Decane isomers

In the alkane series, as the number of carbon atoms increases, the number of structural isomers increases rapidly. For example, butane, C4H10, has two isomers decane, C10H22, has 75 isomers and the alkane C30H62 has over 400 million, or 4 X 10, possible isomers Obviously, most of these isomers do not exist in nature nor have they been synthesized. Nevertheless, the numbers help to explain why carbon is found in so many more compounds than any other element. 

Trimethylbicyclo[3.1.1]hept-2-ene optical isomer> Decane. ... 

FIGURE 1.10 Two isomers of decahydronaphthalene, or bicyclo[4.4.0]decane. (a) Trans isomer b) cis isomer. 

The decalin (bicyclo[4.4.0]decane) ring system provides another important system for study of conformational effects in cyclohexane rings. Equilibration of the cis and trans isomers reveals that the trans isomer is favored by about 2.8 kcal/mol. Note that this represents a change in configuration, not conformation. The energy difference can be analyzed by noting that the cis isomer has three more gauche butane interactions that are... 

The occurrence of syn elimination in 5-decyl systems has been demonstrated with the use of diastereomeric deuterium-labeled substrates. Stereospecifically labeled 5-substituted decane derivatives were prepared and subjected to appropriate elimination conditions. By comparison of the amount of deuterium in the E and Z isomers of the product, it was... 

MonofluoToalkanes and vicinal difluoroalkanes are dehydrofluonnated if strong enough bases are applied [10 12] In 5-fluorononane and fluorocyclodo-decane, elimination by means of sodium methoxide in methanol gives cis- and trans allcenes in respective yields of 8 and 21% and in ratios of 1 2 2 2 4, however, the bulky lithium diisopropyl amide m tetrahydrofuran produces trdns-isomers almost exclusively The strength of the base does not have much effect on the rate of elimination, but the lithium cation causes considerable acceleration [10] (equation 10)... 

The HLB numbers decrease with increasing chain length, e.g., from 13.25 for sodium decane 1-sulfonate to 9.45 for the C18 homolog [72]. Typical HLB numbers for positional isomers range from 12.3 for sodium dodecane 1-sulfonate to 13.2 for the more hydrophilic 6 isomer [73]. The HLB numbers of alkanesulfonates are less influenced by the isomeric position of the functional group and by substituents than the cM values [68]. HLB numbers can be correlated with partition coefficients for the distribution of a surfactant between the aqueous and oily phases, which emphasizes that the partition coefficient is dependent on the carbon number [68]. 

As the number of carbon atoms in the alkane increases, so does the number of possible stractural isomers. Thousands of different alkanes exist, because there are no limits on the length of the carbon chain. Regardless of the number of the chain length, alkanes have tetrahedral geometry around all of their carbon atoms. The structure of decane, Cio H22, shown in Figure 9-15. illustrates this feature. Notice that the carbon backbone of decane has a zigzag pattern because of the 109.5° bond angles that characterize the tetrahedron. 

A mixture of decalin (bicyclo[4.4.0]decane) isomers (Fluka, >98%) with a cis-to-trans ratio of 2-to-3 was used as a starting material. The experiments were performed in an electrically heated 300-mL stainless steel autoclave (Parr Industries) at 523 K and 2 MPa. The stirring rate and the starting material-to-catalyst ratio were kept at constant values equal to 1500 rpm and 22 (w/w), respectively. The screened catalysts were crushed and the fraction bellow 63 pm was used in the experiments to suppress internal diffusion. 

Intramolecular cyclopropanation of 4-aryl-1 -diazo-2-butanones 240 allows construction of the bicyclo[5.3.0]decane framework 12). In a reaction sequence analogous to that described above for the intermolecular ketocarbenoid reaction, bicyclo-[5.3.0]deca-l,3,5-trien-8-ones 241 are formed. They rearrange to the conjugated isomers 242 at the high temperatures needed if the reaction is catalyzed by copper 2311 or CuCl 232), but can be isolated in excellent yield from the Rh2(OAc)4-promoted reaction which occurs at lower temperature 233... 

For n-decane isomerization, when a good balance between the metal phase and the acidic phase of the catalysts is reached, the isomerization and cracking yield curves of the catalysts are a unique function of the conversion, meaning that these yields do not depends on the porosity nor the acidity of large pore materials. Formation of the most bulky isomers, such as 4-propylheptane and 3-ethyl-3-methylheptane was favored in mesoporous solids (figure 1). Criteria based on the formation of these particular isomers are linked with mesoporosity and could be useful to discriminate between zeolites catalysts with and without mesopores. 

