Alkane formation, byproduct

Aliphatic amines can be readily oxidized by Pd(II) to imines or iminium salts and hydrido complexes. The latter can transfer hydrogen to alkenes, leading to the formation of alkanes as byproducts of the Heck reaction (last example, Scheme 8.18). Such reactions can be avoided by using alkali carbonates as base instead of aliphatic amines [148]. Treatment of stannanes or organoboron derivatives with electron-deficient alkenes under acidic reaction conditions can also lead to formal products of Michael addition instead of the products of a Heck-type reaction [149, 150] (Scheme8.19). 

Desulphurization of thiols has been accomplished in high yield under phase-transfer conditions using tri-iron dodecacarbonyl (or dicobalt octacarbonyl). The mechanism proposed for the formation of the alkanes and the dialkyl sulphide byproducts involves a one electron transfer to the thiol from the initially formed quaternary ammonium hydridoiron polycarbonyl ion pair [14], Similar one electron transfers have been postulated for the key step in the cobalt carbonyl promoted reactions, which tend to give slightly higher yields of the alkanes (Table 11.18). 

When alkanes are the sole products, Eqs. (3.46)-(3.49) represent the principal reactions with the formation of water, hydrogen, coke, and carbon oxides as byproducts eq. (3.49) describes the formation of aromatics ... 

Various spiro[2.n]alkan-4-ones ° i i and bicyclo[n. 1,0]alkan-2-ones ° were converted to the corresponding cyclopropanecarbaldehyde on irradiation in an appropriate solvent, e.g. formation of 4. The yields were generally low due to formation of a number of byproducts, including cyclic acetals and compounds resulting from opening of the cyclopropane ring. 

The reaction pattern includes the formation of PO, its consecutive isomerization to propanal, acetone and ally alcohol on acidic sites and combustion [43aj. Propanal and acrolein are also primary products. The formation of lower alkanes, alkenes, acetaldehyde and methanol results from cracking and oxidative C—C bond cleavage of propene and products. Additional side-reactions may occur in the gas phase, including radical-type oxidation of propene to acrolein, hexadiene and other byproducts. Alkyl dioxanes and alkyl dioxolanes may form via dimerization reactions of PO on acidic catalysts. Indeed, major by-products are heavy compounds that... 

The cracking of alkanes initially produces unsaturated, low molecular weight byproducts which can polymerise and, through coke formation, cause a rapid loss of catalyst activity. This problem can be minimised by using a zeolite with low cokeforming tendencies, e.g. ZSM-S, or by incorporation of a hydrogenation function. 

Alkanes and alkyl aromatic hydrocarbons can be oxidized when heated at rather high (usually above 1(X) °C) temperatures under oxygen. A long induction period can be reduced or eliminated if a donor of free radicals is present. The formation of oxygen-containing products from hydrocarbons and molecular oxygen is always thermodynamically allowed due to the high exothermicity of oxidation reactions. However, this same fact makes these processes usually unselective. The main problem is to prevent various parallel and consecutive oxidation reactions to produce numerous byproducts. Destmction of the carbon... 

Allylboration with 9-BBN derivatives (see B-Allyl-9-borabi-cyclo[33.1]nonane) is an efficient process, resulting in the smooth formation of homoallyUc alcohols (eq Alkynylbo-ranes also undergo 1,2-addition to both aldehydes and ketones. As with other reactions producing B-alkoxy-9-BBN byproducts, the conversion of these to alcohols with Ethanolamine also results in the formation of an alkane-insoluble 9-BBN complex which is conveniently removed, thereby greatly simplifying the workup procedure. 

For autothermal reforming of higher hydrocarbons, the main hydrocarbon byproduct usually observed is methane. The formation of light alkenes is favoured over alkanes in the case of incomplete conversion towards carbon oxides and methane [10, 72, 73]. 

Generally, the Fischer—Tropsch process is operated in the temperature range of 150—300°C to avoid high methane byproduct formation. Increased pressure leads to higher conversion rates and also favors formation of desired long-chain alkanes. Typical pressures are in the range of one to several tens of atmospheres. The FT hydrogenation reaction is catalyzed mainly by Fe and Co catalysts, while the size and... 

---