Question 1

How do alkyl substituents stabilize a carbocationic center to which they are attached?

Accepted Answer

A)  through an inductive donation of electron density to the cationic center 
B)  through an inductive removal of electron density from the cationic center 
C)  through hyperconjugation 
D)  both A and C 
E)  both B and C 
A)  through an inductive donation of electron density to the cationic center 
B)  through an inductive removal of electron density from the cationic center 
C)  through hyperconjugation 
D)  both A and C 
E)  both B and C

Question 2

Do you expect the initiation step in the free radical chlorination of 2,2-dimethylpropane to be endo- or exothermic? Explain briefly, and comment on the sign of DH.

Accepted Answer

The initiation step of this me

Question 3

When 1,1,3,3-tetramethylcyclobutane is brominated at 125°C, the relative reactivity of the 1°: 2°: 3° hydrogens is approximately 1:82:1600. Estimate the amount of each monobromination product.

Accepted Answer

primary br

Question 4

Remove an H+ from the following structure to create the most reactive (least stable) carbanion.

Accepted Answer

The answer of Remove an H+ from the following structure...

Question 5

Provide the major organic product that results when 2,2,4-trimethylpentane is subjected to free radical bromination.

Accepted Answer

The answer of Provide the major organic product that results...

Question 6

The following reaction occurs readily:   Experimentally one finds that if the concentration of I- is doubled, the rate doubles. Also if the concentration of CH3Br is halved, the rate is halved. What is the rate equation for this reaction?

Accepted Answer

Question 7

Given that tertiary H atoms react with a chlorine radical about 5.5 times faster than primary ones, estimate the ratio of the two monochlorinated products that result when 2,3-dimethylbutane undergoes free radical chlorination.

Accepted Answer

1-chloro-2,3-dimethy

Question 8

Which of the halogens below undergoes free radical halogenation with ethane most rapidly?

Accepted Answer

A)  fluorine 
B)  chlorine 
C)  iodine 
D)  bromine 
E)  pyridine 
A)  fluorine 
B)  chlorine 
C)  iodine 
D)  bromine 
E)  pyridine

Question 9

What term describes the highest-energy structure in a molecular collision which leads to reaction?

Accepted Answer

The answer of What term describes the highest-energy structure in...

Question 10

Provide the structure of the transition state in the first propagation step of the free radical chlorination of ethane.

Accepted Answer

The answer of Provide the structure of the transition state...

Question 11

Given the bond dissociation energies below (in kcal/mol), estimate the ΔH° for the propagation step

CH3CH2CH2-H 98
 (CH3)2CH-H 95
Cl-Cl 58
H-Cl 103
CH3CH2CH2-Cl 81
(CH3)2CH-Cl 80

Accepted Answer

A)  -22 kcal/mol 
B)  +22 kcal/mol 
C)  -40 kcal/mol 
D)  +45 kcal/mol 
A)  -22 kcal/mol 
B)  +22 kcal/mol 
C)  -40 kcal/mol 
D)  +45 kcal/mol

Question 12

In an exothermic reaction, are stronger bonds broken and weaker bonds formed or are weaker bonds broken and stronger bonds formed?

Accepted Answer

In an exothermic rea

Question 13

For a given reaction, if ΔG° is greater than zero, then:

Accepted Answer

A)  Keq eq = 0. 
C)  0 eq eq = 1. 
E)  Keq > 1. 
A)  Keq eq = 0. 
C)  0 eq eq = 1. 
E)  Keq > 1.

Question 14

Rank the free radicals (I-III) shown below in order of decreasing stability (i.e., from most stable to least stable).

Accepted Answer

A)  I > III > II 
B)  II > III > I 
C)  I > II > III 
D)  II > I > III 
E)  III > II > I 
A)  I > III > II 
B)  II > III > I 
C)  I > II > III 
D)  II > I > III 
E)  III > II > I

Question 15

Do you expect the initiation step in the free radical chlorination of 2,2-dimethylpropane to have a positive or negative DS? Explain briefly.

Accepted Answer

One expects a positive DS for

Question 16

What accounts for the relatively high stability of the benzyl radical?

Accepted Answer

The unpaired electro

Question 17

Which of the following is true for the termination step of a free radical chlorination reaction?

Accepted Answer

A) ΔH° > 0 and ΔS° > 0 B) ΔH° > 0 and ΔS° 0 D) ΔH° < 0 and ΔS° < 0 E) ΔH° = 0 and ΔS° = 0 A) ΔH° > 0 and ΔS° > 0 B) ΔH° > 0 and ΔS° 0 D) ΔH° < 0 and ΔS° < 0 E) ΔH° = 0 and ΔS° = 0

Question 18

Draw an energy diagram for a two step reaction where the structure of the transition state of the rate determining step most closely resembles the starting material and the overall reaction is exothermic.

