Diamond hydrocarbons

If there is no symmetry in the staggered conformation of a linear alkane, then the numbers of conformers increase by 3 for each additional carbon atom, because a terminal carbon has three possible staggered conformations. When symmetry elements are present, the numbers of conformers are lower. " Thus, -butane has three conformers, namely, the achiral trans, and the two gauche enantiomers, as seen in Figure 1. Diamond hydrocarbons have dualist graphs that are hydrogen-depleted alkane rotamers as mentioned further below.° ... 

The grid coordinates for the ten carbon atoms of adamantane, with the same conventions as those in Figure 1, are presented in Figure 2 (see also Ref. 31 for a graph-theoretical enumeration of isomers of diamond hydrocarbons in terms of their symmetries). 

A.T. Balaban and P.v.R. Schleyer, "Systematic Classification and Nomendature of Diamond Hydrocarbons. I. Graph-Theoretical Enumeration of Polymantanes, Tetrahedron 84 (1978), 3599-609. 

A. T. Balaban and P. v. R. Schleyer, Systematic classification and nomenclature of diamond hydrocarbons. I. Graph-theoretical enumeration of polymantanes. Tetrahedron 34 (1978) 3599-3609. 

Isomers of diamond hydrocarbons (polymantanes) have been enumerated using graph-theoretical methods. Staggered rotamers (conformers) of linear and branched alkanes may also be enumerated. Interestingly, the numbers of isomers of benzenoids, polymantanes, and staggered n-alkane conformers are related with some restrictions. ... 

Interest in the synthesis of diamond [7782-40-3] was first stimulated by Lavoisier s discovery that diamond was simply carbon it was also observed that diamond, when heated at 1500—2000°C, converted into graphite [7782-42-5]. In 1880, the British scientist Haimay reported (1) that he made diamond from hydrocarbons, bone oil, and lithium, but no one has been able to repeat this feat (2). About the same time, Moissan beheved (3) that he made diamond from hot molten mixtures of iron and carbon, but his experiments could not be repeated (4,5). 

If the polymer is completely cross-linked (/= 1) then the modulus (Ej) is known it is that of diamond, 10 GPa. If it has no covalent bonds at all, then the modulus (E2) is that of a simple hydrocarbon like paraffin wax, and that, too, is known it is 1 GPa. 

In a class of reahstic lattice models, hydrocarbon chains are placed on a diamond lattice in order to imitate the zigzag structure of the carbon backbones and the trans and gauche bonds. Such models have been used early on to study micelle structures [104], monolayers [105], and bilayers [106]. Levine and coworkers have introduced an even more sophisticated model, which allows one to consider unsaturated C=C bonds and stiffer molecules such as cholesterol a monomer occupies several lattice sites on a cubic lattice, the saturated bonds between monomers are taken from a given set of allowed bonds with length /5, and torsional potentials are introduced to distinguish between trans and "gauche conformations [107,108]. 

A basic reaction in the CVD of diamond is based on the decomposition of a hydrocarbon, such as methane, as follows ... 

Deposition Precursors. Diamond has been deposited from a large variety of precursors which include, besides methane, aliphatic and aromatic hydrocarbons, alcohols, ketones, and solid polymers such as polyethylene, polypropylene, and polystyrene, and halogens. 

Like diamond, DLC can be obtained by CVD by plasma action in a hydrocarbon atmosphere. Its deposition process differs from that of diamond in as much as the activation is not so much chemical (i.e., the use of hydrogen atoms) but physical. This physical activation is usually obtained by colliding accelerated ions produced by a high-frequency discharge. 

Richter, F., et al., Preparation and Properties of Amorphous Carbon and Hydrocarbon Films, in Applications of Diamond Films and Related Materials (Y. Tzeng, et al., eds.), Elsevier Science Publishers, pp. 819-826 (1991)... 

It has been found from MD simulations that friction of SAMs on diamond decreases with the increasing chain length of hydrocarbon molecules, but it remains relatively constant when the number of carbon atoms in the molecule chain exceeds a certain threshold [44], which confirmed the experimental observations. In simulations of sliding friction of L-B films, Glosli and McClelland [45] identified two different mechanisms of energy dissipation, namely, the viscous mechanism, similar to that in viscous liquid under shear, and the plucking mechanism related to the system instability that transfers the mechanical energy into heat, similar to that proposed in the Tomlinson model (see Chapter 9). On the basis of a series work of simulations performed in the similar... 

Diamondoids, when in the solid state, melt at much higher temperatures than other hydrocarbon molecules with the same number of carbon atoms in their structures. Since they also possess low strain energy, they are more stable and stiff, resembling diamond in a broad sense. They contain dense, three-dimensional networks of covalent bonds, formed chiefly from first and second row atoms with a valence of three or more. Many of the diamondoids possess structures rich in tetrahedrally coordinated carbon. They are materials with superior strength-to-weight ratio. 

Later, the name diamondoids was chosen for all the higher cage hydrocarbon compounds of this series because they have the same structure as the diamond lattice highly symmetrical and strain-free so that their carbon atom structure can be superimposed on a diamond lattice, as shown in Fig. 5 for adamantane, diamantane, and triamantane. These compounds are also known as adamanto-logs and polymantanes. 

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