W-Butane

Included in the table are all compounds for which information was available through the C, compounds. The mass number for the five most important peaks for each compound are listed, followed in each case by the relative intensity in parentheses. The intensities in all cases are normalized to the w-butane 43 peak taken as 100. Another method for expressing relative intensities is to assign the base peak a value of 100 and express the relative intensities of the other peaks as a ratio to the base peak. Taking ethyl nitrate as an example, the tabulated values would be... 

A cross-linked polymer has a density of 0.94 g cm" at 25°C and a molecular weight between crosslinks of 28,000. The conformation of one bond in the middle of the molecule changes from trans to gauche, and the molecule opens up by 120°. In w-butane, the trans to gauche transformation requires about 3.3 kJ mol". Estimate a value for AH of stretching based on this model, and use the law of cosines to estimate the magnitude of the opening up that results. 

Craig s synthesis of nicotine (V to VII, p. 42) proceeds via nomicotine. Nicotinic acid nitrile reacts with the Grignard reagent derived from ethyl y-bromopropyl ether to give 3-pyridyl-y-ethoxypropyl ketone (V). This yields an oily oxime (VI) reducible to a-(3-pyridyl)-a-amino-8-ethoxy-w-butane (VII), which with 48 per cent, hydrobromic acid at 130-3° gives womicotine, and this on methylation yields dZ-nicotine. 

The submitters have detected traces of fra j-butene-2 and propylene among the gases (mainly w-butane and hydrogen) formed on hydrolysis. 

Sufficient dry ether (approximately 100 ml.) is added to bring the organomagnesium products into solution. Aliquot portions of the solution are then added to a known volume of standard hydrochloric acid, and the excess acid is determined by titration with standard base. Yields determined in this way tend to be a few percent higher than those determined by collection of w-butane (Note 12). 

The multi-functionality of metal oxides1,13 is one of the key aspects which allow realizing selectively on metal oxide catalysts complex multi-step transformations, such as w-butane or n-pentane selective oxidation.14,15 This multi-functionality of metal oxides is also the key aspect to implement a new sustainable industrial chemical production.16 The challenge to realize complex multi-step reactions over solid catalysts and ideally achieve 100% selectivity requires an understanding of the surface micro-kinetic and the relationship with the multi-functionality of the catalytic surface.17 However, the control of the catalyst multi-functionality requires the ability also to control their nano-architecture, e.g. the spatial arrangement of the active sites around the first centre of chemisorption of the incoming molecule.1... 

Gao, X. Banares, M.A. Wachs, EE. Ethane and w-butane oxidation over supported vanadium oxide catalysts An in situ UV-visible diffuse reflectance spectroscopic investigation. J. Catal. 1999,188, 325-331. 

The present paper is an attempt to unravel a rather confused aspect of cationoid polymerisations. This concerns the phenomenon comprised in the term monomer complexation of the growing cation . The idea seems to have occurred for the first time in the work of Fontana and Kidder on the polymerisation of propene by AlBr3 and HBr in w-butane [3]. The kinetics indicated a reaction of zero order with respect to monomer, M to explain this, it was assumed that the growing end of the chain, written as a carbenium ion, Pn+, is complexed with M and that the rate-determining growth step is an isomerisation of this complex ... 

For all these reasons, to clarify the subject further, it would be most useful to do conventional kinetic experiments with diminishing [M] and Mayr-type experiments with increasing [M] with the aim of obtaining an overlap of the ranges of [M] for the two types of experiment, and for fairly obvious reasons these experiments should be done in the same polar solvent at fixed dielectric constant with compensation by, say, w-butane. 

Geurink and Klumpp used 2-butanol as the proton source in benzene solvent. They found an exothermic protodelithiation of —221 4 kJmoP for w-butyl lithium and —240 5 kJmol for the isomeric iec-butyl lithium to form the same w-butane product. The difference between the protodelithiation enthalpies is 19 6 kJmoP, the same as the difference between the enthalpies of formation of the two alkyl lithiums. From Table 1, the difference is ca 21 kJmoR, in complete agreement. 

