Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Chapter 2 Molecular Representations Organic Chemistry Second Edition David Klein

Please note: If your clicker system can only hold 5 multiple choice answers, we have provided ‘alternate answers’ for those questions in which the author originally had more than 5 choices. These answers appear on the slides with a green background. If your clicker system can hold more than 5 multiple choice answers, please delete the slides with the green backgrounds, and use the original answers the author has listed. Chapter 2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.1, Which of the following is the best Lewis Structure for CH 2 C(CH 3 )CH 2 CH 3 ? a. b. c. d. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : d A: Connectivity is wrong. In a condensed structural formula, atoms in parenthesis are attached to the previous atom (unless the parenthesis start the formula, in which case they are attached to the following atom). B: Connectivity is correct, but the number of electrons is incorrect. The first two carbons in this drawing have open octets. C: Connectivity and electrons are correct. However, this structure shows charge separation and open octets. It is NOT the best Lewis Structure. For more examples of this type of problem, see SkillBuilder 2.1. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.1, Which of the choices is identical to CH 3 CH 2 CH(OH)CH 2 CH 3 ? a. b. C 5 H 11 O c. d. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c A: Connectivity is wrong. The parenthesis mean the OH is attached to the CH. B: Number of hydrogen atoms is wrong. D: Violation of octet rule on last two carbon atoms. For more examples of this type of problem, see SkillBuilder 2.1. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: Which is the correct bond-line formula for the following structure? a. b. c. d. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c A: Too many carbon atoms. B: CH 3 on the third carbon from the left is missing. D: Too few carbon atoms. For more examples of this type of problem, see SkillBuilder 2.2 and 2.3. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.1, Which is the correct condensed formula for the following structure? a. CH 3 CH 2 CH(OH)CHCH 2 CH 3 b. CH 3 CH 2 CH(OH)CH(CH 2 CH 3 ) 2 c. CH 3 CH 2 (OH)CH(CH 2 CH 3 )CH 3 d. CH 3 CH 2 CH 2 (OH)CH(CH 2 CH 3 )CH 2 CH 3 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b A: CH 2 CH 3 on carbon 4 is missing. C: OH and CH 2 CH 3 are on the wrong carbons and a CH 2 CH 3 is missing. D: Too many hydrogen and too many bonds on carbon #3. For more examples of this type of problem, see SkillBuilder 2.2. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: What functional group is located at the indicated point in the structure below? a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid f. Alkene g. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a Aldehydes are carbonyls that have a carbon group on one side and a hydrogen atom on the other side. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answers: Section: What functional group is located at the indicated point in the structure below? a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a Aldehydes are carbonyls that have a carbon group on one side and a hydrogen atom on the other side. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section What functional group is located at the indicated point in the structure below? a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid f. Alkene g. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d The ether functional group is an oxygen atom with single bonds to carbon on either side of it. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answers: Section What functional group is located at the indicated point in the structure below? a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d The ether functional group is an oxygen atom with single bonds to carbon on either side of it. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: What functional group is located at the indicated point in the structure below? a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid f. Alkene g. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : c Esters are carbonyls with a carbon group on one side and a singly bonded oxygen connected to another carbon group on the other side. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answer: a. Aldehyde b. Ketone c. Ester d. Ether e. Carboxylic acid Section: What functional group is located at the indicated point in the structure below? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Esters are carbonyls with a carbon group on one side and a singly bonded oxygen connected to another carbon group on the other side. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section What functional group is located at the indicated point in the structure below? a. Ketone b. Ether c. Carboxylic acid d. Alkene e. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : a Ketones are carbonyls that have carbon groups on either side of a carbonyl. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section What functional group is located at the indicated point in the structure below? a. Ketone b. Ether c. Carboxylic acid d. Alkene e. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d Alkenes are functional groups that have 2 carbons connected with a double bond. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section What functional group is located at the indicated point in the structure below? a. Ketone b. Ether c. Carboxylic acid d. Alkene e. Alcohol Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: e Alcohols are functional groups that contain an O-H singly bonded to a carbon. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms has only one lone pair? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d, g, i Oxygen with three bonds and a positive charge, neutral nitrogen with three bonds and carbanions have only one lone pair. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms has only one lone pair? a.C b.D c.B and F d.D, G, and I e.F, D and G Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d Oxygen with three bonds and a positive charge, neutral nitrogen with three bonds and carbanions have only one lone pair. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have no lone pairs? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : e, h Nitrogen with four bonds and a positive charge and carbocations have no lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have no lone pairs? a.B b.D c.D and E d.E and H e.D, E and H Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : d Nitrogen with four bonds and a positive charge and carbocations have no lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have two lone pairs? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b, c, f Neutral oxygen with two bonds and nitrogen with two bonds and a negative charge will have two lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have two lone pairs? a.A b.B c.B and C d.A, B, and C e.B, C and F Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: e Neutral oxygen with two bonds and nitrogen with two bonds and a negative charge will have two lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have three lone pairs? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : a Oxygen with three bonds and a negative charge has three lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.4, Which of the indicated atoms have three lone pairs? a.A b.F c.C and F d.A, B, and C e.B, C and F Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : a Oxygen with three bonds and a negative charge has three lone pairs. For more examples of this type of problem, see SkillBuilder 2.4 and 2.