Organic Chemistry : Help with Addition Reactions

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

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Example Question #1 : Help With Addition Reactions

In an addition reaction

Possible Answers:

one sigma bond is broken, and one sigma bond is formed

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

one pi bond is broken, and one pi bond is formed

none of these

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

Correct answer:

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

Explanation:

Addition reactions involve breaking one pi bond (double bond) and forming two sigma bonds in the product. 

Example Question #2 : Help With Addition Reactions

A compound  can be hydrogenated by platinum metal and hydrogen to give . How many rings and double bonds does the original compound have?

The original compound has no triple bonds.

Possible Answers:

3 double bonds and 2 rings

4 double bonds and 2 rings

None of the other answers

4 double bonds and 1 ring

3 double bonds and 1 ring

Correct answer:

3 double bonds and 2 rings

Explanation:

Hydrogenation of a double bond involves the bond breaking and a hydrogen being added to each carbon of that double bond. You can tell the number of double bonds by taking the number of hydrogens added and dividing it by 2.

6 added hydrogen divided by 2 is 3 double bonds.

A hydrocarbon with zero degrees of unsaturation and  carbons has  hydrogens. For every two hydrogens less than , there is one degree of unsaturation. After hydrogenation, our final product has no double bonds. After calculation, we see that it has two degrees of unsaturation. This means that it has two rings.

Example Question #94 : Organic Chemistry

Which of the following reagents are required to convert 1-pentene to pentane?

Possible Answers:

Methanol

Correct answer:

Explanation:

In order to convert an alkene into an alkane, we need a  catalyst.

Example Question #4 : Help With Addition Reactions

Ph = phenyl = benzene

Which reagent would work best to convert  into ?

Possible Answers:

Correct answer:

Explanation:

We can reduce the alkene here by simply adding two hydrogens with  as a reagent.

Example Question #5 : Help With Addition Reactions

1 pentene

Suppose that the given reactant, 1-hexene, is reacted with  in the presence of ultraviolet light. Which of the following is the major product?

Possible Answers:

3 bromo hexane

Bromo pentane

2 bromo pentane

1 2 3 tribromo hexane

Correct answer:

Bromo pentane

Explanation:

In this question, we're told that our starting material, 1-hexene, is being reacted with hydrobromic acid in the presence of ultraviolet (UV) light. To solve this, we need to consider how halogens add to alkenes, specifically in the presence of ultraviolet light.

First, it's important to note that UV light will cause the hydrogen and bromine atoms in  to dissociate as free radicals. Because each of these atoms are electron deficient, they desperately want to react in order to fill their valence shells. And since the double bond in the alkene is electron dense, a reaction will occur between one of the electrons in this double bond and the free radical bromine.

The bromine radical adds to the alkene first at the 1-carbon in an anti-Markovnikov fashion. The reason it adds to this carbon (and not the 2-carbon) is because a secondary free radical is more stable than a primary free radical. Upon formation of this secondary radical, it will react with the hydrogen free radical in solution to generate the finished product, 1-bromohexane.

Example Question #95 : Organic Chemistry

Which of the following electrophiles is matched incorrectly with its catalyst needed for electrophilic aromatic substitution on a benzene ring?

Possible Answers:

All are correctly matched

Correct answer:

Explanation:

A catalyst is often required for an electrophilic aromatic substitution reaction. All reagents are paired with their correct catalysts except for  requires  as a catalyst in order to react with benzene.

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:

Rearrangement

Elimination

Addition

Substitution

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 #8 : Help With Addition Reactions

Screen shot 2016 02 21 at 6.40.08 am

Classify the type of reaction given.

Possible Answers:

Substitution

Elimination

Rearrangement

Addition

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 #2 : Help With Addition Reactions

Screen shot 2016 02 21 at 7.44.55 am

Classify the type of reaction given.

Possible Answers:

Addition

Substitution

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 hydrochloric acid and propyne combine to form the product 2-chloropropene.

Example Question #32 : Organic Concepts

Screen shot 2016 02 21 at 7.45.00 am

Classify the type of reaction given above.

Possible Answers:

Addition

Substitution

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 hydrobromic acid and propene combine to form the product 2-bromopropane.

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