Cyclodecane

Some years ago, when PEF400 was new, it was applied to cyclodecane. Five conformations were selected. Three of them have been found in crystal structures Nos. 1, 2 and 4 in Table 10-3 No. 3 

Results of the use of three of the newly optimised sets are shown in Tables 10-3 and 10-4. Inspection of the valence and torsional 

The two conformers of symmetry. Nos. 2 and 4 of Table 10-3, have conformations like those found in the solid state 

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Molecular size smaller molecules move more quickly than larger ones as a result, C atoms in small molecules relax more slowly than those in large molecules. The C atoms in the more mobile cyclohexanes (T/ = 19-20 s) take longer than those in the more sluggish cyclodecane (f/ = 4 - 5 s)... 

The reaction temperature is important. At temperatures below 75° some sebacoin remains unreduced, while at temperatures above 80° considerable cyclodecane is formed. The submitters report that the reaction run at the reflux temperature gives cyclodecanone in 27% yield and cyclodecane in 32% yield. 

For efficient separation of cyclodecanone from cyclodecane, a 60-cm. column of the simple Podbielniak type may be used. Removal of sebacil cannot be accomplished readily by fractional distillation, since cyclodecanone and sebacil have virtually identical boiling points. 

Studies of cyclodecane derivatives by X-ray crystallographic methods have demonstrated that the boat-chair-boat conformation is adopted in the solid state. (Notice that boat is used here in a different sense than for cyclohexane.) As was indicated in Table 3.7 (p. 146), cyclodecane is significantly more strained than cyclohexane. Examination of the boat-chair-boat conformation reveals that the source of most of this strain is the close van der Waals contacts between two sets of three hydrogens on either side of the molecule. 

Fig. 3.7. Equivalent diamond-lattice conformations of cyClodecane (boat-chair-boat).

The spiro peroxide A, which is readily prepared from cyclohexanone and hydrogen peroxide, decomposes thermally to give substantial amounts of cyclodecane (B) and... 

Examine the structure of cyclodecane, a molecule which contains the same number of carbons as decalin, but only has one ring (a model of the most stable conformation is provided). Compare it to cis and trans decalin. Make a plastic model of cyclodecane. Is it flexible or locked What conformational properties of cyclodecane can be anticipated from the properties of decalins What properties cannot be anticipated How do you account for this ... 

Cyclobutanc, angle strain in. 115-116 conformation of. 115-116 molecular model of, 116 photochemical synthesis of, 1190 strain energy of, 114 torsional strain in, 115-116 Cyclodecane, strain energy of. 114 Cyclodecapentaene, molecular model of, 525, 540... 

Fig. 3. Symmetry elements and torsion angles of cyclohexane (chair conformation) and cyclodecane (stable BCB-conformation)...

In a similar way the potential constant method as described here allows the simultaneous vibrational analysis of systems which differ in other strain factors. Furthermore, conformations and enthalpies (and other properties see Section 6.5. for examples) may be calculated with the same force field. For instance, vibrational, conformational, and energetic properties of cyclopentane, cyclohexane and cyclodecane can be analysed simultaneously with a single common force field, despite the fact that these cycloalkanes involve different distributions of angle and torsional strain, and of nonbonded interactions 8, 17). This is not possible by means of conventional vibrational spectroscopic calculations. 

The simple cycloalkanes (CH2)n with n = 5 to 12 are the compounds most frequently studied by force field calculations (8, 9, 11, 12,17, 21). This preference results from their simple structure, from the abundant available experimental material (structural (46), thermo-chemical (47) and vibrational spectroscopic (27, 48, 49) data), and from the fact that, apart from bond length deformations, all other strain factors (angle deformations, unfavourable torsion angles, strongly repulsive nonbonded interactions) are important for the calculation of their properties. The cycloalkanes are thus good candidates for testing force fields. For a more detailed discussion we choose cyclodecane, a so-called medium-ring compound. 

The problem of the preferred conformation of cyclodecane has been extensively studied by Dunitz et al. (46). In the crystals of seven simple cyclodecane derivatives (mono- or 1,6-disubstituted cyclodecanes) the same conformation was found for the ten-membered ring (BCB-conformation, Fig. 9). It follows from this that the BCB-conformation is an energetically favourable conformation, possibly the most favourable one. Numerous force field calculations support this interpretation Of all calculated conformations BOB corresponded to the lowest potential energy minimum. Lately this picture has become more complicated, however. A recent force field calculation of Schleyer etal. (21) yielded for a conformation termed TCCC a potential energy lower by 0.6 kcal mole-1 than for BCB. (Fig. 9 T stands for twisted TCCC is a C2h-symmetric crown-conformation which can be derived from rrans-decalin by breaking the central CC-bond and keeping the symmetry.) A force field of... 

Fig. 9. Energetically favourable cyclodecane conformations with calculated angles (deg inner values) and torsion angles (53) (force field of Ermer and Lifson (19)). The conformations are further characterised by (from top) conformational symbol (11), symmetry, calculated relative potential energy (AV) and relative enthalpy (AH kcal mole-1 T = 298 K reference BCB AH = AV + AHvibr, see Section 3.3.). For BCB experimental angles and torsion angles (46) are also given (in parentheses)...

The most stable conformation of cyclodecane has a C-C-C bond angles of 117°. 

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