Hw 6: Organic Halogens (copy)

What is the IUPAC name of the following alkyl halide?CH 3 C(CH 3 )Cl(CH 2 ) 2 CH 3

A) 2-chloro-6-methylpentane

B) 6-methyl-2-chloropentane

C) 2-methyl-6-chloropentane

D) 2-chloro-2-methylpentane

E) 2-chloro-5-isopropylpentane

D) 2-chloro-2-methylpentane

Which of the following is the best nucleophile?

A) H 2 O

B) HO -

C) HS -

D) H₃S

E) all are the same

C) HS-

Which of the following is the best nucleophile?

A) H₂O

B) CH₄

C) NH₃

D) HF

E) PH₃

C) NH₃

Which of the following is the best leaving group?

A) F -

B) Cl -

C) I -

D) Br -

E) H₂N -

C) I -

Which of the following is the strongest base?

A) H₂O

B) - OH

C) NH₃

D) - NH₂

E) F -

D) -NH₂

The reactivity order of the following as nucleophiles is:

1. CH₃S -   2. CH₃O-    3. CH₃OH

A) 1> 2 > 3

B) 2 > 3 > 1

C) 2 > 1 > 3

D) 3 > 2 > 1

E) 1 > 3 > 2

A

What is the mechanism of the following reaction?

A) S_N1

B) S_N2

C) E1

D) E2

E) both A and B

B) S_N2

Which statement is true for S_N2 reactions?

A) The rate of the reaction is dependent on the stability of a carbocation.

B) The rate of reaction is dependent on just the substrate.

C) The fastest reaction will occur with a tertiary halide.

D) Displacement occurs with inversion of configuration.

E) The mechanism is a two step process.

D

Which bromide reacts fastest in SN2 reactions?

A) CH₃Br

B) (CH₃)₂CHBr

C) (CH₃)₃CBr

D) (CH₃)₃CCH₂Br

E) CH₃CH₂Br

A) CH₃Br

What is the rate-determining step in an SN1 reaction?

A) Attack of the nucleophile

B) Loss of the leaving group to form a carbocation

C) Deprotonation of the nucleophile

D) Collision between the nucleophile and substrate

E) all are the same

B

Which of the following substrates will react fastest in an SN1 reaction?

A) Methyl chloride

B) Tertiary butyl bromide

C) Primary butyl bromide

D) Secondary butyl bromide

E) The rate is equal for all substrates

B) Tertiary butyl bromide

Polyhalogenated aliphatic compounds have not been used as:

A) food preservatives

B) fire retardants

C) degreasing agents

D) insecticides

E) refrigerants

A

SN1 reactions proceed through which type of intermediate?

A) Carbanion

B) Carbocation

C) Free radical

D) Transition state

E) basic

B) Carbocation 

Which is the correct rate law for an SN1 reaction?

A) Rate = k[substrate][nucleophile]

B) Rate = k[substrate]

C) K[ k[product]

D) Rate = k[nucleophile]

E) Rate = k[substrate]²

B) Rate= k[substrate]

Which of the following solvents favors an SN1 mechanism?

A) Hexane

B) diethyl ether

C) acetone

D) water

E) benzene

D) Water

Which of the following best describes the SN2 reaction mechanism?

A) One-step mechanism with backside attack

B) Elimination followed by nucleophilic attack

C) One-step mechanism with carbocation formation

D) Two-step mechanism with carbocation intermediate

E) Addition followed by nucleophilic attack

A

The slowest step of an SN1 reaction involves:

A) attack of the nucleophile on the substrate to form a pentavalent carbon.

B) breaking the bond between the carbon and the leaving group to give a carbocation.

C) combination of a nucleophile with the carbocation to give the product.

D) loss of a proton from the nucleophile to give the product.

E) none of the above.

B

The S_N2 mechanism for nucleophilic substitution reactions

A) involves two steps and occurs with inversion of configuration.

B) involves one step and occurs with inversion of configuration.

C) involves two steps and occurs with racemization.

D) involves one step and occurs with retention of configuration.

E) involves one step and occurs with racemization.

B) Involve one step and occurs with inversion of configuration

The S_N1 mechanism for nucleophilic substitution reactions

A) involves one step and occurs fastest with primary halides.

B) involves one step and occurs fastest with tertiary halides.

C) involves two steps and occurs fastest with tertiary halides.

D) involves two steps and occurs fastest with primary halides.

E) involves one step and occurs fastest with aromatic halides.

