Ch.11 - Liquids & Phase Changes

McMurry8th EditionChemistryISBN: 9781292336145당신이 사용하는 게 아니라요?교과서 변경

McMurry 8th Edition

Ch.11 - Liquids & Phase Changes

문제 70

11장, 문제 70

Intermolecular forces are important in creating ordered arrangements in liquid crystals. What types of intermolecu- lar forces exist in a sample of the following compound?

검증된 단계별 안내

Identify the functional groups present in the compound. In this case, the compound has a benzene ring with a methoxy group (-OCH3), an amino group (-NH2), and a carboxylic acid group (-COOH).

Determine the types of intermolecular forces each functional group can participate in. The methoxy group can engage in dipole-dipole interactions and London dispersion forces. The amino group can participate in hydrogen bonding, dipole-dipole interactions, and London dispersion forces. The carboxylic acid group can engage in hydrogen bonding, dipole-dipole interactions, and London dispersion forces.

Consider the overall structure of the molecule and how these functional groups might interact with each other and with other molecules. The benzene ring can participate in π-π interactions, which are a type of London dispersion force.

Summarize the types of intermolecular forces present in the compound. These include hydrogen bonding (from the -NH2 and -COOH groups), dipole-dipole interactions (from the -OCH3, -NH2, and -COOH groups), London dispersion forces (from the entire molecule, including the benzene ring), and π-π interactions (from the benzene ring).

Conclude that the compound exhibits a combination of hydrogen bonding, dipole-dipole interactions, London dispersion forces, and π-π interactions, which contribute to the ordered arrangements in liquid crystals.

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주요 개념

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Intermolecular Forces

Intermolecular forces are the attractive forces between molecules that influence physical properties such as boiling and melting points. The main types include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Understanding these forces is crucial for analyzing the behavior of substances, particularly in states of matter like liquids and solids.

Hydrogen Bonding

Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is covalently bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine. In the compound shown, the presence of the -COOH (carboxylic acid) and -NH2 (amine) groups allows for significant hydrogen bonding, which contributes to the compound's solubility and structural properties in liquid crystals.

Liquid Crystals

Liquid crystals are materials that exhibit properties between those of liquids and solid crystals. They have ordered molecular arrangements that can change in response to temperature or electric fields. The intermolecular forces present in liquid crystals, such as hydrogen bonding and van der Waals forces, play a critical role in maintaining their unique phases and behaviors, making them essential in applications like displays and sensors.

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교과서 질문

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교과서 질문

Benzene has a melting point of 5.53 °C and a boiling point of 80.09 °C at atmospheric pressure. Its density is0.8787 g>cm3 when liquid and 0.899 g>cm3 when solid; it has Tc = 289.01 °C, Pc = 48.34 atm, Tt = 5.52 °C, and Pt = 0.0473 atm. Starting from a point at 200 K and 66.5 atm, trace the following path on a phase diagram. (1) First, increase T to 585 K while keeping P constant. (2) Next, decrease P to 38.5 atm while keeping T constant. (3) Then, decrease T to 278.66 K while keeping P constant. (4) Finally, decrease P to 0.0025 atm while keeping T constant. What is your starting phase, and what is your final phase?

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교과서 질문

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