Olefins mineral acid addition

The addition of a cation to an olefin to produce a carbonium ion or ion pair need not end there but may go through many cycles of olefin addition before the chain is eventually terminated by neutralization of the end carbonium ion. Simple addition to the double bond is essentially the same reaction stopped at the end of the first cycle. The addition of mineral acids to produce alkyl halides or sulfates, for example, may be prolonged into a polymerization reaction. However, simple addition or dimerization is the usual result with olefins and hydrogen acids. The polymerization which occurs with a-methyl-styrene and sulfuric acid or styrene and hydrochloric acid at low temperatures in polar solvents is exceptional.291 Polymerization may also be initiated by a carbonium ion formed by the dissociation of an alkyl halide as in the reaction of octyl vinyl ether with trityl chloride in ionizing solvents.292... 

The esters of nitrous acid are characterised by their high velocities of formation and hydrolysis. They are almost instantaneously decomposed by mineral acids and in the method of preparation given this has been taken into account. The slightest excess of hydrochloric acid must be avoided. Advantage is taken of this property of the alkyl nitrites in all cases where it is desired to liberate nitrous acid in organic solvents (in which metallic nitrites are insoluble). Examples addition of N203 to olefines, preparation of solid diazonium salts (p. 286), production of isonitroso-derivatives from ketones by the action of HN02. This synthesis is often also carried out in the manner of the acetoacetic ester synthesis, with ketone, alkyl nitrite, and sodium ethylate the sodium salt of the isonitrosoketone is formed (cf. in this connexion p. 259) ... 

Preparatively it is important that mineral acids, carboxylic acids, and ferf-carbenium ions can be added to olefins via carbenium ion intermediates. Because of their relatively low stability, primary carbenium ions form more slowly in the course of such reactions than the more stable secondary carbenium ions, and these form more slowly than the even more stable tertiary carbenium ions (Hammond postulate ). Therefore, mineral and carboxylic acids add to asymmetric olefins regioselectively to give Markovnikov products (see Section 3.3.3 for an explanation of this term). In addition, these electrophiles add most rapidly to those olefins from which tertiary carbenium ion intermediates can be derived. 

An example of an addition of a mineral acid to an olefin that takes place via a tertiary carbenium ion is the formation of a tertiary alkyl bromide from a 1,1-dialkylethylene and HBr (Figure 3.41). 

The classical method for making tert-butyl esters involves mineral acid-catalysed addition of the carboxylic acid to isobutene but it is a rather harsh procedure for use in any but the most insensitive of substrates [Scheme 6.33].80-82 Moreover, the method is hazardous because a sealed apparatus is needed to prevent evaporation of the volatile isobutene. A simpler procedure [Scheme 6.34] involves use of tert-butyl alcohol in the presence of a heterogeneous acid catalyst — concentrated sulfuric acid dispersed on powdered anhydrous magnesium sulfate. 3 No interna] pressure is developed during the reaction and the method is successful for various aromatic, aliphatic, olefinic, heteroaromatic, and protected amino acids. Also primary and secondary alcohols can be converted into the corresponding /erf-butyl ethers using essentially the same procedure (with the exception of alcohols particularly prone to carbonium ion formation (e.g. p-... 

However, the reaction proceeded only under drastic conditions (pressure 700 upward to 900 atm) in the presence of mineral acids, BFg or metal halogenides. At that time metal carbonyls had been regarded as catalyst poisons. However, Reppe could prove that olefins react with carbon monoxide and water in the presence of metal carbonyls. The reaction products are saturated carboxylic acids. Whereas Ni(CO)4 is the preferred catalyst in the carbonylation of acetylenes, cobalt, rhodium and ruthenium catalysts are equivalent or superior in olefin carbonylation. Also palladium and hydrochloric acid containing catalyst systems are of special activity in hydrocarboxylation [469-471]. Iron has an accelerating effect [472]. Addition of boric acid to Ni or Co catalysts increases the catalyst life and suppresses the formation of insoluble polymer products [473]. 

In a fully synthetic oil, there is almost certainly some mineral oil present. The chemical components used to manufacture the additive package and the viscosity index improver (VI) contain mineral oil. When all these aspects are considered, it is possible for a "fully synthetic" engine oil to surpass mineral oil (Shubkin, 1993). Synthetic oils fall into general ASTM classification (a) synthetic hydrocarbons (poly-a-olefins, alkylated aromatics, cycloaliphatics) (b) organic esters (dibasic acid esters, polyol esters, polyesters) (c) other fluids (polyalkylene glycols, phosphate esters, silicates, silicones, polyphenyl esters, fluorocarbons). 

Figure 3.42 shows an addition of a carboxylic acid to isobutene, which takes place via the ferf-butyl cation. This reaction is a method for forming fert-butyl esters. Because the acid shown in Figure 3.42 is a /3-hydroxycarboxylic add whose alcohol group adds to an additional isobutene molecule, this also shows an addition of a primary alcohol to isobutene, which takes place via the ferf-butyl cation. Because neither an ordinary carboxylic acid nor, of course, an alcohol is sufficiently addic to protonate the olefin to give a carbenium ion, catalytic amounts of a mineral or sulfonic acid are also required here. 

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