Physical Properties of Carboxylic Acid

7 Key excerpts on "Physical Properties of Carboxylic Acid"

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  Organic Reactions and their nomenclature

  • Ramesh Chandra, Snigdha Singh, Aarushi Singh(Authors)
  • 2019(Publication Date)
  • Arcler Press

    (Publisher)

  PROPERTIES OF CARBOXYLIC ACIDS Maximum of the properties of carboxylic acids is due to the existence of the carboxyl group. Some of the chemical and physical properties of these mixtures are explained in this subsection. 5.4.1. Physical Properties of Carboxylic Acids • Carboxylic acid particles are polar because of the presence of two electronegative oxygen atoms. • They also contribute to hydrogen bonding because of the presence of the hydroxyl group and the carbonyl group (C=O). • When positioned in nonpolar solvents, these compounds form dimers through hydrogen bonding between the carbonyl group of one carboxylic acid and the hydroxyl group of the other. Figure 5.2: Hydrogen bonding in carboxylic acid. [Source: https://byjus.com/chemistry/carboxylic-acid-properties/] Carboxylic Acid Reactions and Uses 169 • The solubility of compounds having the carboxyl functional group in the water relies on the extent of the compound. The smaller the compound (the shorter the R group), the greater the solubility. • The boiling point of a carboxylic acid is usually greater than that of water. • These compounds have the capability to contribute protons and are therefore Bronsted-Lowry acids. • They normally have a strong sour fragrance. Though, their esters have sweet smells and are therefore used in perfumes. 5.4.2. Chemical Properties of Carboxylic Acids • The α-carbon related to a carboxylic acid can simply be halogenated through the Hell-Volhard-Zelinsky reaction. • These compounds can be transformed into amines by using the Schmidt response. • A carboxylic acid can be deduced to alcohol by reacting it with hydrogen to origin a hydrogenation reaction. • By reaction with alcohols, these compounds produce esters. 5.5. PHYSICAL PROPERTIES OF CARBOXYLIC AC-IDS The table at the start of this page provided the boiling and melting points for a homologous group of carboxylic acids containing one to ten carbon atoms.

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  eBook - ePub

  Understanding Advanced Organic and Analytical Chemistry

  The Learner's ApproachRevised Edition

  • Kim Seng Chan, Jeanne Tan;;;(Authors)
  • 2016(Publication Date)
  • WS EDUCATION

    (Publisher)

  CHAPTER 10

  Carboxylic Acids and Their Derivatives

  10.1 Introduction

  Carboxylic acids are organic compounds that contain the following carboxyl functional group, denoted as –COOH.

  From the constitutional/structural formula, the carboxyl functional group is a composite of a carbonyl functional group and a hydroxyl group. Similar to that in carbonyl compounds, the carbon atom of the carboxyl functional group is sp2 hybridized and trigonal planar in shape. Thus, it is not surprising that carboxylic acids possess physical and chemical properties similar to both the carbo nyl and hydro

  xyl

  compounds.

  Derivatives of carboxylic acids have the –OH group substituted. For instance, esters contain the functional group –COOR, and acid chlorides the –COCl group.

  10.2 Nomenclature

  Carboxylic acids are named with the suffix –oic acid. Other substituents are named as prefixes accompanied by the appropriate positional numbers. If the carboxylic acid group is considered a substituent, then it is named as the –carboxy prefix (notice that the prefix is not “carboxyl”).

  10.3 Physical Properties

  10.3.1 Melting and Boiling Points

  Melting and boiling points increase with increasing carbon chain length (Table 10.1 ) and decrease with increasing degree of branching. As with alcohols, the trend is accounted for by the increasing strength of instantaneous dipole–induced dipole (id–id) attractive forces due to the greater number of electrons accompanying the increasing carbon chain length, rather than hydrogen-bonding.

  Table 10.1

  The boiling points of carboxylic acids are higher than those of their isomeric ester counterparts (Table 10.2

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  Brown's Introduction to Organic Chemistry

