Chemistry Organic Chemistry I Fall, 2016 Day 3 9/2/16

Chemistry 250-02 Organic Chemistry I Fall, 2016 Day 3 9/2/16
Organic Chemistry I Fall, 2016 Day 3 9/2/16 Key Ideas so Far Molecular Structure and Functional Groups Molecular Shape and VSEPR Theory Lewis Dot (:) Electron Diagrams Formal Charges Now Hybridization Theory Resonance ChemAct 3 and 5

Chem Activity 2

Chem Act 2 Model 5 page 20

Which of the following represents the ground-state electronic configuration for carbon (atomic number 6)? 1s22s22px22py02pz0 1s22s22px12py12pz0 1s22s12px12py1 2pz1 1s12s22px12py1 2pz1 1s22s22px02py02pz2 I am not sure what these symbols mean 20

Electron Energy Levels in Atoms The Problem with Carbon

Work Chem Act 3 Models 1 - 3

In relation to σ bonds, which statement about π bonds is correct ?
π bonds are weaker and π electrons have higher energy π bonds are stronger and π electrons have higher energy π bonds are weaker and π electrons have lower energy π bonds are stronger and π electrons have lower energy π bonds and σ bonds have equal strengths, and their electrons have the same energies

Hybridization in Carbon The sp3 Hybrid (Mixed) Orbital

Chem Act 3 Model 5 CTQ 5 page 27

Chem Act 3 Model 5 CQT 7 page 28 Hybridization at each atom

Chem Act 3 Model 5 CQT 7 page 28

Chem Act 3 Model 6 Double Bond C=C Model 7 Triple Bond CΞC

Sigma (σ) and Pi (π) Bond sp3 sp2

What is the hybridization of nitrogen in :NΞC-CH3 ?
sp sp2 sp3 sp3d nitrogen is not hybridized

What is the hybridization of the :NC carbon in :NΞC-CH3 ?
sp sp2 sp3 sp3d carbon is not hybridized

What is the hybridization of the CH3 carbon in :NΞC-CH3 ?
sp sp2 sp3 sp3d carbon is not hybridized

What is the relative orientation of the two π orbitals in H-CΞC-H ?
60° 90° 109.5° 120° 180°

Chem Act 3 (Exercise 8d) page 33 Hybridization at each atom

What are the hybridizations and bond angles at these atoms ?

Polarity, Acid – Base and Resonance
CHEM Class 5 Wed., Sept., 7, 2016 Polarity, Acid – Base and Resonance ChemActivity 5: Resonance “Relocating Electrons” Not nuclei – you cannot move atoms David Klein’s “Organic Chemistry as a 2nd Language” is a great resource for resonance

Acidity KA pKA = - [log KA] pKA is a measure of energy !

What is the main reason why molecule A is less acidic than molecule B
What is the main reason why molecule A is less acidic than molecule B? A: CH3CH2CH2-H B: CH3CH2O-H There are more hydrogens in A. The C-H bond is weaker than the O-H bond. The conjugate base of A is more stable (lower PE) than the conjugate base of B. In the conjugate base of B, is more stable (lower PE) than the conjugate base of A as the negative charge resides on a more electronegative atom. There is resonance and inductive stabilization of conjugate base of B.

pK RXN = pKA REAGENT ACID – pKA PRODUCT ACID on left on right “RiP = R minus P”
What is K ? What is pKRXN ?

pK RXN = pKA REAGENT ACID – pKA PRODUCT ACID on left on right “RiP = R minus P”
What is K ? What is pKRXN ? pK RXN = = K = 10-(pK) = ca. 10- (-11) = ca. 1011

What is pK RXN ? Which statement about the acid-base equilibrium shown above is incorrect ? the equilibrium favors the products water is a conjugate acid in this equilibrium hydroxide is the strongest base present phenol is 6 times more acidic than water the negative charge in the phenoxide is resonance stabilized

Chem Act 5 Resonance Read Model 1 and complete CTQ 1-3 (5 min.)
Check your answers to CTQ 3 with a neighboring group * Pay attention to lone pairs and formal charges! Read Model 2 and complete CTQ 4-9 (5 min.)

Which of the following statements is false concerning resonance structures?
The arrangement of nuclei in all contributing structures must be the same. The arrangement of electrons in each contributing structure is different. Each atom in a contributing structure must have a completed valence shell. The contributing structures may have different energies. All contributing structures must have the correct number of valence electrons.