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section What is the hybridization of the carbon atoms 1-5 in the following structure? a.C1=sp 3, C2=sp 3, C3=sp 3, C4=sp 3, C5=sp 3 b.C1=sp 3, C2=sp 2, C3=sp 2, C4=sp 3, C5=sp 3 c.C1=sp 2, C2=sp 2, C3=sp 2, C4=sp 2, C5=sp 3 d.C1=sp 3, C2=sp 2, C3=sp 2, C4=sp 2, C5=sp 3 e.C1=sp 2, C2=sp 2, C3=sp 2, C4=sp 2, C5=sp 2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Whenever the carbons adjacent to a double bond are either negatively or positively charged the hybridization will shift to a sp 2 hybrid because of increased opportunities to form new resonance structures. Using the rules of resonance the charged species here can be redrawn using resonance arrows to form a more stable species: Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Determine which of the two main rules of drawing curved arrows the following actions violate, if any rules are broken. Remember that curved arrows should not break single bonds or violate the octet rule. a.1 violates the octet rule, 2 no violation, 3 breaks a single bond b.1 violates the octet rule, 2 violates the octet rule, 3 violates the octet rule c.1 no violation, 2 no violation, 3 breaks a single bond d.1 violates the octet rule, 2 no violation, 3 violates the octet rule e.All are acceptable Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a See section 2.8 and practice problem Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Which of the following represent correct curved arrow notation for drawing resonance structures? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a, b, c D and E have incorrect resonance arrows that would create carbon atoms with 5 bonds. For more examples of this type of problem, see SkillBuilder 2.6. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.8, 2.9, What would be the appropriate final resonance structure that results from the sequence of curved arrow electron transfers shown in the example below? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c See section 2.9, SkillBuilder 2.7 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Sections 2.1, 2, and Are the compounds shown below different resonance forms for the same compound, constitutional isomers, different compounds or the same compound. a.Resonance pair b.Constitutional isomers c.Different compounds d.Same compound Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b See section 2.10, SkillBuilder 2.7 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Which of the following compounds does not have any reasonable resonance structures? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a See conceptual checkpoint 2.32, all of the rest of the options fit the patterns for drawing resonance structures found in figure 2.5 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Which of the following resonance structures contributes the most character to the structure of the overall resonance hybrid. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c See section 2.11, SkillBuilder 2.8. The electronegative oxygen can best stabilize a negative charge, and there is only one charged atom. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Which of the following resonance structures contributes the most character to the structure of the overall resonance hybrid. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: e See section 2.11, SkillBuilder 2.8. The structures with positive charges on the carbons all have incomplete octets, and nitrogen is less electronegative than oxygen, so can better stabilize a positive charge. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 2.8, 2.9, Which of the following are possible resonance structures of structure I? a. A and B b. B, C and D c. A, B and D d. all of them e. none of them Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Resonance structures involve the movement of electrons. You cannot move atoms or violate the octet rule when drawing resonance structures. For more examples of this type of problem, see SkillBuilder 2.8. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: Which off the following options contributes the most character to the overall resonance hybrid of I? a. A b. B c. C d. D Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : b A: This is a good resonance structure but not the best. The best resonance structure has a complete octet on each atom and no charge separation. If charges are present, negative charges should be on the most electronegative atoms and positive charges should be on the least electronegative atom. Here, the negative is on carbon, this is actually 2 nd best resonance structure. B: Correct!! This is the best resonance structure. The best resonance structure a complete octet on each atom and no charge separation. If charges are present, negative charges should be on the most electronegative atoms and positive charges should be on the least electronegative atom. C: This is NOT a good resonance structure. There is a violation of the octet rule. One of the carbons in the ring has 5 bonds. D: This is a good resonance structure but not the best. The best resonance structure has a complete octet on each atom and no charge separation. If charges are present, negative charges should be on the most electronegative atoms and positive charges should be on the least electronegative atom. Here, there is an incomplete octet, this is actually 3 rd best resonance structure. For more examples of this type of problem, see SkillBuilder 2.8. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section Identify which of the indicated lone pairs are localized. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : a, b, d, f A lone pairs is localized if it does not participate in resonance. Lone pairs a, b, d and f do not and can not participate in resonance. For more examples of this type of problem, see SkillBuilder 2.9. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.7 and Use numbers to represent curved arrows that transform the resonance structure shown into the ion’s other important resonance structure. List the number of the arrow’s origin followed by the number of the arrow’s destination a.9 to 8, 6 to 3 b.9 to 8 c.9 to 8, 6 to 4 d.6 to 4 e.6 to 5, 4 to 2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Response: Electron density flows from regions of high electron density to low electron density. See the curved arrows in the diagram below for the changes that result in the most stable resonance structure. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.7 and Use numbers to represent curved arrows that transform the resonance structure shown into the ion’s other important resonance structure. List the number of the arrow’s origin followed by the number of the arrow’s destination a.3 to 2 b.9 to 4 c.3 to 4, 6 to 7 d.6 to 7, 3 to 5 e.6 to 8 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Response: Electron density flows from regions of high electron density to low electron density. See the curved arrows in the diagram below for the changes that result in the most stable resonance structure. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 2.7 and Use numbers to represent curved arrows that transform the resonance structure shown into the ion’s other important resonance structure. List the number of the arrow’s origin followed by the number of the arrow’s destination a.9 to 8, 6 to 3 b.8 to 9 c.3 to 6 d.3 to 6, 8 to 9 e.3 to 2, 8 to 9 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: d Response: See the curved arrows in the diagram below for the changes that result in the most stable resonance structure. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.