Terres

Blakely D W, Kozak E I, Sexton B A and Somor]ai G A 1976 New instrumentation and techniques to monitor chemical surface reactions over a wide pressure range (10 to 10 Terr) in the same apparatus J. Vac. Sc/. Technol. 13 1091... 

These conditions are so harsh that they are applicable only to indoles with the most inert substituents. Cyclization can be achieved at much lower temperatures by using alkyllithium reagents as the base. For example, treatment of o-methylpivalanilide with 3 eq. of n-butyllithium at 25 C gives 2-terr-butylindole in 87% yield[2]. These conditions can be used to make... 

Steric effects of the substituents in positions 4 and 5 cannot shift the protomeric equilibrium sufficiently to permit spectroscopic observation of the thiol form (43b) ultraviolet spectra of 4-terr-butyl-5-methyl-A-4-thia2oline-2-thione (49a) in neutral solvents do not reveal any trace of the thiol protomer (49bi (Scheme 21) (70). 

The 1990 Amendments to the U.S. Clean Air Act require a 50% reduction of sulfur dioxide emissions by the year 2000. Electric power stations are beheved to be the source of 70% of all sulfur dioxide emissions (see Power generation). As of the mid-1990s, no utiUties were recovering commercial quantities of elemental sulfur ia the United States. Two projects had been aimounced Tampa Electric Company s plan to recover 75,000—90,000 metric tons of sulfuric acid (25,000—30,000 metric tons sulfur equivalent) aimuaHy at its power plant ia Polk County, Elorida, and a full-scale sulfur recovery system to be iastaHed at PSl Energy s Wabash River generating station ia Terre Haute, Indiana. Completed ia 1995, the Terre Haute plant should recover about 14,000 t/yr of elemental sulfur. 

A similar design has been developed using a 161 MW plant by The Dow Chemical Company in its Plaquemine, Louisiana location. Destec, Inc. is a power subsidiary of The Dow Chemical Company and has joined with PubHc Service Of Indiana to build a new 230 MW plant near Terre Haute, Indiana. Operation is projected for 1995 (95). 

Di-terr-butylhydroquinone [88-58-4J M 222.3, m 222-223". Crystd from "CgHg or AcOH. 

Critical Terr erature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.66 at 20 °C, (solid) Vapor (Gas) Specific Gravity Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Latent Heat of Vaporization Not pertinent Heat of Combustion Not pertinent Heat of Decomposition Not pertinent. 

TENORAN , chloroxuron, 125 Terbufos, 125 Terephthalic acid, 125 Teiphenyls, 126 TeiTa hidustries Inc., 250 TeiTa Nitrogen Company L.P, 250 TERR-O-GAS , methyl bromide, 126 TESLAC , testosterone, 126 Tessenderlo Cheniie N.V., 145 Testbourne Ltd., 213 TESTODERM , testosterone, 126 Testosterone, 126 Tetrabroniethane, 126 Tetrachlorodifluoroethanes, 12 6... 

These unusual properties of fluorocarbons reflect theu nonpolar character, low polarizability, and overall relatively weak intermolecular attractions Saturated perfluoro-terr-ammes and -dialkyl ethers also closely resemble fluorocarbons rather than typical amines or ethers in their physical properties [4,... 

We noted in Section 2.13 that the common nanes of certain frequently encountered alkyl groups, such as isopropyl and terr-butyl, are acceptable in the lUPAC system. Three alkenyl groups—vinyl, allyl, and isopropenyl—are treated the sane way. 

The difference in stability between stereoisorneric alkenes is even more pronounced with larger alkyl groups on the double bond. A particularly striking exanple compares cis- and rran5-2,2,5,5-tetramethyl-3-hexene, in which the heat of combustion of the cis stereoisomer is 44 kJ/rnol (10.5 kcal/rnol) higher than that of the trans. The cis isomer is destabilized by the large van der Waals strain between the bulky terr-butyl groups on the sfflne side of the double bond. 

