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3.14: The Carboxylic Acid Derivatives

  • Page ID
    107509
  • learning objectives

    • name acid halides, anhydrides, esters, amides, nitriles, and dicarboxylic acids using IUPAC (systematic) and selected common name nomenclature
    • draw the structure of acid halides, anhydrides, esters, amides, and nitriles from IUPAC (systematic) and selected common names

    Note: Nomenclature of thioesters and phosphoesters is also discussed. Ask the professor if this information is required for your course.

    Introduction

    The important classes of organic compounds known as alcohols, phenols, ethers, amines and halides consist of alkyl and/or aryl groups bonded to hydroxyl, alkoxyl, amino and halo substituents respectively. If these same functional groups are attached to an acyl group (RCO–) their properties are substantially changed, and they are designated as carboxylic acid derivatives. Carboxylic acids have a hydroxyl group bonded to an acyl group, and their functional derivatives are prepared by replacement of the hydroxyl group with substituents, such as halo, alkoxyl, amino and acyloxy. The carboxylic acid derivatives can all be hydrolyzed to carboxylic acids. The specific reaction conditions are discussed in the corresponding chapter later in this text, however, the shared pattern of chemical reactivity is summarized in the diagram below.

    acid hydrolysis carbox derivs funct grp labels.png

    IUPAC Nomenclature - One Pattern, so Many Variations

    Apply the IUPAC nomenclature format to carboxylic acid derivatives as summarized below using the suffix or substituent names listed in the table. Some students find esters challenging to name. Carboxylates can be described as independent ions, but require a contain to form compounds. It can be helpful to think of esters as "alkylated carboxylates": identify and name the carboxylate, this name is preceded by the alkyl group branch on the carboxyl oxygen.

    IUPAC overview.png

    Functional Group Structure Suffix Name Substituent Name
    carboxylic acid carboxylic acid generic.png -oic acid carboxy-
    carboxylate carboxylate generic.png -oate see above
    ester ester generic.png -oate alkoxycarbonyl-
    dicarboxylic acid dicarboxylic acid generic.png -dioic acid not applicable
    acyl halide acyl halide generic.png -oyl halide not applicable

    anhydride

    anhydride generic.png

    -anhydride

    not applicable

    amide amide generic.png -amide amido-
    nitrile nitrile generic.png -nitrile cyano-

    Common names

    Most common names were derived from older systems of nomenclature that some may argue were "not systematic at all". However, it is helpful to note that the older systems of nomenclature were often based on shared structural features and/or chemical reactivity. Understanding the older nomenclature systems can offer insights into chemical reactivity and structural patterns. There are some common names that are so prevalent, they need to be memorized. Common names frequently exist when the group bonded to the carbonyl carbon is a methyl group (indicated with "acet" or "acetyl" in the common name) or a hydrogen atom (indicated with "formyl" or "form"). For example CH3C≡N is ethanenitrile (or acetonitrile) and HCONH2 is methanamide (or formamide).

    ch 3 sect 14 common name example structures.png

    The common names for compounds with carbonyl groups often use Greek letters to specify the carbon position relative to the carbonyl carbon.

    carbonyl and Greek labels corrected.png

    Example

    In this text, we will learn about the patterns of reactivity for compounds with for beta-hydroxy carbonyl structures like the one shown below.

    ethyl 3 hydroxy heptanoate.png

    Nomenclature of acid halides

    The nomenclature of acid halides starts with the name of the corresponding carboxylic acid. The –ic acid ending is removed and replaced with the ending -yl followed by the name of the halogen with an –ide ending. This is true for both common and IUPAC nomenclature. The carbonyl carbon is given the #1 location number. It is not necessary to include the location number in the name because it is assumed that the functional group will be on the end of the parent chain.

    Example

    Nomen2.jpg

    Nomenclature of Anhydrides

    The acid anhydride functional group results when two carboxylic acids combine and lose water (anhydride = without water). Symmetrical acid anhydrides are named like carboxylic acids except the ending -acid is replaced with -anhydride. This is true for both the IUPAC and Common nomenclature.

    Symmetrical anhydrides

    A symmetrical anhydride is a carboxylic acid anhydride that has the following general structural formula.

    alt

    where R1=R2= hydrogen atoms, alkyl groups, aryl groups

    Nomen1.jpg

    Unsymmetrical Anhydrides

    A mixed or unsymmetrical anhydride is a carboxylic acid anhydride that has the following general structural formula.

    alt

    where R1≠R2, but are hydrogen atoms, alkyl groups, aryl groups. When naming unsymmetrical acid anhydrides, name both using alkanoic general method and then put the two names alphabetically. Hence, first name each component and alphabetically arranged them followed by spaces and then the word anhydride.

    Nomen2.jpg

    alt

    propanoic anhydride

    alt

    ethanoic propanoic anhydride

    Exercises

    1. Draw the bond-line structure for benzoic anhydride.

    Solution:

    benzoic anhydride.png

    2. What is the common name for the compound below?

    Solution: acetic benzoic anhydride

    Common anhydride names to know

    alt

    acetic anhydride (Try to name this anhydride by the proper name. J )

    alt

    succinic anhydride (Try to name this anhydride by the proper name. J )

    Nomenclature of Esters

    Esters are made from a carboxylic acid and an alcohol.

    alt

    Esters are named as if the alkyl chain from the alcohol is a substituent. No number is assigned to this alkyl chain. This is followed by the name of the parent chain form the carboxylic acid part of the ester with an –e remove and replaced with the ending –oate.

