2- Chloro-3-methylbutane

Our belief that carbocations are intermediates m the addition of hydrogen halides to alkenes is strengthened by the fact that rearrangements sometimes occur For example the reaction of hydrogen chloride with 3 methyl 1 butene is expected to produce 2 chloro 3 methylbutane Instead a mixture of 2 chloro 3 methylbutane and 2 chloro 2 methylbutane results... 

Addition begins m the usual way by protonation of the double bond to give m this case a secondary carbocation This carbocation can be captured by chloride to give 2 chloro 3 methylbutane (40%) or it can rearrange by way of a hydride shift to give a tertiary carbocation The tertiary carbocation reacts with chloride ion to give 2 chloro 2 methylbutane (60%)... 

The submitters purchased 2-chloro-2-methylbutane from Eastman Kodak Company. The checkers prepared the halide as follows. A separatory funnel was charged with 21.5 mL (0.2 mol) of 2-methyl-2-butanol and IQO mL of coned hydrochloric acid. The mixture was shaken vigorously with periodic venting for 10 min. The layers were separated and the 2-chloro-2-methylbutane layer (upper) was washed several times with equal volumes of cold water. The product was dried over calcium chloride and distilled, bp 85 C. 

What evidence is there to support the carbocation mechanism proposed for the electrophilic addition reaction of alkenes One of the best pieces of evidence was discovered during the 1930s by F. C. Whitmore of the Pennsylvania State University, who found that structural rearrangements often occur during the reaction of HX with an alkene. For example, reaction of HC1 with 3-methyl-1-butene yields a substantial amount of 2-chloro-2-methylbutane in addition to the "expected" product, 2-chloro-3-methylbutane. 

Chloro-3-methy1butane 2-Chloro-2-methylbutane (approx. 50%) (approx. 50%)... 

This procedure has been used to effect the following reductions at ca. 150° bromobenzene to benzene (89%), iodo-benzene to benzene (95%), 1-chlorobutane to n-butane (95%), 2-chloro-2-methylbutane to 2-methylbutane (32%), and isopropyl chloroacetate to isopropyl acetate (63%). 

Cadmium carbonate, 82 Carbodemetallation, 11 Carbometallation, 10 Carboxylic acids, 60,86 Ccrium(ni) chloride heptahydrate, 64 a-Chiral aldehyde, 112 Chiral lanthanide, 112 ff Chloro-a-lithio-a-trimethylsilanes, 21 2 Chloro-2-methylbutane, 135 4-Chloro-2-trimethylsilylamsole. 40... 

Rearrangement can also occur after the initial alkylation. The reaction of 2-chloro-2-methylbutane with benzene is an example of this behavior.35 With relatively mild Friedel-Crafts catalysts such as BF3 or FeCl3, the main product is 1. With A1C13, equilibration of 1 and 2 occurs and the equilibrium favors 2. The rearrangement is the result of product equilibration via reversibly formed carbocations. 

This potent inhibitor of cholesterol biosynthesis has been synthesized178 by one-pot esterification of the alcohol 210 with the acid chloride of 2,2-dimethylbutanoic[l-14C] acid, obtained by carbonation of the Grignard reagent prepared from 2-chloro-2-methylbutane (equation 74). Desilylation of 211 afforded [14C]simvastatin 209 in 29% radiochemical yield from 14C-labelled C02. This 14C-labelled drug was needed for elucidation of its metabolic fate in experimental animals. 

Carbon tetrachloride, 0322 Carbon tetrafluoride, 0349 Carbon tetraiodide, 0525 f 1-Chlorobutane, 1637 f 2-Chlorobutane, 1638 f Chlorocyclopentane, 1923 f l-Chloro-l,l-dilluoroethane, 0731 Chlorodilluoromethane, 0369 f Chloroethane, 0848 Chloroform, 0372 f Chloromethane, 0432 f l-Chloro-3-methylbutane, 1986 f 2-Chloro-2-methylbutane, 1987 f Chloromethyl ethyl ether, 1246 f Chloromethyl methyl ether, 0850 f l-Chloro-2-methylpropane, 1639 f 2-Chloro-2-methylpropane, 1640 f 1-Chloropentane, 1988 f 1-Chloropropane, 1243 f 2-Chloropropane, 1244 f l-Chloro-3,3,3-trifluoropropane, 1127 1,2-Dibromoethane, 0785 Dibromomethane, 0395... 

