Which is a stronger acid? c. d. CH3CH2CH2OH or CH3CH2CH2SH

Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

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Bruice 8th Edition

Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry

Problem 27c,d

Chapter 3, Problem 27c,d

Which is a stronger acid?
c. <IMAGE>
d. CH₃CH₂CH₂OH or CH₃CH₂CH₂SH

Verified step by step guidance

Step 1: Understand the concept of acidity. Acidity is determined by the ability of a molecule to donate a proton (H⁺). The strength of an acid is influenced by factors such as electronegativity, bond strength, and the stability of the conjugate base formed after losing a proton.

Step 2: Compare the electronegativity of the atoms bonded to hydrogen in the functional groups. Oxygen (in CH3CH2CH2OH) is more electronegative than sulfur (in CH3CH2CH2SH), meaning it can better stabilize the negative charge on the conjugate base after losing a proton.

Step 3: Consider the bond strength between hydrogen and the atom it is attached to. The O-H bond in CH3CH2CH2OH is stronger than the S-H bond in CH3CH2CH2SH, making it harder for CH3CH2CH2OH to lose a proton compared to CH3CH2CH2SH.

Step 4: Evaluate the stability of the conjugate base. After losing a proton, the conjugate base of CH3CH2CH2OH (CH3CH2CH2O⁻) is less stable than the conjugate base of CH3CH2CH2SH (CH3CH2CH2S⁻) because sulfur can better accommodate the negative charge due to its larger atomic size.

Step 5: Based on the above factors, CH3CH2CH2SH is the stronger acid compared to CH3CH2CH2OH because sulfur's lower electronegativity and larger atomic size allow for better stabilization of the conjugate base, making it easier to donate a proton.

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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 ability of a compound to donate a proton (H+). The strength of an acid is often measured by its pKa value; lower pKa values indicate stronger acids. Understanding the relationship between pKa and acid strength is crucial for comparing different compounds.

Alcohols vs. Thiols

Alcohols (R-OH) and thiols (R-SH) are both functional groups containing a hydroxyl or sulfhydryl group, respectively. Thiols are generally more acidic than alcohols due to the weaker S-H bond compared to the O-H bond, which makes it easier for thiols to release a proton.

Inductive Effect

The inductive effect refers to the electron-withdrawing or electron-donating effects of substituents on the acidity of a compound. Electronegative atoms or groups can stabilize the negative charge of the conjugate base formed after deprotonation, thereby increasing acidity. This concept is important when comparing the acidity of different organic compounds.

Which is a stronger acid? c. <IMAGE>d. CH3CH2CH2OH or CH3CH2CH2SH