The many different conformers resulting from rotation around the carbon-carbon bonds in simple molecules like ethane and w-butane may be shown by Newman projections (Figure 2.7). The most stable is the anti or trans projection where the steric hindrance is minimized. There are a number of eclipsed and gauche arrangements of which only one of... 

A similar description applies to reaction of gauche w-butane leading to the more stable anti conformer. Again, the reaction coordinate may be thought of as a torsion about the central carbon-carbon bond, and... 

Chemists routinely manipulate physical models in an attempt to ascertain what actually occurs during a conformational change. A successful example of this is in showing first-time students of organic chemistry that interconversion between anti and gauche conformers of w-butane involves a simple rotation about the central carbon-carbon bond (see discussion in Chapter 1). Much less satisfactory is the attempt to show the interconversion of chair forms of cyclohexane. Here, computer animations provide a better alternative. 

Figure 7 G(Si) value as a function of the carbon atom numbers in the molecules. When more than one measured value was published, we tried to select the most probable value. Alkanes (1) propane, (2) w-butane, (3) w-pentane, (4) cyclopentane, (5) w-hexane, (6) cyclohexane, (7) w-heptane, (8) cycloheptane, (9) methylcyclohexane, (10) w-octane, (11) cyclooctane, (12) isooctane, (13) w-decane, (14) cyclodecane, (15) cw-decalin, (16) trawx-decalin, (17) w-dodecane, (18) dicyclohexyl, (19) n-hexadecane. (From Refs. 18, 29, 65, 92, 148, and 155.)...

For example, 70 ppb of w-butane would be reported as 280 ppbC. (For nonurban data, mixing ratios (ppb) of the individual compounds are often used instead, so the reader is cautioned to determine how such data are presented.)... 

Mechanism m18 corresponds to the case where the isomerization steps s9, s10, and sl4 are assumed to be very slow compared with steps of hydrogenation and dehydrogenation. In that case, if p and a were taken as negative and t as positive, we would model a situation in which w-butane was dehydrogenating to produce 1-butene and at the same time the 2-butenes were being hydrogenated to produce w-butane. This qualitatively follows the observations of Hnatow (33). 

Figure 12.7 compares the saturated hydrocarbon -butane with the unsaturated hydrocarbon 2-butene. The number of atoms bonded to each of the two middle carbons of w-butane is four, whereas each of the two middle carbons of 2-butene is bonded to only three other atoms—a hydrogen and two carbons. 

Low temperature isomerization catalysts are of the Friedel Crafts type, such as AICI3 and AlBr3, activated with HX, and dissolved in a suitable solvent such as SbCl3. Application of these extremely acidic and corrosive systems requires special handling and disposal of the catalyst and careful pretreatment of the feed-stock to remove contaminating materials. Low temperature isomerization (< 100° C) is used mainly for isomerization of w-butane, which is generally available in sufficient purity by normal refinery processes. 

It will now be instructive to examine the n-butane reaction (76). In this case the reaction follows almost exclusively a single path leading to the formation of sec-butyl radicals. The percentage of the quenching done by the two methylene groups is very nearly the same as that for the tertiary C-H bond in isobutane (i.e. >90%). However, the primary yield of w-butyl radicals ( 2%) from w-butane is decidedly less than that for isobutyl radicals ( " 14%) from isobutane. This behavior can be readily interpreted on the basis of a cyclic transition-state structure, but not with an open-chain transition state. For the two reaction sequences, we may write ... 

At higher temperatures increasing proportions of n-butane join ethane as gas-phase hydrogenation products. On lowering the temperature to room temperature for spectroscopic measurements, physically adsorbed w-butane increasingly contributes to the spectra of adsorbed species. Further temperature rises lead to increasing amounts of chemisorbed n-butyl species in all cases, and finally to gas-phase methane through C—C bond scission. 

Various solid acids were qualified in the literature as superacids on the basis of very different arguments. The most studied solid superacid, sulfated zirconia, and related sulfated oxides were considered as superacids because of their ability to convert w-butane into isobutane at low temperatures. 

---