Cholesteryl nonanoate

The positional order of the molecules within the smectic layers disappears when the smectic B phase is heated to the smectic A phase. Likewise, the one-dimensional positional order of the smectic M phase is lost in the transition to the nematic phase. AH of the transitions given in this example are reversible upon heating and cooling they are therefore enantiotropic. When a given Hquid crystal phase can only be obtained by changing the temperature in one direction (ie, the mesophase occurs below the soHd to isotropic Hquid transition due to supercooling), then it is monotropic. An example of this is the smectic A phase of cholesteryl nonanoate [1182-66-7] (4), which occurs only if the chiral nematic phase is cooled (21). The transitions are aH reversible as long as crystals of the soHd phase do not form. 

The phase transitions of cholesteryl nonanoate have been studied with a new apparatus for thermal analytical microscopy. The enantiomer ratio of some chiral sulphoxides can be changed from racemic to a modest preference for one enantiomeric form by dissolution in a cholesteryl ester in its liquid-crystalline ( cholesteric ) state. 5,6-Epoxycholestan-3-yl p-nitrobenzoates exhibit liquid-crystal properties, but 5,6-diols and dibromides are inactive. ... 

For CD observation, pyrene-2-carboxylic acid methyl ester was dissolved into a cholesteric mixture of 55.5 mole percent of cholesteryl nonanoate and 44.5 mole percent of cholesteryl chloride, which exhibited a pitch band CD with plus sign... 

Cage effect measured by quenching of the escape radicals with CuCl2. Cholesteryl chloride/cholesteryl nonanoate, 35/65, w/w. 

Price, F. P. and Wendorff, J. H. Transitions in mesophase forming systems. Ill, Transformation kinetics and textural changes in cholesteryl nonanoate. J, Phys. Chem. 76, 276 (1972)... 

During the first week of this experiment, you will synthesize cholesteryl nonanoate, which is an ester derivative of cholesterol, and perform some simple characterizations to test your successful synthesis. Cholesteryl nonanoate (ChNon) is known to exhibit a chiral nematic, i.e., a cholesteric, liquid crystalline phase. 

The next step involves the addition of nonanoyl chloride and is also understood using the Lewis definition. The carbonyl (C = 0) group on nonanoyl chloride is very polar, yielding an electron-deficient carbon, which is then a Lewis acid. The negative cholesterol ion is an electron donor, or Lewis base, and reacts with the positive carbon center to form a new bond and release a chloride ion. This chloride ion is then neutralized by the pyridinium ion in another Lewis acid-base reaction to form pyridine hydrochloride. Pyridine hydrochloride is soluble in water, while the newly synthesized cholesteryl nonanoate is not. Addition of the reaction mixture to aqueous sulfuric acid causes only the desired product, cholesteryl nonanoate. 

To purify your product, recrystallize your collected solid from acetone. To accomplish this, transfer the solid to a 125-mL flask. Add a small amount (20 ruL to start) of acetone and a stir bar. Heat to fully dissolve the solid. Add small amounts of acetone, order 1 ruL at a time, as needed, to aid in the dissolution. When solid is dissolved, remove from heat. Cool with the aid of an ice bath. Crystals should form. If they do not, try scratching the inside of the flask with a glass rod. Or, boil off some solvent and recool. Remove these crystals by suction filtration just as you did to collect your impure product. Wash these crystals with a cold 5 ruL portion of acetone and allow them to dry on the filter paper. Transfer to a preweighed vial. Calculate yield of cholesteryl nonanoate from cholesterol and calculate the conversion of cholesterol to cholesteryl nonanoate. 

Using appropriate melting point apparatus, characterize the melting behavior of the purified solid. Cholesteryl nonanoate exhibits a chiral nematic, more commonly known as a cholesteric, liquid crystalline phase around 85°C and melts to the isotropic liquid around 93 C. The cholesteryl nonanoate first melts to form a smectic phase around 75°C and with further heating transforms to the cholesteric phase around 85°C. 

