《Wide thermal range, exclusive occurrence of technically significant chiral nematic phase: synthesis and mesomorphism of cholesterol-based non-symmetric dimers》 was published in Bulletin of Materials Science in 2020. These research results belong to Nayak, Rashmi Ashwathama; Bhat, Sachin A.; Rao, D. S. Shankar; Yelamaggad, C. V.. Quality Control of 4-Bromobutanoic acid The article mentions the following:
Fifteen new non-sym. chiral dimers belonging to three different series have been synthesized and evaluated for their mesomorphic properties. They were formed by interlinking cholesterol with salicylaldimine (SAN) cores (with reverse imine groups) via an ω-oxyalkanoyloxy spacer. Within a series, the length of the terminal n-alkoxy tails had been varied for a fixed even-parity spacer. Three even-parity spacers such as 4-oxybutanoyloxy, 6-oxyhexanoyloxy and 8-oxyoctanoyloxy have been used to join two cores, whereas the terminal tails such as n-butyloxy, n-hexyloxy, n-octyloxy, n-decyloxy and n-dodecyloxy chains have been attached to the SAN core. Microscopic and calorimetric exptl. results show that all the dimers behave identically exhibiting the chiral nematic (N*) phase solely, which was authenticated by powder X-ray diffraction studies carried out on some selected samples. In the vast majority of the cases,the phase was thermodynamically stable, and while cooling, it exists over a wide thermal range covering room temperature(RT)due to supercooling. Finding was notable given the fact that the N* phase possesses technol. significant optical properties. At RT, the N* phase displayed one of the iridescent colors characteristically caused by interference and diffraction of the reflected and scattered light. A comparative study reveals that the lengths of both the terminal chain and central spacer influence the clearing temperature of the dimers, and also the temperature range of the N* phase. The selective reflection measurements revealed that the pitch of the N* phase was either temperature sensitive or temperature insensitive. Temperature-dependent CD (CD) spectra were recorded for the planar texture of the N* phase formed by a dimer, as a representative case. The presence of an intense neg. CD band suggests the left-handed screw sense of the N* phase helix. In the experiment, the researchers used 4-Bromobutanoic acid(cas: 2623-87-2Quality Control of 4-Bromobutanoic acid)
4-Bromobutanoic acid(cas: 2623-87-2) belongs to carboxylic acids. The chief chemical characteristic of the carboxylic acids is their acidity. They are generally more acidic than other organic compounds containing hydroxyl groups but are generally weaker than the familiar mineral acids (e.g., hydrochloric acid, HCl, sulfuric acid, H2SO4, etc.).Quality Control of 4-Bromobutanoic acid
Referemce:
Bromide – Wikipedia,
bromide – Wiktionary