Branched alkanes from alcohols

Waxes mainly function as protective coatings, such as those found on leaf cuticles. They are mixtures of many constituents with high melting points, important members being esters of fatty acids with straight-chain saturated alcohols (fatty alcohols). The fatty acids and alcohols in these wax esters have similar chain lengths, mainly in the range C24 to C28. They have predominantly an even number of carbon atoms because the alcohols are biosynthesized from fatty acids by enzymatic reduction (Eqn 2.7). Lesser amounts of ketones, branched alkanes and aldehydes are present. 

The smoke point is another measure of the tendency of a fuel to produce smoke and this quantity, like SEA, is related to the chemical composition and structure of the fuel. The smoke point is defined as the minimum fuel mass flow rate at which smoke first escapes from the tip of a laminar diffusion flame (see Fig. 2), ie, the residence time of the smoke in the combustion zone becomes too short to effect complete oxidation. The results of the smoke point test are qualitatively similar to the SEA data in Table 15 with respect to chemical structure and smokeforming tendency. In particular, it is found that the smoke-forming tendency, as determined by smoke point measurements, is lowest for oxygenated fuels (alcohols, aldehydes, esters, ethers) and increases through the series alkanes, branched alkanes, alkenes, and aromatics. 

Fig. 7.4. (a) The melting enthalpies of linear alkanes compared with those of the corresponding 1-olefins and branched alkanes as a function of the number of carbon atoms in the molecule. Data from ref. [5]. (b) The same comparison for linear alkanes and the corresponding ketones, carboxylic acids, and alcohols. Data from ref. [5]. 

Today, distillation is a key to production of most commodity chemicals. It is used to make gasoline from crude oil. It is basic to the four most important separations of organics aliphatic from aromatic hydrocarbons, linear from branched hydrocarbons, olefins from alkanes, and alcohols from water. One essay on choosing separation processes starts with the question Why not distillation After then discussing over fifty other processes, it repeats, Are you sure you do not want to use distillation ... 

The complex 8, formed by the addition of 2-propenylmagnesium chloride to 7, adds to aromatic aldehydes, 1-alkanals, a-branched and unbranched alkanals uniformly from the 7 c-face leading to hoinoallylic alcohols with 88-94% ee35 (Method A). After hydrolytic workup, both components can be recycled. Allyl complexes 10, generated from 9, prefer 67-attack and lead to the ent-homoallylic alcohols with excellent enantioselectivity36 (Method B) (Table 8). 

The interdigital secretion of the red hartebeest, A. b. caama, consists of fewer compound classes. It contains a few alkanes and short-chain, branched alcohols, fatty acids, including a few of the higher fatty acids up to octadecanoic acid, an epoxide and the cyclic ethers, rans-(2 ,5.R)-furanoid linalool oxide 23, as-(2JR,5S)-furanoid linalool oxide 24 and ds-(2S,5i )-furanoid linalool oxide 25 (Fig. 5) in a ratio of 2.5 1 1.5 respectively [138]. From the point of view that many of the constituents of the interdigital secretion of this animal are probably of microbial origin, it is interesting that cis- and trans- furanoid linalool oxides have also been found in castoreum [77]. 

The composition of lipids from the silk and cuticule has been reviewed by Schulz (1997a, 1999). These lipids consist primarily of alkanes, as found in other arthropods, with 2-methylalkanes with an even number of carbon atoms in the chain being most abundant, with lesser amounts of alcohols, acids, aldehydes, and wax esters. Recently, a thorough analysis of the silk lipids of N. clavipes (Schulz, 2001) revealed a unique class of lipids from spider silk and cuticle, consisting of straight-chain and branched methyl ethers (1-methoxyalkanes, Fig. 4.4) with chain lengths between 25 and 45 carbon atoms. 

While subjecting two other PQ lots of these components to GC/MS analysis, the polycarbonate formulations were found to be very different from the original. Figure 10-6 shows a second PQ run and Figure 10-7 shows a third PQ run. The second and third PQ lots were found to contain many compounds not found in the original, including phthalates, alkanes, branched chain hydrocarbons, and alcohols. The third run also contained fatty acids. This level of inconsistency led to a production hold on this device and subsequent investigation. 

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