Figure 1 (a) Approach to the Thermodynamic Equilibrium (ATE) of the 4-propylheptane (4PC7) distribution in the n-decane (nCIO) monobranched isomers, (b) distribution of the 3-ethyl-4-methylheptane (3E4MC7) and 3-ethyl-3-methylheptane (3E3MC7) in the nCIO dibranched isomers as a function of the nCio conversion. 

Synonym bicyclo[4.4.0]decane, naphthalane, naphthane Chemical Name decahydronaphthalene (mixed isomers)... 

The bi-functional conversion of 2,2,4-trimethylpentane over Pt/DAY has been recently reported by Jacobs et al. (104). It was compared to the corresponding conversion over Pt/H-ZSM-5 and Pt/H-ZSM-11. All three zeolites had the same chemical composition. The authors found that 2,2,4-trime-thylpentane underwent 3-scission over Pt/DAY, while the formation of feed isomers was favored over the other two catalysts. The differences in reaction products were related to differences in the pore geometry of the zeolites. A similar study was carried out with n-decane. 

Example The El mass spectmm of -decane is typical for this class of hydrocarbons (Fig. 6.18a). Branching of the aliphatic chain supports cleavage of the bonds adjacent to the branching point, because then secondary or tertiary carbenium ions and/or alkyl radicals are obtained (Fig. 6.18b,c). This allows for the identification of isomers to a certain degree. Unfortunately, hydrocarbon molecular ions may undergo skeletal rearrangements prior to dissociations, thereby obscuring structural information. 

Beckey, H.D. Comparison of Field lorrrzation and Chemical Ionization Mass Spectra of Decane Isomers. J. Am. Chem. Soc. 1966,88,5333-5335. 

Figure 13.30 The Gibbs free energy of formation (CBMC calculations) for branched decane isomers relative to linear decane over various framework types [70],...

Constitutional isomerism becomes more complex as the size of the hydrocarbon molecule is increased. For example, there are three constitutional isomers of pentane, C5H12. The number of constimtional isomers increases quite rapidly with an increasing number of carbon atoms. Thus, there are five constimtional isomers of hexane, CeH, nine isomers of heptane, C7H16, 75 isomers of decane, C10H22, and 366,319 isomers of eicosane, C20H42. You can begin to understand why it is possible to make so many different molecules based on carbon. 

Tetranitrodispiro[3.1.3.1 ]decane (24) was obtained as a mixture of isomers by treating the oxime (22) with chlorine in methylene chloride, followed by oxidation with hypochlorite and rednctive dehalogenation of the resnlting gm-chloronitro intermediate (23) with zinc... 

There are four possible structures for such a product (LXXVa-d). The thymine ice-dimer was proven to have the cis-syn configuration (LXXVa) by transformation into an isomer shown to be a derivative of 3,5,9-triazatri-cyclo[5,3,0,0 ] decane of cis-cis-cis configuration (LXXVI) [535-536]. 

Empirically, y-gauche effects are extremely useful in stereochemical analysis. For example, the cis- and trans-fusion of six-membered rings can be easily differentiated, since, in contrast to the trans-isomer of bicyclo[4.4.0]decane, there are gauche-butane fragments in the m-isomer (emphasized bonds) causing upheld signal shifts of the carbons involved (numbers refer to I3C chemical shifts in ppm)49-52. 

Direct irradiation of the (CH)10 hydrocarbon triquinacene (26) in pentane solution gave five different (CH)10 isomers along with some naphthaline and azulene. The two major products were pentacyclo[4.4.0.02 4.03 i0.05,9]dec-7-ene (27), arising from an intramolecular [2 + 2] cycloaddition, and hexacyclo[4.4.0.02,4.03,10.05,8.07 9]decane ( barettane , 28), which is formed via a di-n-methane rearrangement (see Section l.A.2.2.) followed by an intramolecular [2 + 2] cycloaddition,50... 

Obviously, the system of adding a prefix to the name of the compound to denote the structural configuration will become unwieldy as the number of different structural configurations increases. Consider decane, which has 75 isomers. A more systematic nomenclature is desirable. 

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