Organic Chemistry : Reactions by Product

Study concepts, example questions & explanations for Organic Chemistry

varsity tutors app store varsity tutors android store

Example Questions

← Previous 1 3 4

Example Question #1 : Hydrocarbons

Untitled

What is the IUPAC name of the given molecule?

Possible Answers:

3,3,5-trimethylnonane

None of these

4,6-dimethyl-6-ethylpentane

3,3,5-trimethyloctane

2,2,4-trimethyloctane

Correct answer:

3,3,5-trimethyloctane

Explanation:

The longest carbon chain that can be formed is eight carbons. The base molecule is octane.

Using IUPAC rules, substituents should have the lowest possible numbers; thus, we start counting carbons from the right side rather than the left. If you count from the correct side, there are two methyl groups on carbon 3 and one on carbon 5. Thus, the name of the moleculue is 3,3,5-trimethyloctane.

Example Question #1 : Organic Chemistry

Untitled

How could you brominate the compound?

Possible Answers:

None of these

Bromine gas

Hydrobromic acid

Bromine and peroxides

Bromine and UV light

Correct answer:

Bromine and UV light

Explanation:

The given molecule is an alkane. The only way to brominate an alkane is with bromine gas and UV light. The energy from the light serves to creat two radical bromines. These radicals are capable of bonding with alkanes. If the given compound were an alkene, either hydrobromic acid or bromine and peroxides would work.

Example Question #1 : Help With Alkane Synthesis

Predict the absolute configuration about the double bond formed in the given E1 reaction.

Screen shot 2015 06 30 at 11.17.49 pm

Possible Answers:

Z

Racemic Z/E

No elimination reaction would proceed

E

Correct answer:

E

Explanation:

Unlike E2 reactions, in which hydrogen abstraction occurs simultaneously with the dissociation of the leaving group (limiting the configuration of the reaction's product), E1 reactions occur in two distinct steps. The slow rate-determining step that must first occur is the dissociation of the leaving group. Leaving behind a carbocation intermediate, it is often necessary to consider possible carbocation rearrangements that would stabilize the positive charge.

In this case, no such rearrangement is favorable as their are no locations of greater stability available.

However, what must be considered is that the intermediate is free to orient itself in its most stable conformation prior to the formation of the double bond in the second step. As a result, the E product (the larger substituents are on oriented opposite one another with respect to the double bond) is yielded primarily.

Example Question #2 : Help With Alkane Synthesis


Img 0605

Which reagents are required to carry out the given reaction?

Possible Answers:

Correct answer:

Explanation:

To carry out this reaction, we need to create a radical as an intermediate, which is an unpaired electron. We do so by introducing , UV light, and heat to the 1-methyl cyclohexane. The light and the heat react with the  to break the bond and create two radical bromine atoms. One of the radical bromine atoms removes a hydrogen from the carbon on the 1-methyl cyclohexane that is most substituted, and a radical carbon is formed. Finally, the second radical bromine reacts with the radical carbon to form the final product.

Example Question #3 : Hydrocarbons

Untitled

What is the IUPAC name of the given diene?

Possible Answers:

3-chloro-2,5-dimethyl-1,5-heptadiene

None of these answers

3-chloro-2,5-dimethyl-2,6-heptadiene

5-chloro-3,6-dimethyl-1,5-heptadiene

5-chloro-3,5-dimethyl-1,6-heptadiene

Correct answer:

5-chloro-3,6-dimethyl-1,5-heptadiene

Explanation:

You must begin counting the carbons so that the first functional substituent has the lowest possible number. In this case, C1 is connected to C2 by the double bond, meaning we start counting from the left.

The longest carbon chain is seven carbons so the parent molecule is heptane. With this numbering, there are methyl groups on carbons 3 and 6 and a chlorine on carbon 5.

Substituents are named in alphabetical order and two double bonds result in a diene. Thus, the correct answer is 5-chloro-3,6-dimethyl-1,5-heptadiene.

Example Question #31 : Organic Chemistry

Untitled

What is the value of  from Huckel's rule for the given aromatic compound?

Possible Answers:

Correct answer:

Explanation:

Huckel's rule states that an aromatic compound must have  delocalized electrons. The electrons in each double bond are delocalized for this molecule. There are nine double bonds, and thus eighteen delocalized electrons.

If 4n+2=18, then n=4.

Example Question #1 : Help With Alkene Synthesis

Which of the following reagents would convert butanone into 2-butene?

Possible Answers:

1. 

2. Heat/

1. 

2. Heat/

1. 

2. 

Correct answer:

1. 

2. Heat/

Explanation:

Two sets of reagents are required to convert butanone into 2-butene. First, we use  to reduce the butanone into a 2-butanol. Second, we use heat and acid to dehydrate the butanol and yield the final desired product.

1. ; 2. Heat/ may seem like an acceptable answer choice. However, note that the Grignard reagent converts the butanone into a tertiary alcohol, rather than a secondary alcohol as needed.

Example Question #4 : Hydrocarbon Products

2-butone is reacted with  to form a product. That product was then heated in acid  to form a final product. What is the final product?

Possible Answers:

Butane

None of these

2-butene

2-butanol

Correct answer:

2-butene

Explanation:

2-butone is a carbonyl compound that can readily be reduced by  into a secondary alcohol, 2-butanol. When 2-butanol is heated in acid, we get dehydration, which leads to 2-butene.

Example Question #1 : Reactions By Product

Noname01

What is the reactant of the given reaction?

Possible Answers:

Noname02

Noname06

Noname04

Noname03

Noname05

Correct answer:

Noname02

Explanation:

This is an addition reaction with 3 products. The unknown reactant reacts with  and gives those three products. Addition reactions begin with double bonded compounds and so these electrons are used to react with some reagent . One needs to work backwards to figure out how something was formed and in this case, there are mechanistic pathways, and one of the pathways involves a hydride shift. These 3 products often exist in different concentrations after the reaction. 

Example Question #6 : Hydrocarbon Products

Which of the following reagents can be used to create a E alkene from an alkyne? 

Possible Answers:

None of these

Correct answer:

Explanation:

Metallic sodium in liquid ammonia creates solvated electrons which can convert an alkyne to an E alkene. The same will not happen when sodium is combined with water, where sodium reacts violently to create sodium hydroxide and hydrogen gas. Lindlar's catalyst is a poisoned catalyst used to form alkenes from alkynes, bud results in a Z conformation. Without the poisoned catalyst, an alkane will be formed. 

← Previous 1 3 4
Learning Tools by Varsity Tutors