  • William H. Brown, Thomas Poon(Authors)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  437 THE NEXT TIME YOU take an aspirin (acetylsalicylic acid) or drink milk (contains lactic acid), you might be reminded of carboxylic acids, another class of organic compounds contain- ing the carbonyl group. Their occurrence in nature is widespread, and they are important com- ponents of foodstuffs such as vinegar, butter, and vegetable oils. The most important chemical property of carboxylic acids is their acidity. Furthermore, carboxylic acids form numerous important derivatives, including esters, amides, anhydrides, and acid halides. In this chapter, we study carboxylic acids themselves; in Chapters 14 and 15, we study their derivatives. 13.1 What Are Carboxylic Acids? The functional group of a carboxylic acid is a carboxyl group, so named because it is made up of a carbonyl group and a hydroxyl group (Section 1.7D). Following is a Lewis structure of the carboxyl group, as well as two alternative representations of it: CO 2 H COOH C O O H Carboxyl group A COOH group. 13 Carboxylic Acids K E Y Q U E S T I O N S 13.1 What Are Carboxylic Acids? 13.2 How Are Carboxylic Acids Named? 13.3 What Are the Physical Properties of Carboxylic Acids? 13.4 What Are the Acid–Base Properties of Carboxylic Acids? 13.5 How Are Carboxyl Groups Reduced? 13.6 What Is Fischer Esterification? 13.7 What Are Acid Chlorides? 13.8 What Is Decarboxylation? H O W TO 13.1 How to Predict the Product of a Fischer Esterification 13.2 How to Predict the Product of a β‐Decarboxylation Reaction C H E M I C A L C O N N E C T I O N S 13A From Willow Bark to Aspirin and Beyond 13B Esters as Flavoring Agents 13C Ketone Bodies and Diabetes The active ingredients in these two over‐the‐counter pain relievers are derivatives of arylpropanoic acids. See Chemical Connections 13A, “From Willow Bark to Aspirin and Beyond.” Inset: A model of (S)‐ibuprofen. Charles D. Winters 13.1 The general formula of an aliphatic carboxylic acid is RCOOH; that of an aromatic carboxylic acid is ArCOOH.

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  Principles of Organic Chemistry

  • Robert J. Ouellette, J. David Rawn(Authors)
  • 2015(Publication Date)
  • Elsevier

    (Publisher)

  2

  Properties of Organic Compounds

  2.1 Structure and Physical Properties

  Each of the millions of organic compounds has unique physical and chemical properties. Thus, we might expect that understanding the relationships between the structure of compounds and their physical properties, such as melting point, boiling point, and solubility, would be a difficult task. Yet we can make reasonable guesses about the physical properties of a compound based on its structure, because organic compounds belong to a small number of classes of substances characterized by their functional groups. These structural units within a molecule are largely responsible for its properties. These properties reflect the attractive intermolecular (between molecules) forces attributable to the functional groups. Intermolecular forces are of three types: dipole-dipole forces, London forces, and hydrogen-bonding forces.

  Dipole-Dipole Forces

  The bonding electrons in polar covalent bonds are not shared equally, and a bond moment results. However, a molecule may be polar or nonpolar depending on its geometry. For example, tetrachloromethane (carbon tetrachloride, CCl4 ) has polar C—Cl bonds, but the tetrahedral arrangement of the four bonds about the central carbon atom causes the individual bond moments to cancel. In contrast, dichloromethane (methylene chloride, CH2 Cl2 ) is a polar molecule with a net polarity away from the partially positive carbon atom toward the partially negative chlorine atoms.

  Polar molecules have a negative “end” and a positive “end.” They tend to associate because the positive end of one molecule attracts the negative end of another molecule. The physical properties of polar molecules reflect this association. An increased association between molecules decreases their vapor pressure, which in turn results in a higher boiling point, because more energy is required to vaporize the molecules. The molecular weights and molecular shapes of acetone and isobutane are similar (Figure 2.1

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  eBook - ePub

  The Chemistry of Carbonyl Compounds and Derivatives

  • Paulo Costa, Ronaldo Pilli, Sergio Pinheiro, Peter Bakuzis(Authors)
  • 2022(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  Figure 5.21 we show a select set of carboxylic acids and some of their physical properties. We can observe that the boiling point increases from formic to butyric acid as a function of the increase in molecular mass and, consequently, the van der Waals intermolecular forces. These four acids are soluble in water and the carboxylic group interacts with water as a hydrogen bond donor and acceptor.

  Figure 5.21 Physical properties of some carboxylic acids.

  Long-chain carboxylic acids, known as fatty acids, are solids or semi-solids at room temperature, and their physical properties are very sensitive to the presence of unsaturation in the structure. Conjugated, aromatic, or dicarboxylic carboxylic acids are generally solids, and water solubility depends on the number of carbon atoms in the structure. For example, benzoic acid is sparingly soluble in water (0.35 g per 100 mL, at 25 °C), while trans -crotonic and oxalic acids are water soluble.

  Although they can form hydrogen bonds with water, esters are generally not water soluble (Figure 5.22 ). Ethyl acetate, commonly used in extractions of organics from aqueous phases, has a solubility of 8.3 g per 100 mL in water, at 20 °C. Esters are soluble in low polarity organic solvents such as alkyl halides and ethers due to dipole–dipole intermolecular interactions with these solvents. They are also soluble in alcohols and if they have high molecular mass, they may be soluble in hydrocarbon solvents as well.

