The amide group, in acetamide as well as in all other amides, is best represented as a resonance hybrid (Section 3-9). Following are two contribut ing structures for the hybrid. H :O = H =O: 1 1 + H — C—C- 1 H -M U «_ , H p p— N—H 1 I 1 !11* 1 1 H H H (a) (b) Show by the use of curved arrows how contributing structure (a) is converted into contributing structure (b). Notice that structure (b) contains an oxygen atom with one bond and three unshared pairs of electrons and that this oxygen bears a negative charge. Compare the Lewis structure of this oxygen with the oxygen atom in the hydroxide ion. Notice that the nitrogen atom of structure (b) has four bonds and bears a positive charge. Compare the Lewis structure and bonding of this nitrogen with the nitrogen in the ammonium ion, NH 4 + . If the acetamide hybrid is best represented by contributing structure (a), predict the H—N—H bond angle. If, on the other hand, the acetamide hybrid is best represented by contributing structure (b), predict the H—N—H bond angle. Proteins are molecules that can be described as polyamides (Chapter 22). Linus Pauling, in his pioneering studies on the structure of proteins, discovered that the actual H—N—H bond angle in each amide bond of a protein is 120°. What does this fact tell you about the relative importance of contributing structures (a) and (b) in the resonance hybrid?

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Introduction to General, Organic a...

11th Edition
Frederick A. Bettelheim + 4 others
Publisher: Cengage Learning
ISBN: 9781285869759
BuyFind

Introduction to General, Organic a...

11th Edition
Frederick A. Bettelheim + 4 others
Publisher: Cengage Learning
ISBN: 9781285869759

Solutions

Chapter 10, Problem 10.59P
Textbook Problem

The amide group, in acetamide as well as in all other amides, is best represented as a resonance hybrid (Section 3-9). Following are two contribut ing structures for the hybrid.

    H :O = H =O: 1 1 +
    H — C—C- 1 H -M U «_ , H p p— N—H 1
    I1!11* 1 1
    H H H
    (a) (b)

  1. Show by the use of curved arrows how contributing structure (a) is converted into contributing structure (b).

  • Notice that structure (b) contains an oxygen atom with one bond and three unshared pairs of electrons and that this oxygen bears a negative charge. Compare the Lewis structure of this oxygen with the oxygen atom in the hydroxide ion.
  • Notice that the nitrogen atom of structure
  • (b) has four bonds and bears a positive charge. Compare the Lewis structure and bonding of this nitrogen with the nitrogen in the ammonium ion, NH4+.

  • If the acetamide hybrid is best represented by contributing structure (a), predict the
  • H—N—H bond angle.

  • If, on the other hand, the acetamide hybrid is best represented by contributing structure (b), predict the H—N—H bond angle.
  • Proteins are molecules that can be described as polyamides (Chapter 22). Linus Pauling, in his pioneering studies on the structure of proteins, discovered that the actual H—N—H bond angle in each amide bond of a protein is 120°. What does this fact tell you about the relative importance of contributing structures (a) and (b) in the resonance hybrid?
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    Chapter 10 Solutions

    Introduction to General, Organic and Biochemistry
    Ch. 10 - 10-11 What important experiment did Wohler carry...Ch. 10 - Answer true or false. In organic compounds, carbon...Ch. 10 - List the four principal elements that make up...Ch. 10 - Think about the types of substances in your...Ch. 10 - 10-15 How many electrons are in the valence shell...Ch. 10 - 10-16 What is the relationship between the number...Ch. 10 - Write Lewis structures for these compounds. Show...Ch. 10 - (a) CH3OCH3 Dimethyl ether (c) C3H_i Ethylene (e)...Ch. 10 - 10-19 Write Lewis structures for these ions. (a)...Ch. 10 - 10-20 Why are the following molecular formulas...Ch. 10 - 10-21 Explain how to use the valence-shell...Ch. 10 - 10-22 Suppose you forget to take into account the...Ch. 10 - Suppose you forget to take into account the...Ch. 10 - 10-24 Use the VSEPR model to predict the bond...Ch. 10 - Prob. 10.25PCh. 10 - Answer true or false. A functional group is a...Ch. 10 - 10-27 What is meant by the term functional group?Ch. 10 - 10-28 List three reasons why functional groups are...Ch. 10 - Draw Lewis structures for each of the following...Ch. 10 - Complete the following structural formulas by...Ch. 10 - What is the meaning of the term tertiary (3° )...Ch. 10 - 10-32 Draw a structural formula for the one...Ch. 10 - 10-33 What is the meaning of the term tertiary (...Ch. 10 - Draw condensed structural formulas for all...Ch. 10 - Draw structural formulas for each of the...Ch. 10 - 10-36 Draw structural formulas for the six ketones...Ch. 10 - 10-37 Draw structural formulas for the eight...Ch. 10 - Draw structural formulas for each of the...Ch. 10 - 10-39 (Chemical Connections 10A) How was Taxol...Ch. 10 - (Chemical Connections 10A) In what way does Taxol...Ch. 10 - Use the VSEPR model to predict the bond angles...Ch. 10 - Silicon is immediately below carbon in Group 4A of...Ch. 10 - 10-43 Phosphorus is immediately below nitrogen in...Ch. 10 - Draw the structure for a compound with the...Ch. 10 - 10-45 Draw structural formulas for the eight...Ch. 10 - Draw structural formulas for the three tertiary...Ch. 10 - 10-47 Which of these covalent bonds are polar, and...Ch. 10 - Of the bonds in Problem 10-47, which is the most...Ch. 10 - Using the symbol 6+ to indicate a partial positive...Ch. 10 - Prob. 10.50PCh. 10 - Following is a structural formula for naphthalene....Ch. 10 - Identify the functional group(s) in each compound...Ch. 10 - Consider molecules with the molecular formula...Ch. 10 - Urea, (NH.,)2CO, is used in plastics and in fertil...Ch. 10 - The compound drawn here is lactic acid, a natural...Ch. 10 - Following is the structural formula of acetylsali-...Ch. 10 - Aspirin is prepared by the reaction of salicylic-...Ch. 10 - Following is the structural formula of acetamide....Ch. 10 - The amide group, in acetamide as well as in all...

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