Question 1

Which of the following compounds could be produced from the following reaction sequence?

Accepted Answer

The reaction sequence involves the conversion of 1-bromobutane to 1-butene via an E2 mechanism using NaOH and heat. Then, the 1-butene undergoes halogenation with Br2 in the presence of an alkene halogenation catalyst (such as NBS) to form a mixture of 1,2-dibromobutane (III) and 2,3-dibromobutane (IV). 
Since the question asks which compound "could be produced," both III and IV are technically correct answers. However, since the question only allows for one choice, III is the best choice because it is the major product (about 80%) in the halogenation of 1-butene under these conditions. IV is the minor product (about 20%) and would only be selected if the question specifically asked for a mixture of products.

Question 2

In dehydration reactions the Zaitsev product will almost always be the major product produced in the reaction.

Accepted Answer

This is because the Zaitsev product is typically the more stable/thermodynamically favored product due to the formation of a more substituted alkene. This phenomenon is known as the Zaitsev rule. However, in certain cases, such as when steric hindrance is present or when the reaction is carried out under kinetic control, non-Zaitsev products may be formed as the major product.

Question 3

In dehydrohalogenation reactions the Zaitsev product will always be the major product produced in the reaction.

Accepted Answer

The Zaitsev product is often the major product because it is typically more stable due to being more substituted. However, the major product can depend on the reaction conditions and the base used. Strong, bulky bases tend to favor the formation of the less substituted (Hofmann) product over the Zaitsev product.

Question 4

Predict the major organic product(s)of the following reaction:

Accepted Answer

The answer of Predict the major organic product(s)of the following...

Question 5

Alkenes and alkynes that are saturated must have an index of hydrogen deficiency equal to zero as they have no carbon-carbon pi electron present in the system.

Accepted Answer

Alkenes and alkynes, even if they are fully saturated, will still have an index of hydrogen deficiency (IHD) greater than zero due to the presence of double or triple bonds. The IHD is calculated as the number of missing hydrogens needed to achieve the maximum number of hydrogens possible for a given molecular formula, and is related to the number of unsaturated sites (pi bonds, rings, or multiple bonds) in the molecule.

Question 6

The main reason why anti-periplaner conformation is preferred in E2 reactions is because the conformation of the hydrogen that is anti to the leaving group provides for a staggered transition state,which is lower in free energy.

Accepted Answer

The anti-periplanar conformation creates a staggered transition state, which leads to a lower free energy of activation and therefore a preferred pathway for E2 reactions. This is a basic concept in organic chemistry.

Question 7

Provide a mechanistic explanation for the formation of the observed products in the following reaction.

Accepted Answer

The answer of Provide a mechanistic explanation for the formation...

Question 8

When an elimination reaction gives the less substituted alkene as the major product,we say that the elimination follows ___'s rule.

Accepted Answer

The answer of When an elimination reaction gives the less...

Question 9

The structure of the product,C,of the following sequence of reactions would be:

Accepted Answer

The answer of The structure of the product,C,of the following...

Question 10

The structure of the product obtained from 2-butyne and Li/C₂H₅NH₂ is:

Accepted Answer

The answer of The structure of the product obtained from...

Question 11

Which would be the major product of the following reaction sequence?

Accepted Answer

The answer of Which would be the major product of...

Question 12

The ambiguous name dimethylcyclopentene does not clearly distinguish between several structures.
a)Draw the structures of all constitutional isomers corresponding to this name.
b)Indicate which of these is likely to be the most stable,i.e,have the smallest heat of combustion,justifying your rationale briefly.
c)Which of these structures represents an achiral molecule?

Accepted Answer

The answer of The ambiguous name dimethylcyclopentene does not clearly...

Question 13

Dehydration of alcohols requires a ___ catalyst.

Accepted Answer

The answer of Dehydration of alcohols requires a ___ catalyst....

Question 14

Predict the major organic product(s)of the following reaction:

Accepted Answer

The answer of Predict the major organic product(s)of the following...

Question 15

When an elimination reaction gives the most stable alkene as the major product,we say that the elimination follows ___'s rule.

Accepted Answer

The answer of When an elimination reaction gives the most...

Question 16

Which would be the major product of the following reaction sequence?

Accepted Answer

The answer of Which would be the major product of...

Question 17

Tertiary carbocations will form the fastest because they have a transition state that is the lowest in free energy.

Accepted Answer

Tertiary carbocations have a greater number of alkyl groups bonded to the carbon atom carrying the positive charge which stabilizes the carbocation. This stabilization causes a lower activation energy for the reaction, leading to a faster reaction rate.

