Explain the relative acidities. CH 2 ═CHCH 2 OH, CH 3 CH 2 CH 2 OH, HC≡CCH 2 OH

Hello everyone in this video and go ahead and discuss the relative cities of our following alcohols. So most stick is going to be the CH three C troop one CC H 20 H. Then follow with our B and C alcohol which she is going to be the least acidic. So all these compounds have differently hybridized carbons near our hydroxy groups that are O H groups or alcohol groups. As we know a SP hybridized atom is going to be more electro negative than the SP two hybridized atom, which is going to be more electro negative than our SP three hybridized atoms. So let's actually write that part out again. That's S P It's going to be more electro negative than the SP two and it's going to be more hybridized or more electro negative than the SP three. Alright. So the acidity increases with the more electro negative substitue into near the item having the proton. Therefore, the alcohol with the SP carbon on the beta position is going to be more acidic than the alcohol with the SP two carbon, which is more acidic than the alcohol with all three SP three hybridized carbon atoms. So our answer then let's actually write this part out as well is that due to stronger electro negativity, the alcohol? So the O H group with S P hybridized carbons is going to be more acidic than our alcohols With the Sp two carbons which then of course more acidic then the alcohol with all SP three hybridized carbons. Alright. So that's going to be my final answer for this problem.

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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
29. Amino Acids4h 20m
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

3. Acids and Bases

Ranking Acidity

Organic Chemistry

3. Acids and Bases

Ranking Acidity

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2:33 minutes

Problem 62b

Textbook Question

Explain the relative acidities.
CH₂═CHCH₂OH, CH₃CH₂CH₂OH, HC≡CCH₂OH

Verified step by step guidance

Step 1: Begin by understanding the concept of acidity. Acidity is determined by the ability of a compound to donate a proton (H⁺). The more stable the conjugate base after losing a proton, the stronger the acid.

Step 2: Analyze the structure of each compound and identify the functional groups. CH2═CHCH2OH contains an alcohol group (-OH) attached to an allylic carbon, CH3CH2CH2OH contains an alcohol group attached to a saturated alkyl chain, and HC≡CCH2OH contains an alcohol group attached to a propargylic carbon (next to a triple bond).

Step 3: Consider the effects of resonance and electronegativity. In CH2═CHCH2OH, the allylic position allows for resonance stabilization of the conjugate base, making it more acidic. In HC≡CCH2OH, the triple bond increases the electronegativity of the adjacent carbon, stabilizing the conjugate base and increasing acidity. CH3CH2CH2OH lacks resonance or significant electronegativity effects, making it the least acidic.

Step 4: Evaluate the inductive effects. Electronegative groups or bonds near the -OH group can pull electron density away, stabilizing the conjugate base. The triple bond in HC≡CCH2OH exerts a stronger inductive effect compared to the double bond in CH2═CHCH2OH, further increasing its acidity.

Step 5: Rank the compounds based on their relative acidities. HC≡CCH2OH is the most acidic due to the strong inductive effect and stabilization of the conjugate base. CH2═CHCH2OH is moderately acidic due to resonance stabilization. CH3CH2CH2OH is the least acidic as it lacks resonance or significant inductive effects.

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Key Concepts

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

Acidity and pKa

Acidity refers to the tendency of a compound to donate a proton (H+) in solution. The strength of an acid is often measured by its pKa value, where lower pKa values indicate stronger acids. Understanding the pKa helps predict the relative acidities of different compounds, as it reflects the stability of the conjugate base formed after deprotonation.

Inductive Effect

The inductive effect describes how the presence of electronegative atoms or groups can influence the acidity of a molecule by stabilizing or destabilizing the conjugate base. Electron-withdrawing groups increase acidity by stabilizing the negative charge on the conjugate base, while electron-donating groups decrease acidity by destabilizing it.

Hybridization and Acidity

The hybridization of the atom bearing the acidic proton significantly affects acidity. For example, sp-hybridized carbons (like in alkynes) hold their electrons closer to the nucleus, resulting in stronger acids compared to sp2 (alkenes) or sp3 (alkanes) hybridized carbons. This is due to the increased s-character in sp hybridization, which stabilizes the negative charge on the conjugate base.

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