Isobutene synthesis

Isobutene synthesis Isobutyric aldehyde, formation Isodewaxing... 

Fig. 4 Mechanism of isobutene synthesis by mevalonate diphosphate decarboxylase (Marliere et al. 2013)...

This pathway was also used in a patent by Marliere (2010), which describes how MDDs from S. cerevisiae and 10 other microorganisms were analysed for isobutene synthesis. From the tested genes, MDD from Picrophilus torridus (an obligate aerobic archaeon) expressed in E. coli achieved the highest isobutene production rate. 

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. 

The three isomers constituting n-hutenes are 1-hutene, cis-2-hutene, and trans-2-hutene. This gas mixture is usually obtained from the olefinic C4 fraction of catalytic cracking and steam cracking processes after separation of isobutene (Chapter 2). The mixture of isomers may be used directly for reactions that are common for the three isomers and produce the same intermediates and hence the same products. Alternatively, the mixture may be separated into two streams, one constituted of 1-butene and the other of cis-and trans-2-butene mixture. Each stream produces specific chemicals. Approximately 70% of 1-butene is used as a comonomer with ethylene to produce linear low-density polyethylene (LLDPE). Another use of 1-butene is for the synthesis of butylene oxide. The rest is used with the 2-butenes to produce other chemicals. n-Butene could also be isomerized to isobutene. ... 

The catalytic asymmetric cyclopropanation of an alkene, a reaction which was studied as early as 1966 by Nozaki and Noyori,63 is used in a commercial synthesis of ethyl (+)-(lS)-2,2-dimethylcyclo-propanecarboxylate (18) by the Sumitomo Chemical Company (see Scheme 5).64 In Aratani s Sumitomo Process, ethyl diazoacetate is decomposed in the presence of isobutene (16) and a catalytic amount of the dimeric chiral copper complex 17. Compound 18, produced in 92 % ee, is a key intermediate in Merck s commercial synthesis of cilastatin (19). The latter compound is a reversible... 

The preparation of mono- and di-tm-butylcyclopentadienes 1 and 2 starting from monomeric cyclopentadiene was reported first in 1963 [23]. It was noted that the nucleophilic attack of the cyclopentadienide anion on ferf-alkyl halide has to compete with elimination reaction giving isobutene. The yield of the di- and tri-fer/-butylcyclopentadienes 2 and 3 was therefore reported to be modest to low [23, 24], Recently an elegant improvement for this synthesis using phase transfer catalysis was presented (Eq. 1), but the availability of the tri-substituted derivative... 

Ammonium salts have also been used as catalysts in the synthesis of t-BuNH2 from NH3 and isobutene in water (Eq. 4.7). The co-produced t-BuOH can be recycled [97]. 

Linalool is an important fragrance and fragrance precursor (esters) with an annual production of over 15 000 t. Some 50% is made by semi-synthesis from a- and / -pinene, the other part is made synthetically starting from isobutene via 6-methylhept-5-en-2-one (9). Addition of an acetylene fragment followed by partial hydrogenation (Pd) leads to linalool. 

Above we have mentioned several heterogeneous applications such as the OCT process and SHOP. Neohexene (3,3-dimethyl-1-butene), an important intermediate in the synthesis of fine chemicals, is produced from the dimer of isobutene, which consists of a mixture of 2,4,4-trimethyl-2-pentene and 2,4,4-trimethyl- 1-pentene. Cross-metathesis of the former with ethene yields the desired product. The catalyst is a mixture of W03/Si02 for metathesis and MgO for isomerisation at 370 °C and 30 bar. The isobutene is recycled to the isobutene dimerisation unit [48],... 

In 1976 he was appointed to Associate Professor for Technical Chemistry at the University Hannover. His research group experimentally investigated the interrelation of adsorption, transfer processes and chemical reaction in bubble columns by means of various model reactions a) the formation of tertiary-butanol from isobutene in the presence of sulphuric acid as a catalyst b) the absorption and interphase mass transfer of CO2 in the presence and absence of the enzyme carboanhydrase c) chlorination of toluene d) Fischer-Tropsch synthesis. Based on these data, the processes were mathematically modelled Fluid dynamic properties in Fischer-Tropsch Slurry Reactors were evaluated and mass transfer limitation of the process was proved. In addition, the solubiHties of oxygen and CO2 in various aqueous solutions and those of chlorine in benzene and toluene were determined. Within the framework of development of a process for reconditioning of nuclear fuel wastes the kinetics of the denitration of efQuents with formic acid was investigated. 

Synthesis from Isobutene and Formaldehyde. 3-Methyl-3-buten-l-ol, obtained from isobutene and formaldehyde [43], isomerizes to form 3-methyl-2-buten-... 

Modern methods of peptide synthesis began with the solid-phase method introduced by Merrifield299 in 1962 (Fig. 3-15). To begin the synthesis a suitably protected amino acid is covalently linked to a polystyrene bead. The blocking f-butoxycarbonyl (Boc) group is removed as isobutene by an elimination reaction to give a bound amino acid with a free amino group. 

A one-pot synthesis of the conjugated ketenedithioacetals (7) and (8) involving indirect lithiation of propene or isobutene via the potassio deriviative reaction with carbon disulfide and 5,5-dimethylation has been reported [68]. It illustrates some aspects of the reaction of organometallics with CS2. 

Concerning the application of gallium alkoxides, one can mention the selective catalytic activity of Ga(OPh)3in the condensation reactions of isobutene with phenols. In(OR)3 is used for the preparation of solutions for production of ln203 and In2Oj-related conduction films [1618] and also in the synthesis of volatile precursors for MOCVD deposition of In2Oj [830]. 

The reaction of isobutene with hexa-1,5-diene catalysed by Re207/Al2C>3/Bu4Sn at 40 °C gives >20% yield of 6-methylhepta-l,5-diene, an intermediate in the synthesis of... 

In many olefmic reactions activation of the C=C double bond occurs, although in many reactions at least one C-H bond is transformed. Established processes are summarized in Table 3. Examples of liquid-phase reactions are the synthesis of ethers, especially methyl tert-butyl ether by reacting olefins (isobutene) and alcohol (methanol) in the liquid phase at slightly elevated temperature and pressure (Table 3, entry 22). Different processes developed differ only slightly in feed composition and design, which is optimized for heat removal [2]. 

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