Which of the following statements is false concerning resonance structures?
The arrangement of nuclei in all contributing structures must be the same. The arrangement of electrons in each contributing structure is different. Each atom in a contributing structure must have a completed valence shell. The contributing structures may have different energies. All contributing structures must have the correct number of valence electrons. false

Consider all equivalent resonance structures for carbonate anion shown below What is the formal charge on Oxygen? –1 –2/3 –1/2 –1/3

Chem Act 5 Resonance Read Model 3 and answer CTQ (10 min.)

Anions with the negative charge residing on carbons are called carbanions (i.e. “carbon anions”). In the methyl anion (:CH3) the carbon is sp3 hybridized What is the hybridization of carbon 1 in the allyl anion? sp3 sp2 sp sp3d carbon 1 is not hybridized

Which is likely the stronger base?
Roughly the same I need pKA values to determine this.

Chem Act 5 Resonance Complete Model 4 (CTQ 17-19) (5 min.)
Complete Models 5 & 6 (CTQ 20-23) (7 min.) Continue to Models 7 & 8 (CTQ 24-30) (remaining time) CTQ 33: make sure you don’t violate the octet rule!

Which is the stronger acid?
B About the same B

Common Arrow-Drawing Mistakes
Head of arrow points into outer space. Show exactly where the electrons are flowing. bad

Head of arrow points to an atom when the moving electrons are actually becoming a new π bond. bad bad

Tail of an arrow is drawn from a “+” charge. bad bad * Start with the electron source and go with the electron flow - source to sink - so ‘MINUS GOES TO PLUS’ !

Which of the following structures has a legal set of ‘moving electron’ arrows?
B C None of the above All of the above

Bond Pair and Lone Pair Electrons

Bonding Models Ionic Covalent

How to make a Molecule take two atoms, mix thoroughly, bake at …

Electrons as Waves

Combining Atomic Orbitals makes Molecular Orbitals-2 kinds of these

Combining of Atomic Orbitals

Hybridization (s + np)

Hybridization in Boron The sp2 Hybrid Orbitals

Stereodrawing of Organic Molecules

Nitrogen and Oxygen sp3 Hybrid Orbitals

The Single (sigma) Bond C-C bonding in Ethane H3C-CH3
The Single (sigma) Bond C-C bonding in Ethane H3C-CH3

The Double (pi) Bond C-C Bonding in Ethene H2C=CH2

Representations of Ethene

Representations of Ethyne

Alkenes and Alkynes C=C and C≡C Bonds

Comparison of C-C and C-H Bonds

How To Represent Organic Molecules

Worked Example Interpreting Line-Bond Structures
Carvone, a substance responsible for the odor of spearmint, has the following structure. How many hydrogens are bonded to each carbon ? What is the molecular formula of carvone ? What different kinds of carbons are there ?

Problem 1) How many H’s are bonded to the C’s
Problem 1) How many H’s are bonded to the C’s ? 2) What types of Carbons are there ?

Based on the octet rule, which of the following line-bond structures is/are correct?
A and B A and C B and D Only B Only C All of them None of them 20

How many hydrogen atoms are present in the naturally-occurring terpene α-terpinene shown below?
14 15 16 17 18 I’m not sure how to do this problem 20

How many hydrogen atoms are present in the compound cholesterol shown below?
4 5 38 44 46 I’m not sure how to do this problem 20

ethane < ethylene < acetylene
What is the correct order of carbon-carbon bond lengths in ethane, ethene (ethylene) and ethyne (acetylene)? ethane < ethylene < acetylene ethane < acetylene < ethylene ethylene < ethane < acetylene ethylene < acetylene < ethane acetylene < ethane < ethylene acetylene < ethylene < ethane All the carbon-carbon bonds are the same length 20

Select the best condensed structural formula for the following molecule:
(CH3)2CHCH2COHOHCOH CH3CH3CHCH2C(OH)2CHO (CH3)2CHCH2C(OH)2CHO (CH3)2CHCH2C(OH)2COH CH3CHCH3CH2C(OH)2CHO

Which of the following represents the ground-state electronic configuration for carbon (atomic number 6)? 1s22s22px22py02pz0 1s22s22px12py12pz0 1s22s12px12py1 2pz1 1s12s22px12py1 2pz1 1s22s22px02py02pz2 I am not sure what these symbols mean 20