  Figure 5.22 Physical properties of some esters, lactones, and anhydrides.

  Exercise

  Explain the differences in both solubility and boiling point of ethyl butyrate and γ-butyrolactone.

  Vitamin C and its Biological Role

  Vitamin C, also known as ascorbic acid, is an essential nutrient that cannot be synthesized by our body and needs to be present in our diet, being found in fruits such as oranges, lemons, papaya, and acerola, and in vegetables such as broccoli, parsley, and red pepper. Vitamin C is involved in collagen biosynthesis and is therefore important for cell tissue repair. It may also act as an antioxidant at the cellular level, being converted to dehydroascorbic acid in the presence of oxidants, as shown below.

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  Introduction to General, Organic, and Biochemistry

  • Frederick Bettelheim, William Brown, Mary Campbell, Shawn Farrell(Authors)
  • 2019(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  476 Carboxylic Acids 17 CONTENTS 17.1 Carboxylic Acids 17.2 Names of Carboxylic Acids 17.3 Physical Properties of Carboxylic Acids 17.4 Soaps and Detergents 17.5 Characteristic Reactions of Carboxylic Acids 17.1 Carboxylic Acids In this chapter, we study carboxylic acids, another class of organic com-pounds containing the carbonyl group. The carboxylic acid functional group can be represented in any one of three ways: 9 C 9 OH 9 COOH 9 CO 2 H O 17.2 Names of Carboxylic Acids A. IUPAC Names The longest carbon chain that contains the carboxylic acid functional group is used to obtain the IUPAC name of an acyclic carboxylic acid. Drop the final -e from the name of the parent alkane and replace it with -oic acid. Number the chain beginning with the carbonyl carbon of the carboxylic acid. Because this carbonyl carbon is understood to be carbon 1, there is no © Ruslan Mitin/Shutterstock.com These foods can contain low levels of harmful trans fats. Copyright 2020 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. need to give it a number in the final IUPAC name. In the following exam-ples, the common name is given in parentheses. 3-Methylbutanoic acid (Isovaleric acid) OH O 1 3 Hexanoic acid (Caproic acid) OH O 1 6 4 When a carboxylic acid also contains an i OH (hydroxyl) group, we indi-cate its presence by adding the prefix hydroxy -. When it contains a primary (1°) amine, we indicate the presence of the i NH 2 group with amino -. When a carboxylic acid also contains a ketone or aldehyde group, we indicate the presence of that group by the prefix -oxo .

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  Understanding Advanced Chemistry Through Problem Solving

  The Learner's ApproachVolume 2

  • Kim Seng Chan, Jeanne Tan(Authors)
  • 2014(Publication Date)
  • WSPC

    (Publisher)

  CHAPTER 10

  CARBOXYLIC ACIDS AND THEIR DERIVATIVES

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  Boiling point and solubility of carboxylic acids and their derivatives

  —  A carboxylic acid has a higher boiling point than an alcohol of similar molecular weight. This is because of the stronger and more extensive hydrogen bonding between the carboxylic acid molecules:

  —  The stronger hydrogen bonding arises because of the electron-withdrawing carbonyl functional group, which causes the O–H bond to be more polar. More extensive hydrogen bonding arises because of the presence of 4 lone pair of electrons and one H atom in the -COOH functional group. The strong and extensive hydrogen bonding even causes the carboxylic acid to form dimers.

  —  Low-molecular-weight carboxylic acids are highly soluble in water because of their ability to form strong and extensive hydrogen bonding with water molecules. Importantly, the partial dissociation of the weak acid in water further enhances the solubility of the acid due to the formation of ion–dipole interaction:

  —  Acyl chloride is more volatile than its corresponding carboxylic acid because of the weaker intermolecular forces of the permanent dipolepermanent dipole type as compared to the acid. It also hydrolyzes much more readily in water, releasing HCl a strong acid, which fully dissociates in water. Hence, the acidic nature of acid chloride in water in water arise mainly from the dissociated HCl.

  —  Esters are also polar analog molecules of the carboxylic acid, and are relatively soluble in water due to the ability of the ester functional group to form hydrogen bonding with the water molecules.

  —  Amides are solid at room temperature because of the stronger and more extensive hydrogen bonding made possible by the presence of the –NH2 group (for primary amides) and the lone pair of electrons on the carbonyl (C=O) oxygen atom.

  Acidity of carboxylic acids

  —  Carboxylic acids are the strongest organic acid. This is because, with the negative charge on the carboxylate ion being dispersed through resonance, two equivalent resonance structures are formed. In these two equivalent resonance structures, the negative charge “sits” on two highly electronegative oxygen atoms:

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