Methylbutene

PROPERTIES RESEARCH GRADE PURE GRADE TECHNICAL GRADE 

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Rule 2. When atoms attached directly to a double-bonded carbon have the same priority, the second atoms are considered and so on, if necessary, working outward once again from the double bond or chiral center. For example, in l-chloro-2-methylbutene, in CH3 the second atoms are H, H, H and in CH2CH3 they are C, H, H. Since carbon has a higher atomic number than hydrogen, the ethyl group has the next highest priority after the chlorine atom. 

The experimental isotope effects have been measured for the reaction of 2-methylbutene with formaldehyde with diethylaluminum chloride as the catalyst,27 and are consistent with a stepwise mechanism or a concerted mechanism with a large degree of bond formation at the TS. B3LYP/6-31G computations using H+ as the Lewis acid favored a stepwise mechanism. 

Methyldichlorosilane was by far the most reactive in hydrosilation of 1,1-disubstituted olefins. Trialkylsilanes did not add at all, even at 120°C. Trichlorosilane gave complicated results involving isomerization of olefins and dimerization of a-methylstyrene, and products were not optically active. 2-Methylbutene-2 and trichlorosilane gave two adducts, 2-meth-ylbutyltrichlorosilane and 3-methylbutyltrichlorosilane. The latter required isomerization of the olefin. 2,3-Dimethylbutene-l gave one adduct in 70% yield, and it was optically slightly active [0.8% (R) isomer]. 

The synthetic importance of non-nucleophilic strong bases such as lithium diisopro-pylamide (LDA) is well known but its synthesis involves the use of a transient butyl lithium species. In order to shorten the preparation and make it economically valuable for larger scale experiments an alternate method of synthesis has been developed which also involves a reaction cascade (Scheme 3.14) [92]. The direct reaction of lithium with diisopropylamine does not occur, even with sonication. An electron transfer agent is necessary, and one of the best in this case is isoprene. Styrene is used in the commercial preparation of LDA, but it is inconvenient in that it is transformed to ethylbenzene which is not easily removed. It can also lead to undesired reactions in the presence of some substrates. The advantages of isoprene are essentially that it is a lighter compound (R.M.M. = 68 instead of 104 for styrene) and it is transformed to the less reactive 2-methylbutene, an easily eliminated volatile compound. In the absence of ultrasound, attempts to use this electron carrier proved to be unsatisfactory. In this preparation lithium containing 2 % sodium is necessary, as pure lithium reacts much more slowly. 

Source Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission rate of 2-methylpropene was 40.1 mg/kg of pine burned. Emission rates of 2-methylbutene were not measured during the combustion of oak and eucalyptus. 

Thermal isomerization of 1,1 dimethylcyclopropane yields 3-methylbutene-l and 2-methylbutene-2 in approximately equal amounts and also about 1% of 2-methylbutene-l.31... 

Butene-2. The experimental results for the reaction of methylene with cis and trans butene-2 are summarized in Table III. In the liquid phase and in the gas phase at high pressures (>200 mm.) the major products are 1,2-dimethylcyclopropane (addition to double bond), pentane-2, and 2-methylbutene-2 (insertion products), and the steric configuration of the butene-2 is predominantly retained in the products... 

With decreasing pressure two principal effects are to be noted. Retention of stereospecificity is diminished in the products 1,1-dimethylcyclopropane and pentene-2, and the proportions of 2-methylbutene-2, 2-methylbutene-l, and, to a slight extent, pentene-2 increase, largely at the expense of the cis addition isomer of 1,2-dimethylcyclopropane. These are the results to be expected from geometric and structural isomerization of the initial products. The thermal isomerization of cis-... 

Condensation of salicylaldehydes with 2-chloro-3-formylbutene and analogs gave 2-methylenechromcnc derivatives.227 The direct reaction of salicylaldehyde with 2-methyl-2-chlorobutane or 2-methylbutene with catalysts to give 2,2,3-trimethylchromene is reported in a patent228 The structure of the products from salicylaldehyde and dipheny-lenes229,230 has been revised, (see Section V,B).231... 

Figure 13.23. Examples of vapor-liquid equilibria in presence of solvents, (a) Mixture of-octane and toluene in the presence of phenol, (b) Mixtures of chloroform and acetone in the presence of methylisobutylketone. The mole fraction of solvent is indicated, (c) Mixture of ethanol and water (a) without additive (b) with 10gCaCl2 in 100 mL of mix. (d) Mixture of acetone and methanol (a) in 2.3Af CaCl2 ip) salt-free, (e) Effect of solvent concentration on the activity coefficients and relative volatility of an equimolal mixture of acetone and water (Carlson and Stewart, in Weissbergers Technique of Organic Chemistry IV, Distillation, 1965). (f) Relative volatilities in the presence of acetonitrile. Compositions of hydrocarbons in liquid phase on solvent-free basis (1) 0.76 isopentane + 0.24 isoprene (2) 0.24 iC5 + 0.76 IP (3) 0.5 iC5 + 0.5 2-methylbutene-2 (4) 0.25-0.76 2MB2 + 0.75-0.24 IP [Ogorodnikov et al., Zh. Prikl. Kh. 34, 1096-1102 (1961)].

In additions of diborane, the major product is formed by the attachment of boron to the less substituted carbon. For example, addition of diborane to 1-hexene (31) gives a product that has 94 percent of the boron attached to the terminal carbon. Similarly, diborane added to 2-methylbutene-2 (32) gives 98 percent of boron incorporation at C3.58... 

A solution of 6.0 mL of borane-methyl sulfide complex (10M BH3 in methyl sulfide) in 45 mL THF was placed in a He atmosphere, cooled to 0 °C, treated with 12.6 g of 2-methylbutene, and stirred for 1 h while returning to room temperature. To this there was added a solution of the impure 3,4-diethoxy-5-methylthiostyrene in 25 mL THF. This was stirred for 1 h during which time the color deepened to a dark yellow. The excess borane was destroyed with about 2 mL MeOH (all this still in the absence of air). There was then added 11.4 g elemental iodine followed by a solution of 2.4 g NaOH in 30 mL of boiling MeOH, added over the course of 10... 

The amides of alkali and alkaline-earth metals catalyse hydrogen exchange in hydrocarbons even in the absence of liquid ammonia. For example, the heterogeneous deuterium exchange of benzene and 2-methylbutene-l occurs with a considerable velocity on solid KND2 and Ca(ND2)2 at 70°. This gives rise to the isomerization of 2-methyl-butene-1 to 2-methylbutene-2 (Shatenshtein et al., 1958a). 

This conclusion is supported by observations of the isomerization of unsaturated hydrocarbons catalysed by potassium amide not only in ammonia solution (Shatenshtein and Vasil eva, 1954 Shatenshtein et al., 1954) but also by solid amides of alkali and alkaline-earth metals (Shatenshtein et al., 1958a). For example, diallyl rearranges to dipropenyl, pentene-1 to pentene-2, and 2-methylbutene-l to 2-methyl-butene-2. Subsequently, a further number of examples of isomerization... 

The following illustration shows the preparation of 2-methylbutene by a Wittig reaction. 

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