Tert Butylbenzene

Figure 12 7 illustrates attack on the benzene ring by tert butyl cation (step 1) and subsequent formation of tert butylbenzene by loss of a proton from the cyclohexadienyl cation intermediate (step 2)... 

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... 

Step 2 Loss of a proton from the cyclohexadienyl cation intermediate yields tert butylbenzene C(CH3)3... 

The partial rate factors for nitration of tert-butylbenzene are... 

Carbon-hydrogen stretching vibrations with frequencies above 3000 cm are also found m arenes such as tert butylbenzene as shown m Figure 13 33 This spectrum also contains two intense bands at 760 and 700 cm which are characteristic of monosub stituted benzene rings Other substitution patterns some of which are listed m Table 13 4 give different combinations of peaks... 

The parent system 4 has also been jnepared employing a double reductive ring closure of a dinitrodiphenylbenzene derivative (Scheme 25). The required starting material, 195, was prepared using a palladium-catalyzed coupling of 1,4-dibromo-2,5-dinittobenzene with phenylboronic acid and after reaction with tri-ethylphosphite in hot tert-butylbenzene, 4 could be isolated in a moderate yield (92JHC1237). 

The carbocation electrophile in a Friedel-Crafts reaction can be generated in ways other than by reaction of an alkyl chloride with AICI3. For example, reaction of benzene with 2-methylpropene in the presence of H3PO4 yields tert-butylbenzene. Propose a mechanism for this reaction. 

In triethylamine instead of benzene the reaction products are completely different, and are indicative of a homolytic process involving an initial electron transfer from triethylamine followed by a hydrogen atom transfer. Scheme 10-68 gives the major products, namely 1,3,5-tri-tert-butylbenzene (10.36, 20%), the oxime 10.39 (18%), formed from the nitroso compound 10.38, and the acetanilide 10.37 (40%). ESR and CIDNP data are consistent with Scheme 10-68. In their paper the authors discuss further products which were found in smaller yields. 

Figure 1.15 Fast analysis of a test mixture on a 10 cm x 4.6 mm I.D. column packed with 3 micrometer octa< ecylsilanized silica with a mobile phase flow rate of 3.4 mi. i.n (acetonitrile-water 7 3) and operating pressure of ca. 340 atmospheres. Peaks 1 uracil, 2 phenol, 3 - nitrobenzene, 4 - toluene, 5 -ethylbenzene, 6 - isopropylbenzene, and 7 - tert.-butylbenzene. (Reproduced with permission from ref. 222. Copyright Friedr. Vieweg 6 Sohn).

The rate of addition is also inversely proportional to the level of congestion. In some cases this depends on whether molecules are being hydrogenated individually or in competition. For example, in competition, 1,3-di-tert-butylbenzene hydrogenates faster than its 1,4-isomer however, individually, the 1,4-isomer hydrogenates faster than the 1,3-isomer. 

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