Methyl-branched alcohols

As the decade ended, a new monohydric alcohol phthalate based on mixed C7-C9-C11 straight chain and single methyl branched alcohols was introduced by Monsanto Co. The alcohols are produced by the oxo process from straight chain alpha olefins. The phthalate competed directly with 610P, especially in the automotive upholstery market where it gained rapid acceptance. 

Very-long-chain methyl-branched alcohols (C38 to >C44) and their esters with short-chain acids (C2 to C5) represent a novel class of long-chain internal lipids which mainly occur during insect metamorphosis (Nelson, 1993). The very-long-chain methyl-branched alcohols were first characterized in the internal lipids of developing pupae (pharate adults)... 

Guo, L., Nelson, D.R., Fatland, C.L. and Blomquist, G. J. (1992). Very long-chain methyl-branched alcohols and their acetate esters in pupae of the southern armyworm, Spodoptera eridania Identification and biosynthesis. Insect Biochem. Mol. Biol., 22, 277-283. 

Nelson, D. R. and Fatland, C. F. (1997). Very long-chain methyl-branched alcohols and their acetate esters in the internal lipids of lepidopteran pupae Cochylis hospes, Diatraea grandiosella, Homoeosoma electellum, Heliothis virescens and Helicoverpa zea. Comp. Biochem. Physiol., 116B, 243-256. 

The oxo-process is based on a hydroformylation reaction and uses an olefin, hydrogen, and carbon monoxide as raw materials and the transition metal hydrocarbonyl [HM(CO) ] as the catalyst cobalt is the most commonly used metal today. The resulting aldehydes are further converted to corresponding alcohols with special hydrogenation catalysts (based on nickel, copper, chromite, etc.). The derived oxo-alcohols are odd numbered and with some side branching. Some catalysts are used to limit the degree of 2-methyl branched alcohols to 25%. 

Further, the results obtained enabled the correlation of the composition of the volatile fraction of Parmigiano-Reggiano cheese with sensory attributes [42], This subsequent investigation evidences the significance of the flavor in deflning the quality of a food product and, in addition, the contribution of the different volatile compound classes or of the individual substances to the sensory attributes. For example, esters, particularly methyl butanoate, ethyl hexanoate, and isobutyl acetate, are found to be positively related to the fragrant and fruity notes of aged cheese. Short-chain methyl-branched alcohols, secondary products of proteolysis, contribute to a positive maturation component of the aroma, in opposition to the sharp stimuli of free fatty acids (Fig. 6). 

Based on mechanistic and kinetic studies of the higher alcohol synthesis from synthesis gas, it has been shown that the ethanol in the mixed-oxygenate product is produced from intermediates derived from methanol, not CO [103,109]. Kinetic models of the synthesis have been developed that are able to explain the observed product distribution [110,111]. These models are based on a detailed understanding of the reaction mechanism in which two types of reactions dominate aldol condensation, which yields primarily 2-methyl branched alcohols, and Cl coupling reactions, which yield linear alcohols [106,111]. Estimates of the parameters of the kinetic models that quantitatively describe the oxygenate product distributions suggest that the rate of ethanol formation is about an order of magnitude lower than the rate of production of branched alcohols [111,112]. On the Cs/Cu/Zn catalysts, this results in a minimum in yield of ethanol compared with the yields of methanol, 1-propanol, and 2-methyl-1 propanol. Althou methanol conversion to ethanol has been confirmed as part of the hi er alcohol synthesis from synthesis gas, this synthesis does not offer a plausible route for the conversion of methanol to ethanol. Under the reaction conditions methanol rapidly decomposes, even at a pressme of 0.1 MPa [113], to yield an equilibrium mix of methanol, CO, and H2. Furthermore, as shown by the data in T able 7, the yield of ethanol remains low even with methanol in the feed. 

Pupae of a number of lepidopterans make very long-chain methyl-branched alcohols and acetates, like those shown for the southern armyworm Spodoptera eridania in Figure 3.18. From studies with... 

Historically, isobutyl alcohol was an unwanted by-product of the propylene Oxo reaction. Indeed, isobutyraldehyde the precursor of isobutyl alcohol was occasionally burned for fuel. However, more recentiy isobutyl alcohol has replaced -butyl alcohol in some appHcations where the branched alcohol appears to have preferred properties and stmcture. However, suppHes of isobutyl alcohol have declined relative to overall C-4 alcohols, especially in Europe, with the conversion of many Oxo plants to rhodium based processes which give higher normal to isobutyraldehyde isomer ratios. Further the supply of isobutyl alcohol at any given time can fluctuate greatly, since it is the lowest valued derivative of isobutyraldehyde, after neopentyl glycol, methyl isoamyl ketone and certain condensation products (10). 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

A great portion of the formed 2-alkyl-branched alcohols, especially in the hydroformylation products of n-a-olefins, consists of the low-branched 2-methyl alcohols (Fig. 4). 

Leptogenys peuqueti W-PG Trail following Series of 14 related methyl-branched secondary alcohols acetates 136 137 [178]... 

Another route to a methyl-branched derivative makes use of reductive cleavage of spiro epoxides ( ). The realization of this process was tested in the monosaccharide series. Hittig olefination of was used to form the exocyclic methylene compound 48. This sugar contains an inherent allyl alcohol fragmenC the chiral C-4 alcohol function of which should be idealy suited to determine the chirality of the epoxide to be formed by the Sharpless method. With tert-butvl hydroperoxide, titanium tetraisopropoxide and (-)-tartrate (for a "like mode" process) no reaction occured. After a number of attempts, the Sharpless method was abandoned and extended back to the well-established m-chloroperoxybenzoic acid epoxida-tion. The (3 )-epoxide was obtained stereospecifically in excellent yield (83%rT and this could be readily reduced to give the D-ribo compound 50. The exclusive formation of 49 is unexpected and may be associated with a strong ster chemical induction by the chiral centers at C-1, C-4, and C-5. 

Except in the case of isobutyraldehyde, where the non-optimized poor yield may be due to the high volatility of the resulting product, the alcohols are formed in good yields. When the aldehyde is sterically hindered (entries 1-2), a-allylation is observed. Conversely, branched alcohols result from unhindered or aromatic aldehydes (entries 4 to 6). Starting from 3-methyl-2-butenal (entry 5), a fluorinated analog of Artemisia alcohol is formed in one step27. 

Surface lipids of plants. The thick cuticle (Fig. 1-6) that covers the outer surfaces of green plants consists largely of waxes and other lipids but also contains a complex polymeric matrix of cutin (stems and leaves) or suberin (roots and wound surfaces).135/135a Plant waxes commonly have C10 - C30 chains in both acid and alcohol components. Methyl branches are frequently present. A major function of the waxes is to inhibit evaporation of water and to protect the outer cell layer. In addition, the methyl branched components may inhibit enzymatic breakdown by microbes. Free fatty acids, free alcohols, aldehydes, ketones, 13-dike tones, and alkanes are also present in plant surface waxes. Chain lengths are usually C20 - C35.136 Hydrocarbon formation can occur in other parts of a plant as well as in the cuticle. Thus, normal heptane constitutes up to 98% of the volatile portion of the turpentine of Pin us jeffreyi.81... 

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