Question 1

What is the main purpose for using metal-ions as catalysts in the following hydrolysis reaction?

Accepted Answer

A) increases the rate by making water a stronger base,thereby increasing its electrophilicity 
B) increases the rate by making water a stronger base,thereby increasing its nucleophilicity 
C) increases the rate by making water a stronger acid,thereby increasing its nucleophilicity 
D) increases the rate by making water a stronger acid,thereby increasing its electrophilicity 
E) increases the rate by making water a stronger acid,thereby decreasing its nucleophilicity 
A) increases the rate by making water a stronger base,thereby increasing its electrophilicity 
B) increases the rate by making water a stronger base,thereby increasing its nucleophilicity 
C) increases the rate by making water a stronger acid,thereby increasing its nucleophilicity 
D) increases the rate by making water a stronger acid,thereby increasing its electrophilicity 
E) increases the rate by making water a stronger acid,thereby decreasing its nucleophilicity

Question 2

Propose a step-by-step mechanism for the general-acid catalyzed reaction shown below.

Accepted Answer

The answer of Propose a step-by-step mechanism for the general-acid...

Question 3

Give the final step for the mechanism for glucose-6-phosphate isomerase.

Accepted Answer

A) In the ring opening reaction,a base catalyst removes a proton from the OH group and an acid catalyst aids in the departure of the leaving group by protonating it. 
B) A base catalyst removes a proton from the a-carbon of the aldehyde. 
C) The enol is converted to a ketone. 
D) The ester group is hydrolyzed. 
E) The conjugate base of the acid catalyst and the conjugate acid of the base catalyst catalyze ring closure. 
A) In the ring opening reaction,a base catalyst removes a proton from the OH group and an acid catalyst aids in the departure of the leaving group by protonating it. 
B) A base catalyst removes a proton from the a-carbon of the aldehyde. 
C) The enol is converted to a ketone. 
D) The ester group is hydrolyzed. 
E) The conjugate base of the acid catalyst and the conjugate acid of the base catalyst catalyze ring closure.

Question 4

Which of the following statements account for the remarkable catalytic ability of enzymes?

Accepted Answer

A) proper positioning and specificity of active site and substrate 
B) proper positioning of amino acid side chains that serve as catalytic groups 
C) ability of the groups on the enzyme to stabilize transition states 
D) A and B 
E) all of the above 
A) proper positioning and specificity of active site and substrate 
B) proper positioning of amino acid side chains that serve as catalytic groups 
C) ability of the groups on the enzyme to stabilize transition states 
D) A and B 
E) all of the above

Question 5

Which of the following intermediates is produced in the second step of the mechanism for bovine chymotrypsin hydrolysis of a peptide bond?

Accepted Answer

A) epoxy-enzyme intermediate 
B) carboxy-enzyme intermediate 
C) acyl-enzyme intermediate 
D) phenoxy-enzyme intermediate 
E) oxy-enzyme intermediate 
A) epoxy-enzyme intermediate 
B) carboxy-enzyme intermediate 
C) acyl-enzyme intermediate 
D) phenoxy-enzyme intermediate 
E) oxy-enzyme intermediate

Question 6

Give the first step for the mechanism for serine protease.

Accepted Answer

A) Histidine functions as a base ,increasing the nucleophilicity of serine,which attacks the carbonyl group. 
B) The tetrahedral complex collapses,expelling the amino group. 
C) Water attacks the acyl group of the acyl-enzyme intermediate. 
D) The tetrahedral intermediate collapses,expelling serine. 
E) The negatively charged oxygen hydrogen bonds with two peptide bonds. 
A) Histidine functions as a base ,increasing the nucleophilicity of serine,which attacks the carbonyl group. 
B) The tetrahedral complex collapses,expelling the amino group. 
C) Water attacks the acyl group of the acyl-enzyme intermediate. 
D) The tetrahedral intermediate collapses,expelling serine. 
E) The negatively charged oxygen hydrogen bonds with two peptide bonds.

Question 7

In the hydrolysis of methyl trifluoroacetate,give two purposes of the zinc catalyst.You may choose more than one answer.

Accepted Answer

A) increases the rate of the first step by providing a metal-bound hydroxide ion 
B) increases the rate of the second step by decreasing the basicity of the leaving group 
C) increases the rate of the second step by increasing the basicity of the leaving group 
D) increases the rate of the first step by providing a metal-bound water molecule 
E) increases the rate of the last step by replacing alkoxide with hydroxide 
A) increases the rate of the first step by providing a metal-bound hydroxide ion 
B) increases the rate of the second step by decreasing the basicity of the leaving group 
C) increases the rate of the second step by increasing the basicity of the leaving group 
D) increases the rate of the first step by providing a metal-bound water molecule 
E) increases the rate of the last step by replacing alkoxide with hydroxide

Question 8

"Being in the right place...can be the most powerful factor of all in determining how fast a reaction goes." In terms of reaction rate theory,this statement refers to the ________ for a reaction.