Question 18

Draw the structures of all stereoisomers of 2-chloro-4-methyl-3-hexene,clearly showing all stereochemical details,using appropriate 3-D representations (dash-wedge,etc.)as relevant.

Accepted Answer

The answer of Draw the structures of all stereoisomers of...

Question 19

In a dehydration reaction,the leaving group is ___.

Accepted Answer

The answer of In a dehydration reaction,the leaving group is...

Question 20

In acid catalyzed dehydration of alcohol,the acid catalyst is always regenerated in the reaction process.

Accepted Answer

In the acid-catalyzed dehydration of alcohols, the acid catalyst (usually sulfuric acid or phosphoric acid) acts as a proton donor, helping to form a carbocation intermediate. The acid catalyst itself does not react with the alcohol or the resulting alkene. Therefore, it is not consumed in the reaction and can be used again to catalyze further reactions. This allows the acid catalyst to be regenerated in the reaction process.

Quiz 7: Alkenes and Alkynes I

Which of the following compounds could be produced from the following reaction sequence?

In dehydration reactions the Zaitsev product will almost always be the major product produced in the reaction.

In dehydrohalogenation reactions the Zaitsev product will always be the major product produced in the reaction.

Predict the major organic product(s) of the following reaction:

Alkenes and alkynes that are saturated must have an index of hydrogen deficiency equal to zero as they have no carbon-carbon pi electron present in the system.

The main reason why anti-periplaner conformation is preferred in E2 reactions is because the conformation of the hydrogen that is anti to the leaving group provides for a staggered transition state,which is lower in free energy.

Provide a mechanistic explanation for the formation of the observed products in the following reaction.

When an elimination reaction gives the less substituted alkene as the major product,we say that the elimination follows ___'s rule.

The structure of the product,C,of the following sequence of reactions would be:

The structure of the product obtained from 2-butyne and Li/C₂H₅NH₂ is:

Which would be the major product of the following reaction sequence?

Dehydration of alcohols requires a ___ catalyst.

Predict the major organic product(s) of the following reaction:

When an elimination reaction gives the most stable alkene as the major product,we say that the elimination follows ___'s rule.

Which would be the major product of the following reaction sequence?

Tertiary carbocations will form the fastest because they have a transition state that is the lowest in free energy.

Draw the structures of all stereoisomers of 2-chloro-4-methyl-3-hexene,clearly showing all stereochemical details,using appropriate 3-D representations (dash-wedge,etc.)as relevant.

In a dehydration reaction,the leaving group is ___.

In acid catalyzed dehydration of alcohol,the acid catalyst is always regenerated in the reaction process.

Quiz 7: Alkenes and Alkynes I

Which of the following compounds could be produced from the following reaction sequence?

In dehydration reactions the Zaitsev product will almost always be the major product produced in the reaction.

In dehydrohalogenation reactions the Zaitsev product will always be the major product produced in the reaction.

Predict the major organic product(s) of the following reaction:

Alkenes and alkynes that are saturated must have an index of hydrogen deficiency equal to zero as they have no carbon-carbon pi electron present in the system.

The main reason why anti-periplaner conformation is preferred in E2 reactions is because the conformation of the hydrogen that is anti to the leaving group provides for a staggered transition state,which is lower in free energy.

Provide a mechanistic explanation for the formation of the observed products in the following reaction.

When an elimination reaction gives the less substituted alkene as the major product,we say that the elimination follows ___'s rule.

The structure of the product,C,of the following sequence of reactions would be:

The structure of the product obtained from 2-butyne and Li/C2H5NH2 is:

Which would be the major product of the following reaction sequence?

Dehydration of alcohols requires a ___ catalyst.

Predict the major organic product(s) of the following reaction:

When an elimination reaction gives the most stable alkene as the major product,we say that the elimination follows ___'s rule.

Which would be the major product of the following reaction sequence?

Tertiary carbocations will form the fastest because they have a transition state that is the lowest in free energy.

Draw the structures of all stereoisomers of 2-chloro-4-methyl-3-hexene,clearly showing all stereochemical details,using appropriate 3-D representations (dash-wedge,etc.)as relevant.

In a dehydration reaction,the leaving group is ___.

In acid catalyzed dehydration of alcohol,the acid catalyst is always regenerated in the reaction process.

The structure of the product obtained from 2-butyne and Li/C₂H₅NH₂ is: