Organic Chemistry : Help with Substitution Reactions

Study concepts, example questions & explanations for Organic Chemistry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #21 : Reactions Types

A solvolysis reaction occurs when dimethyl bromoethane is placed in methanol.

What is the final product?

Possible Answers:

2-methoxy-2-methylpropane

2-ethoxy-3-propanoic acid

3-methoxy-2-ethylbutane

3-isoproxy-1-butanol

Correct answer:

2-methoxy-2-methylpropane

Explanation:

A solvolysis reaction is simply an  reaction where the solvent acts as a nucleophile.

In this case, we start with a tertiary alkyl halide. Bromine, a stellar leaving group, leaves the substrate and leaves a carbocation intermediate. The methanol is then free to attack the carbon chain at the site of the carbocation to form an ether. The correct answer is 2-methoxy-2-methylpropane.

Example Question #111 : Organic Chemistry

Which of the following reagents would convert 2-butanol into 2-bromobutane?

Possible Answers:

Correct answer:

Explanation:

The correct answer is .

Alcohol is a horrible leaving group.  is often employed to convert an alcohol group into a bromine group so that additional substitution and elimination reactions can ensue.

Example Question #23 : Reactions Types

Screen shot 2015 11 09 at 2.33.03 pm

Screen shot 2015 11 09 at 2.41.49 pm

Possible Answers:

II only

III only

I only

I and II

Correct answer:

II only

Explanation:

Cyanide is a weak base and a good nucleophile, and the solvent is aprotic; therefore, the  product is favored. This involves 100% inversion of stereochemistry; therefore II is favored.

Example Question #24 : Reactions Types

Question 10

Which of these molecules would undergo a faster SN2 reaction?

Possible Answers:

They would react at the same rate.  

3-iodo-1-butene

2-iodobutane

Neither would undergo the reaction.

Correct answer:

3-iodo-1-butene

Explanation:

The double bond in 3-iodo-1-butene would stabilize the transition state through resonance. This would make the transition state lower in energy due to its increased stability. Thus, the reaction would be faster as reactions with lower activation energies proceed at faster rates. 

Example Question #25 : Reactions Types

Question 10

Would this reaction proceed through an SN1 or SN2 mechanism?

Possible Answers:

 SN1

Neither

SN2

Both

Correct answer:

 SN1

Explanation:

This reaction would use an  SN1 mechanism because the leaving group, bromine, is on a tertiary carbon, which is a carbon attached to three other carbon atoms. The bulk of these methyl groups would make SN2 impossible, but it would make the carbocation produced by an  SN1 reaction very stable. The methyl group would lead to hyperconjugation, which is a type of resonance that stabilizes transition states. 

Example Question #22 : Reactions Types

Screen shot 2016 02 21 at 6.39.54 am

Classify the type of reaction given.

Possible Answers:

Substitution

Addition

Elimination

Rearrangement

Correct answer:

Substitution

Explanation:

A substitution reaction is a chemical reaction that occurs when the reactants exchange atoms to form new products. In the reaction given the chloride in chloromethane  is substituted for the hydroxide in sodium hydroxide to form methanol. Also the hydroxide in sodium hydroxide is substituted for the chloride in chloromethane to form sodium chloride.

Example Question #23 : Reactions Types

Screen shot 2016 02 22 at 11.06.36 am

 Classify the type of reaction given.

Possible Answers:

Substitution

Catalytic

Elimination

Addition

Correct answer:

Substitution

Explanation:

A substitution reaction is a chemical reaction that occurs when the reactants exchange atoms to form new products. In the reaction given the chloride and hydroxyl groups in water and 2-chloro-2-methylpropane are exchanged in the reactants to form two new products.

Example Question #24 : Reactions Types

Screen shot 2016 02 22 at 11.02.15 am

Classify the type of reaction given.

Possible Answers:

Substitution

Heterolytic

reaction

Addition

Correct answer:

Substitution

Explanation:

A substitution reaction is a chemical reaction that occurs when the reactants exchange atoms to form new products. In the reaction given the chloride in 1-chloro-4-nitrobenzene  is substituted for the hydroxide in sodium hydroxide to form 4-nitrophenol. Also the hydroxide in sodium hydroxide is substituted for the chloride in 1-chloro-4-nitrobenzene to form sodium chloride.

Example Question #25 : Reactions Types

Screen shot 2016 02 21 at 7.20.51 am

Classify the type of reaction given.

Possible Answers:

Addition

Elimination

Substitution

Rearrangement

Correct answer:

Substitution

Explanation:

A substitution reaction is a chemical reaction that occurs when the reactants exchange atoms to form new products. In the reaction given the hydrogen atom in benzene is substituted for the nitro group in nitric acid to form nitrobenzene.

Example Question #31 : Reactions Types

What is the product of the reaction shown?


Image8

Possible Answers:

None of these

Correct answer:

Explanation:

The reaction shown is a nucleophilic substitution reaction. The molecule shown is a primary alkyl bromide, and the nucleophile that will be used is the iodide anion (). In this type of reaction the iodide will displace the bromide on the organic molecule, generating iodoethane ().

Learning Tools by Varsity Tutors