Like the reaction of terr-butyl alcohol with hydrogen chloride step 2, in which tert-butyloxonium ion dissociates to (CH3)3C and water, is rate-deter-mining. Because the rate-determining step is unimolecular-, the overall dehydration process is refened to as a unimolecular elimination and given the symbol El. 

Further insight into the E2 mechanism comes from stereochemical studies. One such experiment compares the rates of elimination of the cis and trans isomers of 4-terr-butyl-cyclohexyl bromide. 

Although both stereoisomers yield 4-terr-butylcyclohexene as the only alkene, they do so at quite different rates. The cis isomer reacts over 500 times faster than the trans. 

We can extend the general principles of electrophilic addition to acid-catalyzed hydration. In the first step of the mechanism shown in Figure 6.9, proton transfer to 2-methylpropene fonns terr-butyl cation. This is followed in step 2 by reaction of the cai-bocation with a molecule of water acting as a nucleophile. The alkyloxonium ion fonned in this step is simply the conjugate acid of terr-butyl alcohol. Deprotonation of the alkyloxonium ion in step 3 yields the alcohol and regenerates the acid catalyst. 

Step 2 Water acts as a nucleophile to capture terr-butyl cation ... 

Solvent Effects on the Rate of Substitution by the S/s/1 Mechanism. Table 8.6 lists the relative rate of solvolysis of terr-butyl chloride in several media in order of increasing dielectric constant (e). Dielectric constant is a measure of the ability of a material, in this case the solvent, to moderate the force of attraction between oppositely charged particles compared with that of a standard. The standard dielectric is a vacuum, which is assigned a value e of exactly 1. The higher the dielectric constant e, the better the medium is able to support separated positively and negatively charged species. Solvents... 

As a practical matter, elimination can always be made to occur quantitatively. Strong bases, especially bulky ones such as terr-butoxide ion, react even with primary alkyl halides by an E2 process at elevated temperatures. The more difficult task is to find conditions that promote substitution. In general, the best approach is to choose conditions that favor the Sn2 mechanism—an unhindered substrate, a good nucleophile that is not strongly basic, and the lowest practical temperature consistent with reasonable reaction rates. 

The first-order rate constant for ethanolysis of the allylic chloride 3-chloro-3-methyl-l-butene is over 100 times greater than that of terr-butyl chloride at the same temperature. 

Figure 12.7 illustrates attack on the benzene ring by rerr-butyl cation (step 1) and subsequent formation of terr-butylbenzene by loss of a proton from the cyclohexadienyl cation intermediate (step 2). 

One drawback to Friedel-Crafts alkylation is that reanangements can occur, especially when primary alkyl halides are used. For exanple, Friedel-Crafts alkylation of benzene with isobutyl chloride (a primary alkyl halide) yields only terr-butylbenzene. 

Step 2 Loss of a proton from the cyclohexadienyl cation inteimediate yields terr-butylbenzene. 

Here, the electrophile is terr-butyl cation fonned by a hydride migration that accompanies ionization of the carbon-chlorine bond. 

When two positions aie compaiably activated by alkyl groups, substitution usually occurs at the less hindered site. Nitration of p-terr-butyltoluene takes place at positions ortho to the methyl group in preference to those ortho to the larger rerr-butyl group. This is an example of a steric effect. 

Because osmium tetraoxide is regenerated in this step, alkenes can be converted to vicinal diols using only catalytic amounts of osmium tetraoxide, which is both toxic and expensive. The entire process is perfonned in a single operation by simply allowing a solution of the alkene and rerr-butyl hydroperoxide in terr-butyl alcohol containing a small fflnount of osmium tetraoxide and base to stand for several hours. 

The rerr-butyl group is cleaved as the conesponding carbocation. Loss of a proton from terr-butyl cation converts it to 2-methylpropene. Because of the ease with which a tert-butyl group is cleaved as a car bocation, other acidic reagents, such as trilluoroacetic acid, may also be used. 

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