As mentioned above you will be studying mixtures of cholesteryl nonanoate and cholesteryl chloride rather than the pure materials. Mixtures are used for the convenience of working at temperatures closer to room temperature. To prepare a mixture of a given composition, use the mole fraction composition scale. A mole fraction of a component in a mixture is defined as the number of moles of that component in the mixture divided by the total number of moles of all components in the mixture. To actually prepare a mixture, add the desired amounts of each component to a screw cap vial. Mix the components physically with a spatula to make a reasonably uniform mixture of the solids. Place the vial in a sample oven whose temperature has been set to about 100°C and allow the solids to melt and mix. 

In the 1960s, there was already a forerunner of photochemically induced phase transition in LC (20). When mixtures of cholesteryl iodide and cholesteryl bromide with cholesteryl nonanoate were exposed to UV irradiation, the helical pitch of cholesteric LC changes as a result of photodecomposition of the halides. The reflected color shifts gradually to red with progression of photodecomposition. Pattern-wise imaging was demonstrated but the image was blurred within 15 min. since LC of small molecules is a viscous fluid. 

The temperature dependent, low resolution (10 MHz) NMR spin lattice relaxation times of liquid-crystalline cholesteryl butyrate and cholesteryl nonanoate were examined by Cutler(18). 

For instance, mechanistically important inductions of optical activity have been observed in products from unlmolecular transformations of achiral solutes when conducted in cholesteric phases. These transformations involve selection by solvent matrices between subtle intramolecular shape changes of the solutes. Thus, Nakazakl et al.(20) found that irradiation of phenyl - 2-(2-benzo-[c]phenanthryl)ethylene and I2 in the cholesteric phase of 3/2 (w/w) cholesteryl nonanoate/... 

The discovery of the liquid crystal state should be traced back to a story taking place one hundred years ago. Austria botanist F. Reinitzer observed a peculiar phenomenon in 1888 — under a microscope (Reinitzer, 1888), cholesteryl nonanoate melted into a cloudy liquid at 145.5 °C as the temperature rose to 178.5 °C, it suddenly became clear. When cooling down, the substance briefly appeared violet-blue just before becoming an... 

Fig. 4.1.5. Reflexion spectrum from a monodomain cholesteric film at normal incidence. Full curve experimental spectrum for a mixture of cholesteryl nonanoate, cholesteryl chloride and cholesteryl acetate in weight ratios 21 15 6 at 24 °C (intensity in arbitrary units). Broken curve spectrum computed from the exact theory for a film thickness of 21.0 ftm and pitch 0.4273 foa. (After Dreher...

Fig. 4.1.12. Experimental circular dichroism curves versus wavelength, (a) Pure cholesteryl nonanoate (CN), (6) CN+0.98 per cent by weight of PAA. Sample thickness in both cases 6.S foa. (After reference 28.)...

The first experiments demonstrating the effect were conducted on cholesteryl nonanoate in which was dissolved small quantities of PAA or n-p-methoxybenzylidene-/>-phenylazoaniline.< The temperature of the system was adjusted so that the reflexion band overlapped with the strongly linearly dichroic absorption band of the solute molecule. Under these circumstances, the circular dichroism exhibits the features predicted by theory (fig. 4.1.12). Similar measurements were reported subsequently by Aronishidze et (fig. 4.1.13). 

Fig. 5.5.3. Pitch versus temperature in cholesteryl nonanoate prior to the smectic A-cholesteric transition (74 °C) the crosses are values obtained from observations of the Grandjean-Cano walls and the circles from the wavelengths of maximum reflexion. (After Kassubek and Meier. >)...

Definition Ester of cholesterol and the fatty acids obtained from macadamia nut oil Uses Emollient in cosmetics Cholesteryl nonanoate CAS 1182-66-7 EINECS/ELINCS 214-658-3 Synonyms Cholest-5-ene-3p-yl nonanoate 5-Cholesten-3p-ol 3-nonanoate Cholesteryl pelargonate 3p-Hydroxy-5-cholestene 3-nonanoate o-Nonanoylcholesterol Definition Ester of cholesterol and nonanoic acid Empirical C36H62O2... 

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