Hydrolysis of tert-butyl bromide

Hughes and Ingold observed that the hydrolysis of tert butyl bromide which occurs readily is characterized by a first order rate law... 

FIGURE 8 5 The SnI mecha nism for hydrolysis of tert butyl bromide... 

The SnI mechanism for the hydrolysis of tert-butyl bromide is presented as a series of elementary steps in Mechanism 8.2, as a potential energy diagram in Figure 8.5, and in abbreviated form as ... 

They found that the rate of hydrolysis depends only on the concentration of tert butyl bromide Adding the stronger nucleophile hydroxide ion moreover causes no change m... 

In contrast, the hydrolysis of tm-butyl bromide (2-bromo-2-methylpropane) occurs in a stepwise manner (reaction 1.1b). In the first slow step, the C-Br bond breaks, with the bromine atom taking both electrons from the bond and leaving as a negatively charged bromide ion. The remainder of the molecule is the positively charged tert-butyl cation (2-methylprop-2-yl cation). This is a highly reactive intermediate, which reacts rapidly with the hydroxide ion to form the corresponding alcohol. 

They found that the rate of hydrolysis depends only on the concentration of tert-butyl bromide. Adding the stronger nucleophile hydroxide ion, moreover, causes no change in the rate of substitution, nor does this rate depend on the concentration of hydroxide. Just as second-order kinetics was interpreted as indicating a bimolecular rate-determining step, first-order kinetics was interpreted as evidence for a unimolecular rate-determining step—a step that involves only the alkyl halide. 

Regardless of all these approximations, a valuable mechanistic conclusion can be drawn hydrolysis of tert-butyl iodide is a dissociative process. Since most reactions that produce carbonium ion appear to have transition states closely resembling carbonium ion, it seems reasonable to assume that the isotope effect for the hydrolysis of tert-butyldimethylsulfonium iodide in water is a good approximation of the maximum isotope effect for the C-S bond cleavage. In sharp contrast to this is the very small isotope effect in the E2 reaction of 2-phenylethyldimethylsulfonium bromide with hydroxide ion in water ... 

Xu, M. Basile, F. Voorhees, K. J. Differentiation and classification of user-specified bacterial groups by in situ thermal hydrolysis and methylation of whole bacterial cells with tert-butyl bromide chemical ionization ion trap mass spectrometry. Anal. Chim. Acta 2000, 418,119-128. 

As a result of the inductive and hyperconjugative effects it is to be expected that tertiary carbonium ions will be more stable than secondary carbonium ions, which in turn will be more stable than primary ions. The stabilization of the corresponding transition states for ionization should be in the same order, since the transition state will somewhat resemble the ion. Thus the first order rate constant for the solvolysis of tert-buty bromide in alkaline 80% aqueous ethanol at 55° is about 4000 times that of isopropyl bromide, while for ethyl and methyl bromides the first order contribution to the hydrolysis rate is imperceptible against the contribution from the bimolecular hydrolysis.217 Formic acid is such a good ionizing solvent that even primary alkyl bromides hydrolyze at a rate nearly independent of water concentration. The relative rates at 100° are tertiary butyl, 108 isopropyl, 44.7 ethyl, 1.71 and methyl, 1.00.218>212 One a-phenyl substituent is about as effective in accelerating the ionization as two a-alkyl groups.212 Thus the reactions of benzyl compounds, like those of secondary alkyl compounds, are of borderline mechanism, while benzhydryl compounds react by the unimolecular ionization mechanism. 

From Ingold, Structure and Mechanism in Organic Chemistry, 315. See Ingold, with L. C. Bateman, K. A. Cooper, and E. D. Hughes, "Mechanism of Substitution at a Saturated Carbon Atom. Pt. XIII. Mechanism Operative in the Hydrolysis of Methyl, Ethyl, Isopropyl, and Tert.-Butyl Bromides in Aqueous Solutions," JCS... 

The asymmetric alkylation of glycine derivatives constitutes a general means of accessing a wide range of natural and unnatural oc-amino acids.111 Recently it has been established that the quaternary ammonium salt, (lS,2S,4S,5/ ,l / )-l-anthracen-9-yl)methyl-2-[benzyloxy(quinolin-4-yl)methyl]-5-ethyl-l-azoniabicyclo [2.2.2]octane bromide, is a highly effective catalyst in the asymmetric liquid-liquid phase-transfer alkylation of tert-butyl AI-(diphenylmethylene)glycinate. Subsequent hydrolysis of the imine provides access to a wide range of a-amino acid fcrt-butyl... 

Figure 8. Top, synthesis of 9-deoxy-9-fluoro-NANA from 6-deoxy-6-f1uoro-N-acetyl-D-glucosamine (27). (a) Potassium di-tert-butyl-oxaloacetate-MEOH (epimerization), (b) condensation and hydrolysis. Bottom, synthesis of 9-deoxy-9-fluoro-NANA from NANA (27). (a) Benzyl bromide-Ba(OH)o-DMF, (b) AcOH-HoO (70%),...

A sequential Larock and cross-coupling strategy may solve the problem of regioselectivity that appears by using alkynes with two similar brrlky substituents (2009T3120). Larock heteroannulation of substituted 2-iodoanilines and alkynyldimethylsilyl tert-butyl ether afford 3-substituted indole-2-silanols after hydrolysis. The cross-coupling between sodium 2-indolylsilanolate salts with aryl bromides and chlorides successfully afforded multisubstituted indoles (Scheme 6). The development of an alkynyldimethylsilyl terf-butyl ether as a masked silanol equivalent enabled a smooth... 

Acrylic acid cannot be polymerized by ATRP which is sensitive to the presence of acids. Moreover, since many of the ligand systems utilized are nitrogen-based, protonation of the nitrogen may occur, disrupting its coordination to the metal center. The solution to this problem is to polymerize protected monomers, followed by a deprotection step to generate the polyacid. Thus Davis and Matyjaszewski (2000) synthesized poly(acrylic acid) (PAA) via hydrolysis of poly(tert-butyl acrylate) (PrBA), which, in turn, was obtained by ATRP of iBA using a CuBr/PMDETA catalyst system in conjunction with an alkyl bromide, such as methyl-2-bromopropionate (MBrP), as the initiator. The monomer conversion was 93% after 320 min at 60°C. 

Scheme 1034. The synthesis of (l/ )-l-phenylpropylamine hydrochloride. Beginning with tert-butyl disnlfide, oxidation with hydrogen peroxide in the presence of VO(acac>2 and (5 )-2-(A -3,5-di-f-butylsaIicylidene)amino-3,3-dimethyl-l-butanol prodnces the chiral sulfinate (5 )-f-butyl-f-butanethiosulfinate. Then, addition of the sulfinate in THF (oxocyclopentane, THF) to a suspension of lithium amide (L1NH2) in Uquid ammonia (NHs )) generates K)-t-butanesulfinamide. The optically active sulfinamide reacts with propanal to form the corresponding sulfinimine. Reaction of the latter with phenylmagnesium bromide (CtllsMgBr) in ether yields A -(l-phenylpropyl)-f-butanesulhnamide and hydrolysis in methanolic HCI generates the corresponding (IR)-l-phenylpropylamine hydrochloride. The cartoon drawing of the presumed cyclic transition state is used to account for the stereochemical outcome. But see Hose, D. R. I Mahon, M. E Molloy, K. C. Raynham, T Wills, M. /. Chem. Soc. Perkin Trans. 7,1996, 7, 691.

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