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Ch. 2 - General Chemistry Translated: Finding the Electrons
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
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All textbooksMullins 1st EditionCh. 2 - General Chemistry Translated: Finding the ElectronsProblem 43
Chapter 1, Problem 43

The sulfur and oxygen in methanethiol and methanol are both sp3 hybridized. Why is the S―H bond longer than the O―H bond?
Comparison of methanethiol and methanol structures highlighting S―H and O―H bonds.

Verified step by step guidance
1
Understand the concept of bond length: Bond length is the distance between the nuclei of two bonded atoms. It depends on the size of the atoms and the type of bond (single, double, etc.). Larger atoms tend to form longer bonds because their electron clouds are more spread out.
Compare the atomic sizes of sulfur (S) and oxygen (O): Sulfur is in Period 3 of the periodic table, while oxygen is in Period 2. Atoms in Period 3 are larger than those in Period 2 because they have an additional electron shell. This means sulfur has a larger atomic radius than oxygen.
Relate atomic size to bond length: Since sulfur is larger than oxygen, the S―H bond will naturally be longer than the O―H bond. The larger size of sulfur increases the distance between the sulfur nucleus and the hydrogen nucleus compared to the oxygen-hydrogen bond.
Consider hybridization and bond type: Both sulfur and oxygen in methanethiol and methanol are sp³ hybridized, meaning they form single bonds with hydrogen. The hybridization does not significantly affect the bond length in this case, as the difference is primarily due to the atomic size of sulfur and oxygen.
Conclude the reasoning: The S―H bond is longer than the O―H bond because sulfur is a larger atom than oxygen, leading to a greater bond length due to the increased distance between the bonded nuclei.

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Key Concepts

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

Hybridization

Hybridization is the concept in organic chemistry that describes the mixing of atomic orbitals to form new hybrid orbitals. In the case of methanethiol and methanol, both sulfur and oxygen are sp³ hybridized, meaning they form four equivalent orbitals for bonding. This hybridization influences the geometry and bond characteristics of the molecules.
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Bond Length

Bond length refers to the distance between the nuclei of two bonded atoms. It is influenced by factors such as atomic size, bond order, and the presence of lone pairs. In general, larger atoms form longer bonds; thus, the S―H bond in methanethiol is longer than the O―H bond in methanol due to sulfur's larger atomic radius compared to oxygen.
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Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a bond. Oxygen is more electronegative than sulfur, which affects the bond character. The stronger attraction in the O―H bond leads to a shorter bond length compared to the S―H bond, where the weaker attraction results in a longer bond.
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Related Practice
Textbook Question

Rank the following molecules by the length of the indicated bond from shortest to longest.

(a)

(b)

(c)

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Textbook Question

A molecular orbital diagram is shown for the C―Cl bond in chloromethane. If two more electrons were added to chloromethane, where would the electrons go?

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Textbook Question

How might electrons be excited from π to π* based on the molecular orbital diagram shown? [This will be relevant in Chapter 21.]

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Textbook Question

Each pair of structures represents two valid resonance structures. Use the arrow-pushing formalism to justify the formation of the one on the left from the one on the right.

(a)

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Use hybrid orbitals to draw the following molecules.

(c)

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Textbook Question

Use hybrid orbitals to draw the following molecules.

(d)

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