Accepted Answer

The answer of Draw an energy diagram for a two...

Question 19

If ΔG° for a given reaction at 25°C is less than zero, which of the following statements also correctly describes this reaction at this temperature?

Accepted Answer

A)  The reaction must be exothermic. 
B)  The reaction must be endothermic. 
C)  Keq is greater than zero. 
D)  Both A and C are true. 
E)  Both B and C are true. 
A)  The reaction must be exothermic. 
B)  The reaction must be endothermic. 
C)  Keq is greater than zero. 
D)  Both A and C are true. 
E)  Both B and C are true.

Question 20

When Br radical reacts with 1-butene (CH3CH2CH=CH2), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.

Accepted Answer

CHS1U1B13S1U1B0 @#IMG-DLM& HCH =

Exam 4: The Study of Chemical Reactions

How do alkyl substituents stabilize a carbocationic center to which they are attached?

Do you expect the initiation step in the free radical chlorination of 2,2-dimethylpropane to be endo- or exothermic? Explain briefly, and comment on the sign of DH.

When 1,1,3,3-tetramethylcyclobutane is brominated at 125°C, the relative reactivity of the 1°: 2°: 3° hydrogens is approximately 1:82:1600. Estimate the amount of each monobromination product.

Remove an H+ from the following structure to create the most reactive (least stable) carbanion.

Provide the major organic product that results when 2,2,4-trimethylpentane is subjected to free radical bromination.

The following reaction occurs readily: Experimentally one finds that if the concentration of I- is doubled, the rate doubles. Also if the concentration of CH3Br is halved, the rate is halved. What is the rate equation for this reaction?

Given that tertiary H atoms react with a chlorine radical about 5.5 times faster than primary ones, estimate the ratio of the two monochlorinated products that result when 2,3-dimethylbutane undergoes free radical chlorination.

Which of the halogens below undergoes free radical halogenation with ethane most rapidly?

What term describes the highest-energy structure in a molecular collision which leads to reaction?

Provide the structure of the transition state in the first propagation step of the free radical chlorination of ethane.

Given the bond dissociation energies below (in kcal/mol), estimate the ΔH° for the propagation step CH3CH2CH2-H 98 (CH3)2CH-H 95 Cl-Cl 58 H-Cl 103 CH3CH2CH2-Cl 81 (CH3)2CH-Cl 80

In an exothermic reaction, are stronger bonds broken and weaker bonds formed or are weaker bonds broken and stronger bonds formed?

For a given reaction, if ΔG° is greater than zero, then:

Rank the free radicals (I-III) shown below in order of decreasing stability (i.e., from most stable to least stable).

Do you expect the initiation step in the free radical chlorination of 2,2-dimethylpropane to have a positive or negative DS? Explain briefly.

What accounts for the relatively high stability of the benzyl radical?

Which of the following is true for the termination step of a free radical chlorination reaction?

Draw an energy diagram for a two step reaction where the structure of the transition state of the rate determining step most closely resembles the starting material and the overall reaction is exothermic.

If ΔG° for a given reaction at 25°C is less than zero, which of the following statements also correctly describes this reaction at this temperature?

When Br radical reacts with 1-butene (CH3CH2CH=CH2), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.

Introduction and Review

Structure and Properties of Organic Molecules

Structure and Stereochemistry of Alkanes

Stereochemistry

Alkyl Halides: Nucleophilic Substitution and Elimination

Structure and Synthesis of Alkenes

Reactions of Alkenes

Alkynes

Structure and Synthesis of Alcohols

Reactions of Alcohols

Infrared Spectroscopy and Mass Spectrometry

Nuclear Magnetic Resonance Spectroscopy

Ethers, Epoxides, and Thioethers

Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Aromatic Compounds

Reactions of Aromatic Compounds

Ketones and Aldehydes

Amines

Carboxylic Acids

Carboxylic Acid Derivatives

Condensations and Alpha Substitutions of Carboxyl Compounds

Carbohydrates and Nucleic Acids

Amino Acids, Peptides, and Proteins

Lipids

Synthetic Polymers

Filters

The following reaction occurs readily: Experimentally one finds that if the concentration of I^- is doubled, the rate doubles. Also if the concentration of CH₃Br is halved, the rate is halved. What is the rate equation for this reaction?

Given the bond dissociation energies below (in kcal/mol), estimate the ΔH° for the propagation step CH₃CH₂CH₂-H 98 (CH₃)₂CH-H 95 Cl-Cl 58 H-Cl 103 CH₃CH₂CH₂-Cl 81 (CH₃)₂CH-Cl 80

When Br radical reacts with 1-butene (CH₃CH₂CH=CH₂), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.