Isobutenes

Tertiary butyl alcohol, trimethyl carbinol, tertiary butanol. 2-methyl-2-propanol, Me3COH. Colourless prisms, m.p. 25°C, b.p. 83°C. Prepared by absorbing isobutene (2-methylpropene) in sulphuric acid, neutralizing and steam distilling the liquor. Converted to isobutene by heating with oxalic acid. Potassium-/-buloxide is a very strong base. 

Melbylpropene, isobutylene, isobutene, Me2C CH2 Prepared by heating r-butanol with oxalic acid. 

For general reactions see olefins. The butylenes are used to prepare 2-butanol. I-Butene and isobutene are formed into widely used polymers. 

Krilium The trade name of a soil conditioner. The solid form of Krilium has as active in-gredienl a copolymer of about equal molar proportions of vinyl ethanoate and the partial methyl ester of maleic acid. It may be formulated with lime, bentonite, etc. In aqueous form, Krilium contains a copolymer of about equal molar proportions of isobutene and ammonium maleamate. Other polymers are also used. 

For each type of component, its relative reactivity in ozone formation was taken into account which makes it possible to characterize by weighting the behavior of the overall motor fuel under the given experimental conditions. The overall reactivity is in fact governed by a limited number of substances ethylene, isobutene, butadiene, toluene, xylenes, formaldehyde, and acetaldehyde. The fuels of most interest for reducing ozone formation are those which contribute towards minimizing emissions of the above substances. 

A second family is based on isobutene polymers (PIB) having molecular weights from 600 to 2000 that are equally important raw materials for detergent additives. So as to render them reactive with the hydrophilic part, they can be chlorinated or condensed with the maleic anhydride. A third way is based on the utilization of polypropylphenols of molecular weights between 600 and 3000. 

Ethers result from the selective addition of methanol or ethanol to the isobutene contained in C4 olefin fractions. Ethers are used as components in gasoline because of their high octane blending value (RON and MON). 

Figure Bl.7.11. Van t HofF plot for equilibrium data obtained for die reaetion of isobutene with anuuonia in a high pressure ion soiiree (reprodueed from data in [19]).

Table 6.3. Sample molecules acetone and isobutene described by atom pair (ap) descriptors.

To a suspension of 2.0 mol of finely powdered 2-butyne-l,4-d1ol (note 1) in 600 ml of dry dichloromethane were added 50 g of anhydrous p-toluenesulfon1c acid (note 2). Isobutene (6 mol) was introduced with vigorous stirring. The flow was adjusted in such a way that only a small amount escaped from the solution (note 3). The reaction was slightly exothermic, so that no external cooling was applied. 

When all of the isobutene had been introduced, stirring was stopped (note 4) and the flask was allowed to stand overnight. The reaction mixture was then washed five times with ice-water. The organic layer was dried over K2CO3 and after filtration the solvent was removed in a water-pump vacuum. Distillation of the remaining... 

If this is not the case, additional isobutene must be introduced and the mixture be allowed to stand for a longer period. 

The /-butoxycarbonyl group (Boc, "t-box ) has been eMens vely used in peptide synthesis, and Boc derivatives of many amino acids are commercially available. The customary reagent for the preparation from the amine is t-butyl azidoformate in water, dioxane/water, DMSO, or DMF. The cleavage by acids of medium strength proceeds with concomitant loss of isobutene and carbon dioxide (L.A. Carpino, 1957, 1973 see section 4.1.2.2). 

To illustrate the specific operations involved, the scheme below shows the first steps and the final detachment reaction of a peptide synthesis starting from the carboxyl terminal. N-Boc-glycine is attached to chloromethylated styrene-divinylbenzene copolymer resin. This polymer swells in organic solvents but is completely insoluble. ) Treatment with HCl in acetic acid removes the fert-butoxycarbonyl (Boc) group as isobutene and carbon dioxide. The resulting amine hydrochloride is neutralized with triethylamine in DMF. 

Other Dimer Olefins. Olefins for plasticizer alcohols are also produced by the dimerization of isobutene [115-11-7] 4 8 codimerization of isobutene and / -butene [25167-67-3]. These highly branched octenes lead to a highly branched isononyl alcohol [68526-84-1] product. BASE, Ruhrchemie, ICl, Nippon Oxocol, and others have used this source. 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

Polybutenes. Polybutenes are produced by controlled polymerization of butenes and isobutene (isobutylene) (see Butylenes). A typical polyisobutylene stmcture is... 

Olefin Separation. Olefin-containing streams are separated either by the OlefinSiv process (Union Carbide Corp.) separating / -butenes from isobutenes in the vapor phase, or the Olex process (Universal Oil Product) a Hquid-phase process. 

The free phosphine is Hberated upon the removal of the acid catalyst with water. Tri-/-butylphosphine [998-40-3] is prepared by the acid-cataly2ed addition of isobutene to phosphine. 

Methyl tert-Butylluther Methyl /-butyl ether (MTBE) is an increasingly important fuel additive. Platinum—tin and other PGM catalysts are used for the dehydrogenation of isobutane to isobutene, an intermediate step in MTBE manufacture. 

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