Accepted Answer

A) probability factor 
B) energy factor 
C) resonance effect 
D) inductive effect 
A) probability factor 
B) energy factor 
C) resonance effect 
D) inductive effect

Question 9

Give the halide that is the most reactive as a nucleophilic catalyst.

Accepted Answer

A) iodide 
B) bromide 
C) chloride 
D) fluoride 
E) All react equally. 
A) iodide 
B) bromide 
C) chloride 
D) fluoride 
E) All react equally.

Question 10

Which of the following is not true about serine proteases?

Accepted Answer

A) They are called serine proteases because they are able to break the peptide chain at the serine linkage. 
B) Endopeptidases and serine proteases are synonyms with each other. 
C) Trypsin,chymotrypsin,and elastase are all serine proteases. 
D) Serine proteases catalyze the hydrolysis of protein peptide chains. 
E) They are called serine proteases because they all have a serine residue that participates in the catalytic process. 
A) They are called serine proteases because they are able to break the peptide chain at the serine linkage. 
B) Endopeptidases and serine proteases are synonyms with each other. 
C) Trypsin,chymotrypsin,and elastase are all serine proteases. 
D) Serine proteases catalyze the hydrolysis of protein peptide chains. 
E) They are called serine proteases because they all have a serine residue that participates in the catalytic process.

Question 11

Which of the following is the best definition of a catalyst?

Accepted Answer

A) It increases the rate of a chemical reaction. 
B) It decreases the rate of a reaction. 
C) It decreases activation energy. 
D) It increases activation energy. 
E) A and C 
A) It increases the rate of a chemical reaction. 
B) It decreases the rate of a reaction. 
C) It decreases activation energy. 
D) It increases activation energy. 
E) A and C

Question 12

Predict the product of the following reaction involving general acid catalysis.
(Hint: Six membered ring is formed through intramolecular cyclization.)

Accepted Answer

The answer of Predict the product of the following reaction...

Question 13

________ molarity is the concentration of the reactant that would be required to give the corresponding intermolecular reaction the same rate as its intramolecular counterpart.

Accepted Answer

A) Effective 
B) Entropic 
C) Enthalpic 
D) Hyperionic 
E) Deficient 
A) Effective 
B) Entropic 
C) Enthalpic 
D) Hyperionic 
E) Deficient

Question 14

Which of the following sets of amino acids is found in all serine proteases?

Accepted Answer

A) arginine,histidine,serine 
B) arginine,aspartate,serine 
C) proline,histidine,serine 
D) aspartate,histidine,serine 
E) aspartate,proline,serine 
A) arginine,histidine,serine 
B) arginine,aspartate,serine 
C) proline,histidine,serine 
D) aspartate,histidine,serine 
E) aspartate,proline,serine

Question 15

A pure sample of the trans-2-bromocyclopentanol enantiomer shown below reacts with HCl.The reaction proceeds by way of a bromonium ion.What is/are the product(s)of the reaction?

Accepted Answer

A) I only 
B) II only 
C) I and III 
D) II and IV 
A) I only 
B) II only 
C) I and III 
D) II and IV

Question 16

Hydrolysis of esters occurs more rapidly in the presence of catalytic imidazole.Explain this phenomenon and provide the structure of the acyl imidazole intermediate which is formed in the catalyzed process.

Accepted Answer

Imidazole is a better nucleophile than w

Question 17

Describe the reaction coordinate diagram for a specific-acid-catalyzed reaction.

Accepted Answer

A) one peak 
B) two peaks,second peak is larger 
C) two peaks,second peak is smaller 
D) two peaks,equal size 
E) three peaks,middle peak is larger 
A) one peak 
B) two peaks,second peak is larger 
C) two peaks,second peak is smaller 
D) two peaks,equal size 
E) three peaks,middle peak is larger

Question 18

Describe the first step of a general-base-catalyzed dehydration of a hydrate.

Accepted Answer

A) Base abstracts a proton,electron pair from O-H bond goes to oxygen. 
B) Negative charge from oxygen forms double bond,hydroxide departs as leaving group. 
C) Base abstracts a proton,electron pair from O-H bond forms a double bond,hydroxide departs as leaving group. 
D) Hydroxide departs as leaving group,then negative charge from oxygen forms a double bond. 
E) Electron pair from O-H bond forms a double bond,base abstracts a proton. 
A) Base abstracts a proton,electron pair from O-H bond goes to oxygen. 
B) Negative charge from oxygen forms double bond,hydroxide departs as leaving group. 
C) Base abstracts a proton,electron pair from O-H bond forms a double bond,hydroxide departs as leaving group. 
D) Hydroxide departs as leaving group,then negative charge from oxygen forms a double bond. 
E) Electron pair from O-H bond forms a double bond,base abstracts a proton.

