Question 1

Which of the following structures is a ketene?

Accepted Answer

A ketene consists of a C=C=O functional group. The only structure that fits this description is II, which has a double bond between two carbons with a carbonyl group attached to one of them. None of the other structures have this functional group.

Question 2

From left to right, what is the approximate hybridization of the indicated carbons in the structure shown here?

Accepted Answer

A

Question 3

Which of the following compounds is the thermodynamic product of the reaction shown here?

Accepted Answer

The thermodynamic product is formed under conditions of high temperature and long reaction times. This leads to the formation of the product with the most stable double bond configuration, which in this case is trans. Option C is the only trans isomer among the given compounds, indicating that it is the thermodynamic product.

Question 4

When 1,3 -butadiene reacts with chlorine, a  50/50  mixture of 3,4 -dichloro-1-butene and (E)-1,4-dichloro-2-butene is generated. When the same diene is reacted with bromine, the 3,4 -dibromo-1-butene is the predominant product.. What could explain the difference in regioselectivity?

Accepted Answer

The answer of When 1,3 -butadiene reacts with chlorine, a...

Question 5

Which of the following molecules contains the most acidic hydrogen?

Accepted Answer

The answer of Which of the following molecules contains the...

Question 6

How many nodes are there in the highest energy  molecular orbital for  1,3,5 -hexatriene?

Accepted Answer

The answer of How many nodes are there in the...

Question 7

Which of the following statements about the reaction shown here is true?

Accepted Answer

The major product under kinetic conditions is determined by the fastest and most accessible reaction pathway. In this case, the 1,2 addition product is favored under kinetic conditions because it involves a shorter distance for the nucleophile to approach the electrophilic center (protonated carbon) compared to the 1,4 addition pathway. This effect is known as proximity effects. Carbocation stability would only come into play under thermodynamic conditions, where the reaction is allowed to reach equilibrium and the most stable product is favored. Therefore, option B is the correct answer.

Question 8

Which of these statements about thermodynamic and kinetic control is true?

Accepted Answer

Reactions under equilibrium conditions favor the thermodynamic product because the system has enough time and energy to overcome activation barriers and reach the most stable product configuration.

Question 9

Which structure contains the longest C-C bond?

Accepted Answer

The answer of Which structure contains the longest C-C bond?

...

Question 10

Which of the structures shown is in the s-cis conformation?

Accepted Answer

The answer of Which of the structures shown is in...

Question 11

Rank these dienes in order of increasing heats of hydrogenation.

Accepted Answer

The answer of Rank these dienes in order of increasing...

Question 12

Which of the structures shown is in the s-trans conformation?

Accepted Answer

The answer of Which of the structures shown is in...

Question 13

Which of the following structures is the product of 1,2 addition of HCl to the molecule shown here?

Accepted Answer

1,2 addition of HCl adds the chloride ion to the carbon that has the most hydrogen atoms. In the given molecule, that would be the middle carbon of the double bond. The resulting structure would have the chloride and the remaining hydrogen on adjacent carbons, resulting in a 3-chloro compound. The methyl group remains on the same carbon as before, so the correct answer is 3-chloro-3-methyl-1-hexene.

Question 14

Which of these structures is a conjugated diene?

Accepted Answer

The answer of Which of these structures is a conjugated...

Question 15

Which of these alkynes will not isomerize in the presence of NaNH₂ ?

Accepted Answer

The answer of Which of these alkynes will not isomerize...

Question 16

In the rearrangement of 2-butyne to 1-butyne, what causes the reaction to go to completion?

Accepted Answer

The answer of In the rearrangement of 2-butyne to 1-butyne,...

Question 17

Which of these structures is the product of 1,4 addition of HBr to the molecule shown here?

Accepted Answer

The answer of Which of these structures is the product...

Question 18

Which of these compounds can exist as cis/trans isomers?

Accepted Answer

The answer of Which of these compounds can exist as...

Question 19

Rank the following C₄H₆ isomers in order of increasing ΔH_f values:

Accepted Answer

The answer of Rank the following C₄H₆ isomers in...

Question 20

Which of the following structures is chiral?

Accepted Answer

The answer of Which of the following structures is chiral?

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Quiz 13: Dienes and the Allyl System: 2p Orbitals in Conjugation

Which of the following structures is a ketene?

From left to right, what is the approximate hybridization of the indicated carbons in the structure shown here?

Which of the following compounds is the thermodynamic product of the reaction shown here?

When 1,3 -butadiene reacts with chlorine, a 50/50 mixture of 3,4 -dichloro-1-butene and (E) -1,4-dichloro-2-butene is generated. When the same diene is reacted with bromine, the 3,4 -dibromo-1-butene is the predominant product.. What could explain the difference in regioselectivity?

Which of the following molecules contains the most acidic hydrogen?

How many nodes are there in the highest energy molecular orbital for 1,3,5 -hexatriene?

Which of the following statements about the reaction shown here is true?

Which of these statements about thermodynamic and kinetic control is true?

Which structure contains the longest C-C bond?

Which of the structures shown is in the s-cis conformation?

Rank these dienes in order of increasing heats of hydrogenation.

Which of the structures shown is in the s-trans conformation?

Which of the following structures is the product of 1,2 addition of HCl to the molecule shown here?

Which of these structures is a conjugated diene?

Which of these alkynes will not isomerize in the presence of NaNH₂ ?

In the rearrangement of 2-butyne to 1-butyne, what causes the reaction to go to completion?

Which of these structures is the product of 1,4 addition of HBr to the molecule shown here?

Which of these compounds can exist as cis/trans isomers?

Rank the following C₄H₆ isomers in order of increasing ΔH_f values:

Which of the following structures is chiral?

Quiz 13: Dienes and the Allyl System: 2p Orbitals in Conjugation

Which of the following structures is a ketene?

From left to right, what is the approximate hybridization of the indicated carbons in the structure shown here?

Which of the following compounds is the thermodynamic product of the reaction shown here?

When 1,3 -butadiene reacts with chlorine, a 50/50 mixture of 3,4 -dichloro-1-butene and (E) -1,4-dichloro-2-butene is generated. When the same diene is reacted with bromine, the 3,4 -dibromo-1-butene is the predominant product.. What could explain the difference in regioselectivity?

Which of the following molecules contains the most acidic hydrogen?

How many nodes are there in the highest energy molecular orbital for 1,3,5 -hexatriene?

Which of the following statements about the reaction shown here is true?

Which of these statements about thermodynamic and kinetic control is true?

Which structure contains the longest C-C bond?

Which of the structures shown is in the s-cis conformation?

Rank these dienes in order of increasing heats of hydrogenation.

Which of the structures shown is in the s-trans conformation?

Which of the following structures is the product of 1,2 addition of HCl to the molecule shown here?

Which of these structures is a conjugated diene?

Which of these alkynes will not isomerize in the presence of NaNH2 ?

In the rearrangement of 2-butyne to 1-butyne, what causes the reaction to go to completion?

Which of these structures is the product of 1,4 addition of HBr to the molecule shown here?

Which of these compounds can exist as cis/trans isomers?

Rank the following C4H6 isomers in order of increasing ΔHf values:

Which of the following structures is chiral?

Which of these alkynes will not isomerize in the presence of NaNH₂ ?

Rank the following C₄H₆ isomers in order of increasing ΔH_f values: