl-and p-alkoxysubstituted toluenes and phenylcyclopropanes I-III involves intermediate formation of ipso-σ-complexes IV-VI which are then converted into relatively stable cyclohexadiene adducts VII-IX (Scheme 1) [1][2][3][4][5][6][7][8][9][10]. Adducts like VII-IX can be isolated; however, they usually undergo acid-catalyzed transformations during the process.…”

mentioning

confidence: 99%

Transformations of para-Substituted Benzylcyclopropanes, Allylbenzenes, and Diphenylmethanes under Nitration with Nitric Acid in Acetic Anhydride

et al. 2005

View full text Add to dashboard Cite

Electrophilic nitration of benzylcyclopropanes, allylbenzenes, and diphenylmethanes containing ortho,para-orienting substituents in the para position of the benzene ring results mainly in replacement of the cyclopropylmethyl, allyl, or benzyl group, respectively (ipso substitution). The nitration of 4-cyclopropylallylbenzene is not accompanied by nitrodealkylation, and the products are only 2-and 3-nitro-4-cyclopropylallylbenzenes.Up to now, direct proofs have been obtained that electrophilic nitration of p-alkyl-and p-alkoxysubstituted toluenes and phenylcyclopropanes I-III involves intermediate formation of ipso-σ-complexes IV-VI which are then converted into relatively stable cyclohexadiene adducts VII-IX (Scheme 1) [1-10]. Adducts like VII-IX can be isolated; however, they usually undergo acid-catalyzed transformations during the process. These transformations give rise to not only conventional electrophilic substitution products but OMe III HNO 3 /Ac 2 O NO 2 OMe

show abstract

Ipso-nitration of p-t-butyltoluene. A 1,2 adduct

Cited by 10 publications

References 0 publications

Ipso attack in aromatic nitration

Ipso attack in aromatic nitration

Hydrodynamic lift forces on solutes in a tilted nanopillar array: A computer simulation study

Transformations of para-Substituted Benzylcyclopropanes, Allylbenzenes, and Diphenylmethanes under Nitration with Nitric Acid in Acetic Anhydride

Contact Info

Product

Resources

About