What observations made by Reinitzer on cholesteryl benzoate suggested that this substance possesses a liquid crystalline phase?

Verified step by step guidance

Step 1: Understand the context of the problem by recognizing that cholesteryl benzoate is a compound that was studied for its unique phase behavior, which led to the discovery of liquid crystals.

Step 2: Note that Reinitzer observed cholesteryl benzoate under different temperature conditions to study its phase transitions.

Step 3: Identify that Reinitzer observed two distinct melting points for cholesteryl benzoate, which was unusual for a pure compound.

Step 4: Recognize that the first melting point indicated a transition from a solid to a cloudy liquid, suggesting an intermediate phase between solid and liquid.

Step 5: Understand that the second melting point indicated a transition from the cloudy liquid to a clear liquid, confirming the presence of a liquid crystalline phase.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Liquid Crystals

Liquid crystals are a state of matter that has properties between those of conventional liquids and solid crystals. They can flow like a liquid but have some degree of molecular order, which allows them to exhibit unique optical properties. This phase is crucial in applications like LCD screens, where the alignment of liquid crystal molecules can be manipulated by electric fields.

Phase Transitions

Phase transitions refer to the changes in the state of matter, such as from solid to liquid or liquid to gas, often influenced by temperature and pressure. In the context of cholesteryl benzoate, observing a transition between different phases can indicate the presence of a liquid crystalline phase, characterized by specific temperature ranges where the material exhibits distinct optical and thermal behaviors.

Optical Properties

Optical properties are characteristics of materials that define how they interact with light, including refractive index, birefringence, and transparency. Reinitzer's observations of cholesteryl benzoate likely included changes in these properties at certain temperatures, which are indicative of the liquid crystalline phase, as liquid crystals can exhibit unique optical phenomena due to their ordered molecular arrangement.

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Physical Properties

Related Practice

Textbook Question

Use the phase diagram of neon to answer the following questions. (b) What can you say about the strength of the intermolecular forces in neon and argon based on the critical points of Ne and Ar (see Table 11.5.)?

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Textbook Question

At 25 °C gallium is a solid with a density of 5.91 g/cm³. Its melting point, 29.8 °C, is low enough that you can melt it by holding it in your hand. The density of liquid gallium just above the melting point is 6.1 g/cm³. Based on this information, what unusual feature would you expect to find in the phase diagram of gallium?

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Textbook Question

Indicate whether each statement is true or false: (a) The liquid crystal state is another phase of matter, just like solid, liquid, and gas. (b) Liquid crystalline molecules are generally spherical in shape. (d) Molecules that exhibit a liquid crystalline phase show weaker-than-expected intermolecular forces. (e) Molecules containing only carbon and hydrogen are likely to form liquid crystalline phases. (f) Molecules can exhibit more than one liquid crystalline phase.

Textbook Question

Indicate whether each statement is true or false: (c) Molecules that exhibit a liquid crystalline phase do so at well-defined temperatures and pressures.

Textbook Question

For a given substance, the liquid crystalline phase tends to be more viscous than the liquid phase. Why?