2:4: 4-Trimethyl-2-pentene

When high purity isobutylene is not required, the acid extract from the rich stage may be heated for a few minutes to 250-300°F, and then quickly cooled. Under these conditions the isobutylene dimerizes to form largely 2,4,4, trimethyl pentene-1. This is known as the dimer process and may be used to concentrate i-butenes for dehydrogenation feed, the isobutylene dimer being added to the motor gasoline pool. Trimers, as well as codimers with normal butenes are also produced. 

Carbocation 1 can undergo hydride and methyl shifts to yield 2,3,4-trimethyl-pentenes ... 

A series of runs were made in which sulfuric acid was added in small increments to a 4 1 mixture of isobutane and 2.2,4-trimethyl pentene-1 at -30 C or -20 C. Increased amounts of the feed isoolefin reacted as more acid was added. Almost no reaction products were noted in the hydrocarbon phase at A/0 ratios of 0.25 or less. When the A/0 ratio was increased to 0.5, C9 - C Q hydrocarbons were formed during a 1.5 hour period during which tYme most of the original isoolefin reacted. 

Second-Step Runs with Reaction Products from 2,2,4-Trimethyl-pentene-1 ... 

Trimethylpentenes protonate rapidly to form TMP s. As Indicated above, trimethylpentenes can be formed by fragmentation of heavy Isoalkyl cations. Furthermore the protonations of trimethyl pentenes and other olefins are to some extent at lease reversible. Hence, small concentrations of trimethyl pentenes are present in alkylation reactors during especially the initial stages of alkylation Mosby and Albright (1) for example found small amounts of olefins when the alkylation product was quenched and neutralized. 

Figure 1. Time-on-stream behaviour of l.OPt/ZSM-58 and 0.54Pd/ZSM-58 in the competitive hydrogenation of an equimolar hexene-(l)/2,4,4-trimethyl-pentene-(l) mixture (reaction conditions T = 70 °C, W/F ikenes = 10 gh/mol).

Similarly, the hydroboration of 2,4,4-trimethyl-pentene with 1 equiv 2,3-dimethyl-2-butyl (thexyl) borane followed by heating the mixture at 200°C gives, after oxidation, 2,4,4-trimethyl-l,5-pentanediol in 81 % yield ... 

Of particular commercial interest, in connection with the effect of the olefin structure on the nature of the products of the Oxo reaction, is the behavior of diisobutylene. Diisobutylene is a mixture of 2,4,4-trimethyl-pentene-2 (I) and 2,4,4-trimethylpentene-l (II). Only one product results from treatment of the mixture of isomers ... 

Kwon et al. [176] have studied the intercalation of octylamine into H2Sii4029 XH2O (from magadiite) from -hexane, hexadecane, mesitylene, and 2,2,4-trimethyl pentene solvents. These systems form gels, and the competitive... 

CuHn< (u-Acetoxy-nonylaldehyd 2 II169. Dinropyl-acetyl-carbinol-acetat 2 II169. 0-0BrMthoxy>2.2.4-trimethyl.penten-(3). 

Addition. The tertiary butyl carbonium ion reacts with a butylene molecule to form branched Cg trimethyl pentene carbonium ions ... 

The intramolecular oxidative earbonylation has wide synthetie applieation. The 7-lactone 247 is prepared by intramolecular oxycarbonylation of the alke-nediol 244 with a stoichiometric amount of Pd(OAc)2 under atmospheric pres-sure[223]. The intermediate 245 is formed by oxypalladation, and subsequent CO insertion gives the acylpalladium 246. The oxycarbonylation of alkenols and alkanediols can be carried out with a catalytic amount of PdCl2 and a stoichiometric amount of CuCb, and has been applied to the synthesis of frenolicin(224] and frendicin B (249) from 248[225]. The carbonylation of the 4-penten-l,3-diol 250, catalyzed by PdCl2 and CuCl2, afforded in the c -3-hydroxytetrahydrofuran-2-aeetie acid lactone 251[226J. The cyclic acetal 253 is prepared from the dienone 252 in the presence of trimethyl orthoformate as an accepter of water formed by the oxidative reaction[227]. 

Together these two products contain all eight carbons of the starting alkene The two carbonyl carbons correspond to those that were doubly bonded m the original alkene One of the doubly bonded carbons therefore bears two methyl substituents the other bears a hydrogen and a tert butyl group The alkene is identified as 2 4 4 trimethyl 2 pentene (CH3)2C=CHC(CH3)3 as shown m Figure 6 15... 

The same reaction that gave 2 4 4 trimethyl 2 pentene also yielded an isomeric alkene This second alkene produced formaldehyde and 4 4 dimethyl 2 pentanone on ozonolysis Identify this alkene... 

FIGURE6 15 Ozonolysis of 2 4 4 trimethyl 2 pentene On cleavage each of the doubly bonded carbons becomes the carbon of a carbonyl (C=0) group... 

Step 3 Loss of a proton from this carbocation can produce either 2 4 4 trimethyl 1 pentene or 2 4 4 trimethyl 2 pentene... 

---