Organic Chemistry : Hydrocarbon Products

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

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Example Question #1 : Help With Alkene Synthesis

Screen shot 2015 12 30 at 6.43.54 pm

What is the major product for the reaction given?

Possible Answers:

Screen shot 2015 12 30 at 6.48.56 pm

Screen shot 2015 12 30 at 6.49.10 pm

Screen shot 2015 12 30 at 6.49.00 pm

Screen shot 2015 12 30 at 6.49.04 pm

Correct answer:

Screen shot 2015 12 30 at 6.49.00 pm

Explanation:

The reason this is the major product is because on tertiary alcohols are best dehydrated based on the E1 mechanism below:

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Example Question #11 : Reactions By Product

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What is the major product for the reaction given?

Possible Answers:

Screen shot 2015 12 30 at 7.22.44 pm

Screen shot 2015 12 30 at 7.22.53 pm

Screen shot 2015 12 30 at 7.22.58 pm

Screen shot 2015 12 30 at 7.23.02 pm

Correct answer:

Screen shot 2015 12 30 at 7.22.53 pm

Explanation:

The reason this is the major product is because tertiary alcohols are best dehydrated based on the E1 mechanism below:

Screen shot 2015 12 31 at 11.16.42 am

Example Question #1 : Help With Alkene Synthesis

Screen shot 2015 12 30 at 6.42.35 pm

What is the major product for the reaction given?

Possible Answers:

Screen shot 2015 12 30 at 6.48.40 pm

Screen shot 2015 12 30 at 6.48.53 pm

Screen shot 2015 12 30 at 6.42.50 pm

Screen shot 2015 12 30 at 6.48.49 pm

Correct answer:

Screen shot 2015 12 30 at 6.42.50 pm

Explanation:

Below is the mechanism for the reaction given to form the alkene:

Screen shot 2015 12 31 at 11.21.32 am 

Example Question #3 : Hydrocarbons

What is the best reagent for abstracting a hydrogen from ethyne?

Possible Answers:

None of these

Correct answer:

Explanation:

The triple bond in ethyne makes the hydrogens slightly more acidic than those found in ethane. A very strong base, such as the conjugate base of ammonia, would be able to abstract that hydrogen. The abstraction turns the base into ammonia. It also creates a carbanion that can be used for chain extension and alkyne synthesis.

Example Question #1 : Hydrocarbons

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What is the product of the compound when it reacts with two equivalents of base?

Possible Answers:

2-pentene

2-pentyne

1-pentene

1-pentyne

None of these

Correct answer:

2-pentyne

Explanation:

For each equivalent of base, a pi bond is formed between the carbons initially bound to the bromine atoms. For each bond formed, a bromine leaving group leaves the hydrocarbon. One equivalent of base abstracts a hydrogen. The electrons from the bond to the hydrogen create a pi bond. This occurs twice, and a triple bond is formed. The result is a 5-carbon chain with a triple bond between the second and third carbons. This molecule is 2-pentyne.

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