F-butyl ions

Here again, the plasma ions will mainly react through proton transfer to the sample, but polar molecules will also form adducts with the f-butyl ions (M + 57)+ and with C3H3+, yielding (M + 39)+ among others. 

Condon (130), in discussing the formation of 2,5-dimethylhexane from the reaction of isobutane with A1C13, postulates a protonated cyclopropane intermediate to explain the skeletal isomerization of the 2,2,4-trimethylpentyl ion, which he presumes was formed by attack of f-butyl ion on isobutylene. In this reaction the isobutylene was produced by removal of a proton from the initially formed f-butyl ion. The cyclic intermediate can be avoided if part of this isobutylene was first converted to butenyl ions which then added to the remaining isobutylene to provide the 2,5-dimethylhexyl skeleton directly. 

Table III gives the rate constants for the reactions of f-butyl ions with several alkanes. Also shown are the rate constants for the reaction of the NO ion,...

The formation of 2,3-di-f-butyl-l-methylthiirenium chloride from fran5-3-chloro-4-methylthio-2,2,5,5-tetramethyl-3-hexene is quantitative (by NMR) in liquid sulfur dioxide (Scheme 128) (82JOC590). Similar thiirenium ions are intermediates in the reactions of -thiovinyl derivatives (79MI50600). 

The allylic position of olefins is subject to attack by free radicals with the consequent formation of stable allylic free radicals. This fact is utilized in many substitution reactions at the allylic position (cf. Chapter 6, Section III). The procedure given here employs f-butyl perbenzoate, which reacts with cuprous ion to liberate /-butoxy radical, the chain reaction initiator. The outcome of the reaction, which has general applicability, is the introduction of a benzoyloxy group in the allylic position. 

In view of the chemical nature of alkylaluminums and methyl halides, complexation is most likely to be rapid and complete, i. e. K is large. Indeed Me3 Al and a variety of Lewis bases were found to complex rapidly2. Initiation, i.e., f-butyl cation attack on monomer, is also rapid since it is an ion molecule reaction which requires very little activation energy. Thus, it appears that Rj t. and hence initiator reactivity are determined by the rate of displacement Ri and ionization R2. 

Trimethylsilyl iodide (TMSI) cleaves methyl ethers in a period of a few hours at room temperature.89 Benzyl and f-butyl systems are cleaved very rapidly, whereas secondary systems require longer times. The reaction presumably proceeds via an initially formed silyl oxonium ion. 

The stereochemistry of oxymercuration has been examined in a number of systems. Conformationally biased cyclic alkenes such as 4-r-butylcyclohexene and 4-f-butyl-l-methycyclohexene give exclusively the product of anti addition, which is consistent with a mercurinium ion intermediate.17,22... 

The reaction gives better yield with dienes, styrenes, or alkenes substituted with EWGs than with simple alkenes. These groups increase the rate of capture of the aryl radical. The standard conditions for the Meerwein arylation employ aqueous solutions of diazonium ions. Conditions for in situ diazotization by f-butyl nitrite in the presence of CuCl2 and acrylonitrile or styrene are also effective.115... 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

The urine samples were analyzed using a modified version of a published method.8 The method involved fortification of the urine samples with an internal standard 3,4,5-trichloro-2-pyridinyl, which is a structural isomer of the 3,5,6-TCP metabolite of chlorpyrifos hydrolysis of labile acid conjugates to 3,5,6-TCP solvent extraction derivitization to the f-butyl-dimethylsilyl ester of 3,5,6-TCP and subsequent negative-ion chemical ionization gas chromatography/mass spectrometry (GC/MS) analysis. Creatinine was determined in urine using a modification of a method of Fabiny and Erting-shausen.9... 

