Which substitution reaction takes place more rapidly? a. CH 3 CH 2 Br + H 2 O or CH 3 CH 2 Br + HO −

Welcome back, everyone or the following substitution reactions determine which would react faster. We're given two reactions. The first one is a one chloro with we dimethyl butane plus water. And the second one is a one chloro with we then methyl butane plus hydroxide. We can illustrate the two reactions. As follows. In each case, we have our butane chain, we have our Chloro substi bonded to carbon number. Oh one. And the main difference is that this exactly same starting material reacts with two different nu files. In the first reaction, the substrate reacts with water. And then the second one, it reacts with hydroxide. First of all, we have to predict the type of reaction that is favorable in this case. And for that purpose, let's evaluate our substrate. In each case, that's a primary alky halite because the living group is bonded to the carbon atom that only has a one neighboring carbon. Also that exactly same substrate has a good living group, it is the chloral group. And because it's exactly the same leaving group, in each case, it doesn't determine the reaction rate. So if we have exactly the same substrate, that means it is actually the nu file which determines the reaction rate. The first nu phy or water is molecular, it doesn't have any charge. And that means it must be a weak nuclear file. The second nuclear file is charged, which means that it is a strong nu file because we have a negative charge on oxygen and oxygen. Whenever it is negatively charged is a strong nuclei. Primary substrates undergo a substitution reaction via an S N two pathway. And we have to recall that essence reactions require strong nu files. So that means we don't even expect to observe any product for the first reactions. We can say that practically we have no reaction for the first one. And for the second one, since we have a strong nuclear file, the hydroxide an I will attack the electro pyo carbon followed by the loss of the leaving group. And we are going to produce our substitution product by simply replacing the plural group. What the hydroxy group. Therefore, we can conclude that between the two reactions, the second one will react faster because we have a primary substrate which will undergo an essence reaction and an essence reaction requires a strong nuclei. And the second reaction is the one that has a strong nuclear file as opposed to the first one, which has a weak nuclear file. Thank you for watching.

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1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
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30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

7. Substitution Reactions

Nucleophilic Substitution

Organic Chemistry

7. Substitution Reactions

Nucleophilic Substitution

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3:51 minutes

Problem 14a

Textbook Question

Which substitution reaction takes place more rapidly?
a. CH₃CH₂Br + H₂O or CH₃CH₂Br + HO⁻

Verified step by step guidance

Step 1: Understand the type of substitution reaction involved. Both reactions involve nucleophilic substitution, where a nucleophile replaces a leaving group (Br−) in the molecule CH3CH2Br. The two reactions differ in the nucleophile: H2O (neutral) versus HO− (charged).

Step 2: Analyze the nucleophiles. H2O is a neutral molecule, while HO− is a negatively charged ion. Generally, negatively charged nucleophiles are stronger than neutral ones because they have a higher electron density, making them more reactive.

Step 3: Consider the reaction mechanism. CH3CH2Br is a primary alkyl halide, which typically undergoes SN2 (bimolecular nucleophilic substitution) reactions. In SN2 reactions, the rate depends on both the nucleophile and the substrate. A stronger nucleophile (HO−) will lead to a faster reaction compared to a weaker nucleophile (H2O).

Step 4: Evaluate the solvent effects. H2O is a polar protic solvent, which can stabilize the nucleophile through hydrogen bonding, reducing its reactivity. HO−, being a stronger nucleophile, is less affected by this stabilization and remains highly reactive.

Step 5: Conclude based on the above analysis. The reaction CH3CH2Br + HO− will take place more rapidly than CH3CH2Br + H2O due to the stronger nucleophilicity of HO− and the preference for SN2 mechanisms in primary alkyl halides.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. The rate of these reactions can depend on the strength and concentration of the nucleophile, as well as the nature of the leaving group. Understanding the mechanisms, such as SN1 and SN2, is crucial for predicting which reaction will occur more rapidly.

Nucleophile Strength

Nucleophile strength refers to the ability of a species to donate an electron pair to form a bond with an electrophile. Stronger nucleophiles, like HO− (hydroxide ion), are more reactive than weaker ones, such as H2O (water). This concept is essential for determining the rate of substitution reactions, as stronger nucleophiles typically lead to faster reactions.

Solvent Effects

The choice of solvent can significantly influence the rate of nucleophilic substitution reactions. Polar protic solvents, like water, can stabilize ions and slow down reactions involving strong nucleophiles, while polar aprotic solvents can enhance nucleophile reactivity. Understanding how solvents interact with reactants helps predict the outcome and speed of the reaction.

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