Organic Chemistry : Organic Chemistry

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #1 : Help With Addition Reactions

Screen shot 2016 02 21 at 6.40.00 am

Classify the type of reaction given.

Possible Answers:

Addition

Rearrangement

Substitution

Elimination

Correct answer:

Addition

Explanation:

An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and ethylene combine to form the product 1-chloropropane.

Example Question #2 : Help With Addition Reactions

Screen shot 2016 02 21 at 6.40.08 am

Classify the type of reaction given.

Possible Answers:

Substitution

Addition

Rearrangement

Elimination

Correct answer:

Addition

Explanation:

An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants 2-butene and molecular hydrogen combine to form the product butane.

Example Question #3 : Help With Addition Reactions

Screen shot 2016 02 21 at 7.44.55 am

Classify the type of reaction given.

Possible Answers:

Substitution

Addition

Elimination

Rearrangement

Correct answer:

Addition

Explanation:

An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrochloric acid and propyne combine to form the product 2-chloropropene.

Example Question #4 : Reactions Types

Screen shot 2016 02 21 at 7.45.00 am

Classify the type of reaction given above.

Possible Answers:

Rearrangement

Addition

Substitution

Elimination

Correct answer:

Addition

Explanation:

An addition reaction is a reaction in which the reactants react to combine and form one product. It is the opposite of an elimination reaction. In the reaction given, the reactants hydrobromic acid and propene combine to form the product 2-bromopropane.

Example Question #101 : Organic Chemistry

What is the major product of the following reaction?

Image1

Possible Answers:

None of these

Correct answer:

Explanation:

The reaction shown is a Markovnikov addition of a hydracid (HX) across a double bond. According to Markovnikov's rule, the hydrogen gets added to the lesser-substituted carbon in the double bond, and the halide (in this case, ) gets added to the more-substituted carbon. Thus, the correct answer is .

Example Question #102 : Organic Chemistry

Which of the following reaction conditions favors an SN1 mechanism?

Possible Answers:

Weak electrophile

Weak base

Strong base

Strong nucleophile

Protic solvent

Correct answer:

Protic solvent

Explanation:

SN1 reactions occur in two steps. First, the leaving group leaves, forming a carbocation. Next, the weak nucleophile attacks the carbocation (beware of rearrangements during this step). The protic solvent stabilizes the carbocation intermediate. 

Example Question #103 : Organic Chemistry

Which of the following reaction conditions favors an SN2 mechanism?

Possible Answers:

Weak base

Tertiary alkyl halide substrate

Strong base

Strong nucleophile

Protic solvent

Correct answer:

Strong nucleophile

Explanation:

SN2 reactions undergo substitution via a concerted mechanism. Thus, no carbocation is formed, and an aprotic solvent is favored. Furthermore, tertiary substituted substrates have lowest reactivity for SN2 reaction mechanisms due to steric hindrance.

Example Question #104 : Organic Chemistry

Which of the following characteristics does not reflect an SN2 reaction mechanism?

Possible Answers:

Concerted mechanism

Aprotic solvent

Stereochemical inversion of the carbon attacked (backside attack)

Tertiary substrate

Strong nucleophile

Correct answer:

Tertiary substrate

Explanation:

SN2 reaction mechanisms are favored by methyl/primary substrates because of reduced steric hindrance. No carbocation is formed via an SN2 mechanism since the mechanism is concerted; thus a strong nuclephile is used.

Example Question #105 : Organic Chemistry

Which of the following characteristics does not reflect an SN1 reaction mechanism?

Possible Answers:

Formation of a racemic mixture of products

Unimolecular reaction rate

Use of a protic solvent

Formation of a carbocation intermediate

Use of a strong nucleophile

Correct answer:

Use of a strong nucleophile

Explanation:

All of the given answers reflect SN1 reactions, except the claim that SN1 reactions are favored by weak nucleophiles.

SN1 reactions occur in two steps and involve a carbocation intermediate. The product demonstrates inverted stereochemistry (no racemic mixture). Tertiary substrates are preferred in this mechanism because they provide stabilization of the carbocation.

Example Question #106 : Organic Chemistry

In a substitution reaction __________.

Possible Answers:

two sigma bonds are broken and one pi bond is formed

one sigma bond is broken and one sigma bond is formed

one sigma and one pi bond are broken, and two sigma bonds are formed

one pi bond is broken and two sigma bonds are formed

one pi bond is broken and one pi bond is formed

Correct answer:

one sigma bond is broken and one sigma bond is formed

Explanation:

Substitution reactions—regardless of the mechanism—involve breaking one sigma bond, and forming another sigma bond (to another group).

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