Section 1.2 1. Which of the following are constitutional isomers of C4H10?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a and c The molecular formula indicates which and how many atoms are in the compound. Each carbon is tetravalent and each hydrogen is monovalent. For more examples of this type of problem, see SkillBuilder 1.1. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answers: Section 1.2 1. Which of the following are constitutional isomers of C4H10? a. A and B b. B and C c. A and C d. A, B and C e. D Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : c The molecular formula indicates which and how many atoms are in the compound. Each carbon is tetravalent and each hydrogen is monovalent. For more examples of this type of problem, see SkillBuilder 1.1. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

3. Which of the following is not a reasonable Lewis Structure?
Section: 1.3 3. Which of the following is not a reasonable Lewis Structure? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c, The fluorine atom only needs one electron added in a covalent bond not 2, so this structure is electron deficient For more examples of this type of problem, see SkillBuilder 1.3 and 1.4. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

For more examples of this type of problem, see SkillBuilder 1.4.
Answer: b For more examples of this type of problem, see SkillBuilder 1.4. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

6. Which of the indicated bonds are polar covalent bonds?
Section: 1.5 6. Which of the indicated bonds are polar covalent bonds? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: 1, 3, 5, 6 Carbon-carbon bonds, carbon-hydrogen bonds are nonpolar. Bonds between carbon and chlorine, carbon and oxygen, oxygen and hydrogen are all polar because the difference in electronegativity is between 0.5 and 1.7. For more examples of this type of problem, see SkillBuilder 1.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

6. Which of the indicated bonds are polar covalent bonds?
Alternate Answers: Section: 1.5 6. Which of the indicated bonds are polar covalent bonds? a. 1, 2, 3, 4, 5, 6, 7 b. 1, 3, 5, 6 c. 1, 3, 4, 7 d. 3, 5, 6, 7 e. 1, 3, 4, 5, 6 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b Carbon-carbon bonds, carbon-hydrogen bonds are nonpolar. Bonds between carbon and chlorine, carbon and oxygen, oxygen and hydrogen are all polar because the difference in electronegativity is between 0.5 and 1.7. For more examples of this type of problem, see SkillBuilder 1.5. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.5 7. Using your knowledge of electronegativity determine the order of decreasing polarity for the bonds between dissimilar atoms in the following molecules a. 1>3>5>2>4 b. 3>1>5>4>2 c. 1>3>2>5>4 d. 5>4>2>1>3 e. 3>1>2>5>4 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: e See section 1.5, the electronegativity difference for K and Cl is the largest for this series, and would be considered an ionic bond, as would the bond between H and F based on the Pauling electronegativities. The bonds between C and H would be considered to be covalent, and the rest are polar covalent Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.6 8. What is the electron configuration of a nitrogen ion with a single negative charge and what neutral atom shares the same electron configuration? a. 1s22s22p2 b. 1s22s22p3 c. 1s22s22p4 d. 1s22s12p3 e. Carbon f. Oxygen g. Phosphorous Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c and f A negative charge will add one electron to the electron configuration of an atom. Nitrogen (atomic number 7) with a negative charge will have 8 electrons and have the same electron configuration as neutral oxygen. For more examples of this type of problem, see SkillBuilder 1.6. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answers: Section: 1.6 8. What is the electron configuration of a nitrogen ion with a single negative charge and what neutral atom shares the same electron configuration? a. 1s22s22p2, oxygen b. 1s22s22p4, oxygen c. 1s22s22p2, carbon d. 1s22s22p4, carbon Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b A negative charge will add one electron to the electron configuration of an atom. Nitrogen (atomic number 7) with a negative charge will have 8 electrons and have the same electron configuration as neutral oxygen. For more examples of this type of problem, see SkillBuilder 1.6. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.6 9. What is the electron configuration of an oxygen ion with a single positive charge and what neutral atom shares the same electron configuration? a. 1s22s22p3 b. 1s22s22p4 c. 1s22s22p5 d. 1s22s12p4 e. Nitrogen f. Fluorine g. Sulfur Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a and e A positive charge will subtract one electron from the electron configuration of an atom. Oxygen (atomic number 8) with a positive charge will have 7 electrons and have the same electron configuration as neutral nitrogen. For more examples of this type of problem, see SkillBuilder 1.6. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Alternate Answers: Section: 1.6 9. What is the electron configuration of an oxygen ion with a single positive charge and what neutral atom shares the same electron configuration? A. 1s22s22p3, nitrogen B. 1s22s22p3, fluorine C. 1s22s12p4, nitrogen D. 1s22s12p4, fluorine Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: a A positive charge will subtract one electron from the electron configuration of an atom. Oxygen (atomic number 8) with a positive charge will have 7 electrons and have the same electron configuration as neutral nitrogen. For more examples of this type of problem, see SkillBuilder 1.6. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.6 What element would be expected to have the following energy diagram for the electron configuration in the ground state? a. boron b. carbon c. nitrogen d. oxygen e. phosphorous Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.9 11. Give the names associated with the orbitals in the following molecular orbital diagram. 1. __________, 2. ___________ 3. __________, 4. ___________ 1. bonding MO, 2. LUMO, 3. antibonding MO, 4. HOMO 1. antibonding MO, 2. LUMO, 3. bonding MO, 4. HOMO 1. bonding MO, 2. HOMO, 3. antibonding MO, 4. LUMO Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.6, 1.7, 1.8, 1.9 14. What is the correct diagram of overlapping atomic orbitals for the pi system of the following structure? a. b. c. d. e. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer : e These diagrams use lines to indicate sigma bonds and atoms involved in multiple bonds have p-orbitals. An atom with a double bond is represented by a single pair of p-orbitals. An atom with a triple bond or a pair of double bonds is represented by a pair of p-orbitals. The pair of p-orbitals must be oriented at right angles to each other (i.e. one vertical and one horizontal as if on the x and y axis of a coordinate system). Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

