Methanol homologation

There are two possible pathways to homologate methanol with carbon dioxide the CO2 insertion path and CO insertion path (Scheme 2). As for the former, Fukuoka et al. reported that the cobalt-ruthenium or nickel bimetallic complex catalyzed acetic acid formation from methyl iodide, carbon dioxide and hydrogen, in which carbon dioxide inserted into the carbon-metal bond to form acetate complex [7]. However, the contribution of this path is rather small because no acetic acid or its derivatives are detected in this reaction. Besides, the time course... 

Esters of the homologous acids are prepared by adding silver oxide in portions rather than in one lot to a hot solution or suspension of the diazo ketone in an anhydrous alcohol (methyl, ethyl or n-propyl alcohol) methanol is generally used and the silver oxide is reduced to metallic silver, which usually deposits as a mirror on the sides of the flask. The production of the ester may frequently be carried out in a homogeneous medium by treating a solution of the diazo ketone in the alcohol with a solution of silver benzoate in triethylamlne. 

Chem Systems Inc. proposed a process in which ben2yl alcohol obtained by an undisclosed direct oxidation of toluene is homologated with synthesis gas to yield 2-phen5iethyl alcohol, which is then readily dehydrated to styrene (57). This process eliminates the intermediate formation of methanol from synthesis gas but does require the independent production of ben2yl alcohol. 

Nelson and Scliut investigated the reaction of 5a-cholestanone (lb) with diazomethane in a search for a direct, one-step preparation of A-homo ketones. Using a large excess of diazomethane generated in situ from A-methyl-nitrosourea with potassium hydroxide in ether-methanol at 0°, 5a-cholestanone (lb) is converted into the 7-membered ring homolog (3b) as the predominant product. Both theoretically possible A-homo ketones can be expected with an unsymmetrically-substituted cyclohexanone such as 5a-cholestanone (lb). 

PerD32 Perry, D. The number of structural isomers of certain homologs of methane and methanol. J. Amer. Chem. Soc. 54 (1932) 2918-2920. 

Figure 2. Photoreduction of 2,3,7,8-tetrachlorodi-benzo- -dioxin (I) (2 mg/liter in methanol) as compared with that of the 2,3,7-trichloro-homolog (II) (20), 1971 by AAAS...

Detectability may be a significant problem with homologous series of unsaturated compounds, particularly //-alkanes. For these compounds, refractive index detection or evaporative light-scattering, both of which are described elsewhere in the book, may be of use. Indirect photometry is a useful detection scheme for compounds that do not absorb in the UV. Acetone, methylethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, and acetophenone are added to an acetonitrile/water mobile phase, generating a negative vacancy peak when the nonchro-mophoric analyte emerges and a positive peak if the ketone is adsorbed and displaced.70 Dodecyl, tetradecyl, cetyl, and stearyl alcohols also have been derivatized with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole and the derivatives separated on Zorbax ODS in a mobile phase of methanol and 2-propanol.71... 

Paracoccus denitrificans, a facultatively methylotrophic bacterium, is able to grow and accumulate PHAs on methanol. Recombinant P. denitrificans strains with increased expression levels of all PHA synthetic enzymes were investigated for the enhanced production of PHA. The PHA content and PHA accumulation rate of recombinant P. denitrificans with homologous overexpression of PHA synthase were 2 and 2.7 times higher, respectively, than those of the wild strain, suggesting that the step of PHA synthase was limited in PHA biosynthesis [111]. 

The formation of the a-methyl derivative is extremely surprising. We can propose a reasonable mechanism based on Wender s proposed mechanism for cobalt catalyzed CO homologation of methanol (5). 

Where acetic is the starting acid (eq. 1), homologation selectively yields the corresponding C3+ aliphatic carboxylic acids. Since acetic acid is itself a "syngas" chemical derived from methanol via carbonylation (2,3), this means the higher MW carboxylic acids generated by this technique could also be built exclusively from C0/H2 and would thereby be in-depent of any petroleum-derived coreactant. 

Wender and coworkers conclude that cobalt-catalyzed benzyl alcohol homologation involves the intermediate formation of car-bonium ions (8). However, since the methyl cation (CH3+) is unstable and difficult to form (9), it is more likely that methanol homologation to ethanol proceeds via nucleophilic attack on a protonated methyl alcohol molecule. Protonated dimethyl ether and methyl acetate forms have been invoked also by Braca (10), along with the subsequent formation of methyl-ruthenium moieties, to describe ruthenium catalyzed homologation to ethyl acetate. 

Reduction of C02 past formic acid generates formaldehyde, methanol or methane (Eqs. (16-18)), and ethanol can be produced by homologation of the methanol. The liberation of water makes these reactions thermodynamically favorable but economically less favorable. The reductions typically require much higher temperatures than does the reduction to formic acid, and consequently few homogeneous catalysts are both kinetically capable and able to withstand the operating conditions. 

Ethanol production by homologation of methanol can be achieved by hydrogenation of C02 (Eq. (20)) [116], Sasaki s group showed that both Ru and Co car-... 

Iron-catalyzed carbonylations, 34 124-125 Fe(CO)5/amine catalysts, 34 124 homologation of methanol, 34 124 proposed mechanism for, 34 125 Iron complexes... 

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