Tert -butyl

Example 2.5 tert-Butyl hydrogen sulfate is required as an intermediate in a reaction sequence. This can be produced by the reaction between isobutylene and moderately concentrated sulfuric acid ... 

Series reactions occur in which the tert-butyl hydrogen sulfate reacts to unwanted tert-butyl alcohol ... 

The commercial constant boiling point alcohol, b.p. 80°/760 mm., containing 88 per cent, of tert..butyl alcohol, may be used 28-5 g. are required. 

The tert.-butyl alcohol should be dried over quicklime or anhydrous calcium sulphate and distilled. 

In an alternative procedure 26 g. of anhydrous ferric chloride replace the aluniiniuni chloride, the mixture is cooled to 10°, and the 50 g. of tert.-butyl chloride is added. The mixture is slowly warmed to 25° and maintained at this temperature until no more hydrogen chloride is evolved. The reaction mixture is then washed with dilute hydrochloric acid and with water, dried and fractionally distilled. The yield of tert.-butyl benzene, b.p. 167- 170°, is 60 g. 

The reagent Is expensive and poisonous, consequently the hydroxylation procedure is employed only for the conversion of rare or expensive alkenes (e.g., in the steroid field) into the glycols. Another method for hydroxylation utilises catalytic amounts of osmium tetroxide rather than the stoichiometric quantity the reagent is hydrogen peroxide in tert.-butyl alcohol This reagent converts, for example, cyc/ohexene into cis 1 2- t/ohexanedlol. 

Prepare anhydrous tert.-butyl alcohol by refluxing the commercial product with sodium ca. 4 g. per 100 ml.) until the metal is about two-thirds dissolved and then distilling. Free metal should be present during the distillation. 

Besides the tert-butyl cation, we also succeeded in preparing and studying the related isopropyl and the terf-amyl cations. The isopropyl cation was of particular relevance. 

Figure 6.1, H NMR spectra of (a) the tert-butyl cation [trimethylcarbenium ion, (CH jj-jC ] [b) the tert-amyl cation [dimethyletbylcarbenium ion, (CH3)3C -C2H 5] and (c) the isopropyl cation [dimethylcarbenium ion, (CH3)2C Hj (60 MHz, in SbF5 S02CIF solution, —60°C).

Figure 9.2. Carbon Is photoelectron spectrum Is core-hole-state spectra for the 2-norbornyl cation of tert-butyl cation and Clark s simulated spectra for the classical and nonclassical ions.

The selectivity relationship merely expresses the proportionality between intermolecular and intramolecular selectivities in electrophilic substitution, and it is not surprising that these quantities should be related. There are examples of related reactions in which connections between selectivity and reactivity have been demonstrated. For example, the ratio of the rates of reaction with the azide anion and water of the triphenylmethyl, diphenylmethyl and tert-butyl carbonium ions were 2-8x10 , 2-4x10 and 3-9 respectively the selectivities of the ions decrease as the reactivities increase. The existence, under very restricted and closely related conditions, of a relationship between reactivity and selectivity in the reactions mentioned above, does not permit the assumption that a similar relationship holds over the wide range of different electrophilic aromatic substitutions. In these substitution reactions a difficulty arises in defining the concept of reactivity it is not sufficient to assume that the reactivity of an electrophile is related... 

Kinetic data are available for the nitration of a series of p-alkylphenyl trimethylammonium ions over a range of acidities in sulphuric acid. - The following table shows how p-methyl and p-tert-h xty augment the reactivity of the position ortho to them. Comparison with table 9.1 shows how very much more powerfully both the methyl and the tert-butyl group assist substitution into these strongly deactivated cations than they do at the o-positions in toluene and ferf-butylbenzene. Analysis of these results, and comparison with those for chlorination and bromination, shows that even in these highly deactivated cations, as in the nitration of alkylbenzenes ( 9.1.1), the alkyl groups still release electrons in the inductive order. In view of the comparisons just... 

The method is basically an application of the Wacker oxidation except that the catalyst used is palladium acetate ( Pd(AcO)2 or Pd(02CCH3)2). the solvent is acetic acid or tert-butyl alcohol and the oxygen source is the previously suggested hydrogen peroxide (H202)[17]. 

METHOD 3 [114]-Phenol and 30% H2O2 in molar ratios of 10 3 to 10 8 is heated at 70 C for 8-10 hours to give -15% catechol. Addition of tert-butyl alcohol increases the yield. 

Note 1. If not kept under nitrogen in well closed bottles, tert.-butyl propargyl... 

The mixture was then cooled to 30-40°C and the dissolved acetylene was sucked Over" in a water-pump vacuum (10-20 mmHg) and condensed in a receiver cooled at -78°C. The contents of the receiver were shaken three times with 20-ml portions of ice-water in a small separating funnel or dropping funnel in order to remove small amounts of tert.-butyl alcohol. After drying over a very small amount of... 

To a solution of 0.40 mol of butyllithium in about 280 ml of hexane were added 300 ml of dry THF at -20 to -40 0. Subsequently 0.40 mol of freshly distilled tert.-butyl propargyl ether was added, keeping the temperature below -30°C. Freshly distilled acetaldehyde (0.40 mol) was then added at the same temperature during about 15 min. The cooling bath was removed and, after an additional 15 min, 200 ml of an aqueous solution of 30 g of ammonium chloride were introduced. After separation of the layers the aqueous layer was extracted twice with diethyl ether and the combined solutions were dried over magnesium sulfate and concentrated in... 

The rate of the reaction decreases with increasing number of substituents in the acetylenic halide, and it is higher with acetylenic bromides than with the corresponding chlorides. Methyl magnesium iodide gives equal amounts of 1,1- and 1,3--substitution products, whereas tert.-butylmagnesium bromide does not react. However, for some tert.-butyl substituted allenes there exists an attractive com-... 

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