Isobutyl halides

First convert fert-butyl chloride into an isobutyl halide. 

In the same way, isobutylene could yield either of two products, isobutyl halide or / r/-butyl halide here the orientation of addition is such that the / r/-butyl halide greatly predominates. 

Leucine has been prepared by the hydrolysis of isobutyl-hydantoin with barium hydroxide by reduction and hydrolysis of a-oximinoisocaproate by racemization of /-leucine by the action of ammonia and hydrogen cyanide on isovaleralde-hyde followed by hydrolysis by the action of heat on isobutyl-malonylazidic acid followed by hydrolysis by the action of ammonia on a-bromoisocaproic acid by the condensation of isobutyl halides and sodio aminomalonic ester or sodio benzoyl-aminomalonic ester followed by hydrolysis by the condensation of isobutyraldehyde and hippuric acid followed by reduction and hydrolysis. The method described above is essentially the Fischer method and is undoubtedly the best and cheapest procedure for the synthesis of large amounts of this amino acid. 

Isobutyl halides and other isobutyl compounds rearrange readily to tert-butyl compounds for the older literature see Whitmore and Lux.869 However, PBr3 (see page 223) converts isobutyl alcohol into isobutyl bromide in good yield with less than 1% of tert-butyl bromide.869... 

PROBLEM 7.24 It was noticed as early as 1862 that treatment of isobutyl halides, (CH3)2CHCH2—X, with silver acetate, Ag OAc ( OAc is the acetate ion, a weak nucleophile, and Ag is a strong Lewis acid, especially toward chloride), produced tert-hnty acetate, (CH3)3C—OAc, and isobutene. Use the stability order of carbocations (p. 292) to provide an explanation for this behavior. Hint Reason backward from the structure of the product. What ion must be present to form this product ... 

One drawback to Fnedel-Crafts alkylation is that rearrangements can occur espe cially when primary alkyl halides are used For example Friedel-Crafts alkylation of benzene with isobutyl chloride (a primary alkyl halide) yields only tert butylbenzene... 

Isobutyl bromide (l-bromo-2-methylpropane) [78-77-3] M 137.0, b 91.2 , d 1.260, n 1.437. Partially hydrolysed to remove any tertiary alkyl halide, then fractionally distd, washed with cone H2SO4, water and aqueous K2CO3, then redistd from dry K2CO3. [Dunbar and Hammett J Am Chem Soc 72 109 7950.1... 

A major problem with the sulfoxide synthesis using menthyl sulfmates is its failure to produce optically pure dialkyl sulfoxides. The prerequisite menthyl alkanesulfinates are oils which have resisted separation into the individual epimers. The menthyl phenyl methanesulfmates are an exception the R epimer is crystalline . One solution to this problem, at least for preparing methyl alkyl sulfoxides, was achieved using cholesteryl methanesulfmates (27) . Both epimers were crystalline and could be separated by fractional crystallization, although in poor yield. Treatment of the epimers with n-propyl, n-butyl, isobutyl, p-tolyl and benzyl magnesium halides yielded the respective methyl alkyl sulfoxides (28) in greater than 95% e.e. and in 32 to 53% yields. 

R3T1 compounds, eg, methyl [3003-15A], ethyl [687-82-1], isobutyl [3016-08-8], and phenyl [30034)4-1] thallium(III), are usually prepared by the reaction between a dialkyl or diarylthallium halide and an oiganolithium reagent in ether (16) ... 

SAMPLE SOLUTION (a) Isopropyl bromide, (CH3)2CHBr, is a secondary alkyl halide, whereas isobutyl bromide, (CH3)2CHCH2Br, is primary. Because the ratedetermining step in an SN1 reaction is carbocation formation and secondary car-bocations are more stable than primary ones, isopropyl bromide is more reactive Jthan isobutyl bromide in nucleophilic substitution by the SN1 mechanism. ... 

Recently, Kunz reported that dialkylaluminum chlorides add in a 1,4-mode to N-(a,f3-unsaturated acyl)oxazolidones (9 Scheme 3),12 while high enantioselectivity is obtained with the chiral N-(a, 3-un-saturated acyl)oxazolinone (11). Typically, higher dialkylaluminum halides (R = ethyl, isobutyl) do not... 

The following qualitative observations on the action of liquid ammonia on organic compounds are mainly by E. C. Franklin and C. A. Kraus, those in brackets are by G. Gore. Aliphatic compounds.—Halides methyl iodide, m. chloroform, reacts, and m. bromoform, m. iodoform, v.s., ethyl bromide and iodide, s. ethylene bromide, s. ethylidene chloride, m. isobutyl bromide, s. amyl bromide, s.s. tribromomethane, v.s. nitrotriohloromethane, m. perehloroethane (n.s.) perchloroethylene (m.) dichloroacetylene (s.). Alcohols methyl, m. ethyl, m. propyl, m. normal butyl,... 

Formation of a symmetrical sulphide (a) (e.g. dipropyl sulphide, Expt 5.204), is conveniently effected by boiling an alkyl halide (the source of carbocations) with sodium sulphide in ethanolic solution. Mixed sulphides (b) are prepared by alkylation of a thiolate salt (a mercaptide) with an alkyl halide (cf. Williamson s ether synthesis, Section 5.6.2, p. 583). In the case of an alkyl aryl sulphide (R-S Ar) where the aromatic ring contains activating nitro groups (see Section 6.5.3, p. 900), the aryl halide is used with the alkyl thiolate salt. The alternative alkylation of a substituted thiophenol is described in Section 8.3.4, p. 1160. The former procedure is illustrated by the preparation of isobutyl 2,4-dinitrophenyl sulphide (Expt 5.205) from l-chloro-2,4-dinitrobenzene and 2-methylpropane-1-thiol. 

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