17. What is the molecular geometry at C in CO2?
Section: 1.10 17. What is the molecular geometry at C in CO2? a. linear b. trigonal planar c. tetrahedral d. trigonal bipyramidal e. octahedral Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

18. What is the molecular geometry at C in CH4?
Section: 1.10 18. What is the molecular geometry at C in CH4? a. linear b. square planar c. square pyramidal d. tetrahedral e. octahedral Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.10 19. What is the hybridization, electronic arrangement, and molecular geometry of the nitrogen atom 1 in the following molecule? a. sp, tetrahedral, trigonal planar b. sp2, trigonal planar, trigonal planar c. sp2, trigonal planar, bent d. sp3, tetrahedral, trigonal planar e. sp3, tetrahedral, trigonal pyramidal Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.10 20. What is the hybridization, electronic arrangement, and molecular geometry of the nitrogen atom 2 in the following molecule? a. sp, tetrahedral, trigonal planar b. sp2, trigonal planar, trigonal planar c. sp2, trigonal planar, bent d. sp3, tetrahedral, trigonal planar e. sp3, tetrahedral, trigonal pyramidal Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section: 1.10 21. What is the hybridization and molecular geometry of the nitrogen atom 3 in the following molecule? a. sp, linear b. sp, not relevant c. sp2, bent d. sp2, trigonal planar e. sp3, tetrahedral Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

22 . Which of the following are polar molecules?
Section: 1.11 22 . Which of the following are polar molecules? a. A and B b. C, D and E c. C and E d. D and E e. all of the above f. none of the above Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: c Structures A and D have polar bonds but no net dipole. Structure B has no polar bonds. Structures C and E have polar bonds and a net dipole. For more examples of this type of problem, see SkillBuilder 1.9. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

22. Which of the following are polar molecules?
Alternate Answers: Section: 1.11 22. Which of the following are polar molecules? a. A and B b. C, D and E c. C and E d. D and E e. all of the above Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Section 1.12 23. Using calculated and measured dipole moments can be used to give a rough approximation of % ionic character, which will be used later in the book as a measure of reactivity at certain atoms. Using the data in the table below, determine which of the carbons labeled 1 – 4 will have the highest partial positive charge. Bond type % ionic character C-O 10% C-Cl 22% O-H 33% C=O 41% a. carbon 1 b. carbon 2 c. carbon 3 d. carbon 4 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b See section The concept of % ionic character will be an important tool in determining the site of probable reaction as you learn more about reactions and mechanisms later in the book. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

24. Which of the following has the highest boiling point?
Section 1.12 24. Which of the following has the highest boiling point? a. propane b. hexanol c. ethyl alcohol d. hexane Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: b For boiling point, the hydrogen bonding of the alcohol is the most powerful intermolecular force. In this example, the alcohol with the largest molecular weight will have a higher boiling point due to greater dispersion forces. For more examples of this type of problem, see SkillBuilder 1.10. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Answer: B These compounds have the same molecular weight but different polarities. The polar compound B will have intermolecular dipole-dipole interactions whereas the nonpolar A compound will only have dispersion forces holding the molecules together. For more examples of this type of problem, see SkillBuilder 1.10. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.

Chemistry Organic Chemistry I Fall, 2016 Day 3 9/2/16

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Chemistry Organic Chemistry I Fall, 2016 Day 3 9/2/16

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