Please heellppppppppp!!!!
How do you expect the following series of compounds to compare in behavior in the two tests?(Sn1/Sn2 reaction)
CH3-CH=CH-CH2-Br CH3-C=CH-CH3
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Br
CH3-CH2-CH2-CH2-Br
Please help me answer this question, I really don't understand and don't know how to answer this question. Thanks.
You might want to look at http://en.wikipedia.org/wiki/SN1_reaction and the similar page for SN2.
You are looking for how stable is the carbocation that is formed, the more stable the more likely that the reaction is SN1 rather than SN2.
so which is the more stable?
CH3-CH=CH-CH2+
CH3-C=C(+)H-CH3
CH3-CH2-CH2-CH2+
There is also the question which carbocation is also likely to rearrange?
To compare the behavior of the given compounds in Sn1/Sn2 reactions, we need to analyze the structural and electronic factors that influence the reaction mechanism.
1. CH3-CH=CH-CH2-Br:
In this compound, the attached bromine atom is on a primary carbon, which means it is less hindered. The beta-carbon (attached to the bromine) is also primary and not sterically hindered. Due to these factors, this compound is expected to undergo both Sn1 and Sn2 reactions.
2. CH3-C=CH-CH3:
In this compound, the attached bromine atom is on a tertiary carbon, which is a highly hindered position. The beta-carbon (attached to the bromine) is also tertiary and highly sterically hindered. This compound is expected to undergo Sn1 reactions more readily rather than Sn2 reactions. The high steric hindrance will make the backside attack in Sn2 reactions more difficult.
3. CH3-CH2-CH2-CH2-Br:
In this compound, the attached bromine atom is on a primary carbon, which is less hindered. However, the beta-carbon, in this case, is not accessible due to the long carbon chain (four carbon atoms) between the bromine and the beta-carbon. This steric hindrance will make the Sn2 reaction unlikely. Therefore, this compound is expected to undergo Sn1 reactions more readily.
To summarize:
- CH3-CH=CH-CH2-Br: Can undergo both Sn1 and Sn2 reactions.
- CH3-C=CH-CH3: More likely to undergo Sn1 reactions due to high steric hindrance.
- CH3-CH2-CH2-CH2-Br: More likely to undergo Sn1 reactions due to steric hindrance and lack of Sn2 accessibility.
Remember, these predictions are based on general trends and factors. The actual reaction behavior may also depend on specific reaction conditions and other factors not mentioned in the question.
To compare the behavior of the series of compounds in Sn1/Sn2 reactions, we need to analyze the structure of each compound and consider the factors that influence Sn1 and Sn2 reactions.
1. Sn1 Reaction:
- In Sn1 reactions, the rate-determining step is the formation of the carbocation intermediate.
- Therefore, compounds that can form stable carbocations (tertiary > secondary > primary) will favor Sn1 reactions.
- Polar solvents (such as protic solvents like water or alcohol) are preferred in Sn1 reactions.
2. Sn2 Reaction:
- In Sn2 reactions, the nucleophile directly attacks the substrate, leading to a concerted reaction.
- Therefore, compounds that have accessible carbon atoms with little steric hindrance will favor Sn2 reactions.
- Aprotic solvents (such as acetone or DMF) are favored in Sn2 reactions.
Now, let's compare the compounds in the series:
Compound 1: CH3-CH=CH-CH2-Br
- This compound has a primary carbon that can undergo Sn2 reactions.
- The double bond may hinder some nucleophiles, depending on their size and charge.
- In terms of Sn1 reactions, the primary carbon will not favor carbocation formation.
- Overall, this compound is likely to undergo Sn2 reactions more readily.
Compound 2: CH3-C=CH-CH3-Br
- This compound has a secondary carbon that can undergo Sn2 reactions.
- The presence of a double bond does not affect the availability of the carbon atom for nucleophilic attack.
- In terms of Sn1 reactions, the secondary carbon is more favorable for carbocation formation compared to Compound 1.
- Overall, this compound may have a similar reactivity to Compound 1 but might also show some preference for Sn1 reactions.
Compound 3: CH3-CH2-CH2-CH2-Br
- This compound has a quaternary carbon that cannot undergo Sn2 reactions.
- The presence of three other alkyl groups around the carbon atom leads to significant steric hindrance, making Sn2 reactions unlikely.
- In terms of Sn1 reactions, the quaternary carbon is highly favorable for carbocation formation.
- Overall, this compound is likely to undergo Sn1 reactions more readily.
In summary, Compound 1 is expected to show a stronger preference for Sn2 reactions, Compound 2 may show a somewhat balanced behavior with both Sn1 and Sn2 reactions, and Compound 3 is expected to show a stronger preference for Sn1 reactions due to its quaternary carbon.