The hemispherands, spherands, calixarenes, and related derivatives. A number of hosts for which the pre-organization criterion is half met (the hemispherands) (Cram et al., 1982) or fully met (the spherands) (Cram, Kaneda, Helgeson Lein, 1979) have been synthesized. An example of each of these is given by (251) and (252), respectively. In (251), the three methoxyl groups are conformationally constrained whereas the remaining ether donors are not fixed but can either point in or out of the ring. This system binds well to alkali metal ions such as sodium and potassium as well as to alkylammonium ions. The crystal structure of the 1 1 adduct with the f-butyl ammonium cation indicates that two linear +N-H - 0... 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

Hydroperoxides undergo reduction with aqueous Fe(II), which turns to aqueous Fe(III). The reaction can be followed at 305 nm (e = 2095 M cm ) ° . Although the stoichiometry of this process is straightforward, with two Fe(II) ions being consumed per molecule of hydroperoxide, the mechanism involves an alkoxide free radical, RO", that may undergo -elimination, H abstraction from R—H, or a 1,2-H-shift and reaction with other components in the system. A case in point is the determination of f-butyl hydroperoxide which consumes under 1 mol of Fe(II) per mol of analyte under inert gas cover, while in the presence of O2 four mols are consumed, pointing to extensive side reactions of the RO" free radical, both without and with O2 in the system. ... 

The oxaziridine ring itself is stable towards alkali there is, for instance, no substitutive ring opening by hydroxyl ions as in oxiranes. 2-f-Butyl-3-phenyloxaziridine (56) is not attacked by methoxide ion in methanol during 12 h at room temperature 3-isopropyl-2-r-octyloxaziridine does not react at room temperature with either solid potassium hydroxide or potassium methoxide solution (57JA5739). 

Thiepane (35) has been converted to 2-acetoxythiepane (137) by a homolytic mechanism using f-butyl peracetate in the presence of a copper(I) ion catalyst (67JCS(C)1130). Similarly, a-chlorination of thiepane (35) by N- chlorosuccinimide (NCS) to yield 2-chlorothiepane (132) probably occurred by a free radical pathway (Scheme 27) (69JHCU5). 

The presence of four methyl groups at positions 4 and 5 of the dioxolan ring causes a larger decrease in 0- (Tables 12, 13) than in kH<. It is possible that in the hydroxide-ion catalysed reaction there is, superimposed on the steric effect, an electronic effect of the methyl groups which causes a decrease in the leaving group ability of the alkoxide ion due to their electronreleasing inductive effect. A similar effect is observed in the hydroxide-ion catalysed breakdown of benzaldehyde f-butyl and methyl hemiacetals for which / -( )/ -( ) = 37. 

Thermal decomposition of Zn(CH3)2 or its co-pyrolysis with other organoelement compounds has been studied mass spectrometrically ". Only two Zn-containing ions ([ZnCH3]+ and [Zn]+) were detected at 100 °C from the co-pyrolysis of an equimolar mixture of f-butyl(allyl)selenium and dimethylzinc " . The relative intensities of the peaks corresponding to the [ZnCH3]+ and [Zn]+ ions diminish as the temperature increases, becoming negligible at T > 320 °C. 

Simple acyl cations RCO+ have been prepared45 in solution and the solid state.40 The acetyl cation CH3CO is about as stable as the f-butyl cation (see, for example, Table 5.1). The 2,4,6-trimethylbenzoyl and 2,3,4,5,6-pentamethylbenzoyl cations are especially stable (for steric reasons) and are easily formed in 96% H2S04.47 These ions are stabilized by a canonical form containing a triple bond (G), though the positive charge is principally located on the carbon,48 so that F contributes more than G. 

It may be noted that the pseudo-first-order rate law for an Sn2 reaction in the presence of a large excess of Y [Eq. (2)) is the same as that for an ordinary SnI reaction [Eq. (3)]. It is thus not possible to tell these cases apart by simple kinetic measurements. However, we can often distinguish between them by the common-ion effect mentioned above. Addition of a common ion will not markedly affect the rate of an Sn2 reaction beyond the effect caused by other ions. Unfortunately, as we have seen, not all SnI reactions show the common-ion effect, and this test fails for f-butyl and similar cases. 

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