CHLORO-2-METHYLBUTANE N-METHYLPYRROLIDINE PIPERIDINE tert-BUTYLFORMAMIDE ISOPENTANE NEOPENTANE n-PENTANE... 

Draw structural formulae for the organic products formed when 2-chloro-2-methylbutane is heated under reflux with (a) aqueous potassium hydroxide and (b) ethanolic potassium hydroxide. 

I) 1-Bromo-l-methylcyclohexane (II) 2-Chloro-2-methylbutane (III) 2,2,3-TrImethyl-3-bromopentane. 

Regardless of whether the Pd-catalyzed coupling or alkyne metathesis is utilized to make PAEs, the critical step is the synthesis of the diiodoarene monomers. In this section some of the more interesting syntheses are showcased. The synthesis of dipropynyldi-tert-butylnaphthalene is shown in Scheme 5. Starting from naphthalene, Friedel-Crafts alkylation with 2-chloro-2-methylbutane gives a mixture of two di-tert-butylnaphthalenes that are separated by crystallization. Iodination of the correct isomer is followed by a Pd-catalyzed coupling of propyne to the diiodide to give the desired l,5-dipropynyl-3,8-di-tert-butyl-naphthalene [56] ready for ADIMET. 

Problem 4,33 Synthesize (a) 2-methylpentane from CH,CH=CH—CH(CH,), (b) isobutane from isobutyl chloride, (c) 2-methyl-2-deuterobutane from 2-chloro-2-methylbutane. Show all steps. ... 

Dimethylpropane. b) CHjCHjCHjCH CH, gives 2-chloropentane and 3-chloropentane. 2-Methyl-butane gives 2-chloro-3-methylbutane. (c) 2-Methylbutane gives 2-chloro-2-methylbutane. 

Methyl-1-butene 2-Chloro-3-methylbutane 2-Chloro-2-methylbutane... 

With halides such as 2-chloro-2-methylbutane, which can give different alkenes depending on the direction of elimination, the El reaction is like the E2 reaction in tending to favor the most stable or highly substituted alkene ... 

In a multistep synthesis, the overall percent yield is the product of the fractional yields in each step times 100 and decreases rapidly with the number of steps. For this reason, a low-yield step along the way can mean practical failure for the overall sequence. Usually, the best sequence will be the one with the fewest steps. Exceptions arise when the desired product is obtained as a component of a mixture that is difficult to separate. For example, one could prepare 2-chloro-2-methylbutane in one step by direct chlorination of 2-methyl-butane (Section 4-5A). But because the desired product is very difficult to separate from the other, isomeric monochlorinated products, it is desirable to use a longer sequence that may give a lower yield but avoids the separation problem. Similar separation problems would be encountered in a synthesis that gives a mixture of stereoisomers when only one isomer is desired. Again, the optimal synthesis may involve a longer sequence that would be stereospecific for the desired isomer. 

How would you expect the fraction of elimination toward the methyl groups, as opposed to elimination toward the methylene group, to compare in E1 and E2 reactions of 2-chloro-2-methylbutane and the corresponding deuterium-labeled chloride, 2-chloro-2-methylbutane-3-D2 Give your reasoning. (Review Sections 8-8 and 15-6B.)... 

Cognate preparation. 2-ChIoro-2-methylbutane. Use 22 g (27 ml, 0.25 mol) of 2-methylbutan-2-ol (t-pentyl alcohol) and 65 ml of concentrated hydrochloric acid. Distil the chloride twice from a Claisen flask with fractionating side-arm or through a short column. Collect the 2-chloro-2-methylbutane at 83-85 °C the yield is 18 g (68%). Record the p.m.r. spectrum (CC14, TMS) and assign the signals which appear at 51.01 (t, 3H), 1.51 (s, 6H) and 1.73 (q, 2H) note the overlap of the latter two signals. 

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