N-Docosane

Kern and Findenegg measured the adsorption of n-docosane (C22H46) in heptane solution to graphite [403], They used a porous graphite with a specific surface area of 68 m2g 1 as determined from BET adsorption isotherms with N2. Tmax, which is assumed to correspond to monolayer coverage, is found to be 88.9 /.xmol/g. Can you conclude something about the structure of the adsorbed molecules What is the area occupied by one molecule compared to its size ... 

Results of detailed GC-MS analysis of these two fractions are reported in Table 17.2 (volatile oil column and waxes column). Anise waxes were formed mainly by n-pentacosane (35.7%), n-heneicosane (25.8%), n-tricosane (10.3%), n-docosane (9.0%) and n-tetracosane (6.2%). Volatile oil contained 94.2% of anethole (cis and trnns). In the oil, estragole (1.4%), limonene (1.7%), linalool (0.3%), two terpineol isomers (0.3%) and linalyl acetate (0.3%) were also present. Caryophyllene (0.5%) and trans-bergamotene (0.7%) were the main compounds among sesquiterpenes. 

Fig. 5.13. Gas chromatogram of silylated phenolic acids. Peaks 1 = p-hydroxybenzoic 2 = vanillic 3 = syringic 4 = p-coumaric 5 = ferulic 6 = sinapic acid 7 = n-docosane. Conditions glass column, 9 ft. X 1/4 in. O.D., 3% UCW-98 on Chromosorb W HP<100-120 mesh) nitrogen flow-rate, 40 ml/ min temperature programme, 6°C/min from 100°C. (Reproduced from J. Chromatogr., 71 (1972) 149, by courtesy of H. Morita.)...

Flfure 2.28. Adsorption of long-chain alkanes from n-heptane on various grades of graphite, (a, left). Enthalpy isotherms for n-docosane (n-CjjH g) (a, right), correlation with the enthalpy of adsorption for a reference sample (b) adsorption Isotherms for four alkanes on Vulcan 3G. (Redrawn from H.E. Kem, G.H. Findenegg, J. Colloid Interface Set 75 (1980) 346.)... 

The good definition of these systems implies that the models of sec. 2.4 apply. Kern and Flndenegg ) fitted the experimental results for the adsorption of n-docosane from n-heptane on Vulcan 3G graphite at 25, 35 and 45°C with 12.4.34b] assuming 0 and r = 2.67. A good fit was obtained with a lateral Interaction parameter 2° of 1.16, 1.10 and 0.91 and equilibrium constants of 13.9, 10.6 and 8.2 for the three temperatures, respectively. The standard enthalpy of displacement of r moles of n-heptane by 1 mole of n-docosane was calculated from the temperature dependence of K. The value of -54.4 kJ mole obtained compared very well with the calorimetric result at monolayer coverage, -58.8 kJ mole L... 

Figure 2.29. Adsorption of n-docosane (n-C22H4g) from heptane on graphite (Vulcan 3G). Influence of temjjerature. The drawn curves represent a fit by Eq. (2.4.34b. (max) Is the monolayer capacity of n-docosane (= 88.86 pmol g"M (source as fig. 2.28).

Fall, D. J., and K. D. Luks. 1984. Phase equilibria behavior of the systems carbon dioxide + n-dotriacontane and carbon dioxide + n-docosane. J. Chem. Eng. Data 29 413. 

Concentration levels (n = repetitions) n-Pentadecane n-Docosane n-Hexacosane n- Tetradecanoic acid methylester n- Pentadecanoic acid methylester n- Hexadecanoic acid methylester 2,2,4,4,6,8,8-Hepta- methylnonane... 

Figure 3.12. The Raman spectrum of n-docosane (file RAMAN ALKANC22) with annotations.

Reports are used to display numerical or text information, typically the result of an evaluation or the parameters associated with a spectrum, hiformation of this type is stored in report blocks double-clicking on a report block (exception peak tables) will automatically open a report window. A blank report window can be opened from the Window menu (see Chapter 9). As an example, the report of the peak picking data for the Raman spectrum of n-docosane is shown in Fig. 3.17. 

Figure 11.7. The Curve Fit setup window after fit, displaying the result for the Raman spectrum of n-docosane (file RAMAN ALKAN22) in the C-H stretching region between 2760 and 3080 cm . ...

Figure 11.16. Peak picking for the Raman spectrum of n-docosane in the spectral range 800-1600 cm using the parameter values Peak < [abs] 0.1 and Peak > [abs] 0.06.

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