Diamantane

Diamantane [2292-79-7] M 188.3, m 234-235 . Purified by repeated crystn from MeOH or pentane. Also dissolved in CH2CI2, washed with 5% aq NaOH and water, and dried (MgS04). The soln was concentrated to a small volume, an equal weight of alumina was added, and the solvent evaporated. The residue was placed on... 

If 14 or more carbons are present, the product may be diamantane or a substituted diamantane. These reactions are successful because of the high thermodynamic stability of adamantane, diamantane, and similar diamond-like molecules. The most stable of a set of C H isomers (called the stabilomer) will be the end product if the reaction reaches equilibrium. Best yields are obtained by the use of sludge ... 

Figure 1, Molecular structures of adamantane, diamantane, and triamantane, the smaller diamondoids, with chemical formulas C10H16, C14H20, and CigH24, respectively.

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. 

These compounds are chemically and thermally stable and strain-free. These characteristics cause high melting points (m.p.) in comparison to other hydrocarbons. For instance, the m.p. of adamantane is estimated to be 269 °C, yet it sublimes easily, even at atmospheric pressure and room temperature. The melting point of diamantane is about 236.5 °C and the melting point of triamantane is estimated to be 221.5 °C. The available melting point data for diamondoids are reported in Table I. 

Figure 5. The relation between lattice diamond structure and (a) adamantane, (b) diamantane, and (c) triamantane structures.

Vapor Pressure Equations of Adamantane and Diamantane for Eiquid-Vapor and Solid-Vapor Phase Transitions... 

Diamantane (CAS No 2292-79-7) pentacyclo[7.3.1.1 -. 0 -. 0 ]tetrade-cane, also known as decahydro-3,5,l,7-[1.2.3.4]-butanetetraylnaphtalene, can exist in gas, liquid, and three different solid crystallme states. Higher diamondoids possess two or more solid crystalline states [5],... 

In Table III we also report the average of the available data for molar enthalpies, molar entropies, and molar heat capacities of adamantane and diamantane as measured and reported by various investigators [10, 19-30]. 

In Table IV we report the available enthalpies of formation, sublimation, and combustion of methyl-adamantanes, dimethyl-adamantane, trimethyl-adamantane, and tetramethyl-adamantane and compare them with the same properties of adamantane as measured by various investigators [29, 30]. Also reported in Table IV are the same properties for 1-methyI-diamantane, 3-methyI-diamantane, and 4-methyI-diamantane as compared with the diamantane data. 

A number of other thermodynamic properties of adamantane and diamantane in different phases are reported by Kabo et al. [5]. They include (1) standard molar thermodynamic functions for adamantane in the ideal gas state as calculated by statistical thermodynamics methods and (2) temperature dependence of the heat capacities of adamantane in the condensed state between 340 and 600 K as measured by a scanning calorimeter and reported here in Fig. 8. According to this figure, liquid adamantane converts to a solid plastic with simple cubic crystal structure upon freezing. After further cooling it moves into another solid state, an fee crystalline phase. 

Figure 7. Vapor-Uquid-soUds (plastic crystal 2, plastic crystal 2, crystal 3) phase diagram of diamantane. This diagram is based on the data of Table II. The shaded area between vapor and plastic crystal 2 and crystal 3 phase transitions is indicative of the error range of the available data.

AfJ phase transition Diamantane (solid I-solid III) 4.445 kJ/gmol 407.22 ... 

Note-. Solid adamantane possesses two crystalline phases and diamantane exists in three crystalline phases. 

Thermodynamic Properties of Methyl Derivatives of Adamantane and Diamantane." In this table the average of the values reported by various investigators are reported. 

The solubilities of adamantane and diamantane in supercritical (dense) methane, ethane, and carbon dioxide gases have been measured by a number of investigators [35-37] at a few temperatures with various pressures and solvent densities. These measurements are reported in Figs. 9-12. 

A graphical representation of diamantane solubility data [36] in various supercritical solvents (carbon dioxide and ethane at 333 K and methane at 353 K) is shown in Fig. 12. 

Figure 12. Effect of pressure on solubility (in units of mole fraction) of diamantane in dense (supercritical) gases at 333 K (for carbon dioxide and ethane) and at 353 K (for methane). Data from Ref. [35].

Naturally occurring adamantane is generally accompanied by small amounts of alkylated adamantane 2-methyl- 1-ethyl- and probably 1-methyl- 1,3-dimethyl- adamantane and others [3], Diamantane, triamantane, and their alkyl-substituted compounds are also present in certain petroleum crude oils. Their concentrations in cmde oils are generally lower than that of adamantane and its alkyl-substituted compounds. 

Adamantane and diamantane are usually the dominant diamondoids found in petroleum and natural gas pipeline deposits [74, 75]. This is because diamondoids are soluble in light hydrocarbons at high pressures and temperatures. Upon expansion of the petroleum fluid coming out of the underground reservoir and a drop in its temperature and pressure, diamondoids could deposit. 

Figure 15 Gas chromatogram of a gas condensate (NGL = natural gas liquid) sample [74]. The peak with retention time of 5.70 eluted between nCis and nCis is indicative of the probable existence of diamantane in the sample.

Figure 16. Gas chromatogram of a crude oil sample showing the possible existence of adamantane and diamantane in the sample.

Figure 17. Gas chromatogram of a diamondoid-rich gas condensate (NGL) sample showing clusters of peaks representing adamantanes, diamantanes, triamantanes, and tetramantanes. Taken from Ref. [11] with permission.

Diamantane-based polymers are synthesized to take advantage of their stiffness, chemical and thermal stability, high glass transition temperature, improved solubility in organic solvents, and retention of their physical properties at high temperatures. All these special properties result from their diamantane-based molecular structure [90]. Polyamides are high-temperature polymers with a broad range of applications in different scientific and industrial fields. However, their process is very difficult because of poor solubility and lack of adequate thermal stability retention [90]. Incorporation of 1,6- or... 

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