Question 19

Give the first step of the mechanism for aldolase.

Accepted Answer

A) Fructose-1,6,-diphosphate forms an imine with a lysine residue at the active site of the enzyme. 
B) A tyrosine residue functions as a base catalyst to cleave the bond between C-3 and C-4. 
C) The enamine intermediate rearranges to an imine. 
D) Hydrolysis of the imine releases dihydroxyacetone phosphate. 
E) A molecule of glyceraldehyde-3-phosphate is expelled. 
A) Fructose-1,6,-diphosphate forms an imine with a lysine residue at the active site of the enzyme. 
B) A tyrosine residue functions as a base catalyst to cleave the bond between C-3 and C-4. 
C) The enamine intermediate rearranges to an imine. 
D) Hydrolysis of the imine releases dihydroxyacetone phosphate. 
E) A molecule of glyceraldehyde-3-phosphate is expelled.

Question 20

Show why typical metal-bound water has a considerably lower pKa than that of water.

Accepted Answer

The metal ion binds to water making it e

Exam 22: Catalysis in Organic Reactions and in Enzymatic Reactions

What is the main purpose for using metal-ions as catalysts in the following hydrolysis reaction?

Propose a step-by-step mechanism for the general-acid catalyzed reaction shown below.

Give the final step for the mechanism for glucose-6-phosphate isomerase.

Which of the following statements account for the remarkable catalytic ability of enzymes?

Which of the following intermediates is produced in the second step of the mechanism for bovine chymotrypsin hydrolysis of a peptide bond?

Give the first step for the mechanism for serine protease.

In the hydrolysis of methyl trifluoroacetate,give two purposes of the zinc catalyst.You may choose more than one answer.

"Being in the right place...can be the most powerful factor of all in determining how fast a reaction goes." In terms of reaction rate theory,this statement refers to the ________ for a reaction.

Give the halide that is the most reactive as a nucleophilic catalyst.

Which of the following is not true about serine proteases?

Which of the following is the best definition of a catalyst?

Predict the product of the following reaction involving general acid catalysis. (Hint: Six membered ring is formed through intramolecular cyclization.)

________ molarity is the concentration of the reactant that would be required to give the corresponding intermolecular reaction the same rate as its intramolecular counterpart.

Which of the following sets of amino acids is found in all serine proteases?

A pure sample of the trans-2-bromocyclopentanol enantiomer shown below reacts with HCl.The reaction proceeds by way of a bromonium ion.What is/are the product(s)of the reaction?

Hydrolysis of esters occurs more rapidly in the presence of catalytic imidazole.Explain this phenomenon and provide the structure of the acyl imidazole intermediate which is formed in the catalyzed process.

Describe the reaction coordinate diagram for a specific-acid-catalyzed reaction.

Describe the first step of a general-base-catalyzed dehydration of a hydrate.

Give the first step of the mechanism for aldolase.

Show why typical metal-bound water has a considerably lower pKa than that of water.

Remembering General Chemistry: Electronic Structure and Bonding

Acids and Bases: Central to Understanding Organic Chemistry

An Introduction to Organic Compounds: Nomenclature, physical Properties, and Structure

Isomers: the Arrangement of Atoms in Space

Alkenes: Structure,nomenclature,and an Introduction to Reactivity - Thermodynamics and Kinetics

The Reactions of Alkenes - the Stereochemistry of Addition Reactions

The Reactions of Alkynes - Introduction to Multistep Synthesis

Delocalized Electrons: Their Effect on Stability, pka, and the Products of a Reaction - Aromaticity and Electronic Effects: an Introduction to the Reactions of Benzene

Substitution and Elimination Reactions of Alkyl Halides

Reactions of Alcohols, ethers, epoxides, amines and Sulfur-Containing Compounds

Organometallic Compounds

Radicals

Mass Spectrometry,infrared Spectroscopy,and Uvvis Spectroscopy

Nmr Spectroscopy

Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

Reactions of Aldehydes and Ketones

Reactions at the Α-Carbon

Reactions of Benzene and Substituted Benzenes

More About Amines - Reactions of Heterocylic Compounds

The Organic Chemistry of Carbohydrates

Amino Acids,peptides,and Proteins

The Organic Chemistry of the Coenzymes, compounds Derived From Vitamins

The Organic Chemistry of the Metabolic Pathways

The Organic Chemistry of Lipids

The Chemistry of the Nucleic Acids

Synthetic Polymers

Pericyclic Reactions

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