C) Involve two steps and occurs fastest with tertiary halides 

The energy-reaction diagram below is for

A) an S_N2 reaction

B) an S_N1 reaction

C) an E2 reaction

D) an E1 reaction

E) both S_N1 and E1 reactions

F) Both S_N2 and E2 reactions

B) an S_N1 reaction

What is the correct rate law for an SN2 reaction?

A) Rate = k[substrate]

B) Rate = k[nucleophile]

C) Rate = k[substrate][nucleophile]

D) Rate = k[substrate]²

E) Rate = k[nucleophile]²

C) Rate= k[substrate][nucleophile]

What is the rate-determining step in an E1 reaction?

A) Loss of the base

B) Formation of the carbocation

C) Attack by the nucleophile

D) Elimination of the proton

E) Attack by the base

B) Formation of the carbocation

What is the correct rate law for an E1 reaction?

A)

B) Rate = k[base]

C) Rate = k[substrate]

D) Rate = k[base]²

E) Rate = k[substrate][base]

C) Rate= k[substrate]

When 1-bromobutane is reacted with the bulky base, potassium tert-butoxide, in tert-butyl alcohol, the major elimination product is:

A) 1-butene

B) cis-2-butene

C) trans-2-butene

D) butyl tert-butyl ether

E) butyl alcohol

A) 1-butene

Which of the following substrates is most reactive in an E1 reaction?

A) Methyl chloride

B) Tertiary butyl bromide

C) Primary butyl bromide

D) Secondary butyl bromide

E) The rate is equal for all substrates

B) Tertiary butyl bromide 

In E1 reactions, what is the role of the base?

A) To attack the carbocation directly

B) To generate the leaving group

C) To remove a proton from the β-carbon

D) To replace the leaving group

E) To add a proton on the substrate

C) To remove a proton from the β-carbon

What is the defining feature of the E2 reaction mechanism?

A) Two-step mechanism with carbocation intermediate

B) Simultaneous removal of a proton and leaving group in one step

C) Involves nucleophilic substitution

D) Proceeds only with tertiary substrates

B) Simultaneous removal of a proton and leaving group in one step

What is the rate law for an E2 reaction?

A) Rate = k[substrate]

B) Rate = k[base]

C) Rate = k[substrate][base]

D) Rate = k[base]²

E) Rate = k[base][product]

C) Rate= k[substrate][base]

What alkyne is produced when a base reacts with CH₃CH₂CH₂I?

A) 2-pentyne

B) 1-pentyne

C) 2-pentene

D) 1-pentene

E) butyne

B) 1-pentyne 

Which of the following substrates reacts fastest via the E2 mechanism?

A) Primary alkyl bromide

B) Methyl bromide

C) Secondary alkyl bromide

D) Tertiary alkyl bromide

E) All of the above

D) Tertiary alkyl bromide 

Which of the following is a polar aprotic solvent?

A) H₂O

B) CH₃CN

C) CH₃OH

D) (CH₃)₂S=O

E) both B and D

E) both B and D

What is the rate-determining step in an SN1 reaction?

The loss of the leaving group to form a carbocation

Which type of carbocation is most stable in SN1 reactions? Give reasons.

Tertiary carbocation. It is stabilized by hyperconjugation and inductive effects from three alkyl groups 

Why are primary alkyl halides not suitable for SN1?

Because Primary carbocations are too unstable to form, so SN1 cannot occur

Which type of halide (methyl, primary, secondary, tertiary) is best for SN2 and why?

Methyl and Primary halides. Because less steric hindrance allows easy backside attack in SN2

Why are bulky groups near the reaction site a problem in SN2 reactions?

Because they block the nucleophile’s backside attack, slowing or preventing SN2

What type of solvent favors SN2 reactions: polar protic or aprotic ? Explain.

Polar aprotic solvents. They don’t solvate anions strongly, keeping nucleophiles reactive 

How does SN2 differ from SN1 in terms of intermediate formation?

SN2 has no intermediate, while SN1 forms a carbocation intermediate

What condition is required between the leaving group and β-hydrogen in E2?

The β-hydrogen and leaving group must be anti-periplanar (opposite sides)

Write the general rate law for an E2 reaction.

Rate= k[substrate][base]

What kind of substrate is most reactive in E2?

Tertiary Substrates 

How does the strength of the base affect the E1 reaction?

Base strength has little effect on E1 rate 

What is the role of the base in E2?

It removes a β-hydrogen, forming the double bond

What type of substrate (primary, secondary, tertiary) favors E1?

The Tertiary substrates

What kind of solvent is ideal for E1 reactions?

Polar protic solvents