    Example

    Ester2.jpg

    Exercises

    3. Draw the bond-line structure for phenyl hexanoate.

    Solution

    phenyl hexanoate.png

    4. What is the IUPAC name for the compound below?

    methyl benzoate.png

    Solution

    methyl benzoate

    Nomenclature of Lactones (Cyclic Esters)

    Cyclic esters are called lactones. A Greek letter identifies the location of the alkyl oxygen relative to the carboxyl carbonyl group.

    Nomenclature of Amides

    Primary amides

    Primary amides are named by changing the name of the acid by dropping the -oic acid or -ic acid endings and adding -amide. The carbonyl carbon is given the #1 location number. It is not necessary to include the location number in the name because it is assumed that the functional group will be on the end of the parent chain.

    alt alt alt

    methanamide or formamide (left), ethanamide or acetamide (center) , benzamide (right)

    Amide1.jpg

    Exercises

    5. Draw the bond-line structure for 3-chloro-N-ethylbenzamide.

    Solution

    3chloroNethyl benzamide.png

    6. What is the IUPAC name the compound below?

    alt

    Solution

    pentanamide

    Secondary amides

    Secondary amides are named by using an upper case N to designate that the alkyl group is on the nitrogen atom. Alkyl groups attached to the nitrogen are named as substituents. The letter N is used to indicate they are attached to the nitrogen. Tertiary amides are named in the same way.

    alt

    N-methylpropanamide

    Amide2.jpg

    Exercises

    7. Draw the bond-line structure for N,N-dimethylformamide.

    Solution

    8. What are the IUPAC and common names the compound below?

    alt

    Solution

    N-phenylethanamide and N-phenylacetamide, respectively

    Cyclic amides are called lactams. A Greek letter identifies the location of the nitrogen on the alkyl chain relative to the carboxyl carbonyl group.

    lactam nomen examples with names.png

    Nomenclature of Nitriles

    Name the parent alkane (include the carbon atom of the nitrile as part of the parent) followed with the word -nitrile. The carbon in the nitrile is given the #1 location position. It is not necessary to include the location number in the name because it is assumed that the functional group will be on the end of the parent chain. A nitrile substituent, e.g. on a ring, is named carbonitrile.

    include the location number in the name because it is assumed that the functional group will be on the end of the parent chain.

    Example

    (3-methylbutanenitrile (or isovaleronitrile) cyclopentanecarbonitrile

    Nomenclature of Thioesters

    Thiosters are made from a carboxylic acid and an thiol.

    alt

    Thioesters are named as if the alkyl chain from the alcohol is a substituent. No number is assigned to this alkyl chain. This is followed by the name of the parent chain from the carboxylic acid part of the thioester named as an alkane with the ending –thiooate.

    Example

    alt

    Nomenclature of Phosphates

    Phosphoryl groups are derivatives of phosphoric acid, a strong acid that is commonly used in the laboratory. The fully deprotonated conjugate base of phosphoric acid is called a phosphate ion, or inorganic phosphate (often abbreviated 'Pi'). When two phosphate groups are linked to each other, the linkage is referred to as a 'phosphate anhydride', and the ion is called 'inorganic pyrophosphate' (abbreviation PPi).

    image002.png

    When a phosphate ion is attached to a carbon atom on an organic molecule, the chemical linkage is referred to as a phosphate ester, and the whole species is called an organic monophosphate. Glucose-6-phosphate is an example.

    image004.png

    If an organic molecule is linked to two or three phosphate groups, the resulting species are called organic diphosphates and organic triphosphates.

    image006.png

    Isopententyl diphosphate and adenosine triphosphate (ATP) are good examples:

    image008.png

    Oxygen atoms in phosphate groups are referred to either 'bridging' and 'non-bridging', depending on their position. An organic diphosphate has two bridging and five non-bridging oxygens.

    image010.png

    When a single phosphate is linked to two organic groups, the term 'phosphate diester' is used. The backbone of DNA is composed of phosphate diesters.

    image012.png

    The term 'phosphoryl group' is a general way to refer to all of the phosphate-based groups mentioned in the paragraphs above.

    Recall that phosphate groups on organic structures are sometimes abbreviated simply as 'P', a convention that we will use throughout this text. For example, glucose-6-phosphate and isopentenyl diphosphate are often depicted as shown below. Notice that the 'P' abbreviation includes the oxygen atoms and negative charges associated with the phosphate groups.

    image014.png

    Exercise

    1. Name the following compounds using IUPAC conventions

    (a)alt

    (b) alt

    (c)alt

    (d)alt

    (e)alt

    (f)alt

    (g)alt

    (h)alt

    (i)alt

    Answer

    1.

    a) 3-methylpentanoyl chloride

    b) 2-cyclopentylacetamide

    c) propyl2-methylpropanoate

    d) cyclohexylbutanoate

    e) tert-butylcyclopentanecarboxylate

    f) 1-methylbutylcyclopentane carboxylate

    g) N-methyl-3-butenamide

    h) (S)-2-hydroxypropanoyl phosphate

    i) propyl 2,3-dimethyl-2-butenethioate

    Contributors and Attributions

    Richard Banks (Boise State University)